CORE 2 CBLM Service Consumer Electronic Products and Systems - PDFCOFFEE.COM (2024)

PARTS OF A COMPETENCY-BASED LEARNING MATERIAL PACKAGE References/Further Reading Performance Criteria Checklist Operation/Task/Job Sheet Self Check Answer Key Self Check Information Sheet Learning Experiences Learning Outcome Summary

Module Content Content Module Module List of Competencies Content Module Content Module Content Front Page

In our efforts to standardize CBLM, the above parts are recommended for use in Competency Based Training (CBT) in Technical Education and Skills Development Authority (TESDA) Technology Institutions. The next sections will show you the components and features of each part.

Date Developed:

Electronic Products Assembly and Servicing NC II

December 2015

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Developed by: Nolito Carreras Joel N. Coralde

Revision # 1

ICONNECT GLOBAL INSTITUTE, INC. Poblacion Central, Ocampo, Camarines Sur

Sector : INFORMATION AND COMMUNICATION TECHNOLOGY Qualification Title: ELECTRONIC PRODUCTS ASSEMBLY AND SERVICING NC II Unit of Competency: SERVICE CONSUMER ELECTRONIC PRODUCTS AND SYSTEMS

Module Title: SERVICING CONSUMER ELECTRONIC PRODUCTS AND SYSTEMS

ICONNECT GLOBAL INSTITUTE, INC. Poblacion Central, Ocampo, Camarines Sur

Date Developed:

Electronic Products Assembly and Servicing NC II

December 2015

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Developed by: Nolito Carreras Joel N. Coralde

Revision # 1

Consumer Electronics Servicing NCII

COMPETENCY-BASED LEARNING MATERIALS

List of Competencies

No.

Unit of Competency

Module Title

Code

1.

ASSEMBLE ELECTRONIC PRODUCTS

ASSEMBLING ELECTRONIC PRODUCTS

ELC724335

2.

SERVICE CONSUMER ELECTRONIC PRODUCTS AND SYSTEMS

SERVICING CONSUMER ELECTRONIC PRODUCTS AND SYSTEMS

3.

SERVICE INDUSTRIAL ELECTRONIC MODULES, PRODUCTS AND SYSTEMS

SERVICING INDUSTRIAL ELECTRONIC MODULES PRODUCTS AND SYSTEMS

ELC724336

ELC724337

MODULE CONTENT

Date Developed:

Electronic Products Assembly and Servicing NC II

December 2015

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UNIT OF COMPETENCY MODULE TITLE MODULE DESCRIPTOR

: SERVICE CONSUMER ELECTRONIC PRODUCTS AND SYSTEMS : SERVICING CONSUMER ELECTRONIC PRODUCTS AND SYSTEMS : THIS MODULE COVERS THE KNOWLEDGE, SKILLS AND ATTITUDES REQUIRED TO INSTALL AND SERVICE CONSUMER ELECTRONIC PRODUCTS AND SYSTEMS. IT INCLUDES COMPETENCIES IN INSTALLING, MAINTENANCE AND REPAIRING AUDIO-VIDEO PRODUCTS/ SYSTEMS AND DOMESTIC ELECTRONIC APPLIANCES AND HOME SECURITY SYSTEM.

NOMINAL DURATION

: 50 hours.

LEARNING OUTCOME NO. Upon completion of this module, the trainee/student must be able to: LO1. LO2. LO3. LO4. LO5.

Prepare unit, tools and workplace for installation and service Install consumer electronic products and systems Diagnose faults and defects of consumer electronic products and systems Maintain/Repair consumer electronic products Re-assemble and test repaired consumer electronic product

ASSESSMENT CRITERIA: 1. Complete check-up of consumer electronic products and systems is conducted and defects are identified, verified and documented against customer description. 2. Manuals and service information required for installation are acquired as per standard procedure. 3. Repair/maintenance history is verified in line with the company procedures. 4. Workplace is set/prepared for installation job in line with the client’s requirements. 5. Necessary tools, test instruments and personal protective equipment are prepared in line with job requirements

LO1

PREPARE UNIT, TOOLS AND WORKPLACE FOR INSTALLATION AND SERVICE

Contents:

 

Mensuration/Mathematics Drawing and Schematic Diagram Date Developed:

Electronic Products Assembly and Servicing NC II

December 2015

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                                    

Environmental Safety Hand and Power Tools Proper Care and Use of Tools Test and Measuring Instruments Care and use of Test and Measuring instrument Audio-Video Products and Systems Domestic Electronic Appliances Principles Of Electrical Circuits Fundamentals Of Direct Current Circuits Fundamentals Of Alternating Current Circuits Fundamentals Of Electronic Components And Circuits Fundamentals Of Digital Logics, Components & Circuits Fundamentals Of Microprocessor Circuits And Programming Analysis Of Troubles And Isolation Techniques Principles Of Sound And Acoustics Fundamentals Of Audio Amplifiers Fundamentals Of Audio Source & Noise Reduction System Fundamentals Of AM &FM Receivers Principles Of Vision And Color Fundamentals Of Color Television Fundamentals Of Video Sources & Noise Reduction System AM Transmission And Reception FM Transmission And Reception Analog TV Transmission And Reception Digital HDTV Transmission And Reception Audio Video Sources And Formats Pulse Code Modulation Home Theater System Digital Noise Reduction System CCTV System Infrared Remote Control System Motor And Motor Control System LED And Lighting System Heat And Heating Control System Solar Cell And Battery Management System Microcontroller Microcontroller Interfacing

Assessment Criteria

 

Complete check-up of industrial electronic components, products and systems is conducted and defects are identified, verified and documented against customer description. Repair/maintenance history is verified in line with the company procedures. Date Developed:

Electronic Products Assembly and Servicing NC II

December 2015

Document No. EPAS-01 Issued by: Page

Developed by: Nolito Carreras Joel N. Coralde

Revision # 1

  

Service manuals and service information required for repair/maintenance are acquired as per standard procedure. Workplace is set/prepared for repair job in line with the company requirements. Necessary tools, test instruments and personal protective equipment are prepared in line with job requirements

Conditions Students/trainees must be provided with the following:  Learning elements and manuals  Working area/bench  PPE  Tools, equipment and test instruments  Needed audio-video products and systems  Needed consumer appliances  Service manuals/schematics  ESD free working area/bench  Needed electronic spare parts/supplies Assessment Method: 1. 2. 3. 4.

Written Test Practical Demonstration w/ oral questioning Interview Portfolio

Date Developed:

Electronic Products Assembly and Servicing NC II

December 2015

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Learning Experiences Learning Outcome 1 : PREPARE UNIT, TOOLS AND WORKPLACE FOR INSTALLATION AND SERVICE Learning Activities Fundamentals of Electronic and Electricity § How to Diagnose, Troubleshoot, Repair AM and FM Radio Television and Domestic Appliances Maintaining Training Facilities, Disposal of toxic waste. How to use and Read components, More techniques in Repairing Audio/video products and Domestic Appliances.

Special Instructions Individual performance terminate and connection and repair Audio Video Products and systems. Diagnose fault and errors from Basic to advance electronics and digitals

Date Developed:

Electronic Products Assembly and Servicing NC II

December 2015

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Information Sheet 1.1-1 Mensuration Math

Measurement and Calculation All of these variations of the so called "Ohm's Law" are mathematically equal to one another. Name Formula sign Unit V or E voltage volt I current ampere (amp) R resistance ohm P power watt

Symbol V A Ω W

What is the formula for electrical current? When the current is constant: I=ΔQ/Δt I is the current in amps (A) Δ Q is the electric charge in coulombs (C), that flows at time duration of Δ t in seconds (s). Voltage V =

current I ×

resistance R

Power P = voltage V × current I In electrical conductors, in which the current and voltage are proportional to each other, ohm's law applies: V ~ I or V ⁄ I = const. Constantan wires or other metal wires held at a constant temperature meet well ohm's law. "V ⁄ I = R = const." ist not the law of ohm. It is the definition of the resistance. Thereafter, in every point, even with a bent curve, the resistance value can be calculated. For many electrical components such as diodes ohm's law does not apply.

"Ohm's Law" has not been invented by Mr. Ohm "U ⁄ I = R = const." is not the law of Ohm or Ohm's law. It is the definition of the resistance. Thereafter, in every point - even with a bent curve - the resistance value can be calculated. Date Developed:

Electronic Products Assembly and Servicing NC II

December 2015

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Ohm's law "postulates" following relationship: When a voltage is applied to an object, the electric current flowing through it changes the strength proportional to the voltage. In other words, the electrical resistance, defined as the quotient of voltage and current is constant, and that is independent of voltage and current. The name of the law "honors" Georg Simon Ohm, who could prove this relationship for some simple electrical conductors as one of the first searchers. "Ohm's Law" has really not been invented by Ohm.

Tip:

Ohm's

magic

triangle

The magic V I R triangle can be used to calculate all formulations of ohm's law. Use a finger to hide the value to be calculated. The other two values then show how to do the calculation.

The symbol I or J = Latin: influare, international ampere, and R = resistance. V = voltage or electric potential difference, also called voltage drop, or E = electromotive force (emf = voltage). Voltage drop calculations DC / single phase calculation The voltage drop V in volts (V) is equal to the wire current I in amps (A) times twice the wire length L in feet (ft) times the wire resistance per 1000 feet R in ohms (Ω / kft) divided by 1000: Vdrop (V) = Iwire (A) × Rwire (Ω) = Iwire (A) × (2 × L (ft) × Rwire (Ω / kft) / 1000 (ft / kft)) The voltage drop V in volts (V) is equal to the wire current I in amps (A) times twice the wire length L in meters (m) times the wire resistance per 1000 meters R in ohms (Ω / km) divided by 1000: Vdrop (V) = Iwire (A) × Rwire (Ω) = Iwire (A) × (2 × L (m) × Rwire (Ω / km) / 1000 (m / km))

If the unit of power

P = I × V and of voltage V = I · R is needed,

look for "The Big Power Formulas": Calculations: power (watt), voltage, current, resistance

Date Developed:

Electronic Products Assembly and Servicing NC II

December 2015

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Some persons think that Georg Simon Ohm calculated the "specific resistance". Therefore they think that only the following can be the true ohm's law.

Quantity of resistance

R = resistance ρ = specific resistance l = double length of the cable A = cross section

Ω Ω×m m mm2

Electrical conductivity (conductance) σ (sigma) = 1/ρ Specific electrical resistance (resistivity) ρ (rho) = 1/σ Electrical conductor Silver Copper Gold Aluminium Constantan

Electrical conductivity Electrical conductance σ = 62 S·m/mm² σ = 58 S·m/mm² σ = 41 S·m/mm² σ = 36 S·m/mm² σ = 2.0 S·m/mm²

Electrical resistivity Specific resistance ρ = 0.0161 Ohm∙mm²/m ρ = 0.0172 Ohm∙mm²/m ρ = 0.0244 Ohm∙mm²/m ρ = 0.0277 Ohm∙mm²/m ρ = 0.5000 Ohm∙mm²/m

Difference between electrical resistivity and electrical conductivity The conductance in siemens is the reciprocal of the resistance in ohms. Simply enter the value to the left or the right side. The calculator works in both directions of the ↔ sign. Electrical 58

conductivity σ

S · m / mm² σ=1/ρ

Specific elec. resistance ρ 0.017241

Ohm ∙ mm² / m ρ=1/σ

siemens S = 1/Ω or ohm Ω = 1/S

The value of the electrical conductivity (conductance) and the specific electrical resistance (resistivity) is a temperature dependent material constant. Mostly it is given at 20 or 25°C.

Resistance R = ρ × (l / A) or R = l / (σ × A) Date Developed:

Electronic Products Assembly and Servicing NC II

December 2015

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For all conductors the specific resistivity changes with the temperature. In a limited temperature range it is approximately linear: where α is the temperature coefficient, T is the temperature and T0 is any temperature, such as T0 = 293.15 K = 20°C at which the electrical resistivity ρ (T0) is known.

Cross-sectional area - cross section - slice plane Now there is the question: How can we calculate the cross sectional area (slice plane) A from the wire diameter d and vice versa? Calculation of the cross section A (slice plane) from diameter d: r = radius of the wire d = diameter of the wire Calculation diameter d from cross section A (slice plane):

Cross section A of the wire in mm2 inserted in this formula gives the diameter d in mm.

Calculation − Round cables and wires: • Diameter to cross section and vice versa • Electric voltage V = I × R

(Ohm's law VIR)

Electrical voltage = amperage × resistance (Ohm's law) Please enter two values, the third value will be calculated.

Electric power P = I × V

(Power law PIV)

Electric power = amperage × voltage (Watt's Law) Please enter two values, the third value will be calculated.

Date Developed:

Electronic Products Assembly and Servicing NC II

December 2015

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Electric Power P

watts

Amperage I

amps

Voltage V

volts

reset

P=I×V

I=P/V

V=P/I

Ohm's law. V = I × R, where V is the potential across a circuit element, I is the current through it, and R is its resistance. This is not a generally applicable definition of resistance. It is only applicable to ohmic resistors, those whose resistance R is constant over the range of interest and V obeys a strictly linear relation to I. Materials are said to be ohmic when V depends linearly on R. Metals are ohmic so long as one holds their temperature constant. But changing the temperature of a metal changes R slightly. When the current changes rapidly, as when turning on a light, or when using AC sources, slightly non-linear and non-ohmic behavior can be observed. For non-ohmic resistors, R is current-dependent and the definition R = dV/dI is far more useful. This is sometimes called the dynamic resistance. Solid state devices such as thermistors are non-ohmic and non-linear. A thermistor's resistance decreases as it warms up, so its dynamic resistance is negative. Tunnel diodes and some electrochemical processes have a complicated I to V curve with a negative resistance region of operation. The dependence of resistance on current is partly due to the change in the device's temperature with increasing current, but other subtle processes also contribute to change in resistance in solid state devices.

Calculation: Parallel Resistance (Resistor) Calculator Color Code Calculator for Resistors Electric Current, Electric Power, Electricity and Electric Charge

How electricity works. Ohm's Law clearly explained. The Formula Wheel - Formulas of Electrical EngineeringOhm's law as acoustic equivalent

Date Developed:

Electronic Products Assembly and Servicing NC II

December 2015

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SELF-TEST Question 1. Find the resistance in the circuit. a. Given E=220V R=50Ω I=145A I=12A Required R=? E=?

b. Given E=45V

C. Given

R=34Ω required I=?

required

2. Calculate the total resistance. a. Given R1=51.25Ω R2=75.8Ω R3=70.040Ω R4=18.25Ω Required RT=? ET=? PT=? IT=? 3. Find the following value for the circuit. Given R1=10Ω R2=30Ω R3=50Ω Required a. ER1=________________________ b. ER2=________________________ c. ER3=________________________ d. IR= ________________________ e. RT= ________________________

Date Developed:

Electronic Products Assembly and Servicing NC II

December 2015

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Decimal, Hexadecimal, Octal, Binary

De He Oct c x

0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15

0 1 2 3 4 5 6 7 8 9 A B C D E F

Bin

00 0000000 0 0 00 0000000 1 1 00 0000001 2 0 00 0000001 3 1 00 0000010 4 0 00 0000010 5 1 00 0000011 6 0 00 0000011 7 1 01 0000100 0 0 01 0000100 1 1 01 0000101 2 0 01 0000101 3 1 01 0000110 4 0 01 0000110 5 1 01 0000111 6 0 01 0000111 7 1

De He Oct

Bin

De He Oct c x

Bin

De He Oct c x

Bin

De He Oct c x

Bin

02 0001000 0 0 02 0001000 1 1 02 0001001 2 0 02 0001001 3 1 16 10 02 0001010 17 11 4 0 18 12 02 0001010 19 13 5 1 20 14 02 0001011 21 15 6 0 22 16 02 0001011 23 17 7 1 24 18 03 0001100 25 19 0 0 26 1A 03 0001100 27 1B 1 1 28 1C 03 0001101 29 1D 2 0 30 1E 03 0001101 31 1F 3 1 03 0001110 4 0 03 0001110 5 1 03 0001111 6 0 03 0001111 7 1

04 0010000 0 0 04 0010000 1 1 04 0010001 2 0 04 0010001 3 1 32 20 04 0010010 33 21 4 0 34 22 04 0010010 35 23 5 1 36 24 04 0010011 37 25 6 0 38 26 04 0010011 39 27 7 1 40 28 05 0010100 41 29 0 0 42 2A 05 0010100 43 2B 1 1 44 2C 05 0010101 45 2D 2 0 46 2E 05 0010101 47 2F 3 1 05 0010110 4 0 05 0010110 5 1 05 0010111 6 0 05 0010111 7 1

06 0011000 0 0 06 0011000 1 1 06 0011001 2 0 06 0011001 3 1 48 30 06 0011010 49 31 4 0 50 32 06 0011010 51 33 5 1 52 34 06 0011011 53 35 6 0 54 36 06 0011011 55 37 7 1 56 38 07 0011100 57 39 0 0 58 3A 07 0011100 59 3B 1 1 60 3C 07 0011101 61 3D 2 0 62 3E 07 0011101 63 3F 3 1 07 0011110 4 0 07 0011110 5 1 07 0011111 6 0 07 0011111 7 1

De He Oct

Dec He Oct

Dec He Oct

Bin

Date Developed:

Electronic Products Assembly and Servicing NC II

December 2015

Bin

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Revision # 1

Bin

c

x

c

10 0100000 0 0 10 0100000 1 1 10 0100001 2 0 10 0100001 3 1 64 40 10 0100010 65 41 4 0 66 42 10 0100010 67 43 5 1 68 44 10 0100011 69 45 6 0 70 46 10 0100011 71 47 7 1 72 48 11 0100100 73 49 0 0 74 4A 11 0100100 75 4B 1 1 76 4C 11 0100101 77 4D 2 0 78 4E 11 0100101 79 4F 3 1 11 0100110 4 0 11 0100110 5 1 11 0100111 6 0 11 0100111 7 1

Dec

He Oct x

Bin

x

x

12 0101000 0 0 12 0101000 1 1 12 0101001 2 0 12 0101001 3 1 80 50 12 0101010 81 51 4 0 82 52 12 0101010 83 53 5 1 84 54 12 0101011 85 55 6 0 86 56 12 0101011 87 57 7 1 88 58 13 0101100 89 59 0 0 90 5A 13 0101100 91 5B 1 1 92 5C 13 0101101 93 5D 2 0 94 5E 13 0101101 95 5F 3 1 13 0101110 4 0 13 0101110 5 1 13 0101111 6 0 13 0101111 7 1

Dec

He Oct x

Bin

14 0 96 14 97 1 98 14 99 2 10 14 0 3 60 10 14 61 1 4 62 10 14 63 2 5 64 10 14 65 3 6 66 10 14 67 4 7 68 10 15 69 5 0 6A 10 15 6B 6 1 6C 10 15 6 7 2 D 10 15 6E 8 3 6F 10 15 9 4 11 15 0 5 11 15 1 6 15 7

Dec

He Oct x

x

011000 00 011000 01 011000 10 011000 11 011001 00 011001 01 011001 10 011001 11 011010 00 011010 01 011010 10 011010 11 011011 00 011011 01 011011 10 011011 11

Bin

11 16 2 0 11 16 3 1 11 16 4 2 11 16 5 3 70 11 16 71 6 4 72 11 16 73 7 5 74 11 16 75 8 6 76 11 16 77 9 7 78 12 17 79 0 0 7A 12 17 7B 1 1 7C 12 17 7 2 2 D 12 17 7E 3 3 7F 12 17 4 4 12 17 5 5 12 17 6 6 12 17 7 7

Dec

011100 00 011100 01 011100 10 011100 11 011101 00 011101 01 011101 10 011101 11 011110 00 011110 01 011110 10 011110 11 011111 00 011111 01 011111 10 011111 11

He Oct x

Bin

12 80 20 100000 14 90 22 100100 16 A0 24 101000 17 B0 26 101100 8 81 0 00 4 91 0 00 0 A1 0 00 6 B1 0 00 12 82 20 100000 14 92 22 100100 16 A2 24 101000 17 B2 26 101100 9 83 1 01 5 93 1 01 1 A3 1 01 7 B3 1 01 13 84 20 100000 14 94 22 100100 16 A4 24 101000 17 B4 26 101100 0 85 2 10 6 95 2 10 2 A5 2 10 8 B5 2 10 Date Developed:

Electronic Products Assembly and Servicing NC II

December 2015

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13 86 20 1 87 3 13 88 20 2 89 4 13 8A 20 3 8B 5 13 8C 20 4 8 6 13 D 20 5 8E 7 13 8F 21 6 0 13 21 7 1 13 21 8 2 13 21 9 3 14 21 0 4 14 21 1 5 14 21 2 6 14 21 3 7

Dec

He Oct x

19 C0 30 2 C1 0 19 C2 30 3 C3 1 19 C4 30 4 C5 2 19 C6 30 5 C7 3 19 C8 30 6 C9 4 19 C 30 7 A 5 19 C 30 8 B 6

100000 11 100001 00 100001 01 100001 10 100001 11 100010 00 100010 01 100010 10 100010 11 100011 00 100011 01 100011 10 100011 11

14 96 22 7 97 3 14 98 22 8 99 4 14 9A 22 9 9B 5 15 9C 22 0 9 6 15 D 22 1 9E 7 15 9F 23 2 0 15 23 3 1 15 23 4 2 15 23 5 3 15 23 6 4 15 23 7 5 15 23 8 6 15 23 9 7

Bin

Dec

110000 00 110000 01 110000 10 110000 11 110001 00 110001 01 110001 10

20 8 20 9 21 0 21 1 21 2 21 3 21 4

100100 11 100101 00 100101 01 100101 10 100101 11 100110 00 100110 01 100110 10 100110 11 100111 00 100111 01 100111 10 100111 11

He Oct x

D 0 D 1 D 2 D 3 D 4 D 5 D 6

32 0 32 1 32 2 32 3 32 4 32 5 32 6

Bin

110100 00 110100 01 110100 10 110100 11 110101 00 110101 01 110101 10

16 A6 24 3 A7 3 16 A8 24 4 A9 4 16 AA 24 5 A 5 16 B 24 6 A 6 16 C 24 7 A 7 16 D 25 8 A 0 16 E 25 9 AF 1 17 25 0 2 17 25 1 3 17 25 2 4 17 25 3 5 17 25 4 6 17 25 5 7

Dec

22 4 22 5 22 6 22 7 22 8 22 9 23 0

He Oct x

E0 34 E1 0 E2 34 E3 1 E4 34 E5 2 E6 34 E7 3 E8 34 E9 4 E 34 A 5 E 34 B 6

Date Developed:

Electronic Products Assembly and Servicing NC II

December 2015

101000 11 101001 00 101001 01 101001 10 101001 11 101010 00 101010 01 101010 10 101010 11 101011 00 101011 01 101011 10 101011 11

Bin

111000 00 111000 01 111000 10 111000 11 111001 00 111001 01 111001 10

17 B6 26 9 B7 3 18 B8 26 0 B9 4 18 B 26 1 A 5 18 B 26 2 B 6 18 B 26 3 C 7 18 B 27 4 D 0 18 B 27 5 E 1 18 BF 27 6 2 18 27 7 3 18 27 8 4 18 27 9 5 19 27 0 6 19 27 1 7

Dec

He Oct x

24 F0 36 0 F1 0 24 F2 36 1 F3 1 24 F4 36 2 F5 2 24 F6 36 3 F7 3 24 F8 36 4 F9 4 24 FA 36 5 FB 5 24 FC 36 6 F 6

Bin

111100 00 111100 01 111100 10 111100 11 111101 00 111101 01 111101 10

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101100 11 101101 00 101101 01 101101 10 101101 11 101110 00 101110 01 101110 10 101110 11 101111 00 101111 01 101111 10 101111 11

Revision # 1

19 C 30 9 C 7 20 C 31 0 D 0 20 C 31 1 E 1 20 CF 31 2 2 20 31 3 3 20 31 4 4 20 31 5 5 20 31 6 6 20 31 7 7

110001 11 110010 00 110010 01 110010 10 110010 11 110011 00 110011 01 110011 10 110011 11

21 5 21 6 21 7 21 8 21 9 22 0 22 1 22 2 22 3

D 7 D 8 D 9 D A D B D C D D D E D F

32 7 33 0 33 1 33 2 33 3 33 4 33 5 33 6 33 7

110101 11 110110 00 110110 01 110110 10 110110 11 110111 00 110111 01 110111 10 110111 11

23 1 23 2 23 3 23 4 23 5 23 6 23 7 23 8 23 9

E 34 C 7 E 35 D 0 E 35 E 1 EF 35 2 35 3 35 4 35 5 35 6 35 7

Date Developed:

Electronic Products Assembly and Servicing NC II

December 2015

111001 11 111010 00 111010 01 111010 10 111010 11 111011 00 111011 01 111011 10 111011 11

24 D 36 7 FE 7 24 FF 37 8 0 24 37 9 1 25 37 0 2 25 37 1 3 25 37 2 4 25 37 3 5 25 37 4 6 25 37 5 7

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111101 11 111110 00 111110 01 111110 10 111110 11 111111 00 111111 01 111111 10 111111 11

Revision # 1

SELF-TEST Question 1. Convert the following binary to decimal a. 10101012 b. 10111112 2. Convert the following decimal to octal a. 16710 b. 34510 3. Covent the hexa decimal to the decimal number. a. AD316 b.6Fb16 4. Convert the octal number to the decimal number a. 2578 b.2318 5. Calculate the addition and multiplication. a. 10101 + 100112

b.11001 X 10011

Date Developed:

Electronic Products Assembly and Servicing NC II

December 2015

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TASK INSTRUCTION SHEET Title: RESISTANCE MEASUREMENT Performance Objectives: 1. To know the deference ranges of VOM used as an ohmmeter. 2. To distinguish the scale plate of VOM and interpret accurately the scale reading in the relation to the range used. Materials Needed: 1 unit –VOM or equivalent Resistors: ten assorted values ½ watts Miscellaneous: two connecting wires with alligator clips.

Steps/Procedure 1. Determine the coded value of each resistor supplied its color codes fill in the information required in the table. 2. Measure each resistor with the ohmmeter, and fill in the results in the column measured value. 3. The color coded value and the measured value should agree within the tolerance range of the resistor. Indicate the difference between the measured and coded values. 4. Likewise. Fill up and complete the blank columns in the table with the date or information. Assessment Method 1. Write your correct measured value and color coded value in your job instruction sheet then we will check the correct measured one by one. 2. We will collect the papers on the right answer after measured value of the training students. 3. Manual reading of resistance and color coded.

Date Developed:

Electronic Products Assembly and Servicing NC II

December 2015

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TASK SHEET AND INSTRUCTION Title: PRACTICAL VOTAGE OHM’S METER READING Performance Objectives: 1. To know the deference ranges of voltage reading used as DC. Voltmeter, AC. Voltmeter reading and DC. Millimeter. 2. To distinguish the scale plate of VOM and interpret accurately the scale reading in relation to range used. Materials Needed: 1 unit –VOM or equivalent 1pc- operating manual Steps/Procedure 1. Show where 7 ohms would be at Rx1 on the draw ohmmeter scale determine the actual reading by using the four ranges of ohmmeter function of VOM record the reading in the appropriate columns provided. 2. Indicate where 4.2 volts would be at 10- range on the draw AC voltmeter SCALE. Determine the actual reading in the appropriate columns provided. 3. Show the location of 6.8 volts at 10-volt range on the drawn DC voltmeter function of VOM. Record the reading in the appropriate column provided. 4. Indicate the location of 17.5ma range on the drawn DC current meter SCALE determine the actual reading by using the four ranges on the DC current meter function of VOM record the reading in the appropriate columns provided.

Assessment Method

Date Developed:

Electronic Products Assembly and Servicing NC II

December 2015

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1. Write your correct measured value in your job instruction sheet then we will check the correct measured one by one. 2. We will collect the papers on the right answer after measured value of the training students. 3. Practical testing and direct observation.

A schematic, or schematic diagram, is a representation of the elements of a system using abstract, graphic symbols rather than realistic pictures. A schematic usually omits all details that are not relevant to the information the schematic is intended to convey, and may add unrealistic elements that aid comprehension. For example, a subway map intended for passengers may represent a subway station with a dot; the dot doesn't resemble the actual station at all but gives the viewer information without unnecessary visual clutter. A schematic diagram of a chemical process uses symbols to represent the vessels, piping, valves, pumps, and other equipment of the system, emphasizing their interconnection paths and suppressing physical details. In an electronic circuit diagram, the layout of the symbols may not resemble the layout in the circuit. In the schematic diagram, the symbolic elements are arranged to be more easily interpreted by the viewer. How to Draw Schematic Diagrams

A well-drawn schematic makes it easy to understand how a circuit works and aids in troubleshooting; a poor schematic only creates confusion. By keeping a few rules and suggestions in mind, you can draw a good schematic in no more time than it takes to draw a poor one. In this appendix we dispense advice of three varieties: general principles, rules, and hints. We have also drawn some real kneeslappers to illustrate habits to avoid.

General Principles 1. Schematics should be unambiguous. Therefore, pin numbers, parts values, polarities, etc., should be clearly labeled to avoid confusion. 2. A good schematic makes circuit functions clear. Therefore, keep functional areas distinct; don't be afraid to leave blank areas on the page, and don't try to fill the page. There are conventional ways to draw functional subunits; for instance, don't draw a differential amplifier as in Figure E1, because the function won't be easily recognized. Likewise, flip-flops are usually drawn Date Developed:

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with clock and inputs on the left, set and clear on top and bottom, and outputs on the right. 1. Wires connecting are indicated by a heavy black dot; wires crossing, but not connecting, have no dot (don't use a little half-circular ``jog''; it went out in the 1950s). 2. Four wires must not connect at a point; i.e., wires must not cross and connect. 3. Always use the same symbol for the same device; e.g., don't draw flip-flops in two different ways (exception: assertion-level logic symbols show each gate in two possible ways). 4. Wires and components are aligned horizontally or vertically, unless there's a good reason to do otherwise. 5. Label pin numbers on the outside of a symbol, signal names on the inside. 6. All parts should have values or types indicated; it's best to give all parts a label, too, e.g., R7 or IC3.

Hints 1. Identify parts immediately adjacent to the symbol, forming a distinct group giving symbol, label, and type or value. 2. In general, signals go from left to right; don't be dogmatic about this, though, if clarity is sacrificed. 3. Put positive supply voltages at the top of the page, negative at the bottom. Thus, npn transistors will usually have their emitter at the bottom, whereas pnp's will have their emitter topmost. 4. Don't attempt to bring all wires around to the supply rails, or to a common ground wire. Instead, use the ground symbol(s) and labels like +Vcc to indicate those voltages where needed. 5. It is helpful to label signals and functional blocks and show waveforms; in logic diagrams it is especially important to label signal lines, e.g., RESET' or CLK. 6. It is helpful to bring leads away from components a short distance before making connections or jogs. For example, draw transistors as in Figure E2.

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Figure E2: Component leads 7. Leave some space around circuit symbols; e.g., don't draw components or wires too close to an op-amp symbol. This keeps the drawing uncluttered and leaves room for labels, pin numbers, etc. 8. Label all boxes that aren't obvious: comparator versus op-amp, shift register versus counter, etc. Don't be afraid to invent a new symbol. 9. Use small rectangles, ovals, or circles to indicate card-edge connections, connector pins, etc. Be consistent. 10. The signal path through switches should be clear. Don't force the reader to follow wires all over the page to find out how a signal is switched. 11. Power-supply connections are normally assumed for op-amps and logic devices. However, show any unusual connections (e.g., an op-amp run from a single supply, where V- = ground) and the disposition of unused inputs. 12. It is very helpful to include a small table of IC numbers, types, and powersupply connections (pin numbers for Vcc and ground, for instance). 13. Include a title area near the bottom of the page, with name of circuit, name of instrument, by whom drawn, by whom designed or checked, date, and assembly number. Also include a revision area, with columns for revision number, date, and subject. 14. We recommend drawing schematics freehand on coarse graph paper (no reproducing blue, 4 to 8 lines per inch) or on plain paper on top of graph paper. This is fast, and it gives very pleasing results. Use dark pencil or ink; avoid ball-point pen. As an illustration, we've drawn a humble example (Figure E3) showing ``awful'' and ``good'' schematics of the same circuit; the former violates nearly every rule and is almost impossible to understand. See how many bad habits you can find

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illustrated. We've seen all of them in professionally drawn schematics! (Drawing the ``bad'' schematic was an occasion of great hilarity; we laughed ourselves silly.)

Figure E3 (A): An awful schematic

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TASK SHEET AND INSTRUCTION Title: PROJECT AND PCB LAYOUT Performance Objectives: 1. To identify the electronic components used in a regulated power supply. 2. To learn how to make an etching printed circuit board for the regulated power supply projects. 3. To assemble the power supply, and then measure its output voltage Materials Needed: TRANSISTOR: 2SD313 or 2SD526 DIODE: rectifier diode (DIJA) CAPACITORS: 100uf/16v 220uf/12v; 0.01uf/100v RESISTOR: 680 ohms ½ w; 5.6k ½ w Transformer input: 220, output 3v 4.5v 6v 7.5 9v and 12v (750ma) Miscellaneous: Power cord with plug hook up wires and solder. Etc.

Steps/Procedure 1. Your instructor will give you a simple project and schematic diagram study then draw the circuit diagrams in the PCB layout labels all parts. 2. Make an etching printed circuit board for mounting the electronic components 3. In the following assembly steps, the components will be installed on the components side of the board the leads passed through the corresponding holes, and the board turned to solder the components terminals to the printed side. Solder each component immediately after it has been installed on the board. Date Developed:

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Assessment Method 1. Check and verify every procedure during the testing process of training or students. 2. We will collect the papers on the right answer after measured value of the training or students. 3. Practical testing and direct observation and follow up questions. 4. Test and review exercises.

Environment, health and safety Health, Safety and Environment (HSE) is an umbrella term for the laws, rules, guidance and processes designed to help protect employees, the public and the environment from harm. In the workplace, the responsibilities for designing and implementing appropriate procedures is often assigned to a specific department, often called the "HSE" department which is responsible for environmental protection, occupational health and safety at work. HSE management has two general objectives: prevention of incidents or accidents that might result from abnormal operating conditions and reduction of adverse effects that result from normal operating conditions.[1] Regulatory requirements play an important role in the role and HSE managers must identify and understand relevant HSE regulations, the implications of which must be communicated to executive management so the company can implement suitable measures. Organizations based in the United States are subject to EHS regulations in the Code of Federal Regulations, particularly CFR 29, 40, and 49. Still, EHS management is not limited to legal compliance and companies should be encouraged to do more than is required by law, if appropriate.[2] From a health & safety standpoint, it involves creating organized efforts and procedures for identifying workplace hazards and reducing accidents and exposure to harmful situations and substances. It also includes training of personnel in accident prevention, accident response, emergency preparedness, and use of protective clothing and equipment.

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EMERGENCY RESPONSE SERVICES

Chemical Spill Response

Highway/Transportation Spills

Natural Disaster Response

Non-Hazardous/Hazardous Response

Oil Spill Response and Clean

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TASK SHEET AND INSTRUCTION 1. Every trainer you must be able to prepare and provide a simple cleaning material like used clothes and container waste every end of the session. 2. Prepare proper dispose like ferric chloride or etching solution. Material needed: 1. Container 2. Used clothes 3. And hand wash

Hand tool .

A hand tool is any tool that is not a power tool – that is, one powered by hand (manual labor) rather than by an engine.[1] Some examples of hand tools are garden forks, secateurs, rakes, hammers,spanners, pliers, screwdrivers and chisels. Hand tools are generally less dangerous than power tools. Introduction to Electronic Servicing

With countless new electronic products or equipment reaching the market, there is a large demand for electronic repair technicians and engineers. As a result, you Date Developed:

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may be interested in moving into the electronics repair field. The electronic servicing field is considered a prestigious job. If you are really good in your work, there is almost no competition and you can acquire skills that allow you to earn enough money. Servicing is an ideal combination of your intelligence, efficiency and easy mechanical work. By gaining more experiences the efficiency and skills automatically becomes instinctive.

Many electronic equipment servicing operations are simpler than you may think. You will be surprised to learn that most servicing problems have simple causes – worn cables, dirty connectors, a loose screw in the works, and so on. Almost any end-user can check for this kind of problem. However, there may be other problems caused by component failure. You may give up and say “I’m not an expert in electronics”. You may be surprised to learn that many “troubleshooting” jobs do not require much detailed knowledge of electronics. Even in a “professional” troubleshooting operation, the technician or engineer may not have a detailed knowledge of the circuitry. Electronic servicing is not mysterious or difficult; it only requires your patience and some basic knowledge in electronics.

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If you are thinking of becoming an electronics repair technician or engineer, you need proper qualifications. Get at least a certificate in basic electronics or its equivalent through electronic courses. You can go far beyond this by continuing up to a diploma level. As you progress, you will discover your weakness. It’s then up to you to find out more by attending professional courses or reading up related books. Of course, the higher the level you desire, the better. Electronic equipment breaks down every second and we will need good technicians and engineers to ensure a good repairing job is done. So, if you are thinking of joining us – go for it!!!

Hand Tools for Electronics If you're in need of hand tools for electronics — e.g. pliers, cutters, crimpers, strippers, wire wrapping tools, etc. — Circuit Specialists has what you're looking for at the lowest possible prices. We carry screwdrivers, static-safe tweezers, and combination and extraction tools for your electronics projects. Our magnifying table lamps make working with small components a breeze and our grounding wrist straps will keep you free of static so you can work on your devices with peace of mind.

WIRE WRAPPING TOOLS

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Pliers & Cutters for Electronics

Crimping Tools

Miscellaneous Tools

Extraction Tools

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Combination Tools

Cutter & Stripper Tools

Screwdrivers

Static Safe Metallic & Non-Metallic Tweezers

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Allen Wrench set

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Electronic Parts & General Supplies Circuit Specialists carries a truly staggering selection of electronic parts and general supplies for your electronics projects. If you belong to an educational institution you'll want to take a look at our educational electronic lab kitting service; simply submit a component list and we'll deliver your neatly pre-packaged parts and supplies for easy distribution to your students. In addition, Circuit Specialists has electronic kits and development projects that allow you to gain hands-on experience while building basic circuits.

Cable Ties, Wire & Wiring Accessories

Electronic Enclosures

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Educational Lab Kitting Service

Electronic Kits & Development Projects

Educational Fiber Optics & Lasers

Heat Shrink Tubing

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EPROM Programmers & Erasers

Hand Tools for Electronics

Tool Bags & Cases

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Ultrasonic Cleaners

Sockets

Heat Sinks

Switches

Relays

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LED Lighting Products

Potentiometers, Knobs & Trimmers

Power Transformers with Wire Leads

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Semiconductor Devices

Safety Products

Crystals & Oscillators

Batteries & Accessories

Speakers, Buzzers & Microphones

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TASK SHEET AND INSTRUCTION Title: SOLDERING TECHNIQUES Performance Objectives: 1. To tin a soldering gun or soldering iron. 2. To prepare hook up wire and cable for connections. 3. To learn soldering techniques different style (Circle point, Cross point, Side point) Materials Needed: HAND TOOLS: Diagonal cutter, Long nose, soldering iron 30 watt wire stripper and etc. Miscellaneous: Hook -up wire two meter, shielded cable, alligator clip soldering leads.

Steps/Procedure 1. Strip off the installation from the ends of short pieces of hook up wires AWG#22 (stranded) 2. Both ends of stripped wires are examined. Clean the ends of hook up wires, if necessary. 3. Solder the inner conductor and shielded wire neatly, cross points, or side points circle points terminals. 4. Test and verify the connection from end to end of hook up wire is connected. Assessment Method 1. Check and verify every procedure during the testing process of training or students. 2. Practical testing and direct observation. 3. Test and review exercises. Date Developed:

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Not Only Electronic Circuit Can Go Haywire, Our Body And Brain Also Could! Don't believe? Try this Test For Yourself!

You will keep trying it to see if you can outsmart your foot - but you can’t ! 1. While sitting at your electronic repair bench lifts your right foot off the floor and make clockwise circles with it. 2. Now, while doing this, draw the number 6 in the air with your right hand. Your foot will change direction! I told you so! And there is nothing you can do about it! Welcome to the world of body circuit!

Clean, Inspect and Care for Tools

Make it a habit to clean tools after each use before you return them to storage. Wipe them down with a rag or old towel and be sure they are free of dust, grease and debris before you put them into their proper places. This is also an opportunity to look for any damage or defects. Check your tools' handles for splinters, breaks and cracks. Also, make sure that metal parts show no signs of corrosion or rust. Repair or replace any tools that show signs of damage. Cold chisels, log-splitting wedges and other striking tools can be very dangerous if they are not maintained properly. Because these types of tools are used for repeated striking, the surface of the metal head eventually mushrooms out and spreads to form a lip or ridge around the edge. With continued use, there is more spreading and the Date Developed:

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metal lip may continue to thin, split or curl until it finally breaks. If the metal head separates from the handle while in use, this could result in a dangerous projectile. To prevent this hazard, just grind off the metal edges with a powered grinder on a regular basis.

Objectives Upon completion of this chapter, you will be able to answer the following questions:     

What are safe working conditions and procedures? What procedures help protect equipment and data? What procedures help to properly dispose of hazardous computer components and related material? What tools and software are used with personal computer components and what is their purpose? What is proper tool use?

ESD and EMI Electrostatic discharge (ESD), harsh climates, and poor-quality sources of electricity can cause damage to computer equipment. Follow proper handling guidelines, be aware of environmental issues, and use equipment that stabilizes power to prevent equipment damage and data loss. Static electricity is the buildup of an electric charge resting on a surface. Electrostatic discharge (ESD) occurs when this buildup jumps to a component and causes damage. ESD can be destructive to the electronics in a computer system. At least 3000 volts of static electricity must build up before a person can feel ESD. For example, static electricity can build up on you as you walk across a carpeted floor. When you touch another person, you both receive a shock. If the discharge causes pain or makes a noise, the charge was probably above 10,000 volts. By comparison, less than 30 volts of static electricity can damage a computer component. ESD can cause permanent damage to recommendations to help prevent ESD damage:   

electrical

components.

Follow

Keep all components in antistatic bags until you are ready to install them. Use grounded mats on workbenches. Use grounded floor mats in work areas. Date Developed:

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these

Use antistatic wrist straps when working on computers.

Electromagnetic interference (EMI) is the intrusion of outside electromagnetic signals in a transmission media, such as copper cabling. In a network environment, EMI distorts the signals so that the receiving devices have difficulty interpreting them. EMI does not always come from expected sources, such as cellular phones. Other types of electric equipment can emit a silent, invisible electromagnetic field that can extend for more than a mile (1.6 km). There are many sources of EMI:   

Any source designed to generate electromagnetic energy Man-made sources like power lines or motors Natural events such as electrical storms, or solar and interstellar radiations

Wireless networks are affected by radio frequency interference (RFI). RFI is caused by radio transmitters and other devices transmitting in the same frequency. For example, a cordless telephone can cause problems with a wireless network when both devices use the same frequency. Microwaves can also cause interference when positioned in close proximity to wireless networking devices.

Climate Climate affects computer equipment in a variety of ways:   

If the environment temperature is too high, equipment can overheat. If the humidity level is too low, the chance of ESD increases. If the humidity level is too high, equipment can suffer from moisture damage.

Power Fluctuation Types Voltage is the force that moves electrons through a circuit. The movement of electrons is called current. Computer circuits need voltage and current to operate electronic components. When the voltage in a computer is not accurate or steady, computer components might not operate correctly. Unsteady voltages are called power fluctuations. The following types of AC power fluctuations can cause data loss or hardware failure:  

 

Blackout: Complete loss of AC power. A blown fuse, damaged transformer, or downed power line can cause a blackout. Brownout: Reduced voltage level of AC power that lasts for a period of time. Brownouts occur when the power line voltage drops below 80 percent of the normal voltage level. Overloading electrical circuits can cause a brownout. Noise: Interference from generators and lightning. Noise results in poor quality power, which can cause errors in a computer system. Spike: Sudden increase in voltage that lasts for a short period and exceeds 100 percent of the normal voltage on a line. Spikes can be caused by Date Developed:

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lightning strikes, but can also occur when the electrical system comes back on after a blackout. Power surge: Dramatic increase in voltage above the normal flow of electrical current. A power surge lasts for a few nanoseconds, or one-billionth of a second.

Power Protection Devices To help shield against power fluctuation problems, use power protection devices to protect the data and computer equipment: 

Surge suppressor: Helps protect against damage from surges and spikes. A surge suppressor diverts extra electrical voltage that is on the line to the ground. Uninterruptible power supply (UPS): Helps protect against potential electrical power problems by supplying a consistent level of electrical power to a computer or other device. The battery is constantly recharging while the UPS is in use. The UPS provides a consistent quality of power when brownouts and blackouts occur. Many UPS devices can communicate directly with the computer operating system. This communication allows the UPS to safely shut down the computer and save data prior to the UPS losing all electrical power. Standby power supply (SPS): Helps protect against potential electrical power problems by providing a backup battery to supply power when the incoming voltage drops below the normal level. The battery is on standby during normal operation. When the voltage decreases, the battery provides DC power to a power inverter, which converts it to AC power for the computer. This device is not as reliable as a UPS because of the time it takes to switch over to the battery. If the switching device fails, the battery cannot supply power to the computer.

CAUTION UPS manufacturers suggest never plugging in a laser printer to a UPS because the printer could overload the UPS.

Proper Use of Tools Using tools properly helps prevent accidents and damage to equipment and people. This section describes and covers the proper use of a variety of hardware, software, and organizational tools specific to working with computers and peripherals.

Hardware Tools For every job there is the right tool. Make sure that you are familiar with the correct use of each tool and that the correct tool is used for the current task. Skilled use of tools and software makes the job less difficult and ensures that tasks are performed properly and safely. Date Developed:

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A toolkit should contain all the tools necessary to complete hardware repairs. As you gain experience, you learn which tools to have available for different types of jobs. Hardware tools are grouped into four categories:    

ESD tools Hand tools Cleaning tools Diagnostic tools

ESD Tools There are two ESD tools: the antistatic wrist strap and the antistatic mat. The antistatic wrist strap protects computer equipment when grounded to a computer chassis. The antistatic mat protects computer equipment by preventing static electricity from accumulating on the hardware or on the technician.

Hand Tools Most tools used in the computer assembly process are small hand tools. They are available individually or as part of a computer repair toolkit. Toolkits range widely in size, quality, and price. Some common hand tools and their uses are:            

Flat-head screwdriver: Used to tighten or loosen slotted screws. Phillips-head screwdriver: Used to tighten or loosen cross-headed screws. Torx screwdriver: Used to tighten or loosen screws that have a star-like depression on the top, a feature that is mainly found on laptops. Hex driver: Used to tighten or loosen nuts in the same way that a screwdriver tightens or loosens screws (sometimes called a nut driver). Needle-nose pliers: Used to hold small parts. Wire cutters: Used to strip and cut wires. Tweezers: Used to manipulate small parts. Part retriever: Used to retrieve parts from locations that are too small for your hand to fit. Flashlight: Used to light up areas that you cannot see well. Wire stripper: A wire stripper is used to remove the insulation from wire so that it can be twisted to other wires or crimped to connectors to make a cable. Crimper: Used to attach connectors to wires. Punch-down tool: Used to terminate wire into termination blocks. Some cable connectors must be connected to cables using a punch down tool.

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Cleaning Tools Having the appropriate cleaning tools is essential when maintaining and repairing computers. Using the appropriate cleaning tools helps ensure that computer components are not damaged during cleaning. Cleaning tools include the following:    

Soft cloth: Used to clean different computer components without scratching or leaving debris Compressed air: Used to blow away dust and debris from different computer parts without touching the components Cable ties: Used to bundle cables neatly inside and outside of a computer Parts organizer: Used to hold screws, jumpers, fasteners, and other small parts and prevents them from getting mixed together

Diagnostic Tools Diagnostic tools are used to test and diagnose equipment. Diagnostic tools include the following: 

A digital multi-meter, as shown in Figure 2-3, is a device that can take many types of measurements. It tests the integrity of circuits and the quality of electricity in computer components. A digital multi-meter displays the information on an LCD or LED. Figure 2-3.Multimeter

 

A loopback adapter, also called a loopback plug, tests the basic functionality of computer ports. The adapter is specific to the port that you want to test. The toner probe, as shown in Figure 2-4, is a two-part tool. The toner part is connected to a cable at one end using specific adapters, such as an RJ-45, coaxial, or metal clips. The toner generates a tone that travels the length of the cable. The probe part traces the cable. When the probe is in near proximity to the cable to which the toner is attached, the tone can be heard through a speaker in the probe.

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Figure 2-4.Toner Probe Although an external hard drive enclosure is not a diagnostic tool, it is often used when diagnosing and repairing computers. The customer hard drive is placed into the external enclosure for inspection, diagnosis, and repair using a known-working computer. Backups can also be recorded to a drive in an external enclosure to prevent data corruption during a computer repair.

Protection Software Tools Each year, viruses, spyware, and other types of malicious attacks infect millions of computers. These attacks can damage operating systems, applications, and data. Computers that have been infected may even have problems with hardware performance or component failure. To protect data and the integrity of the operating system and hardware, use software designed to guard against attacks and to remove malicious programs.

Organizational Tools Keeping accurate records and journals during a busy workday can be challenging. Many organizational tools, such as work-order systems, can help the technician document their work.

Reference Tools A technician must document all repairs and computer problems. The documentation can then be used as a reference for future problems or for other technicians who may not have encountered the problem before. The documents can be paper based, but electronic forms are preferred because they can be easily searched for specific problems. It is important that a technician document all services and repairs. These documents need to be stored centrally and made available to all other technicians. The documentation can then Date Developed:

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be used as reference material for similar problems that are encountered in the future. Good customer service includes providing the customer with a detailed description of the problem and the solution.

Personal Reference Tools Personal reference tools include troubleshooting guides, manufacturer manuals, quick reference guides, and repair journals. In addition to an invoice, a technician keeps a journal of upgrades and repairs. The documentation in the journal includes descriptions of the problem, possible solutions that have been attempted, and the steps taken to repair the problem. Note any configuration changes made to the equipment and any replacement parts used in the repair. This documentation is valuable when you encounter similar situations in the future. 

Notes: Make notes as you go through the troubleshooting and repair process. Refer to these notes to avoid repeating previous steps and to determine what steps to take next. Journal: Document the upgrades and repairs that you perform. Include descriptions of the problem, possible solutions that have been tried to correct the problem, and the steps taken to repair the problem. Note any configuration changes made to the equipment and any replacement parts used in the repair. Your journal, along with your notes, can be valuable when you encounter similar situations in the future. History of repairs: Make a detailed list of problems and repairs, including the date, replacement parts, and customer information. The history allows a technician to determine what work has been performed on a specific computer in the past

Internet Reference Tools The Internet is an excellent source of information about specific hardware problems and possible solutions:      

Internet search engines News groups Manufacturer FAQs Online computer manuals Online forums and chat Technical websites

Miscellaneous Tools With experience, you will discover many additional items to add to the toolkit. Figure 25shows how a roll of masking tape can be used to label parts that have been removed from a computer when a parts organizer is not available.

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Figure 2-5.Parts Labels A working computer is also a valuable resource to take with you on computer repairs in the field. A working computer can be used to research information, download tools or drivers, and communicate with other technicians. Figure 2-6 shows the types of computer replacement parts to include in a toolkit. Make sure that the parts are in good working order before you use them. Using known good components to replace possible bad ones in computers helps you quickly determine which component is not working properly.

Demonstrate Proper Tool Use This section describes the proper use of common tools used to protect, repair, and clean electronic product assembly.

Antistatic Wrist Strap Safety in the workplace is everyone’s responsibility. You are much less likely to injure yourself or damage components when using the proper tool for the job. Before cleaning or repairing equipment, make sure that your tools are in good condition. Clean, repair, or replace items that are not functioning adequately. An example of ESD is the small shock that you receive when you walk across a carpeted room and touch a doorknob. Although the small shock is harmless to you, the same electrical charge passing from you to a computer can damage its components. Selfgrounding or wearing an antistatic wrist strap can prevent ESD damage to computer components. The purpose of self-grounding or wearing an antistatic wrist strap is to equalize the electrical charge between you and the equipment. Self-grounding is done by touching a bare metal part of a computer case. The antistatic wrist strap is a conductor that connects your body to the equipment that you are working on. When static electricity builds up in your body, the

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connection made by the wrist strap to the equipment, or ground, channels the electricity through the wire that connects the strap. As shown in Figure 2-7, the wrist strap has two parts and is easy to wear. Following is the proper procedure for using an antistatic wrist strap:

Step 1. Wrap the strap around your wrist and secure it using the snap or Velcro. The metal on the back of the wrist strap must remain in contact with your skin at all times.

Step 2. Snap the connector on the end of the wire to the wrist strap, and connect the other end either to the equipment or to the same grounding point that the antistatic mat is connected to. The metal skeleton of the case is a good place to connect the wire. When connecting the wire to equipment that you are working on, choose an unpainted metal surface. A painted surface does not conduct electricity as well as unpainted metal. Figure 2-7.Antistatic Wrist Strap

NOTE Attach the wire on the same side of the equipment as the arm wearing the antistatic wrist strap. This helps keep the wire out of the way while you are working. Although wearing a wrist strap helps prevent ESD, you can further reduce the risks by not wearing clothing made of silk, polyester, or wool. These fabrics are more likely to generate a static charge.

NOTE Technicians should roll up their sleeves, remove scarves or ties, and tuck in shirts to prevent interference from clothing. Ensure that earrings, necklaces, and other loose jewelry are properly secured. CAUTION

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Never wear an antistatic wrist strap if you are repairing a CRT monitor or a power supply unit.

Antistatic Mat You might not always have the option to work on a computer in a properly equipped workspace. If you can control the environment, try to set up your workspace away from carpeted areas. Carpets can cause the buildup of electrostatic charges. If you cannot avoid the carpeting, ground yourself to the unpainted portion of the case of the computer on which you are working before touching any components. An antistatic mat is slightly conductive. It works by drawing static electricity away from a component and transferring it safely from equipment to a grounding point, . Following is the proper procedure for using an antistatic mat:

Step 1. Lay the mat on the workspace next to or under the computer case.

Step 2. Clip the mat to the case to provide a grounded surface on which you can place parts as you remove them from the system. Figure 2-8.Antistatic Mat When you are working at a workbench, ground the workbench and the antistatic floor mat. By standing on the mat and wearing the wrist strap, your body has the same charge as the equipment and reduces the probability of ESD. Either connect the table-top mat and the floor mat to each other, or connect both to the electrical earth ground. Reducing the potential for ESD reduces the likelihood of damage to delicate circuits or components. NOTE Always handle components by the edges.

Hand Tools (2.2.4.3) A technician needs to be able to properly use each tool in the toolkit. This topic covers many of the various hand tools used when repairing computers.

Screws Match each screw with the proper screwdriver. Place the tip of the screwdriver on the head of the screw. Turn the screwdriver clockwise to tighten the screw and counterclockwise to loosen the screw. Screws can become stripped if you over-tighten them with a screwdriver. A stripped screw, as shown in Figure 2-9, may get stuck in the screw hole, or it may not tighten firmly. Discard stripped screws. Date Developed:

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Figure 2-9.Stripped Screw

Flat-Head Screwdriver Use a flat-head screwdriver when you are working with a slotted screw. Do not use a flathead screwdriver to remove a Phillips-head screw. Never use a screwdriver as a pry bar. If you cannot remove a component, check to see if there is a clip or latch that is securing the component in place. CAUTION If excessive force is needed to remove or add a component, something is probably wrong. Take a second look to make sure that you have not missed a screw or a locking clip that is holding the component in place. Refer to the device manual or diagram for additional information.

TASK SHEET AND INSTRUCTION Title: DIODE USED AS LAMP CONTROL Performance Objectives: 1. To

construct a simple lamp control device. Date Developed:

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2. To be able to know how to measure AC. And DC. Voltages. 3. To verify experimentally the practical application of a diode. Materials Needed: 1 unit –VOM or equivalent meter DIODE: rectifier diode (IN5408) Bulb 12volts Transformer input: 220, output 3v 4.5v 6v 7.5 9v and 12v (750ma) Miscellaneous: Rotary switch 2 pole 6 position. Fuse 1A plug with cord.

Steps/Procedure 1. Connect the circuit 1 and 2 in accordance with the schematic diagram using the component assigned to you by the instructor. 2. Adjust the voltage selector (rotary) switch for the maximum output voltage. 3. Close the circuit (switch on) measures all voltages at every test point shown in the diagram record steps 1, 2, and 3 for the circuit no. 2. 4. State briefly the parts and function of each component. Assessment Method 1. Check and verify every procedure during the testing process of training or students. 2. We will collect the papers on the right answer after measured value of the training or students. 3. Practical testing and direct observation and follow up questions. 4. Test and review exercises.

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Types of test equipment Basic equipment

Agilent commercial digital voltmeter checking a prototype

The following items are used for basic measurement of voltages, currents, and components in the circuit under test. 

Voltmeter (Measures voltage)

Ohmmeter (Measures resistance)

Ammeter, e.g. Galvanometer or Milliameter (Measurescurrent)

Multimeter e.g., VOM (Volt-Ohm-Milliameter) or DMM (Digital Multimeter) (Measures all of the above)

RLC Meter e.g., RLC meter or Resistance,Inductance and capacitance meter (measure RLC values)

The following are used for stimulus of the circuit under test: 

Power supplies

Signal generator

Digital pattern generator

Pulse generator

Howard piA digital multimeter Date Developed:

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The following analyze the response of the circuit under test: 

Oscilloscope (Displays voltage as it changes over time)

Frequency counter (Measures frequency)

Test probes

Advanced or less commonly used equipment Meters 

Solenoid voltmeter (Wiggy)

Clamp meter (current transducer)

Wheatstone bridge (Precisely measures resistance)

Capacitance meter (Measures capacitance)

LCR meter (Measures inductance, capacitance, resistance and combinations thereof)

EMF Meter (Measures Electric and Magnetic Fields)

Electrometer (Measures charge) Probes[edit]

A multi-meter with a built in clamp facility. Pushing the large button at the bottom opens the lower jaw of the clamp, allowing the clamp to be placed around a conductor (wire). 

RF probe

Signal tracer Analyzers

Logic analyzer (Tests digital circuits)

Spectrum analyzer (SA) (Measures spectral energy of signals) Date Developed:

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Protocol analyzer (Tests functionality, performance and conformance of protocols)

Vector signal analyzer (VSA) (Like the SA but it can also perform many more useful digital demodulation functions)

Time-domain reflect meter (Tests integrity of long cables)

Semiconductor curve tracer Signal-generating devices

Leader Instruments LSG-15 signal generator. 

Signal generator

Frequency synthesiser

Function generator

Digital pattern generator

Pulse generator

Signal injector

Miscellaneous devices[edit] 

Boxcar averager

Continuity tester

Cable tester

Hipot tester

Network analyzer (used to characterize an electrical network of components)

Test light

Transistor tester

Tube tester

Platforms Keithley Instruments Series 4200 CVU Date Developed:

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Several modular electronic instrumentation platforms are currently in common use for configuring automated electronic test and measurement systems. These systems are widely employed for incoming inspection, quality assurance, and production testing of electronic devices and subassemblies. Industry-standard communication interfaces link signal sources with measurement instruments in “rack-and-stack” or chassis-/mainframe-based systems, often under the control of a custom software application running on an external PC. In electromagnetism and electronics, inductance is the property of an electrical conductor by which a change incurrent through it induces an electromotive force in both the conductor itself[1] and in any nearby conductors by mutual inductance.[1] These effects are derived from two fundamental observations of physics: a steady current creates a steady magnetic field described by Oersted's law,[2] and a timevarying magnetic field induces an electromotive force (EMF) in nearby conductors, which is described byFaraday's law of induction.[3] According to Lenz's law,[4] a changing electric current through a circuit that contains inductance induces a proportional voltage, which opposes the change in current (self-inductance). The varying field in this circuit may also induce an EMF in neighbouring circuits (mutual inductance). The term inductance was coined by Oliver Heaviside in 1886.[5] It is customary to use the symbol L for inductance, in honour of the physicist Heinrich Lenz.[6][7] In the SIsystem, the measurement unit for inductance is the henry, with the unit symbol H, named in honor of Joseph Henry, who discovered inductance independently of, but not before, Faraday.

Capacitance Capacitance is the ability of a body to store an electricalcharge. A material with a large capacitance holds moreelectric charge at a given voltage, than one with low capacitance. Any object that can be electrically charged exhibits capacitance, however the concept is particularly important for understanding the operations of thecapacitor, one of the three fundamental electronic components (along with resistors and inductors). The SI unit of capacitance is the farad (symbol: F), named after the English physicist Michael Faraday. A 1 farad capacitor, when charged with 1 coulomb of electrical charge, has a potential difference of 1 volt between its plates.[1]

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TASK SHEET AND INSTRUCTION Title: FUSE TESTING WITH VOM METER Performance Objectives: 1. To know how to use ohmmeter for checking the condition of fuse. 2. To learn how to use the voltmeter for testing and measuring the voltage across the fuse terminals. 3. To become familiar with the different types of the fuse, glass cartage and amperes. Materials Needed: 1 unit –VOM or equivalent meter, power supply Fuse: Glass cartage or equivalent (good, Open)

Steps/Procedure 1. Set the VOM at range RX1 set the meter pointer exactly at zero by shorting the test leads together and adjusting the zero ohm control. 2. Simply connect the test leads to the metal parts of the fuse write the result in figure A as per instruction. 3. Repeat procedure no. 2 for the other fuse. Fill up all needed information, and complete the illustration in figure A and B respectively. Assessment Method 1. Check and verify every procedure during the testing process of training or students. 2. We will collect the papers on the right answer after measured value of the training or students. 3. Practical testing and direct observation. 4. Test and review exercises.

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TASK SHEET AND INSTRUCTION Title: SWICTH TESTING WITH VOM Performance Objectives: 1. To know how to use ohmmeter for checking the condition of a switch. 2. To learn how to use the voltmeter for testing and measuring the voltage across the switch terminals. 3. To become familiar with the different types of switch, SPST, DPDT, TOGGLE, PUSH BUTTON, RELAY. Materials Needed: 1 unit –VOM or equivalent meter, power supply SWITCH: Assorted types (good or defective

Steps/Procedure 1. Set the VOM at range RX1 set the meter pointer exactly at zero by shorting the test leads together and adjusting the zero ohm control. 2. Simply connect the test leads to the metal parts of the fuse write the result in figure A as per instruction. 3. Repeat procedure no. 2 for the other fuse. Fill up all needed information, and complete the illustration in figure A and B respectively. Assessment Method 1. Check and verify every procedure during the testing process of training or students. 2. We will collect the papers on the right answer after measured value of the training or students. 3. Practical testing and direct observation. 4. Test and review exercises.

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Basic Electronics Semiconductor —I • Materials that permit flow of electrons are called Conductors (e.g., gold, silver, copper, etc.). • Materials that block flow of electrons are called Insulators (e.g., rubber, glass, Teflon, mica, etc.). • Materials whose conductivity falls between those of conductors and insulators are called Semiconductors. • Semiconductors are “part-time” conductors Whose conductivity can be controlled? Germanium Semiconductors silicon Semiconductor —II • Silicon is the most common material used to build semiconductor devices. • Si is the main ingredient of sand and it is estimated that a cubic mile of seawater contains 15,000 tons of Si. • Si is spun and grown into a crystalline structure and cut into wafers to make electronic devices. Semiconductor —III • Atoms in a pure silicon wafer contains four electrons in outer orbit (called valence electrons). – Germanium is another semiconductor material with four valence electrons. • In the crystalline lattice structure of Si, the valence electrons of every Si atom are locked up in covalent bonds with the valence electrons of four neighboring Si atoms. – In pure form, Si wafer does not contain any free charge carriers. – An applied voltage across pure Si wafer does not yield electron flow through the wafer. – A pure Si wafer is said to act as an insulator. • In order to make useful semiconductor devices, materials such as phosphorus (P) and boron (B) are added to Si to change Si’s conductivity. 4 valence electrons N-Type Silicon • Pentavalent impurities such as phosphorus, arsenic, antimony, and bismuth have 5 valence electrons. • When phosphorus impurity is added to Si, every phosphorus atom’s four valence electrons are locked up in covalent bond with valence electrons of four neighboring Si atoms. However, the 5th valence electron of phosphorus atom does not find a binding electron and thus remains free to float. When a voltage is applied across the silicon-phosphorus mixture, free electrons migrate toward the positive voltage end. • When phosphorus is added to Si to yield the above effect, we say that Si is doped with phosphorus. The resulting mixture is called N-type silicon (N: negative charge carrier silicon). • The pentavalent impurities are referred to as donor impurities. 5 valence electrons P-Type Silicon —I Date Developed:

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• Trivalent impurities e.g., boron, aluminum, indium, and gallium have 3 valence electrons. • When boron is added to Si, every boron atom’s three valence electrons are locked up in covalent bond with valence electrons of three neighboring Si atoms. However, a vacant spot “hole” is created within the covalent bond between one boron atom and a neighboring Si atom. The holes are considered to be positive charge carriers. When a voltage is applied across the silicon-boron mixture, a hole moves toward the negative voltage end while a neighboring electron fills in its place. • When boron is added to Si to yield the above effect, we say that Si is doped with boron. The resulting mixture is called P-type silicon (P: positive charge carrier silicon). • The trivalent impurities are referred to as acceptor impurities. 3 valence electrons P-Type Silicon —II • The hole of boron atom points towards the negative terminal. • The electron of neighboring silicon atom points toward positive terminal. • The electron from neighboring silicon atom falls into the boron atom filling the hole in boron atom and creating a “new” hole in the silicon atom. • It appears as though a hole moves toward the negative terminal! Diode •A diode is a 2 lead semiconductor that acts as a one way gate to electron flow. – Diode allows current to pass in only one direction. •A pn-junction diode is formed by joining together n-type and p-type silicon. •In practice, as the n-type Si crystal is being grown, the process is abruptly altered to grow p-type Si crystal. Finally, a glass or plastic coating is placed around the joined crystal. •The p-side is called anode and the n-side is called cathode. •When the anode and cathode of a pn-junction diode are connected to external voltage such that the potential at anode is higher than the potential at cathode, the diode is said to be forward biased. –In a forward-biased diode current is allowed to flow through the device. •When potential at anode is smaller than the potential at cathode, the diode is said to be reverse biased. In a reverse-biased diode current is blocked. +-+Water Analogy of Diodes • When water pressure on left overcomes the restoring force of spring, the gate is opened and water is allowed to flow . • When water pressure is from right to left, the gate is pressed against the solid stop and no water is allowed to flow. • Spring restoring force is analogous to 0.6V needed to forward bias a Si diode. Diode: How it Works —I • When a diode is connected to a battery as shown, electrons from the n-side and holes from Date Developed:

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the p-side are forced toward the center by the electrical field supplied • A full-wave rectifier does not block negative swings in the i/p voltage, rather it transforms them into positive swings at the o/p. • To gain an understanding of device operation, follow current flow through pairs of diodes in the bridge circuit. • It is easily seen that one pair (D3-Rout-D2) allows current flow during the +ve half cycle of Vin while the other pair (D4-Rout-D1) allows current flow during the -ve half cycle of Vin. – o/p voltage peak is 1.2V below the i/p voltage peak. – The o/p frequency is twice the i/p frequency. D1 D3 D2 D4 Diode Applications —AC2DC Power Supply •An AC2DC power supply is built using a transformer and a full-wave rectifier. •Transformer is used to step down the voltage i/p. •Rectifier converts AC to pulsed DC. •A filter capacitor is used to smooth out the pulses. •Capacitor must be large enough to store sufficient charge so as to provide a steady current supply to the load: f is rectified signal’s frequency (120Hz). 1/ Load R C f Transistor • A three lead semiconductor device that acts as: – an electrically controlled switch, or – a current amplifier. • Transistor is analogous to a faucet. – Turning faucet’s control knob alters the flow rate of water coming out from the faucet. – A small voltage/current applied at transistor’s control lead controls a larger current flow through its other two leads. Water in Water out Transistor Types: BJT, JFET, and MOSFET • Bipolar Junction Transistor (BJT) – NPN and PNP • Junction Field Effect Transistor (JFET) – N-channel and P-channel • Metal Oxide Semiconductor FET (MOSFET) Date Developed:

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– Depletion type (n- and p-channel) and enhancement type (n- and p-channel) BJT MOSFEJFET T BJT Types • NPN and PNP. – NPN: a small input current and a positive voltage applied @ its base (with VB>VE) allows a large current to flow from collector to emitter. – PNP: a small output current and a negative voltage @ its base (with VB0.6V) is applied to the base of an npn transistor, the pn junction between the base and emitter becomes forward-biased. During forward bias, escaping electrons are drawn to the positive base. • Some electrons exit through the base, but because the p-type base is so thin, the onslaught of electrons that leave the emitter get close enough to the collector side that they begin jumping into the collector. Increasing the base voltage increases the emitter-tocollector electron flow. • Recall, positive current flow is in the direction opposite to the electron flow current flows from collector to emitter. BJT Water Analogy NPN (VB > VE) PNP (VB < VE) Base Collector Emitter NPN Transistor in a Complete Circuit —I Date Developed:

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NPN: VB = VE OFF •Normally OFF. •No current passes from collector to emitter when base is not activated. NPN Transistor in a Complete Circuit —II NPN: VB > VE ON • When VB > VE we have an operating circuit. • Current passes from collector to emitter when base is activated. Transistor Experiment —LED On/Off • Turning the switch on/off turns the LED on/off. JFET • Junction field effect transistors like BJTs are three lead semiconductor devices. • JFETs are used as: – electrically controlled switches, – current amplifiers, and – voltage-controlled resistors. • Unlike BJTs, JFETs do not require a bias current and are controlled by using only a voltage. • JFETs are normally on when VG - VS = 0. • When VG - VS 0, then JFETs become resistive to current flow through the drain-source pair “JFETs are depletion devices.” JFET Types • Two types of JFETs: – n-channel and p-channel. • In n-channel JFET, a –ve voltage applied @ its gate (with VG < VS) reduces current flow from drain to source. It operates with VD > VS. • In p-channel JFET, a +ve voltage applied @ its gate (with VG > VS) reduces current flow from source to drain. It operates with VS > VD. • JFETs have very high input impedance and draw little or no input current – if there is any circuit/component connected to the gate of a JFET, no current is drawn away from or sunk into this circuit. MOSFET • Metal oxide semiconductor FET. • Similar to JFET. • A metal oxide insulator is placed @ the gate to obtain a high input impedance @ the gate – gate input impedance approx. 1014Ω. • Use of insulator as described above yields a low gate-to-channel capacitance. – If too much static electricity builds up on the gate, then the MOSFET may be damaged. MOSFET Types • Enhancement type: – Normally off, thus no current flows through drain-source channel when VG = VS. – When a voltage applied @ the gate causes VG VS the drain-source channel reduces resistance to current flow. • Depletion type: – Normally on, thus maximum current flows through drain-source channel when VG = VS. – When a voltage applied @ the gate causes VG VS the drain-source channel increases resistance to current flow. Date Developed:

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VG < VS VG VG > VS VG < VS > VS Current flow increases with: Current flow decreases with: Optoelectronics Light emitting diodes Infrared detector • In optoelectronics we deal with 2 types of electronic devices. • Light emitting electronic devices: ones that generate electromagnetic energy under the action of electrical field. Example: light emitting diodes (visible and infrared light). • Light detecting devices: ones that transform electromagnetic energy input into electrical current/voltage. Examples: photoresistors, photodiodes, phototransistors, etc. Light-Emitting Diodes (LEDs) LED 101—I • 2 lead semiconductor device. • Light emitting PN-junction diode. – Visible or infrared light. • Has polarity. • Recall diodes act as a one way gate to current flow. – A forward-biased PN-junction diode allows current flow from anode to cathode. • An LED conducts and emits light when its anode is made more positive (approx. 1.4V) than its cathode. – With reverse polarity, LED stops conducting and emitting light. LED 101—II • Similar to diodes, LEDs are current-dependent devices. – LED brightness is controlled by controlling current through LED. • Too little current through LED LED remains OFF. • Small current through LED dimly lit LED. • Large current through LED brightly lit LED. • Too much current through LED LED is destroyed. • A resistor placed in series with LED accomplishes current control Visible-Light LED • Inexpensive and durable. • Typical usage: as indicator lights. • Common colors: green (~565nm), yellow (~585nm), orange (~615nm), and red (~650nm). • Maximum forward voltage: 1.8V. • Typical operating currents: 1 to 3mA. • Typical brightness levels: 1.0 to 3.0mcd/1mA to 3.0mcd /2mA.

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TASK SHEET AND INSTRUCTION Title: ELECTROLYTIC

OHMMETER

CAPACITOR

AND

USE

OF

Performance Objectives: 1. To become familiar with the characteristics of an electrolytic capacitor. 2. To study and understand the meter behavior in checking electrolytic capacitor. 3. To interpret accurately the normal and abnormal condition of an electrolytic capacitor. Materials Needed: 1 unit –VOM or equivalent meter CAPACITORS: Ten Assorted values of electrolytic capacitors.

Steps/Procedure 1. Draw the electrolytic capacitor and VOM with the test probes connection and ohmmeter in the correct polarity. 2. Check the condition of the electrolytic capacitor and describe briefly the meter behavior, dc resistance and condition as indicated thereof. 3. Record the result as shown in the table 1. 4. Repeat the steps 1 and 3 for the following capacitors and write the corresponding results in the table. 5. Identify the components and give the function and parts as indicated in the table II. 6. State briefly your observation or condition. Assessment Method 5. Check and verify every procedure during the testing process of training or students. 6. We will collect the papers on the right answer after measured value of the training or students. 7. Practical testing and direct observation and follow up questions. 8. Test and review exercises. Date Developed:

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• High-brightness LEDs exist. – Used in high-brightness flashers (e.g., bicycle flashers). Blinking LED • Contain a miniature integrated circuit that causes LED to flash from 1 to 6 times/second. • Typical usage: indicator flashers. May also be used as simple oscillators. Tricolor LED • Two LEDs placed in parallel facing opposite directions. • One LED is red or orange, the other is green. • Current flow in one direction turns one LED ON while the other remains OFF due to reverse bias. • Current flow in the other direction turns the first LED OFF and the second LED ON. • Rapid switching of current flow direction will alternatively turn the two LEDs ON giving yellow light. • Used as a polarity indicator. • Maximum voltage rating: 3V • Operating range: 10 to 20mA 7-Segment LED Display • Used for displaying numbers and other characters. • 7 individual LEDs are used to make up the display. • When a voltage is applied across one of the LEDs, a portion of the 8 lights up. • Unlike liquid crystal displays (LCD), 7-segment LED displays tend to be more rugged, but they also consume more power. How LED Works • The light-emitting section of an LED is made by joining n-type and p-type semiconductors together to form a pn junction. • When the pn junction is forward-biased, electrons in the n side are excited across the pn junction and into the p side, where they combine with holes. • As the electrons combine with the holes, photons are emitted. • The pn-junction section of an LED is encased in an epoxy shell that is doped with light scattering particles to diffuse light and make the LED appear brighter. • Often a reflector placed beneath the semiconductor is used to direct the light upward. Photoresistors—I • Light sensitive variable resistors. • Its resistance depends on the intensity of light incident upon it. – Under dark condition, resistance is quite high (M : called dark resistance). – Under bright condition, resistance is lowered (few hundred ). • Response time: – When a photoresistor is exposed to light, it takes a few milliseconds, before it lowers its resistance. – When a photoresistor experiences removal of light, it may take a few seconds to return to its dark resistance. Symbol Photoresistors—II Date Developed:

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• Some photoresistors respond better to light that contains photons within a particular wavelength of spectrum. – Example: Cadmium-sulfide photoresistos respond to light within 400-800nm range. – Example: Lead-sulfide photoresistos respond to infrared light. How PhotoresistorWorks • Special semiconductor crystal, such as cadmium sulfide or lead sulfide is used to make photoresistors. • When this semiconductor is placed in dark, electrons within its structure resist flow through the resistor because they are too strongly bound to the crystal’s atoms. • When this semiconductor is illuminated, incoming photons of light collide with the bound electrons, stripping them from the binding atom, thus creating holes in the process. • Liberated electrons contribute to the current flowing through the device. Photoresistor Application —Light Activated Relay • Light-sensitive voltage divider is being used to trip a relay whenever the light intensity change. • Light-activated circuit: – When the photoresistor is exposed to light, its resistance decreases. – Transistor’s base current and voltage increase and if the base current and voltage are large enough, the collector-emitter pair of the transistor conducts triggering the relay. • The value of R1 in the light-activated circuit should be around 1 KΩ but may have to be adjusted. • Dark-activated relay works in a similar but opposite manner. • R1 in the dark-activated circuit (100KΩ) may also have to be adjusted. • A 6 to 9-V relay with a 500Ω coil can be used in either circuit. Light activated relay Dark activated relay Photodiode • Photodiode is a 2 lead semiconductor device that transforms light energy to electric current. • Suppose anode and cathode of a photodiode are wired to a current meter. – When photodiode is placed in dark, the current meter displays zero current flow. – When the photodiode is expose to light, it acts a a current source, causing current flow from cathode to anode of photodiode through the current meter. • Photodiodes have very linear light v/s current characteristics. – Commonly used as light meters in cameras. • Photodiodes often have built-in lenses and optical filters. • Response time of a photodiode slows with increasing surface area. • Photodiodes are more sensitive than photoresistor. Date Developed:

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Symbol. TASK SHEET AND INSTRUCTION Title: FAMILIARIZATION OF COMPONENT SYMBOLS Performance Objectives: 1. To become familiar with the different components commonly used in electronics and electricity. 2. To describe and interpret the standard symbols for each of these components. Materials Needed: RESISTORS: Assorted types (fixed and variables) CAPACITORS: Assorted types INDUCTORS: Assorted types TUBES AND TRANSISTOR: Assorted types Miscellaneous: rectifiers, transformers, fuse, switch and speaker

Steps/Procedure 1. Your instructor will assign you some electronic components, study, then describe the physical structure or appearance of the components you receive. 2. Draw the electronic or electrical symbols for each part. Assessment Method 1. Check and verify every procedure during the testing process of training or students. 2. We will collect the papers on the right answer after measured value of the training or students. 3. Practical testing and direct observation and follow up questions. 4. Test and review exercises.

Date Developed:

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How Photodiode Works • Photodiode: A thin n-type semiconductor sandwiched with a thicker p-type semiconductor. • N-side is cathode, p-side is anode. • Upon illumination, a # of photons pass from the n-side and into the p-side of photodiode. – Some photons making it into p-side collide with bound electrons within psemiconductor, ejecting them and creating holes. – If these collisions are close to the pninterface, the ejected electrons cross the junction, yielding extra electrons on the n-side and extra holes on the p-side. – Segregation of +ve and -ve charges leads to a potential difference across the pn-junction. – When a wire is connected between the cathode and anode, a conventionally positive current flow from the anode to cathode

Photodiode Applications—Photovoltaic Current Source • Photodiode converts light energy directly into electric current that can be measured with meter. • The input intensity of light and the output current are nearly linear. • Solar cells are photodiodes with very large surface areas. • Compared to usual photodiodes, the large surface area in photodiode of a solar cell yields – a device that is more sensitive to incoming light. – a device that yields more power (larger current/volts). • Solar cells yield more power. • A single solar cell may provide up to 0.5V that can supply 0.1A when exposed to bright light. Solar Cell—I Solar Cell—II Solar Cell Basic Operation—Power Sources • Each solar cell produces an open-circuit voltage from around 0.45 to 0.5 V and may Date Developed:

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generate as much as 0.1 A in bright light. • Similar to batteries, solar cells can be combined in series or parallel. • Adding cells in series, yields output voltage that is the sum of the individual cell voltages. • Adding solar cells in parallel, yields an increased output current vis-à-vis a single solar cell. Solar Cell Basic Operation—Battery Charger • Nine solar cells placed in series can be used to recharge two 1.5 V NiCd cells. • The diode is added to the circuit to prevent the NiCd cells from discharging through the solar cell during times of darkness. • It is important not to exceed the safe charging rate of NiCd cells. To slow the charge rate, a resistor can be placed in series with the batteries. Phototransistor • Phototransistor is a light sensitive transistor. • In one common type of phototransistor, the base lead of a BJT is replaced by a light sensitive surface. • When the light sensitive surface @ the base is kept in darkness, the collector-emitter pair of the BJT does not conduct. • When the light sensitive surface @ the base is exposed to light, a small amount of current flows from the base to the emitter. The small base-emitter current controls the larger collector-emitter current. • Alternatively, one can also use a field-effect phototransistor (Photo FET). • In a photo FET, the light exposure generates a gate voltage which controls a drain-source current. Phototransistor Photo FET How Phototransistor Works • The bipolar phototransistor resembles a bipolar transistor that has extra large p-type semiconductor region that is open for light exposure. • When photons from a light source collide with electrons within the p-type semiconductor, they gain enough energy to jump across the pn-junction energy barrierprovided the photons are of the right frequency/energy. Date Developed:

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• As electrons jump from the p-region into the lower n-region, holes are created in the ptype semiconductor. • The extra electrons injected into the lower ntype slab are drawn toward the positive terminal of the battery, while electrons from the negative terminal of the battery are draw into the upper n-type semiconductor and across the np junction, where they combine with the holes, the net result is an electrons current that flows from the emitter to the collector. Phototransistor Applications—Light Activated Relay • A phototransistor is used to control the base current supplied to a power-switching transistor that is used to supply current to a relay. • When light comes in contact with the phototransistor, the phototransistor turns on, allowing current to pass from the supply into the base of the power-switching transistor. • This allows the power-switching transistor to turns on, and current flows through the relay, triggering it to switch states. • The 100K pot is used to adjust the sensitivity of device by controlling current flow through the phototransistor. Phototransistor Applications—Dark Activated Relay • A phototransistor is used to control the base current supplied to a power-switching transistor that is used to supply current to a relay. • When light is removed from the phototransistor, the phototransistor turns off, allowing more current to enter into the base of the power-switching transistor. • This allows the power-switching transistor to turns on, and current flows through the relay, triggering it to switch states. • The 100K pot is used to adjust the sensitivity of device by controlling current flow through the phototransistor. Phototransistor Applications—Tachometer • A phototransistor is being used as a frequency counter or tachometer. • A rotating disk is connected to a rotating shaft. The rotating disk has one hole in it. • For the given setup, the disk will allow light to pass through the hole once every revolution. • The light passing through the disk triggers the phototransistor into conduction. • A frequency counter is used to count the number of electrical pulses generated.

Date Developed:

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TASK SHEET AND INSTRUCTION Title: CHECKING MICA, MYLAR AND CERAMIC CAPACITORS WITH VOM Performance Objectives: 1. To verify experimentally the storing current capacity of a capacitor. 2. To determine the charging effect of mica, Mylar and ceramic capacitor. Materials Needed: 1 unit –VOM or equivalent CAPACITORS: Ten assorted values of non-polar capacitor Steps/Procedure 1. Draw the circuit connection of VOM test leads in checking the condition of mica, Mylar and ceramic disc capacitor indicate the range of the ohmmeter. 2. Record the result in the table 1 and describe ohmmeter pointer behavior. 3. Identify the group of components and give the function of the VOM. 4. State briefly your observation or conclusion.

Assessment Method 1. Fill up the table of data by using VOM. No. of Capacitance Type of Capacitor Value capacitor

Meter pointer behavior

condition

1 2 3 4 Date Developed:

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5 6

TASK SHEET AND INSTRUCTION Title: CHECKING DIODE WITH AN OHMMETER Performance Objectives: 1. To become familiar with the VOM (volt-ohmmeter) used as diode tester. 2. To identify the anode and cathode and the junction of the diode. 3. To verify experimentally common troubles of a diode and its probable cause. 4. To become familiar with the different types of the diode. Materials Needed: 1 unit –VOM or equivalent meter DIODE: Assorted types of solid state diode (good, open, shorted and leaky) Miscellaneous: two pieces of connecting wires with clip

Steps/Procedure 1. Measure and record the forward and reverse resistance of silicon diode or equivalent as show in the table. 2. Indicate the behavior of the meter pointer. 1. Identify the anode and cathode junction of the diode. 2. Test and verify the connection from end to end diode. 3. State briefly the parts and function of a diode as indicated in the table.

Assessment Method 1. Check and verify every procedure during the testing process of training. 2. Practical testing and direct observation. 3. Test and review exercises.

Date Developed:

Electronic Products Assembly and Servicing NC II

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A multimeter or a multitester, also known as a VOM (Volt-Ohm-Milliammeter), is an electronic measuring instrument that combines several measurement functions in one unit. A typical multimeter can measure voltage, current, and resistance.Analog multimeters use a microammeter with a moving pointer to display readings. Digital multimeters (DMM, DVOM) have a numeric display, and may also show a graphical bar representing the measured value. Digital multimeters are now far more common due to their cost and precision, but analog multimeters are still preferable in some cases, for example when monitoring a rapidly varying value. A multimeter can be a hand-held device useful for basic faultfinding and field service work, or a bench instrument which can measure to a very high degree of accuracy. They can be used to troubleshoot electrical problems in a wide array of industrial and household

devices

such

as electronic

equipment,

motor

controls, domestic

appliances, power supplies, and wiring systems. Operation A multimeter is a combination of a multirange DC voltmeter, multirange AC voltmeter, multirangeammeter, and multirange ohmmeter. An un-amplified analog multimeter combines a meter movement, range resistors and switches. For an analog meter movement, DC voltage is measured with a series resistor connected between the meter movement and the circuit under test. A set of switches allows greater resistance to be inserted for higher voltage ranges. The product of the basic full-scale deflection current of the movement, and the sum of the series resistance and the movement's own resistance, gives the full-scale voltage of the range. As an example, a meter movement that required 1 milliampere for full scale deflection, with an internal resistance of 500 ohms, would, on a 10-volt range of the multimeter, have 9,500 ohms of series resistance.[7]

Date Developed:

Electronic Products Assembly and Servicing NC II

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For analog current ranges, low-resistance shunts are connected in parallel with the meter movement to divert most of the current around the coil. Again for the case of a hypothetical 1 mA, 500 ohm movement on a 1 ampere range, the shunt resistance would be just over 0.5 ohms. Moving coil instruments respond only to the average value of the current through them. To measure alternating current, a rectifier diode is inserted in the circuit so that the average value of current is non-zero. Since the rectified average value and the root-mean-square value of a waveform need not be the same, simple rectifier-type circuits may only be calibrated for sinusoidal waveforms. Other wave shapes require a different calibration factor to relate RMS and average value. Since practical rectifiers have non-zero voltage drop, accuracy and sensitivity is poor at low values. To measure resistance, a small battery within the instrument passes a current through the device under test and the meter coil. Since the current available depends on the state of charge of the battery, a multimeter usually has an adjustment for the ohms scale to zero it. In the usual circuit found in analog multimeters, the meter deflection is inversely proportional to the resistance; so fullscale is 0 ohms, and high resistance corresponds to smaller deflections. The ohms scale is compressed, so resolution is better at lower resistance values. Amplified instruments simplify the design of the series and shunt resistor networks. The internal resistance of the coil is decoupled from the selection of the series and shunt range resistors; the series network becomes a voltage divider. Where AC measurements are required, the rectifier can be placed after the amplifier stage, improving precision at low range. Digital instruments, which necessarily incorporate amplifiers, use the same principles as analog instruments for range resistors. For resistance measurements, usually a small constant current is passed through the device under test and the digital multimeter reads the resultant voltage drop; this eliminates the scale compression found in analog meters, but requires a source of significant current. An autoranging digital multimeter can automatically adjust the scaling network so that the measurement uses the full precision of the A/D converter. Date Developed:

Electronic Products Assembly and Servicing NC II

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In all types of multimeters, the quality of the switching elements is critical to stable and accurate measurements. Stability of the resistors is a limiting factor in the longterm accuracy and precision of the instrument. Quantities measured Contemporary multi-meters can measure many quantities. The common ones are: 

Voltage, alternating and direct, in volts.

Current,

alternating

and

in amperes.

direct,

The frequency range for which AC measurements are accurate must be specified. 

Resistance in ohms.

Additionally, some multi-meters measure: 

Capacitance in farads.

Conductance in Siemens.

Decibels.

Duty cycle as a percentage.

Frequency in hertz.

Inductance in henries.

Temperature in

degrees Celsius or Fahrenheit,

with

an

appropriate

temperature test probe, often thermocouple. Digital multi-meters may also include circuits for: 

Continuity tester; sounds when a circuit conducts

Diodes (measuring

forward

drop

of

diode

junctions),

and transistors (measuring current gain and other parameters) 

Battery checking for simple 1.5-volt and 9-volt batteries. This is a current loaded voltage scale which simulates in-use voltage measurement.

Various sensors can be attached to multi-meters to take measurements such as:

Date Developed:

Electronic Products Assembly and Servicing NC II

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Light level

Acidity/Alkalinity(pH)

Relative humidity

Resolution Resolution and accuracy The resolution of a multi-meter is the smallest part of the scale which can be shown, which is scale dependent. On some digital multi-meters it can be configured, with higher resolution measurements taking longer to complete. For example, a multimeter that has a 1 mV resolution on a 10 V scale can show changes in measurements in 1 mV increments. Absolute accuracy is the error of the measurement compared to a perfect measurement. Relative accuracy is the error of the measurement compared to the device used to calibrate the multi-meter. Most multi-meter datasheets provide relative accuracy. To compute the absolute accuracy from the relative accuracy of a multi-meter add the absolute accuracy of the device used to calibrate the multi-meter to the relative accuracy of the multi-meter. Digital The

resolution

of

a

multi-meter

is

often

specified

in

the

number

of

decimal digits resolved and displayed. If the most significant digit cannot take all values from 0 to 9 is often termed a fractional digit. For example, a multi-meter which can read up to 19999 (plus an embedded decimal point) is said to read 4½ digits. By convention, if the most significant digit can be either 0 or 1, it is termed a halfdigit; if it can take higher values without reaching 9 (often 3 or 5), it may be called three-quarters of a digit. A 5½ digit multi-meter would display one "half digit" that could only display 0 or 1, followed by five digits taking all values from 0 to 9. [9] Such a meter could show positive or negative values from 0 to 199,999. A 3¾ digit meter can display a quantity from 0 to 3,999 or 5,999, depending on the manufacturer. While a digital display can easily be extended in precision, the extra digits are of no value if not accompanied by care in the design and calibration of the analog portions of the multi-meter. Meaningful high-resolution measurements require a good Date Developed:

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understanding of the instrument specifications, good control of the measurement conditions, and traceability of the calibration of the instrument. However, even if its resolution exceeds the accuracy, a meter can be useful for comparing measurements. For example, a meter reading 5½ stable digits may indicate that one nominally 100,000 ohm resistor is about 7 ohms greater than another, although the error of each measurement is 0.2% of reading plus 0.05% of full-scale value. Specifying "display counts" is another way to specify the resolution. Display counts give the largest number, or the largest number plus one (so the count number looks nicer) the multi-meter's display can show, ignoring a decimal separator. For example, a 5½ digit multi-meter can also be specified as a 199999 display count or 200000 display count multi-meter. Often the display count is just called the count in multimeter specifications. The accuracy of a digital multi-meter may be stated in a two-term form, such as "±1% of reading +2 counts", reflecting the different sources of error in the instrument. Analog

Display face of an analog multi-meter Analog meters are older and still preferred by many engineers. One reason for this is that analog meters are more sensitive to changes in the circuit that is being measured. A digital multi-meter samples the quantity being measured and then displays it. Analog multi-meters continuously read the test value. If there are slight changes in readings, the needle of an analog multi-meter will track them while digital multi-meters may miss them or be difficult to read. This continuous tracking feature becomes important when testing capacitors or coils. A properly functioning capacitor should allow current to flow when voltage is applied, then the current slowly Date Developed:

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decreases to zero and this "signature" is easy to see on an analog multi-meter but not on a digital multi-meter. This is similar when testing a coil, except the current starts low and increases. Resistance measurements on an analog meter, in particular, are of low precision due to the typical resistance measurement circuit which compresses the scale heavily at the higher resistance values. Inexpensive analog meters may have only a single resistance scale, seriously restricting the range of precise measurements. Typically an analog meter will have a panel adjustment to set the zero-ohms calibration of the meter, to compensate for the varying voltage of the meter battery. Accuracy Digital multi-meters generally take measurements with accuracy superior to their analog counterparts. Standard analog mult-imeters measure with typically ±3% accuracy,[11] though instruments of higher accuracy are made. Standard portable digital multi-meters are specified to have an accuracy of typically ±0.5% on the DC voltage ranges. Mainstream bench-top multi-meters are available with specified accuracy of better than ±0.01%. Laboratory grade instruments can have accuracies of a few parts per million. Accuracy figures need to be interpreted with care. The accuracy of an analog instrument usually refers to full-scale deflection; a measurement of 30 V on the 100 V scale of a 3% meter is subject to an error of 3 V, 10% of the reading. Digital meters usually specify accuracy as a percentage of reading plus a percentage of fullscale value, sometimes expressed in counts rather than percentage terms. Quoted accuracy is specified as being that of the lower milli-volt (mV) DC range, and is known as the "basic DC volts accuracy" figure. Higher DC voltage ranges, current, resistance, AC and other ranges will usually have a lower accuracy than the basic DC volts figure. AC measurements only meet specified accuracy within a specified range of frequencies. Manufacturers can provide calibration services so that new meters may be purchased with a certificate of calibration indicating the meter has been adjusted to standards Date Developed:

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traceable to, for example, the USNational Institute of Standards and Technology (NIST), or other national standards organization. Test equipment tends to drift out of calibration over time, and the specified accuracy cannot be relied upon indefinitely. For more expensive equipment, manufacturers and third parties provide calibration services so that older equipment may be recalibrated and recertified. The cost of such services is disproportionate for inexpensive equipment; however extreme accuracy is not required for most routine testing.

Multi-meters

used

for

critical

measurements

may

be

part

of

a metrology program to assure calibration. A multi-meter can be assumed to be "average responding" to AC waveforms unless stated as being a "True RMS" type. An average responding multimeter will only meet its specified accuracy on AC volts and amps for purely sinusoidal waveforms. A True RMS responding multimeter on the other hand will meet its specified accuracy on AC volts and current with any waveform type up to a specified crest factor. A meter's AC voltage and current accuracy may have different specifications for different ranges of frequency. Sensitivity and input impedance When used for measuring voltage, the input impedance of the multimeter must be very high compared to the impedance of the circuit being measured; otherwise circuit operation may be changed, and the reading will also be inaccurate. Meters with electronic amplifiers (all digital multimeters and some analog meters) have a fixed input impedance that is high enough not to disturb most circuits. This is often either one or ten megohms; thestandardization of the input resistance allows the use of external high-resistance probes which form avoltage divider with the input resistance to extend voltage range up to tens of thousands of volts. High-end multimeters generally provide an input impedance >10 Gigaohms for ranges less than or equal to 10 V. Some high-end multimeters provide >10 Gigaohms of impedance to ranges greater than 10 V.

Date Developed:

Electronic Products Assembly and Servicing NC II

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Most analog multimeters of the moving-pointer type are unbuffered, and draw current from the circuit under test to deflect the meter pointer. The impedance of the meter varies depending on the basic sensitivity of the meter movement and the range which is selected. For example, a meter with a typical 20,000 ohms/volt sensitivity will have an input resistance of two million ohms on the 100-volt range (100 V * 20,000 ohms/volt = 2,000,000 ohms). On every range, at full scale voltage of the range, the full current required to deflect the meter movement is taken from the circuit under test. Lower sensitivity meter movements are acceptable for testing in circuits where source impedances are low compared to the meter impedance, for example, power circuits; these meters are more rugged mechanically. Some measurements in signal circuits require higher sensitivity movements so as not to load the circuit under test with the meter impedance. Sensitivity should not be confused with resolution of a meter, which is defined as the lowest signal change (voltage, current, resistance...) that can change the observed reading. For general-purpose digital multimeters, the lowest voltage range is typically several hundred millivolts AC or DC, but the lowest current range may be several hundred microamperes, although instruments with greater current sensitivity are available. Multimeters designed for (mains) "electrical" use instead of general electronics engineering use will typically forego the microamps current ranges. Measurement of low resistance requires lead resistance (measured by touching the test probes together) to be subtracted for best accuracy. This can be done with the "delta", "Zero", or "null" feature of many digital multimeters. The

upper

end

of

multimeter

measurement

ranges

varies

considerably;

measurements over perhaps 600 volts, 10 amperes, or 100 megohms may require a specialized test instrument. Burden voltage Any ammeter, including a multimeter in a current range, has a certain resistance. Most multimeters inherently measure voltage, and pass a current to be measured Date Developed:

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through a shunt resistance, measuring the voltage developed across it. The voltage drop is known as the burden voltage, specified in volts per ampere. The value can change depending on the range the meter selects, since different ranges usually use different shunt resistors. The burden voltage can be significant in very low-voltage circuit areas. To check for its effect on accuracy and on external circuit operation the meter can be switched to different ranges; the current reading should be the same and circuit operation should not be affected if burden voltage is not a problem. If this voltage is significant it can be reduced (also reducing the inherent accuracy and precision of the measurement) by using a higher current range. Alternating current sensing Since the basic indicator system in either an analog or digital meter responds to DC only, a multimeter includes an AC to DC conversion circuit for making alternating current measurements. Basic meters utilize a rectifier circuit to measure the average or peak absolute value of the voltage, but are calibrated to show the calculated root mean square (RMS) value for a sinusoidal waveform; this will give correct readings for alternating current as used in power distribution. User guides for some such meters givecorrection factors for some simple non-sinusoidal waveforms, to allow the correct root mean square(RMS) equivalent value to be calculated. More expensive multimeters include an AC to DC converter that measures the true RMS value of the waveform within certain limits; the user manual for the meter may indicate the limits of the crest factor and frequency for which the meter calibration is valid. RMS sensing is necessary for measurements on non-sinusoidal periodic waveforms, such as found in audio signals and variable-frequency drives.

Date Developed:

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Digital multi-meters (DMM or DVOM)

A bench-top multimeter, the Hewlett-Packard 34401. Modern multimeters are often digital due to their accuracy, durability and extra features. In a digital multimeter the signal under test is converted to a voltage and an amplifier with electronically controlled gain preconditions the signal. A digital multimeter

displays

the

quantity

measured

as

a

number,

which

eliminates parallax errors. Modern digital multimeters may have an embedded computer, which provides a wealth of convenience features. Measurement enhancements available include: 

Auto-ranging, which selects the correct range for the quantity under test so that the most significant digits are shown. For example, a four-digit multimeter would automatically select an appropriate range to display 1.234 instead of 0.012, or overloading. Auto-ranging meters usually include a facility to hold the meter to a particular range, because a measurement that causes frequent range changes can be distracting to the user.

Auto-polarity for direct-current readings, shows if the applied voltage is positive (agrees with meter lead labels) or negative (opposite polarity to meter leads).

Sample and hold, which will latch the most recent reading for examination after the instrument is removed from the circuit under test.

Date Developed:

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Current-limited tests for voltage drop across semiconductor junctions. While not a replacement for atransistor tester, this facilitates testing diodes and a variety of transistor types.

A graphic representation of the quantity under test, as a bar graph. This makes go/no-go testing easy, and also allows spotting of fast-moving trends.

A low-bandwidth oscilloscope.[18]

Automotive circuit testers, including tests for automotive timing and dwell signals.[19][better source needed]

Simple data acquisition features to record maximum and minimum readings over a given period, or to take a number of samples at fixed intervals.[20]

Integration with tweezers for surface-mount technology.[21][better source needed]

A combined LCR meter for small-size SMD and through-hole components.[22]

Modern meters may be interfaced with a personal computer by IrDA links, RS232 connections, USB, or an instrument bus such as IEEE-488. The interface allows the computer to record measurements as they are made. Some DMMs can store measurements and upload them to a computer.[23] The first digital multimeter was manufactured in 1955 by Non Linear Systems. [24][25] It is claimed that the first handheld digital multimeter was developed by Frank Bishop of Intron Electronics in 1977,[26] which at the time presented a major breakthrough for servicing and fault finding in the field. Analog multimeters

Inexpensive analog multimeter with a galvanometer needle display A multimeter may be implemented with a galvanometer meter movement, or less often with a bargraph or simulated pointer such as an LCD or vacuum fluorescent display. Date Developed:

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Analog multimeters are common; a quality analog instrument will cost about the same as a DMM. Analog multimeters have the precision and reading accuracy limitations described above, and so are not built to provide the same accuracy as digital instruments. Analog meters are also useful in situations where it is necessary to pay attention to something other than the meter, and the swing of the pointer can be noticed without looking directly at it. This can happen when accessing awkward locations, or when working on cramped live circuitry. Analog meter movements are inherently more fragile physically and electrically than digital meters. Many analog meters have been instantly broken by connecting to the wrong point in a circuit, or while on the wrong range, or by dropping onto the floor. Many analog multi-meters feature a switch position marked "transit" to protect the meter movement during transportation. This feature works by placing a low resistance across the movement winding, resulting in dynamic braking. Sensitive meter movements may be protected in the same manner by connecting a shorting or jumper wire between the terminals when not in use. Meters which feature a shunt across the winding such as an ammeter may not require further resistance to arrest uncontrolled movements of the meter needle because of the low resistance of the shunt. The meter movement in a moving pointer analog multi-meter is practically always a moving-coilgalvanometer of the d'Arsonval type, using either jeweled pivots or taut bands to support the moving coil. In a basic analog multimeter the current to deflect the coil and pointer is drawn from the circuit being measured; it is usually an advantage to minimize the current drawn from the circuit. The sensitivity of an analog multimeter is given in units of ohms per volt. For example, a very low cost multimeter with sensitivity of 1000 ohms per volt would draw 1 milliampere from a circuit at full scale deflection.[27] More expensive, (and mechanically more delicate) multimeters typically have sensitivities of 20,000 ohms per volt and sometimes higher, with 50,000 ohms per volt (drawing 20 microamperes at full scale) being about the upper limit for a portable, general purpose, non-amplified analog multimeter. Date Developed:

Electronic Products Assembly and Servicing NC II

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To avoid the loading of the measured circuit by the current drawn by the meter movement, some analog multimeters use an amplifier inserted between the measured circuit and the meter movement. While this increased the expense and complexity of the meter, by use of vacuum tubes or field effect transistors the input resistance can be made very high and independent of the current required to operate the meter movement coil. Such amplified multimeters are called VTVMs (vacuum tube voltmeters),[28] TVMs (transistor volt meters), FET-VOMs, and similar names. The American

Radio

Relay

League states

in

their Handbook

for

Radio

Communications that analog multimeters that have no amplification circuitry are less Probes A multimeter can utilize a variety of test probes to connect to the circuit or device under test. Crocodile clips, retractable hook clips, and pointed probes are the three most common attachments. Tweezer probes are used for closely spaced test points, as in surface-mount devices. The connectors are attached to flexible, thickly insulated leads that are terminated with connectors appropriate for the meter. Probes are connected to portable meters typically by shrouded or recessed banana jacks, while benchtop meters may use banana jacks or BNC connectors. 2 mm plugs and binding posts have also been used at times, but are less common today. The banana jacks are typically placed with a standardized center-to-center distance of 0.75 in (19 mm), to allow standard adapters or devices such as voltage multiplier or thermocouple probes to be plugged in. Clamp meters clamp around a conductor carrying a current to measure without the need to connect the meter in series with the circuit, or make metallic contact at all. Types to measure AC current use the transformer principle; clamp-on meters to measure small current or direct current require more complicated sensors.

Safety

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An example of input protection on the CAT-IV rated Fluke 28 Series II Multimeter Most multimeters include a fuse, or two fuses, which will sometimes prevent damage to the multimeter from a current overload on the highest current range. (For added safety, test leads with fuses built in are available.) A common error when operating a multimeter is to set the meter to measure resistance or current, and then connect it directly to a low-impedance voltage source. Unfused meters are often quickly destroyed by such errors; fused meters often survive. Fuses used in meters must carry the maximum measuring current of the instrument, but are intended to disconnect if operator error exposes the meter to a low-impedance fault. Meters with inadequate or unsafe fusing were not uncommon; this situation has led to the creation of the IEC61010 categories to rate the safety and robustness of meters. Digital meters are rated into four categories based on their intended application, as set forth by IEC 61010-1] and echoed by country and regional standards groups such as the CEN EN61010 standard. 

Category I: used where equipment is not directly connected to the mains

Category II: used on single phase mains final sub-circuits

Category III: used on permanently installed loads such as distribution panels, motors, and 3-phase appliance outlets

Category IV: used on locations where fault current levels can be very high, such as supply service entrances, main panels, supply meters, and primary overvoltage protection equipment

Each category also specifies maximum transient voltages for selected measuring ranges in the meter. Category-rated meters also feature protections from overcurrent

faults.[34] On

meters

that

allow

interfacing

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isolation may be used to protect attached equipment against high voltage in the measured circuit. Good quality multimeters designed to meet CAT II and above ratings will include High Rupture Capacity ceramic fuses typically rated at more than 20 kA breaking capacity.[35] They

will

also

include

high

energy

overvoltage

MOV

(Metal

Oxide Varistor) protection, and circuit over-current protection in the form of aPolyswitch.[36] DMM alternatives A general-purpose electronics DMM is generally considered adequate for measurements at signal levels greater than one millivolt or one microampere, or below about 100 megohms—levels far from the theoretical limits of sensitivity. Other instruments—essentially similar, but with higher sensitivity—are used for accurate measurements

of

very

small

or

very

large

quantities.

These

include

nanovoltmeters,electrometers (for very low currents, and voltages with very high source resistance, such as one teraohm) and picoammeters. These measurements are limited by available technology, and ultimately by inherent thermal noise. Power supply Analog meters can measure voltage and current using power from the test circuit, but require internal power from the meter for resistance testing; electronic meters always require an internal power supply. Hand-held meters use batteries, while bench meters usually use mains power; either arrangement allows the meter to test devices not connected to an active circuit. Testing often requires that the component under test be isolated from the circuit, as otherwise stray or leakage current paths may distort measurements. Meters intended for testing in hazardous locations or for use on blasting circuits may require use of a manufacturer-specified battery to maintain their safety rating.

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TASK SHEET AND INSTRUCTION Title: TRANSFORMER TESTING WITH VOM Performance Objectives: 4. To learn how to use AC voltmeter for testing and measuring the transformer voltages. 5. To know how to use the ohmmeter for testing and measuring the terminal resistance of a transformer. Materials Needed: 1 unit –VOM or equivalent Transformer: Primary 0,1,3,4.5,5,6,7,9 and 12v rated current 750mA. Date Developed:

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Miscellaneous: Power Cord with Plug 1pc- operating manual

Steps/Procedure 1. Connect the power cord to the input terminals a transformer. check your AC line voltage. 2. Double check your connections. 3. Insert the power plug to the AC line outlet. 4. Set the VOM at 250v AC. 5. With connect at 0-110 or 220 mark of the transformer, measure the AC voltage record the result in the table provided or as per instruction. 6. Repeat procedure for the different connections of the transformer.

Assessment Method 1. Check and verify every procedure during the testing process of training or students. 2. We will collect the papers on the right answer after measured value of the training or students. 3. Practical testing and direct observation.

Audio & Video Products

Analog Devices Advantiv® portfolio of video and audio IC solutions are specifically developed and optimized for advanced television and related box applications. Whether high definition TVs, DVD players, digital video recorders, audio/video receivers, camcorders, or cable and satellite set top boxes, the Advantiv portfolio delivers cost effective analog, digital, and mixed-signal solutions that bring the most advanced TVs to life.

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According to the Consumer Electronics Association, the average household owns 24 consumer electronics products which are responsible for 12 percent of household electricity use. ENERGY STAR certified audio/video equipment is up to 50% more efficient than conventional models. Blu-Ray players that earn the ENERGY STAR label are, on average, 45% more efficient than conventional models. The ENERGY STAR can be found on a wide range of equipment such as: Home-Theater-in-a-Box Systems Sound bars MP3 speaker docks Audio Amplifiers AV receivers Shelf systems Blue-ray Disc players DVD players

What an LED TV Really Is There has been a lot of hype and confusion surrounding the marketing of "LED" TVs. Even many public relations representatives and sales professionals that should know better are falsely explaining what an LED Television is to their prospective customers. To set the record straight, it is important to note that the LED designation refers to the backlight system used in many LCD Televisions, not the chips that produce the image content. LCD chips and pixels do not produce their own light. In order for an LCD television to produce a visible image on a TV screen the LCD's pixels have to be "backlit". For more specifics on the backlighting process needed for LCD Televisions, refer to my article: Demystifying CRT, Plasma, LCD, and DLP Television Technologies. Plasma Technology Plasma televisions, on the other hand, although employing phosphors similar to a CRT, the phosphors are not lit by a scanning electron beam. Instead the phosphors in a Plasma television are lit by superheated charged gas (similar to a Fluorescent light). All the phosphor picture elements (pixels) can be lit at once, rather than having to be scanned by an electron beam as is the case with CRTs. Also, since a scanning electron beam is not necessary, the need for a bulky picture tube (CRT) is eliminated, resulting in a thin cabinet profile. For more technical details, check out How Plasma TV Works (How Stuff Works). Date Developed:

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LCD Technology Taking another approach, which also results in a thin cabinet profile, unlike a traditional CRT televisions, the images on an LCD television are also not "scanned" by an electron beam. The picture elements (pixels) of an LCD Television are merely turned off or on at a specific refresh rate. In other words, the entire image is displayed (or refreshed) all at once every 24th, 30th, 60th, or 120th of a second. Actually, with LCD you can engineer refresh rates of 24, 25, 30, 50, 60, 72, 100, 120, 240, or 480 (so far). However, the most commonly used refresh rates used in LCD TVs is 60 or 120. Keep in mind that refresh rate is not the same as frame rate. For more specifics on what refresh rate is, how it works, and how it is different that frame rate, check out my article: Video Frame Rate vs Screen Refresh Rate. It must also be noted that LCD pixels do not produce there own light. In order for an LCD television to produce a visible image the LCD's pixels have to be "backlit". The backlight, in most cases is constant. What happens in this process is that the pixels are rapidly turned on and off depending on the requirements of the image. If the pixels are off, they don't let the backlight through, when they are on, they let the backlight through. For a more technical look at how this process works, check out: How LCD Works (How Stuff Works). It is important to note that there are new backlight technologies which enhance the pixel on/off process, such as Global Dimming and Local Dimming. These dimming technologies employ anLED-based backlight (either full array or edge light system) rather than traditional Fluorescent backlighting. Global Dimming can vary the amount of backlight hitting all of the pixels for dark or bright scenes, while Local Dimming is designed to hit specific groups of pixels depending on which areas of the image need to be darker or lighter than the rest of the image. For a detailed look at Local Dimming and LED use in LCD TVs, check out an informative article from Home Theater Magazine. DLP Technology Still another technology used in televisions (rear projection televisions, that is) is DLP (Digital Light Processing), invented, developed, and licensed by Texas Instruments. The video image is displayed on the DMD chip. The micromirrors on the chip (remember: each micromirror represents one pixel) then tilt very rapidly as the image changes. This process produces the grayscale foundation for the image. Then, color is added as light passes through a high-speed color wheel and is reflected off of the micromirrors on the DLP chip as they rapidly tilt towards or away from the light source. The degree of tilt of each micromirror coupled with the rapidly spinning color wheel determines the color structure of the projected image. As the amplified light bounces off the micromirrors, it is sent through the lens, reflected off a large single mirror, and onto the screen. Date Developed:

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For further technical explanations on DLP, check out my article: Rear Projection Televisions: DLPas well as the Texas Instruments DLP Website. However, it must be pointed out that DLP technology, while still being used in video projectors, is not longer being used in TVs as Rear Projection TVs, as product class, has been retired (read my report). This means that while there are still many DLP TVs in use, they are no longer being produced for the consumer market. OLED OLED is the newest TV technology available for consumers. It has been used in cell phones, tablets, and other small screen applications for a while - but beginning in 2013 it has been successfully applied to large screen consumer TV applications. OLED stands for Organic Light Emitting Diode. To keep it simple, the screen is made of pixel-sized, organically-based elements (no, they are not actually alive). OLED has some of the characteristics of both LCD and Plasma TVs. What OLED has in common with LCD is that OLED can be laid out in very thin layers, enabling thin TV frame design and energy efficient power consumption. However, just like LCD, OLED is subject to dead pixel defects. Plasma, LCD, DLP, and OLED TVs have a finite number of screen pixels, thus they are "fixed-pixel" displays. Input signals that have higher resolutions must be scaled to fit the pixel field count of the particular Plasma, LCD, DLP, or OLED display. For example, a typical 1080i HDTV broadcast signal needs a native display of 1920x1080 pixels for a one-to-one point display of the HDTV image. However, since Plasma, LCD, DLP, and OLED televisions can only display progressive images, 1080i source signals are always either deinterlaced to 1080p for display on a 1080p TV, or deinterlaced and scaled down to 768p, 720p, or 480p depending on the native pixel resolution of the specific TV. Technically, there is no such thing as a 1080i LCD, Plasma, DLP, or OLED TV.

LED/LCD TVs vs Standard LCD TVs Since LEDs are designed differently than standard fluorescent backlight systems, this means that the new LED backlit LCD sets offer the following differences with standard LCD sets: 1. Lower power consumption. 2. No Mercury used as in some other LCD backlight systems. 3. More balanced color saturation. 4. In LED/LCD TVs using the Full Array blacklight method, there is little or no light leakage in dark scenes. This contributes to even better black levels than traditional or LED Edge-lit LCDtelevisions. 5. LCD TVs that employ Full Array or Direct LED backlighting are thicker than LCD TVs that employ an Edge-lit LED light source. In other words, LED/LCD TVs that use the Edge backlight method can be made thinner than both standard LCD and Full Array LED/LCD televisions.

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LED Television and LCD

Introduction Television at the crossroads Television in substantially its present form has been with us for nearly 50 years. It is a tribute to the National Television Standards Committee (NTSC) that the color television standards agreed upon in the early 1950s have performed remarkably well making quite efficient use of valuable radio spectrum space and the psychovisual characteristics of the human eyebrain system. However, HDTV (High Definition TV) will supplant and ultimately replace the current standards. We will all come to expect its superior resolution, freedom from noise and ghosting, and pure CD sound. Yet, the perceived quality of TV broadcasts and cable will never likely be the major issue with most consumers. Content will continue to be the biggest problem. As of June 2009, all analog broadcasting in the USA has been discontinued by law, except for some low power local transmissions. This (so the justification goes) frees up a large amount of electromagnetic spectrum for other (more lucrative!) applications, since the Digital TV (DTV) channels occupy less bandwidth. Low cost DTV converter boxes enabled existing TVs to receive the digital signals so there was no need to buy new digital TVs, though this did make for one darn good excuse to upgrade to a 60" flat screen HDTV! :) There is plenty of information available elsewhere with regard to the pros and cons of the DTV conversion, the trials and tribulations of people using antennas (as opposed to cable or optical fiber), and the ultimate benefits, real and perceived. Suffice it to say that when digital reception is good, the picture and sound are very very good and there is essentially no comparison with the analog system it replaced. This is true even when a converter box is used with an analog TV in good condition and standard definition digital is better than the best analog. HDTV with multi-channel sound is simply exquisite. However, unlike analog TV, poor reception doesn't result in snow or ghosts, but rather the picture (and sound) totally drops out or (in the case of the video) freezes or pixilates. For Date Developed:

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over-the-air reception, the type of antenna and its orientation becomes much more critical. And even in areas close to the transmitter, local terrain and obstructions in the line-of-sight like hills and buildings may result in problems. Television receiver fundamentals The basic color television receiver must perform the same functions today as 40 years ago. (Since B/W is a subset of the color standard, most references in this document will be for color except as noted). A studio video monitor includes all of the functions of a television receiver except the tuner and IF (which rarely fail except for bad connections or perhaps lightning strikes to the antenna or cable connection). Therefore most of the repair information in this document is applicable to both TVs and studio monitors. Modern computer monitors share many similarities with TVs but the multisync and high scan rate deflection circuitry and more sophisticated power supplies complicates their servicing.

TV Repair Unlike VCRs or CD players where any disasters are likely to only affect your pocketbook, TVs can be dangerous. Read, understand, and follow the set of safety guidelines provided later in this section whenever working on TVs, monitors, or other similar high voltage equipment. If you do go inside, beware: line voltage (on large caps) and high voltage (on CRT) for long after the plug is pulled. There is the added danger of CRT implosion for carelessly dropped tools and often sharp sheetmetal shields which can injure if you should have a reflex reaction upon touching something you should not touch. In inside of a TV or monitor is no place for the careless or naive. Having said that, a basic knowledge of how a TV set works and what can go wrong can be of great value even if you do not attempt the repair yourself. It will enable you to intelligently deal with the service technician. You will be more likely to be able to recognize if you are being taken for a ride by a dishonest or just plain incompetent repair center. For example, a faulty picture tube CANNOT be the cause of a color television only displaying shows in black-and-white. The majority of consumers probably do not know even this simple fact. Such a problem is usually due to a bad capacitor or other 10 cent part. This document will provide you with the knowledge to deal with a large percentage of the problems you are likely to encounter with your TVs. It will enable you to diagnose problems and in many cases, correct them as well. With minor exceptions, specific manufacturers and models will not be covered as there are so many variations that such a treatment would require a huge and very detailed text. Rather, the most common problems will be addressed and enough basic principles of operation will be provided to enable you to narrow the problem down and likely determine a course of action for repair. In many cases, you will be able to do what is required for a fraction of the cost that would be charged by a repair center. Should you still not be able to find a solution, you will have learned a great deal and be able to ask appropriate questions and supply relevant information if you decide to post to Date Developed:

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sci.electronics.repair. It will also be easier to do further research using a repair text such as the ones listed at the end of this document. In any case, you will have the satisfaction of knowing you did as much as you could before taking it in for professional repair. With your new-found knowledge, you will have the upper hand and will not easily be snowed by a dishonest or incompetent technician.

Repair or replace If you need to send or take the TV to a service center, the repair could easily exceed half the cost of a new TV. Service centers may charge up to $50 or more for providing an initial estimate of repair costs but this will usually be credited toward the total cost of the repair (of course, they may just jack this up to compensate for their bench time).

TV Receivers Subsystems of a television set A TV set includes the following functional blocks: 1. Low voltage power supply (some may also be part of (2).) Most of the lower voltages used in the TV may be derived from the horizontal deflection circuits. Sometimes, there is a separate switching power supply but this would be the exception. Rectifier/filter capacitor/regulator from AC line provides the B+ to the switching power supply or horizontal deflection system. Degauss operates off of the line whenever power is turned on (after having been off for a few minutes) to demagnetize the CRT. 2. Horizontal deflection. These circuits provide the waveforms needed to sweep the electron beam in the CRT across and back some 15,734 times per second (for NTSC). The horizontal sync pulse from the sync separator locks the horizontal deflection to the video signal. 3. Vertical deflection. These circuits provide the waveforms needed to sweep the electron beam in the CRT from top to bottom and back 60 times per second (for NTSC). The vertical sync pulse from the sync separator locks the vertical deflection to the video signal. 4. CRT high voltage (also part of (2).) A modern color CRT requires up to 30 kV for a crisp bright picture. Rather than having a totally separate power supply, nearly every TV on the planet derives the HV (as well as many other voltages) from the horizontal deflection using a special transformer called a 'flyback' or 'Line OutPut Transformer (LOPT) for those of you on the other side of the lake. 5. Tuner, IF, AGC, video and audio demodulators. Input is the antenna or cable signal and output are baseband video and audio signals. There is usually someplace inside the TV where line level video and audio are present but it may not be accessible from the outside of the cabinet unless you paid for the more expensive model with the A/V Date Developed:

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option. Very often, the tuner is a shielded metal box positioned on the bottom right (as viewed from the front) separate from the main circuit board. Sometimes it is on the main circuit board. The IF section may be in either place. On older or cheap TVs with a knob tuner, this is usually mounted to the front panel by itself. There are usually separate boxes for the VHF and UHF tuners. 6. Chroma demodulator. Input is the baseband video signal. Outputs are the individual signals for the red, green, and blue video to the CRT. 7. Video drivers (RGB). These are almost always located on a little circuit board plugged directly onto the neck of the CRT. They boost the output of the chroma demodulator to the hundred volts or so needed to drive the cathodes of the CRT. 8. Sync separator. Input is baseband video. Output is horizontal and vertical sync pulses to control the deflection circuits. 9. Audio amplifier/output. The line level audio is amplified to drive a set of speakers. If this is a stereo TV, then these circuits must also perform the stereo demultiplexing. 10. System control. Most modern TVs actually use a microcontroller - a fixed program microcomputer to perform all user interface and control functions from the front panel and remote control. These are becoming increasingly sophisticated. However, they do not fail often. Older TVs use a bunch of knobs and switches and these are prone to wear and dirt. Most problems occur in the horizontal deflection and power supply sections. These run at relatively high power levels and some components run hot. The high voltage section is prone to breakdown and arcing as a result of hairline cracks, humidity, dirt, etc. The tuner components are usually quite reliable unless the antenna experiences a lightning strike. However, it seems that even after 20+ years of solid state TVs, manufacturers still cannot reliably solder the tuner connectors and shields so that bad solder connections in these areas are common even in new sets. Why projection TVs are not just normal TVs in big boxes In order to achieve the necessary brightness with a large display format, three separate monochrome CRTs are used with optics to combine the three images properly at the screen. This creates an entire set of additional problems in design. (The average projection TV has about twice as many parts as its direct-view counterpart. Some of the extra parts are essential for projection because CRT projection tubes require dynamic convergence. The other extra parts have to do with the fact that a more expensive TV also should have some extra features, like Dolby ProLogic sound, a satellite tuner and such.

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Generally, the electronics are based on a standard chassis that is also used for direct-view CRT television. Even the deflection circuits require minor adaptations at most. The highvoltage circuit is different because the EHT, focus and G2 voltages must be distributed over 3 CRTs. So this requires a special high-voltage part, which also includes an EHT capacitor and bleeder. There will be 3 CRT panels with video amplifiers. Because of the extremely high brightness, projection tubes will burn the phosphor screen immediately in fault conditions so a protection circuit is essential. And last but certainly not least, there is the dynamic convergence panel. The heart is a waveform generator IC, often of a Japanese brand but nowadays there's also a digital variant by Philips. The old-fashioned way requires many many potentiometers to program the waveforms. Then there's 5 or 6 convergence amplifiers and a corresponding extra power supply. And usually this is where the single deflection circuits are distributed to the 3 CRTs. At the same time the deflection currents are sensed for the protection circuits. Designing a PTV from a DVTV requires several man-years of work. In the factory, a special corner is devoted to the assembly. There you'll find specially educated people and the speed of the assembly line is a lot lower than usual. It requires many more adjustments, e.g. 3 optical and 3 electrical focus adjustments and then convergence. On-line tech-tips databases A number of organizations have compiled databases covering thousands of common problems with VCRs, TVs, computer monitors, and other electronic equipment. Most charge for their information but a few, accessible via the Internet, are either free or have a very minimal monthly or per-case fee. In other cases, a limited but still useful subset of the for-fee database is freely available. A tech-tips database is a collection of problems and solutions accumulated by the organization providing the information or other sources based on actual repair experiences and case histories. Since the identical failures often occur at some point in a large percentage of a given model or product line, checking out a tech-tips database may quickly identify your problem and solution. In that case, you can greatly simplify your troubleshooting or at least confirm a diagnosis before ordering parts. My only reservation with respect to tech-tips databases in general - this has nothing to do with any one in particular - is that symptoms can sometimes be deceiving and a solution that works in one instance may not apply to your specific problem. Therefore, an understanding of the hows and whys of the equipment along with some good old fashioned testing is highly desirable to minimize the risk of replacing parts that turn out not to be bad. The other disadvantage - at least from one point of view - is that you do not learn much by just following a procedure developed by others. There is no explanation of how the original diagnosis was determined or what may have caused the failure in the first place. Nor is there likely to be any list of other components that may have been affected by overstress and may Date Developed:

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fail in the future. Replacing Q701 and C725 may get your equipment going again but this will not help you to repair a different model in the future. Additional TV technology and repair information CRT Basics Note: Most of the information on TV and monitor CRT construction, operation, interference and other problems. has been moved to the document: TV and Monitor CRT (Picture Tube) Information. The following is just a brief introduction with instructions on degaussing. Color CRTs - shadow masks and aperture grills All color CRTs utilize a shadow mask or aperture grill a fraction of an inch (1/2" typical) behind the phosphor screen to direct the electron beams for the red, green, and blue video signals to the proper phosphor dots. Since the electron beams for the R, G, and B phosphors originate from slightly different positions (individual electron guns for each) and thus arrive at slightly different angles, only the proper phosphors are excited when the purity is properly adjusted and the necessary magnetic field free region is maintained inside the CRT. Note that purity determines that the correct video signal excites the proper color while convergence determines the geometric alignment of the 3 colors. Both are affected by magnetic fields. Bad purity results in mottled or incorrect colors. Bad convergence results in color fringing at edges of characters or graphics. The shadow mask consists of a thin steel or InVar (a ferrous alloy) with a fine array of holes one for each trio of phosphor dots - positioned about 1/2 inch behind the surface of the phosphor screen. With most CRTs, the phosphors are arranged in triangular formations called triads with each of the color dots at the apex of the triangle. With many TVs and some monitors, they are arranged as vertical slots with the phosphors for the 3 colors next to one another. An aperture grille, used exclusively in Sony Trinitrons (and now their clones as well), replaces the shadow mask with an array of finely tensioned vertical wires. Along with other characteristics of the aperture grille approach, this permits a somewhat higher possible brightness to be achieved and is more immune to other problems like line induced moiré and purity changes due to local heating causing distortion of the shadow mask. However, there are some disadvantages of the aperture grille design:    

Weight - a heavy support structure must be provided for the tensioned wires (like a piano frame). Price (proportional to weight). Always a cylindrical screen (this may be considered an advantage depending on your preference. Visible stabilizing wires which may be objectionable or unacceptable for certain applications. Date Developed:

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Apparently, there is no known way around the need to keep the fine wires from vibrating or changing position due to mechanical shock in high resolution tubes and thus all Trinitron monitors require 1, 2, or 3 stabilizing wires (depending on tube size) across the screen which can be see as very fine lines on bright images. Some people find these wires to be objectionable and for some critical applications, they may be unacceptable (e.g., medical diagnosis). Degaussing (demagnetizing) a CRT Degaussing may be required if there are color purity problems with the display. On rare occasions, there may be geometric distortion caused by magnetic fields as well without color problems. The CRT can get magnetized:  

 

if the TV or monitor is moved or even just rotated. if there has been a lightning strike nearby. A friend of mine had a lightning strike near his house which produced all of the effects of the EMP from a nuclear bomb. If a permanent magnet was brought near the screen (e.g., kid's magnet or megawatt stereo speakers). If some piece of electrical or electronic equipment with unshielded magnetic fields is in the vicinity of the TV or monitor.

Degaussing should be the first thing attempted whenever color purity problems are detected. As noted below, first try the internal degauss circuits of the TV or monitor by power cycling a few times (on for a minute, off for at least 20 minutes, on for a minute, etc.) If this does not help or does not completely cure the problem, then you can try manually degaussing. Note: Some monitors have a degauss button, and monitors and TVs that are microprocessor controlled may degauss automatically upon power-on (but may require pulling the plug to do a hard reset) regardless of the amount of off time. However, repeated use of these 'features' in rapid succession may result in overheating of the degauss coil or other components. The 20 minutes off/1 minute on procedure is guaranteed to be safe. (Some others may degauss upon power-on as long as the previous degauss was not done within some predetermined amount of time - they keep track with an internal timer.) On portable TVs, degauss may only function when they are run on AC, not the internal battery. If color purity problems are present, plugging the TV into an AC outlet may be needed to enable it to degauss itself. Commercial CRT Degausses are available from parts distributors like MCM Electronics and consist of a hundred or so turns of magnet wire in a 6-12 inch coil. They include a line cord and momentary switch. You flip on the switch, and bring the coil to within several inches of the screen face. Then you slowly draw the center of the coil toward one edge of the screen and trace the perimeter of the screen face. Then return to the original position of the coil being flat against the center of the screen. Next, slowly decrease the field to zero by backing straight up across the room as you hold the coil. When you are farther than 5 feet away you can release the line switch.

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The key word here is ** slow **. Go too fast and you will freeze the instantaneous intensity of the 50/60 Hz AC magnetic field variation into the ferrous components of the CRT and may make the problem worse. WARNING: Don't attempt to degauss inside or in the back of the set (near the CRT neck. This can demagnetize the relatively weak purity and convergence magnets which may turn a simple repair into a feature length extravaganza! It looks really cool to do this while the CRT is powered. The kids will love the color effects (but then lock your degaussing coil safely away so they don't try it on every TV and monitor in the house!). Bulk tape erasers, tape head degassers, open frame transformers, and the "butt-end" of a Weller soldering gun can be used as CRT demagnetizers but it just takes a little longer. (Be careful not to scratch the screen face with anything sharp. For the Weller, the tip needs to be in place to get enough magnetic field.) It is imperative to have the CRT running when using these whimpers approaches, so that you can see where there are still impurities. Never release the power switch until you're 4 or 5 feet away from the screen or you'll have to start over. I've never known of anything being damaged by excess manual degaussing as long as you don't attempt to degauss *inside* or the back of the set - it is possible to demagnetize geometry correction, purity, and static convergence magnets in the process! However, I would recommend keeping really powerful bulk tape erasers-turned-degassers a couple of inches from the CRT. Another alternative which has been known to work is to place another similar size monitor face-to-face with the suspect monitor (take care not to bump or scratch the screens!) and activate degauss function on the working monitor. While not ideal, this may be enough to also degauss the broken one. If an AC degaussing coil or substitute is unavailable, I have even done degaussed with a permanent magnet but this is not recommended since it is more likely to make the problem worse than better. However, if the display is unusable as is, then using a small magnet can do no harm. (Don't use a 20 pound speaker or magnetron magnet as you may rip the shadow mask right out of the CRT - well at least distort it beyond repair. What I have in mind is something about as powerful as a refrigerator magnet.) Keep degaussing fields away from magnetic media. It is a good idea to avoid degaussing in a room with floppies or back-up tapes. When removing media from a room remember to check desk drawers and manuals for stray floppies, too. It is unlikely that you could actually affect magnetic media but better safe than sorry. Of the devices mentioned above, only a bulk eraser or strong permanent magnet are likely to have any effect - and then only when at extremely close range (direct contact with media container).

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All color CRTs include a built-in degaussing coil wrapped around the perimeter of the CRT face. These are activated each time the CRT is powered up cold by a 3 terminal thermister device or other control circuitry. This is why it is often suggested that color purity problems may go away "in a few days". It isn't a matter of time; it's the number of cold power ups that causes it. It takes about 15 minutes of the power being off for each cool down cycle. These built-in coils with thermal control are never as effective as external coils. Note that while the monochrome CRTs used in B/W and projection TVs and mono monitors don't have anything inside to get magnetized, the chassis or other cabinet parts of the equipment may still need degaussing. While this isn't likely from normal use or even after being moved or reoriented, a powerful magnet (like that from a large speaker) could leave iron, steel, or other ferrous parts with enough residual magnetism to cause a noticeable problem.

TV Placement and Preventive Maintenance General TV placement considerations Proper care of a TV does not require much. Following the recommendations below will assure long life and minimize repairs:   

Subdued lighting is preferred for best viewing conditions but I will not attempt to tell you how to arrange your room! Locate the TV away from extremes of hot and cold. Avoid damp or dusty locations if possible. (Right you say, keep dreaming!) Allow adequate ventilation - TVs use more power than any of your other A/V components. Heat buildup takes its toll on electronic components. Leave at least 3 inches on top and sides for air circulation if the entertainment center does not have a wide open back panel. Do not pile other components like VCRs on top of the TV if possible (see below). Do not put anything on top of the TV that might block the ventilation grill in the rear or top of the cover. This is the major avenue for the convection needed to cool internal components. If possible, locate the VCR away from the TV. Some VCRs are particularly sensitive to interference from the TV's circuitry and while this won't usually damage anything, it may make for less than optimal performance due to RF interference. The reverse is sometimes true as well. In addition, modern VCRs are NOT built like the Brooklyn Bridge! The weight of a TV or stereo components could affect the VCR mechanically, messing up tape path alignment or worse.

If possible, locate your computer monitor away from the TV. Interaction of the electromagnetic fields of the deflection systems may result in one or both displays jiggling, wiggling, or vibrating. Date Developed:

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Locate loudspeakers and other sources of magnetic fields at least a couple of feet from the TV. This will minimize the possibility of color purity or geometry problems. Make sure all input-output video and audio connections are tight and secure to minimize intermittent or noisy pictures and sound. Use proper high quality cable only long enough to make connections conveniently. Finally, store video cassettes well away from all electronic equipment including and especially loudspeakers. Heat and magnetic fields will rapidly turn your priceless video collection into so much trash. The operation of the TV depends on magnetic fields for beam deflection. Enough said.

Preventive maintenance Preventive maintenance for a TV is pretty simple - just keep the case clean and free of obstructions. Clean the screen with a soft cloth just dampened with water and at most, mild detergent. DO NOT use anything so wet that liquid may seep inside of the set around the edge of the picture tube - you could end up with a very expensive repair bill when the liquid shorts out the main circuit board lurking just below. If the set has a protective flat glass faceplate, there is usually an easy way (on newer sets with this type of protection) of removing it to get at the inner face of the CRT. Clean both the CRT and the protective glass with a soft damp cloth and dry thoroughly. If you have not cleaned the screen for quite a while, you will be amazed at the amount of black grime that collects due to the static buildup from the high voltage CRT supply. In really dusty situations, periodically vacuuming inside the case and the use of contact cleaner for the controls might be a good idea but realistically, you will not do this so don't worry about it. For LCD TVs, LCD computer monitors, and laptop displays, the cleaning is particularly critical. The front surface of these facing the viewer is generally not made of glass like those in CRT displays, but rather a plastic layer or film. Thus, any cleaning method that uses harsh chemicals can permanently damage the screen, with or without an anti-reflection coating. Some glass cleaners, acetone (nail polish remover), and other strong solvents can attack the plastic very quickly. By the time you realize there is damage, it may be too late. And, of course, NEVER use anything even mildly abrasive. Warning about using a TV as a computer or video game display "I remember a while back (about 10 years) most home computers used to hook up to televisions. I seem to remember them having some effect on the TV though. I think they made the TV go blurry after a while. I was just wondering what these computers used to do to the televisions to mess them up like that. I thought a TV signal was a TV signal." Date Developed:

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The problem was screen burn. Since computers of that era were mostly text and video games tended to use fixed patterns for scenery, patterns tended to be burned into the phosphor such that they were noticeably darker and less sensitive in those areas. This was exacerbated by the tendency to run those devices at very high brightness levels. Modern computers and video games should not be nearly as much of a risk since the displays are so much more varied and dynamic. Nevertheless, setting the brightness at a moderate level would be prudent. However, projection sets with their much higher intensity CRTs may still be susceptible to screen burn and the manufacturer will likely NOT cover the cost of repairs. There is probably a disclaimer to this effect in the warranty. TV Troubleshooting SAFETY TVs and computer or video monitors are among the more dangerous of consumer electronic equipment when it comes to servicing. (Microwave ovens are probably the most hazardous due to high voltage at high power.) There are two areas which have particularly nasty electrical dangers: the non-isolated line power supply and the CRT high voltage. Major parts of nearly all modern TVs and many computer monitors are directly connected to the AC line - there is no power transformer to provide the essential barrier for safety and to minimize the risk of equipment damage. In the majority of designs, the live parts of the TV or monitor are limited to the AC input and line filter, degauss circuit, bridge rectifier and main filter capacitor(s), low voltage (B+) regulator (if any), horizontal output transistor and primary side of the fly back (LOPT) transformer, and parts of the startup circuit and standby power supply. The fly back generates most of the other voltages used in the unit and provides an isolation barrier so that the signal circuits are not line connected and safer. Since a bridge rectifier is generally used in the power supply, both directions of the polarized plug result in dangerous conditions and an isolation transformer really should be used - to protect you, your test equipment, and the TV, from serious damage. Some TVs do not have any isolation barrier whatsoever - the entire chassis is live. These are particularly nasty. The high voltage to the CRT, while 200 times greater than the line input, is not nearly as dangerous for several reasons. First, it is present in a very limited area of the TV or monitor from the output of the fly back to the CRT anode via the fat HV wire and suction cup connector. If you don't need to remove the main board or replace the fly back or CRT, then leave it alone and it should not bite. Furthermore, while the shock from the HV can be quite painful due to the capacitance of the CRT envelope, it is not nearly as likely to be lethal since the current available from the line connected power supply is much greater.

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Safety guidelines These guidelines are to protect you from potentially deadly electrical shock hazards as well as the equipment from accidental damage. Note that the danger to you is not only in your body providing a conducting path, particularly through your heart. Any involuntary muscle contractions caused by a shock, while perhaps harmless in them, may cause collateral damage - there are many sharp edges inside this type of equipment as well as other electrically live parts you may contact accidentally. The purpose of this set of guidelines is not to frighten you but rather to make you aware of the appropriate precautions. Repair of TVs, monitors, microwave ovens, and other consumer and industrial equipment can be both rewarding and economical. Just be sure that it is also safe!      

Don't work alone - in the event of an emergency another person's presence may be essential. Always keep one hand in your pocket when anywhere around a powered line-connected or high voltage system. Wear rubber bottom shoes or sneakers. Don't wear any jewelry or other articles that could accidentally contact circuitry and conduct current, or get caught in moving parts. Set up your work area away from possible grounds that you may accidentally contact. Know your equipment: TVs and monitors may use parts of the metal chassis as ground return yet the chassis may be electrically live with respect to the earth ground of the AC line. Microwave ovens use the chassis as ground return for the high voltage. In addition, do not assume that the chassis is a suitable ground for your test equipment! If circuit boards need to be removed from their mountings, put insulating material between the boards and anything they may short to. Hold them in place with string or electrical tape. Prop them up with insulation sticks - plastic or wood. If you need to probe, solder, or otherwise touch circuits with power off, discharge (across) large power supply filter capacitors with a 2 W or greater resistor of 100 to 500 ohms/V approximate value (e.g., for a 200 V capacitor, use a 20K to 100K ohm resistor). Monitor while discharging and verify that there is no residual charge with a suitable voltmeter. In a TV or monitor, if you are removing the high voltage connection to the CRT (to replace the fly back transformer for example) first discharge the CRT contact (under the suction cup at the end of the fat HV wire). Use a 1M to 10M ohm 5 W or greater wattage (for its voltage hold off capability, not power dissipation) resistor on the end of an insulating stick or the probe of a high voltage meter. Discharge to the metal frame which is connected to the outside of the CRT. For TVs and monitors in particular, there is the additional danger of CRT implosion - take care not to bang the CRT envelope with your Date Developed:

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tools. An implosion will scatter shards of glass at high velocity in every direction. There is several tons of force attempting to crush the typical CRT. While implosion is not really likely even with modest abuse, why take chances? However, the CRT neck is relatively thin and fragile and breaking it would be very embarrassing and costly. Always wear eye protection when working around the back side of a CRT. Connect/disconnect any test leads with the equipment unpowered and unplugged. Use clip leads or solder temporary wires to reach cramped locations or difficult to access locations. If you must probe live, put electrical tape over all but the last 1/16" of the test probes to avoid the possibility of an accidental short which could cause damage to various components. Clip the reference end of the meter or scope to the appropriate ground return so that you need to only probe with one hand. Perform as many tests as possible with power off and the equipment unplugged. For example, the semiconductors in the power supply section of a TV or monitor can be tested for short circuits with an ohmmeter. Use an isolation transformer if there is any chance of contacting line connected circuits. A Variac(tm) is not an isolation transformer! The use of a GFCI (Ground Fault Circuit Interrupter) protected outlet is a good idea but will not protect you from shock from many points in a line connected TV or monitor, or the high voltage side of a microwave oven, for example. (Note however, that, a GFCI may nuisance trip at power-on or at other random times due to leakage paths (like your scope probe ground) or the highly capacitive or inductive input characteristics of line powered equipment.) A fuse or circuit breaker is too slow and insensitive to provide any protection for you or in many cases, your equipment. However, these devices may save your scope probe ground wire should you accidentally connect it to a live chassis. Don't attempt repair work when you are tired. Not only will you be more careless, but your primary diagnostic tool - deductive reasoning - will not be operating at full capacity. Finally, never assume anything without checking it out for yourself! Don't take shortcuts!

Warning about disconnecting CRT neck board Some manufacturers warn against powering a TV or monitor CRT without the CRT neck board connected. Apparently, without something - anything to drain the charge resulting from the current flow due to residual gas ions inside the CRT, the shortest path may be through the glass neck of the tube to the yoke or from the pins outside the CRT to whatever is nearby. There aren't many ions in a modern CRT but I suppose a few here, a few there, and eventually they add up to enough to cause a major disaster at least on some CRTs.

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This is probably not a problem on small CRTs but for large ones with high high voltages and high deflection angles where the glass of the neck is very thin to allow for maximum deflection sensitivity, the potential does exist for arcing through the glass to the yoke to occur, destroying the CRT. There is really no way to know which models will self destruct but it should be possible to avoid such a disaster by providing a temporary return path to the DAG ground of the CRT (NOT SIGNAL GROUND!!) via the focus or G2 pins preferably through a high value high voltage rated resistor just in case one of these is shorted. This probably applies mostly to large direct-view TVs since they use high deflection angle CRTs but it won't hurt to take appropriate precautions with video and computer monitors as well.

Troubleshooting tips Many problems have simple solutions. Don't immediately assume that your problem is some combination of esoteric complex convoluted failures. For a TV, it may just be a bad connection or blown fuse. Remember that the problems with the most catastrophic impact on operation like a dead TV usually have the simplest solutions. The kind of problems we would like to avoid at all costs are the ones that are intermittent or difficult to reproduce: the occasional interference or a TV that refuses to play 'StarTrek Voyager'. If you get stuck, sleep on it. Sometimes, just letting the problem bounce around in your head will lead to a different more successful approach or solution. Don't work when you are really tired - it is both dangerous (especially with respect to TVs) and mostly non-productive (or possibly destructive). Whenever working on precision equipment, make copious notes and diagrams. You will be eternally grateful when the time comes to reassemble the unit. Most connectors are keyed against incorrect insertion or interchange of cables, but not always. Apparently identical screws may be of differing lengths or have slightly different thread types. Little parts may fit in more than one place or orientation. Etc. Etc. Pill bottles, film canisters, and plastic ice cube trays come in handy for sorting and storing screws and other small parts after disassembly. This is particularly true if you have repairs on multiple pieces of equipment under way simultaneously. Select a work area which is wide open, well lighted, and where dropped parts can be located not on a deep pile shag rug. The best location will also be relatively dust free and allow you to suspend your troubleshooting to eat or sleep or think without having to pile everything into a cardboard box for storage. Another consideration is ESD - Electro-Static Discharge. Some components (like ICs) in a TV are vulnerable to ESD. There is no need to go overboard but taking reasonable precautions such as getting into the habit of touching a **safe** ground point first.

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WARNING: even with an isolation transformer, a live chassis should **not** be considered a safe ground point. When the set is unplugged, the tuner shield or other signal ground points should be safe and effective. A basic set of precision hand tools will be all you need to disassemble a TV and perform most adjustments. These do not need to be really expensive but poor quality tools are worse than useless and can cause damage. Needed tools include a selection of Philips and straight blade screwdrivers, socket drivers, needlenose pliers, wire cutters, tweezers, and dental picks. For adjustments, a miniature (1/16" blade) screwdriver with a non-metallic tip is desirable both to prevent the presence of metal from altering the electrical properties of the circuit and to minimize the possibility of shorting something from accidental contact with the circuitry. A set of plastic alignment tools will be useful for making adjustments to coils and RF transformers. A low power (e.g., 25 W) fine tip soldering iron and fine rosin core solder will be needed if you should need to disconnect any soldered wires (on purpose or by accident) or replace soldered components. A higher power iron or small soldering gun will be needed for dealing with larger components. CAUTION: You can easily turn a simple repair (e.g., bad solder connections) into an expensive mess if you use inappropriate soldering equipment and/or lack the soldering skills to go along with it. If in doubt, find someone else to do the soldering or at least practice, practice, practice, soldering and desoldering on a junk circuit board first! See the document:

Troubleshooting and Repair of Consumer Electronic Equipment for additional info on soldering and rework techniques. For thermal or warm-up problems, a can of 'cold spray' or 'circuit chiller' (they are the same) and a heat gun or blow dryer come in handy to identify components whose characteristics may be drifting with temperature. Using the extension tube of the spray can or making a cardboard nozzle for the heat gun can provide very precise control of which components you are affecting. For info on useful chemicals, adhesives, and lubricants, see "Repair Briefs, an Introduction" as well as other documents available at this site. Test equipment Don't start with the electronic test equipment, start with some analytical thinking. Your powers of observation (and a little experience) will make a good start. Your built in senses and that stuff between your ears represents the most important test equipment you have. However, some test equipment will be needed: 

Multimeter (DMM or VOM) - This is essential for checking of power supply voltages and voltages on the pins of ICs or other components service literature like the Sams' Photo facts described elsewhere in Date Developed:

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this document include voltage measurements at nearly every circuit tie point for properly functioning equipment. The multimeter will also be used to check components like transistors, resistors, and capacitors for correct value and for shorts or opens. You do not need a fancy instrument. A basic DMM - as long as it is reliable - will suffice for most troubleshooting. If you want one that will last for many years, go with a Fluke. However, even the mid range DMMs from Radio Shack have proven to be reliable and of acceptable accuracy. For some kinds of measurements - to deduce trends for example - an analog VOM is preferred (though some DMMs have a bar graph scale which almost as good). Oscilloscope - While many problems can be dealt with using just a multimeter, a 'scope will be essential as you get more into advanced troubleshooting. Basic requirements are: dual trace, 10-20 MHz minimum vertical bandwidth, delayed sweep desirable but not essential. A good set of proper 10X/1X probes. Higher vertical bandwidth is desirable but most consumer electronics work can be done with a 10 MHz scope. A storage scope or digital scope might be desirable for certain tasks but is by no means essential for basic troubleshooting. A video signal source - both RF and baseband (RCA jacks). Unless you are troubleshooting tuner or video/audio input problems, either one will suffice. RF sources include a pair of rabbit ears or an outdoor antenna, a cable connection, or a VCR with a working RF modulator. This will be more convenient than an antenna connection and will permit you to control the program material. In fact, making some test tapes using a camcorder or video camera to record static test patterns will allow you full control of what is being displayed and for how long. Color bar/dot/crosshatch signal generator. This is a useful piece of equipment if you are doing a lot of TV or monitor repair and need to perform CRT convergence and chroma adjustments. However, there are alternatives that are almost as good: a VHS recording of these test patterns will work for TVs. A PC programmed to output a suitable set of test patterns will be fine for monitors (and TVs if you can set up the video card to produce an NTSC/PAL signal. This can be put through a VCR to generate the RF (Channel 3/4) input to your TV if it does not have direct video inputs (RCA jacks).

Incredibly Handy widgets These are the little gadgets and homemade testers that are useful for many repair situations. Here are just a few of the most basic: 

Series light bulb for current limiting during the testing of TVs, monitors, switching power supplies, audio power amplifiers, etc. I built a dual outlet box with the outlets wired in series so that a lamp can be plugged into one outlet and the device under test into the Date Developed:

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other. For added versatility, add a regular outlet and 'kill' switch using a quad box instead. The use of a series load will prevent your expensive replacement part like a horizontal output transistor from blowing if there is still some fault in the circuit you have failed to locate. A Variac. It doesn't need to be large - a 2 A Variac mounted with a switch, outlet and fuse will suffice for most tasks. However, a 5 amp or larger Variac is desirable. If you will be troubleshooting 220 VAC equipment in the US, there are Variacs that will output 0-240 VAC from a 115 VAC line (just make sure you don't forget that this can easily fry your 115 VAC equipment.) By varying the line voltage, not only can you bring up a newly repaired TV gradually to make sure there are no problems but you can also evaluate behavior at low and high line voltage. This can greatly aid in troubleshooting power supply problems. Warning: a Variac is not an isolation transformer and does not help with respect to safety. You need an isolation transformer as well. Isolation transformer. This is very important for safely working on live chassis equipment. Since all modern TVs use a line connected power supply, it is essential. You can build one from a pair of similar power transformers back-to-back (with their highest rated secondaries connected together. I built mine from a couple of similar old tube type TV power transformers mounted on a board with an outlet box including a fuse. Their high voltage windings were connected together. The unused low voltage windings can be put in series with the primary or output windings to adjust voltage. Alternatively, commercial line isolation transformers suitable for TV troubleshooting are available for less than $100 - well worth every penny. Variable isolation transformer. You don't need to buy a fancy combination unit. A Variac can be followed by a normal isolation transformer. (The opposite order also works. There may be some subtle differences in load capacity.).

CAUTION: Keep any large transformer of this type well away from your monitor or TV. The magnetic field it produces may cause the picture to wiggle or the colors to become messed up - and you to think there is an additional problem! 

Degaussing coil. Make or buy. The internal degaussing coil salvaged from a defunct TV doubled over to half it original diameter to increase its strength in series with a 200 W light bulb for current limiting will work just fine. Or, buy one from a place like MCM Electronics - about $15 for one suitable for all but the largest TVs. Also, see the section: Degaussing (demagnetizing) a CRT.

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Safe discharging of capacitors in TVs and video monitors It is essential - for your safety and to prevent damage to the device under test as well as your test equipment - that large or high voltage capacitors be fully discharged before measurements are made, soldering is attempted, or the circuitry is touched in any way. Some of the large filter capacitors commonly found in line operated equipment store a potentially lethal charge. This doesn't mean that every one of the 250 capacitors in your TV need to be discharged every time you power off and want to make a measurement. However, the large main filter capacitors and other capacitors in the power supplies should be checked and discharged if any significant voltage is found after powering off (or before any testing - the CRT capacitance in a TV or video monitor, for example, can retain a dangerous or at least painful charge for days or longer!) The technique I recommend is to use a high wattage resistor of about 5 to 50 ohms/V of the working voltage of the capacitor. This isn't critical - a bit more or less will be fine but will affect the time it takes to fully discharge the capacitor. The use of a current limiting resistor will prevent the arc-welding associated with screwdriver discharge but will have a short enough time constant so that the capacitor will drop to a low voltage in at most a few seconds (dependent of course on the RC time constant and its original voltage). Obviously, make sure that you are well insulated! 

For the main capacitors in a TV or monitor power supply which might be 400 uF at 200 V, this would mean a 5K, 10W resistor. RC = 2 seconds. 5RC = 10 seconds. A lower wattage resistor can be used since the total energy in not that great. If you want to be more high tech, you can build the capacitor discharge circuit outlined in the companion document: Capacitor Testing, Safe Discharging, and Other Related Information. This provides a visible indication of remaining charge and polarity. For the CRT, use a several M ohm resistor good for 30 kV or more (or a string of lower value resistors to obtain this voltage rating). A 1/4 watt job will just arc over! Discharge to the chassis ground connected to the outside of the CRT - NOT SIGNAL GROUND ON THE MAIN BOARD as you may damage sensitive circuitry. The time constant is very short - a ms or so. However, repeat a few times to be sure, then use a shorting clip as these capacitors have a way of recovering a painful charge if left alone - there have been too If you are not going to be removing the CRT anode connection, replacing the flyback, or going near the components on the little board on the neck of the CRT, I would just stay away from the fat red wire and what it is connected to including the focus and screen wires. Repeatedly shoving a screwdriver under the anode cap risks scratching the CRT envelope which is something you really do not want to do.

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Again, always double check with a reliable voltmeter! Reasons to use a resistor and not a screwdriver to discharge capacitors: 1. It will not destroy screwdrivers and capacitor terminals. 2. It will not damage the capacitor (due to the current pulse). 3. It will reduce your spouse's stress level in not having to hear those scary snaps and crackles. Additional information on discharging CRTs 'Dag' is short for Aquadag. It is a type of paint made of a graphite pigment which is conductive. It is painted onto the inside and outside of picture tubes to form the 2 plates of a high voltage filter capacitor using the glass in between as dielectric. This capacitor is between .005uF and .01uF in value. This seems like very little capacity but it can store a substantial charge with 25,000 volts applied. The outside "Dag" is always connected to the circuit chassis ground via a series of springs, clips, and wires around the picture tube. The high voltage or "Ultor" terminal must be discharged to chassis ground before working on the circuit especially with older TV's which didn't use a voltage divider to derive the focus potential or newer TV's with a defective open divider. CAUTION: The Dag coating/springs/clips/etc. may not be the same as signal ground on the main board. Discharging to that instead could result in all sorts of expensive blown components. Discharging between the CRT anode cap and Dag should be low risk though it is best to use a HV probe or properly rated high value resistor. . Removing the CRT HV connector WARNING: Make sure the CRT has been discharged FIRST! The rubber part is usually not glued down so it can be lifted rather easily. However, there may be some silicone type grease between the rubber boot (that looks like a suction cup) and the CRT glass to seal out dust. A metal clip with a spring keeping it spread out attaches inside the button. While there are a variety of types of clips actually used, pushing the connector to one side and/or squeezing it in the appropriate direction (peel up one side of the rubber to inspect) while gently lifting up should free it. Probably :-). The clip (when removed) and CRT button look sort of like this: ||======= HV Cable /\ Date Developed:

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Clip (Removed)

| _|

| |_

(No DAG coating in vicinity of HV connector) ____________.-.___________ CRT ____________|______|___________ Glass Metal Button Replacement is done in reverse order! This isn't rocket science and excessive force should not be needed! :-) Safe troubleshooting techniques for line powered TVs TVs are particularly dangerous with respect to troubleshooting due to the fact that a substantial portion of their circuitry - sometimes all of it - is directly line connected. Even if your are working in a totally unrelated area like the sound circuits, awareness of the general design and location of the line-connected circuits can prove to be a life saver. These designs may take several forms: 1. Separate switch mode power supply (SMPS): In this case, only the primary side of the power supply is line connected. The remainder of the TV is usually isolated from the line by the high frequency transformer and feedback device (transformer or opt isolator) of the switch mode power supply. 2. On-board SMPS: A portion of the circuitry on the main board is directly line-connected. In the best case, this is restricted to the area around the power cord connections and well marked on both top and bottom but don't count on it. Again, the rest of the TV may be isolated but avoiding hazardous areas is more difficult especially in cramped quarters. 3. Flyback derived power supply: A non-isolated linear (usually) power supply provides B+ to the horizontal deflection (and startup circuit). All other system power is derived from secondary windings on the flyback transformer. Similar comments to (2) above apply. (1) to (3) may be found in TVs with A/V inputs and outputs. 4. Full hot chassis: A bridge rectifier/filter capacitor/linear regulator provides some voltages including B+. The fly back secondary’s provide the remaining voltages. All share a common return which is at the intersection of two of the diodes of the bridge rectifier. There is no isolation. Always use an isolation transformer, whatever kind of design is used in the equipment you are troubleshooting. There are very few situations in which an isolation transformer will hurt. If you use it automatically, you will never have a chance to screw up. Date Developed:

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Identify the appropriate ground point (return) for your multimeter or scope. These should be marked in the Sams' Photofact or service manual. There may be several such returns such as: non-isolated, signal, and CRT. Selecting the wrong one - even momentarily connecting to it can ruin your whole day. If you are not using an isolation transformer (a no-no), connecting your scope to the wrong ground point can result in (1) blown fuses and/or blown parts, and a very dangerous situation and (2) readings that don't make sense generally with distorted power line frequency signals of high amplitude.  Use the non-isolated ground (A) (with your isolation transformer on the TV *only* for measurements of voltage on the line-connected power supply.  Use the signal ground (B) for all measurements of tuner, IF, video, and sound circuits. Whenever you get a reading or waveform that is grossly wrong, confirm that you are using the proper ground point! Note that failures of fusible resistors in the *return* of the HOT or power supply chopper or elsewhere can also result in points that should be near ground floating at unexpected voltage levels. The general arrangement of components for a typical TV using a linear B+ supply with isolated auxiliary supplies for the signal circuits is shown below including the (linear) lineconnected power supply, horizontal deflection output (drive, horizontal output transistor, flyback), and a typical Aux power supply output.

For this power supply, what if?: 1. You connect your scope ground clip to the non-isolated ground (A) and you are *not* using an isolation transformer? Answer: you blow the line fuse and/or melt your scope probe ground lead. Other parts may be damaged as well. In effect, you have just shorted across the bottom diode of the bridge. 2. You attempt to monitor a video signal with your scope ground connected to the non-isolated ground (A)? Answer: you see only a highly distorted power line waveform of roughly 100 V p-p In effect; you are measuring across one of the diodes of the bridge rectifier, stray capacitance, etc. The series light bulb trick When powering up a TV (or any other modern electronic devices with expensive power semiconductors) that has had work done on any power circuits, it is desirable to minimize the chance of blowing your newly installed parts should there still be a fault. There are two ways of doing this: Date Developed:

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use of a Variac to bring up the AC line voltage gradually and the use of a series load to limit current to power semiconductors. Actually using a series load - a light bulb is just a readily available cheap load - is better than a Variac (well both might be better still) since it will limit current to (hopefully) nondestructive levels. What you want to do is limit current to the critical parts - usually the horizontal output transistor (HOT). Most of the time you will get away with putting it in series with the AC line. However, sometimes, putting a light bulb directly in the B+ circuit will be needed to provide adequate protection. In that location, it will limit the current to the HOT from the main filter capacitors of line connected power supplies. This may also be required with some switch mode power supplies as they can still supply bursts of full (or excessive) current even if there is a light bulb in series with the AC line. Actually, an actual power resistor is probably better as its resistance is constant as opposed to a light bulb which will vary by 1:10 from cold to hot. The light bulb, however, provides a nice visual indication of the current drawn by the circuit under test. For example:  

Full brightness: short circuit or extremely heavy load - a fault probably is still present. Initially bright but then settles at reduced brightness: filter capacitors charge, then lower current to rest of circuit. This is what is expected when the equipment is operating normally. There could still be a problem with the power circuits but it will probably not result in an immediate catastrophic failure. Pulsating: power supply is trying to come up but shutting down due to overcurrent or overvoltage condition. This could be due to a continuing fault or the light bulb may be too small for the equipment.

Note: for a TV or monitor, it may be necessary (and desirable) to unplug the degauss coil as this represents a heavy initial load which may prevent the unit from starting up with the light bulb in the circuit. The following are suggested starting wattages:   

40 W bulb for VCR or laptop computer switching power supplies. 100 W bulb for small (i.e., B/W or 13 inch color) TVs. 150 to 200 W bulb for large color or projection TVs.

A 50/100/150 W (or similar) 3-way bulb in an appropriate socket comes in handy for this but mark the switch so that you know which setting is which! Depending on the power rating of the equipment, these wattages may need to be increased. However, start low. If the bulb lights at full brightness, you know there is still a major fault. If it flickers or the TV (or other device) does not quite come fully up, then it should be safe to go to a larger bulb. Resist the temptation to immediately remove the series light bulb totally Date Developed:

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from the circuit at this point - I have been screwed by doing this. Try a larger one first. The behavior should improve. If it does not, there is still a fault present. Specific considerations before poking around inside a TV or monitor Both electrical and mechanical dangers lurk: 

Main filter capacitor(s). This is the most dangerous (not the HV as you would expect). Fortunately, these capacitors will normally discharge in a few minutes or less especially if the unit is basically working as the load will normally discharge the capacitors nearly fully as power is turned off. With TVs, the main filter capacitor is nearly always on the mainboard. Monitors are more likely to have a separate power supply module. However, you should check across this capacitor - usually only one and by far the largest in the set - with a voltmeter and discharge as suggested in the section: Safe discharging of capacitors in TVs and video monitors if it holds more than a few volts (or wait longer) before touching anything. Some of these are as large as 1,000 uF charged to 160 V - about 13 w-s or a similar amount of energy as that stored in an electronic flash. This is enough to be potentially lethal under the wrong circumstances.

High Voltage capacitor formed by the envelope of the CRT. It is connected to the flyback transformer by the fat (usually red) wire at the suction cup (well, it looks like one anyhow) attached to the CRT. This capacitor can hold a charge for quite a while - weeks in the case of an old tube type TV! If you want to be doubly sure, discharge this also. However, unless you are going to be removing the HV connector/flyback, it should not bother you. The energy stored is about 1 w-s but if you touch it or come near to an exposed terminal, due to the high voltage, you will likely be handed *all* the energy and you *will* feel it. The danger is probably more in the collateral damage when you jump ripping flesh and smashing your head against the ceiling. Some people calibrate their jump based on voltage - about 1 inch/V. :-). There will be some HV on the back of the circuit board on the neck of the CRT but although you might receive a tingle but accidentally touching the focus or screen (G2) pins, it is not likely to be dangerous.

CRT implosion risk. Don't hammer on it. However, it is more likely that you will break the neck off the tube since the neck is relatively weak. This will ruin your whole day and the TV or monitor but will Date Developed:

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likely not result in flying glass everywhere. Just, don't go out of your way to find out. Sharp sheet metal and so forth. This is not in itself dangerous but a reflex reaction can send your flesh into it with nasty consequences.

Dusting out the inside of a TV The first thing you will notice when you remove the cover is how super dusty everything is. Complements to the maid. You never dreamed there was that much dust, dirt, and grime, in the entire house! Use a soft brush (like a new paintbrush) and a vacuum cleaner to carefully remove the built up dust. Blowing off the dust will likely not hurt the TV unless it gets redeposited inside various controls or switches but will be bad for your lungs - and will spread it all over the room. Don't turn anything - many critical adjustments masquerade as screws that just beg to be tightened. Resist the impulse for being neat and tidy until you know exactly what you are doing. Be especially careful around the components on the neck of the CRT - picture tube - as some of these are easily shifted in position and control the most dreaded of adjustments - for color purity and convergence. In particular, there will be a series of adjustable ring magnets. It is a good idea to mark their position in any case with some white paint, 'white out', or a Magic Marker so that if they do get moved - or you move them deliberately, you will know where you started.

Troubleshooting a TV with the main board disconnected There are times when it is desirable to remove the chassis or main board and work on it in a convenient location without having to worry about the equipment which will simulate the critical functions but this is rarely an option for the doit-yourselfer. My approach is usually to do as much work as possible without removing the main board and not attempt to power it up when disconnected since there are too many unknowns. Professionals will plug the chassis into a piece of equipment which will simulate the critical functions. Note that if you have a failure of the power supply - blown fuse, startup, etc., then it should be fine to disconnect the CRT since these problems are usually totally unrelated. Tests should be valid. However, if you really want to do live testing with the main board removed, here are some considerations. There are usually several connections to the CRT and cabinet: 

Deflection yoke - since the horizontal coils are part of the horizontal flyback circuit, there could be problems running without a yoke. This could be anything from it appearing totally dead to an overheating or blown horizontal output transistor. There may be no problems. Vertical and any convergence coils may or may not be problems as well.

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 

  

CRT video Driver board - pulling this should not usually affect anything except possibly video output and bias voltages. CRT 2nd anode - without the CRT, there will be no capacitor to filter the high voltage and you would certaily want to insulate the HV connector **real** well. I do not know whether there are cases where damage to flyback could result from running in thie manner, however. Front panel controls - disconnecting these may result in inability to even turn the set on, erratic operation, and other unexpected behavior. Degauss - you just won't have this function when disconnected. But who cares - you are not going to be looking at the screen anyhow. Remote sensor - no remote control but I doubt that the floating signals will cause problems. Speakers - there will be no audio but this should not cause damage.

If you do disconnect everything, make sure to label any connectors whose location or orientation may be ambiguous. Most of the time, these will only fit one way but not always.

TV Adjustments These include both controls accessible to the user (and often not understood) as well as internal adjustments that may need to be touched up due to the aging of components or following a repair. User picture adjustment For general viewing, subdued lighting but not total darkness is probably best. However, for most dramatic impact, a darkened environment may be preferred. Make the following adjustments under the expected viewing conditions. Tune to a strong channel or play a good quality tape. Turn the brightness, contrast, and color controls all the way down. Center the tint control (NTSC, may not be present on PAL sets). Increase the brightness until a raster is just visible in the darkest (shadow) areas of the picture and then back off until it **just** disappears. Increase the contrast until the desired intensity of highlights is obtained. Since brightness and contrast are not always independent, go back and forth until you get the best picture. Initially adjust the color control for pastel shades rather than highly saturated color. Set the tint control for best flesh tones. Then, increase the color control to obtain the desired degree of color saturation. Date Developed:

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Internal adjustments All of the service adjustments are accomplished either using controls inside the set (though some may be accessible by holes in the rear of the cabinet). These are usually pots on the main board and CRT neck boards, or in newer TVs, mostly via a service menu accessed from the remote or by using a manufacturer specific computer interface.

Focus adjustment On a decent TV, you should be able to make out the individual scanning lines. If they are fuzzy, especially in bright areas, then focus may need to be adjusted. The focus pot is usually located on the flyback transformer or on an auxiliary panel nearby. Where there are two adjustment knobs on the flyback transformer, the top one is generally for focus and the bottom one is for G2. The focus wire usually comes from the flyback or the general area or from a terminal on a voltage the multiplier module (if used). It is usually a wire by itself going to the little board on the neck of the CRT. Let the set warm up for at least half an hour. Display a good quality signal. Turn the user color control all the way down and the brightness and contrast controls all the way up. This will be the worst case. Adjust the focus control for best overall sharpness - you may not be able to get it perfect everywhere - center as well as corners. If best focus is at one end of the focus pot's range and still not good enough, there may be a problem in the focus divider, focus pot, or some related component.

Adjustment of the internal SCREEN and color controls The screen should be adjusted with a white pattern (snow from the tuner should do or turn the user COLOR control all the way down to get a black and white picture). Put the set in Service mode (horizontal line) if it has such a switch in the back or inside. If not, just use the raster in a darkened room. Adjust screen for a dim white line (raster). If the line is not white at its dimmest point, you will need to adjust the drive and cutoff controls for R, G, & B. Alternatively, you can use the following procedure: Turn R, G, and B screen (or background) controls down. Now turn color control fully counterclockwise -- off. Now turn up red screen until the screen just shows a red hue. Now turn red gun down until red tint just goes away. Now do the same with the green and blue screen controls. Now adjust the two DRIVE controls for the best black and white picture. That`s all there is to it. I don`t like to work with just a thin "SETUP" line. Cartoons seem to be the best thing to have on while doing the above procedure. You can also use just plain snow (no program) if you prefer. If you can obtain a good b@w pic. when you`re done, the tube is good and the set if most likely functioning properly. Be patient and go slow while watching the large mirror that you are using during this procedure. (LEE) Date Developed:

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Optimal procedure for setting brightness/background and screen adjustments For slight tweaks, the following is not necessary. However, if someone turned all the internal controls or if you are making significant changes that affect G2 (screen), then following the procedure below is desirable to achieve best performance and maximize life of the CRT. The typical user controls - brightness and contrast can, of course, be set arbitrarily, depending on video content and ambient lighting conditions. Set the user brightness and contrast controls in the middle for the following adjustments and let the set warm up for 20 minutes or so.

The usual adjustment procedure is as follows: 

 

Use any low-level adjustments to set a black picture with all 3 cathode voltages at the specified level (e.g. 130 V) above the VG1 voltage (may be 0 V or 12 V or 20 V ?). (These are typically called RGB brightness, bias, or background level and are often on the little board on the neck of the CRT but not always --- sam). Adjust VG2 (screen) until one colour just starts too light up, turn it back down until the screen is just black again. (Occasionally, there are two G2 controls - one on the flyback and another on the CRT neck board or elsewhere. If so, they control are basically in series - leave the one on the flyback alone if the other one has enough range.) Now adjust 2 of the 3 low-level black controls until the other 2 colours just light up, and then back to black again. Select a white picture and use 2 low-level white (RGB drive or gain, also generally on the neck board --- sam) controls to set the proper colour temperature for white to your own taste. Check your black calibration again, may have to iterate a bit.

Color balance adjustment Color balance needs adjustment if the highlights and/or shadows of a black and white picture (turn the color control all the way down) are not a perfectly neutral gray. To adjust the color balance: Turn the color control all the way down so that you get what should be a B/W picture. Set the user brightness and contrast controls about mid-range. The tint control should not matter (if it does at this point, you have other chroma problems or an 'autocolor' switch is on limiting the range of some controls). Adjust the sub-brightness controls (may be called color screen, background, or the like) so that the dark areas of the picture are just visible and neutral gray. Then, adjust the color gain controls until the brightest areas are neutral white but not so bright that there is 'color bleeding' in the highlights.

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This should get you close. If something is still shifting after warmup and get some cold-spray or even a little blower and try to locate the component that is drifting. Most likely a transistor or capacitor.

Remember:  

Brightness sets black level; it should ideally be as black as the screen itself, no more, no less. Contrast sets white level. Too bright and vertical lines start to bend. Using just these concepts, you can get REAL close to a proper alignment.

CRT purity adjustment Purity on modern CRTs is usually set by a combination of a set of ring magnets just behind the deflection yoke on the neck of the CRT and the position of the yoke fore-aft. As always, mark the starting position of all the rings and make sure you are adjusting the correct set if rings! Use the following purity adjustment procedure as a general guide only. Depending on the particular model TV, the following purity adjustment procedure may substitute green for red depending on the arrangement of the guns in the CRT. This description is based on the Sams' Photofact for the RCA CTC111C chassis which uses a slot-mask CRT. The procedures for dot-mask and Trinitron (aperture grille) CRTs will vary slightly. See you service manual! Obtain a white raster (sometimes there is a test point that can be grounded to force this). Then, turn down the bias controls for blue and green so that you have a pure red raster. Let the set warm up for a minimum of 15 minutes. Loosen the deflection yoke clamp and move the yoke as far back as it will go, Adjust the purity magnets to center the red vertical raster on the screen. Move the yoke forward until you have the best overall red purity. Now, move the yoke forward until you have the best overall red purity. Tighten the clamp securely and reinstall the rubber wedges (if you set has these) to stabilize the yoke position. Reset the video adjustments you touched to get a red raster. CRT convergence adjustment In the good old days when TVs were TVs (and not just a picture tube with a little circuit board attached) there were literally drawers full of knobs for setting convergence. One could spend hours and still end up with a less than satisfactory picture. As the technology progressed, the number of electronic adjustments went down drastically so that today there are very few if any.

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Unless you want a lot of frustration, I would recommend not messing with convergence. You could end up a lot worse. I have no idea what is used for convergence on your set but convergence adjustments are never quite independent of one another. You could find an adjustment that fixes the problem you think you have only to discover some other area of the screen is totally screwed. In addition, there are adjustments for geometry and purity and maybe others that you may accidentally move without even knowing it until you have buttoned up the set. Warning: Accurately mark the original positions - sometimes you will change something that will not have an obvious effect but will be noticeable later on. So it is extremely important to be able to get back to where you started. If only red/green vertical lines are offset, then it is likely that only a single ring needs to be moved - and by just a hair. But, you may accidentally move something else! If you really cannot live with it, make sure you mark everything very carefully so you can get back to your current state. A service manual is essential! Convergence is set using a white crosshatch or dot test pattern. If you do not have a test pattern generator, any static scene (from a camcorder or previously recorded tape, for example) with a lot of fine detail will suffice. Turn the color control all the way down so you have a B/W picture. Static convergence sets the beams to be coincident in the exact center of the screen. This is done using a set of ring magnets behind the purity magnets on the CRT neck.

Tilted picture You have just noticed that the picture on your fancy (or cheap) TV is not quite horizontal - not aligned with the front bezel. Note that often there is some keystoning as well where the top and bottom or left and right edges of the picture are not quite parallel - which you may never have noticed until now. Since this may not be correctable, adjusting tilt may represent a compromise at best between top/bottom or left/right alignment of the picture edges. You may never sleep again knowing that your TV picture is not perfect! BTW, I can sympathize with your unhappiness. Nothing is more annoying than a just noticeable imperfection such as this. However, since TVs always overscan, the only time you will really notice a minor tilt without going out of your way to look for it is if there is text or graphics near the edge of the screen. There are several possible causes for a tilted picture: 1. Set orientation. The horizontal component of the earth's magnetic field affects this slightly. Therefore, if you rotate the TV you may be able to correct the tilt. Of course, it will probably want to face the wall!

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Other external magnetic fields can sometimes cause a rotation without any other obvious effects - have you changed the TV's location? Did an MRI scanner move in next door? 2. Need for degaussing. Most of the time, magnetization of the CRT will result in color problems which will be far more obvious than a slight rotation. However, internal or external shields or other metal parts in the set could become magnetized resulting a tilt. More extensive treatment than provided by the built-in degaussing coil may be needed. Even, the normal manual degaussing procedure may not be enough to get close enough to all the affected parts. 3. You just became aware of it but nothing has changed. Don't dismiss this offhand. It is amazing how much we ignore unless it is brought to our attention. Are you a perfectionist? 4. There is an external tilt control which may be misadjusted. Newer Sony monitors have this (don't know about TVs) - a most wonderful addition. Too bad about the stabilizing wires on Trinitron CRTs. A digital control may have lost its memory accidentally. The circuitry could have a problem. 5. There is an internal tilt control that is misadjusted or not functioning. The existance of such a control is becoming more common. 6. The deflection yoke on the CRT has gotten rotated or was not oriented correctly at the time of the set's manufacture. Sometimes, the entire yoke is glued in place in addition to being clamped adding another complication. If the TV was recently bumped or handled roughly, the yoke may have been knocked out of position. But in most cases, the amount of abuse required to do this with the yoke firmly clamped and/or glued would have totally destroyed the set in the process. There is a risk (in addition to the risk of frying yourself on the various voltages present inside an operating TV) of messing up the convergence or purity when fiddling with the yoke or anything around it since the yoke position on the neck of the tube and its tilt may affect purity and convergence. Tape any rubber wedges under the yoke securely in place as these will maintain the proper position and tilt of the yoke while you are messing with it. (Don't assume the existing tape will hold - the adhesive is probably dry and brittle). 7. The CRT may have rotated slightly with respect to the front bezel. Irrespective of the cause of the tilt, sometimes it is possible to loosen the 4 (typical) CRT mounting screws and correct the tilt by slightly rotating the CRT. This may be easier than rotating the yoke. Just make sure to take proper safety precautions when reaching inside! B/W TV size, position, and geometry adjustments These tend to be a lot simpler and less critical than for color monitors or TV sets. Date Developed:

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On a B/W TV you will probably see some of the following adjustments: 1. Position - a pair of rings with tabs on the neck of the CRT. There may be electronic position adjustements as well though this is not that common on small TVs. 2. Width and height (possibly linearity as well) controls. There may be some interaction between size and linearity - a crosshatch test pattern is best for this. Vertical adjustments are almost always pots while horizontal (if they exist) may be pots and/or coils. Size will normally be set for 5-10% overscan to account for line voltage fluctuations and component drift. Confirm aspect ratio with test pattern which includes square boxes. 3. Geometry - some little magnets either on swivels around the yoke or glued to the CRT. If these shifted, the the edges may have gotten messed up - wiggles, dips, concave or convex shapes. There may be a doxen or more each mostly affecting a region around the edge of the raster. However, they will not be totally independent. Check at extremes of brightness/contrast as there may be some slight changes in size and position due to imperfect HV regulation. There may be others as well but without a service manual; there is no way of knowing for sure. Sams' often has folders for B/W TVs. Just mark everything carefully before changing - then you will be able to get back where you started.

Low Voltage Power Supply Problems Low voltage power supply fundamentals TVs require a variety of voltages (at various power levels) to function. The function of the low voltage power supply is to take the AC line input of either 115 VAC 60 Hz (220 VAC 50 Hz or other AC power in Europe and elsewhere) and produce some of these DC voltages. In all cases, the power to the horizontal output transistor of the horizontal deflection system is obtained directly from the low voltage power supply. In some cases, a variety of other DC voltages are derived directly from the AC line by rectification, filtering, and regulation. In other designs, however, most of the low voltages are derived from secondary windings on the flyback (LOPT) transformer of the horizontal deflection system. In still other designs, there is a separate switchmode power supply that provides some or all of these voltages. There are also various (and sometimes convoluted) combinations of any or all of the above. There will always be: 1. A power switch, relay, or triac to enable main power. Date Developed:

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2. A set of rectifiers - usually in a bridge configuration - to turn the AC into DC. Small ceramic capacitors are normally placed across the diodes to reduce RF interference. 3. One or more large filter capacitors to smooth the unregulated DC. In the U.S., this is most often a voltage around 150-160 V DC. In countries with 220 VAC power, it will typically be around 300-320 V DC. 4. A discrete, hybrid, or IC regulator to provide stable DC to the horizontal deflection system. Sometimes feedback from a secondary output of the flyback or even the high voltage is used. This regulator may be either a linear or switching type. In some cases, there is no regulator. 5. Zero or more voltage dividers and/or regulators to produce additional voltages directly from the line power. This relatively rare except for startup circuits. These voltages will not be isolated from the line. 6. A degauss control circuit usually including a thermistor or Posistor (a combination of a heater disk and Positive Temperature Coefficient (PTC) thermistor in a single package). When power is turned on, a relatively high AC current is applied to the degauss coil wrapped around the periphery of the CRT. The PTC thermister heats up, increases in resistance, and smoothly decreases the current to nearly zero over a couple of seconds. 7. A startup circuit for booting the horizontal deflection if various voltages to run the TV are derived from the flyback. This may be an IC or discrete multivibrator or something else running off a non-isolated voltage or the standby power supply. 8. A standby power supply for the microcontroller and remote sensor. Usually, this is a separate low voltage power supply using a small power transformer for line isolation. However, some sets use other (probably cheaper) approaches. See below. Always use an isolation transformer when working on a TV but this is especially important for your safety - when dealing with the non-isolated line operated power supply. Read and follow the information in the section: Safety guidelines. Standby power supplies Where the TV has a remote control (which most do nowadays), there needs to be some source of voltage(s) for the remote receiver, microcontroller, and other circuitry that watch for the 'power on' commend. These sets are never totally off. The standby supply may consist of: 

A low voltage power transformer feeding one or more sets of rectifiers, filter capacitors, and possibly regulators.

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A power surge could cause the primary of the transformer to open up. There may also be a thermal fuse under the outer layers of insulation which blew either due to overheating or a power surge. However, if the primary is open, it is best to replace the transformer rather than attempting repair it. 

One or more voltage dividers connected directly to the AC line feeding rectifiers, filter capacitors, and possibly regulators. Open resistors and dried up capacitors are common failures since the resistors are often not rated adequately and run hot, in close proximity to the capacitors.

A portion of the main (switchmode) power supply that runs all the time. Failures could be almost anything that would affect normal operation of the power supply as well as problems with the control circuitry.

Typical TV power supply front end The partial schematic below is similar to those found in the majority of TVs sold in countries with 110 to 120 VAC power. Many parts are not shown including the power switch or relay, RFI bypass capacitors across the rectifier diodes, and RFI line filter. Bypass resistor Line fuse Main bridge Fusable +----/\/\-----+ _ rectifier resistor | +-----+ | H o--_ --+------|>|---+---/\/\--+---+---| REG |---+---+---o B+ | | | +-----+ | | +---|>|---+ C1 _|_ Main | _|_ Regulator 115 VAC | | 400 uF --- filter | --- output +--|---| N o---------+---| G - Power line earth ground via building wiring

 The line fuse is typically 2 to 4 A, usually a normal fast blow type. Even so, it may not blow as a result of faults down the line - the fusable resistor or regulator may fail first.  The main bridge rectifier is often composed of 4 discrete diodes (similar to 1N400Xs) but may also be a single unit. Failures - usually shorted diodes are common.  The main filter capacitor can range in size from 200 to 800 uF or more at 200 to 250 V. THIS CAN BE LETHAL! A typical TV may continue to work at normal line voltage without any noticeable degradation in performance (hum bars, hum in sound, or shutdown) even if this capacitor is reduced in value by 75%. Its uF value is therefore not critical. Date Developed:

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 The regulator is often an IC or hybrid module. Failures resulting in no or reduced output, or no regulation are common.  The regulator output capacitor is needed for the B+ regulator to function properly. If this capacitor is reduced in value or develops a high ESR, regulation may fail resulting in instability, oscillation, or excessive B+ and shutdown.  The regulator bypass resistor reduces the amount of current control needed of the regulator. Caution: even if the regulator has been pulled, the B+ line will have substantial voltage as a result of this resistor. Totally dead set This can be as simple as a bad outlet (including blown fuse or tripped circuit breaker due to some other fault), switched outlet and the switch is off, or bad cordset. 

Plug a lamp into the outlet to make sure it is live. If the lamp works, then the problem is the TV. It not, the outlet is defective or the fuse is blown or the circuit breaker is tripped. There is another very simple explanation that is sometimes overlooked: This is a switched outlet. You always wondered what that wall switch was for that didn't seem to do anything and you flipped randomly. :-) Well, now you know! Try wiggling the TV's cord both at the outlet (also push the wire toward the plug) and TV (also push the cord toward the TV) with the set on and/or while pressing the power-on button. If you can get a response, even momentarily, the cord likely has broken wires internally.

Intermittently dead set - bad corset There are two problems which are common with the line cord on appliances. Don't overlook these really simple things when troubleshooting your vacuum cleaner - or fancy electronic equipment! If wiggling the cord has an effect, then the following are likely causes: 

Repeated flexing results in the internal conductors breaking either at the plug or appliance end. If flexing the cord/squeezing/pulling results in the device going on and off, it is bad. If the problem is at the plug end, cut off the old plug a couple of inches beyond the problem area and replace just he plug. If the problem is at the appliance end, an entire new cordset is best though you can probably cut out the bad section and solder what remains directly to the mainboard. In either case, observe the polarity of the cord wires - they will be marked in some way with a ridge or stripe. It is important that the new plug be of the same type (polarized usually) and that the cord is wired the same way.

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The prongs do not fit snugly into older worn outlets. This can usually be remedied by using a pointed tool like an awl or utility knife to spread apart the pair of leaves often used to form each prong of the plug. If the prongs are made of solid metal, it may be possible to spread them apart - widen the space between them. Alternatively, get a 3 to 2 prong adapter just to use as an intermediate connector. Spread the leaves of its prongs. However, a new outlet is best. Bad connections on the mainboard. As you flex the cord, it is also stressing the attachment to the mainboard and affecting some marginal solder joints.

It is important to deal with these symptoms as soon as possible as erratic power cycling can lead to much more serious and expensive problems down the road. Power button on set is flakey If the on/off (or other button) on the set itself behaves erratically but the remote control works fine, then it could be a dirty button or cable or other connections to the switch PCB, particularly if the buttons on the set itself are rarely used. There could possibly be a bad pullup resistor or something of that sort - but is it worth the effort to locate? Why not just continue to use the remote? There is no reason to suspect that it will develop similar symptoms. However, there is some risk that if the button is dirty, you may find the TV coming on at random times in the middle of the night (of course!). I think I have an older Sylvania that does that sort of thing - don't really know as I never use the power button on the set! If power is controlled by a hard switch - a pull or click knob, or mechanical push-push switch and this has become erratic due to worn contacts, replacements are available but often only directly from the original manufacturer to physically fit and (where applicable) have the volume or other controls built in. As an alternative, consider mounting a small toggle switch on the side of the cabinet to substitute for the broken switch. This will almost certainly be easier and cheaper - and quite possibly, more reliable. TV blows fuse A blown fuse is a very common type of fault due to poor design very often triggered by power surges due to outages or lightning storms. However, the most likely parts to short are easily tested, usually in-circuit, with an ohmmeter and then easily removed to confirm. Note that it *may be* useful to replace a fuse the *first* time it blows (though it would be better to do some basic checks for shorted components first as there is a small chance that having a fuse blow the second time could result in additional damage which would further complicate the troubleshooting process). However, if the new one blows, there is a real problem and the only use in feeding the TV fuses will be to keep the fuse manufacturer in business! Date Developed:

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Sometimes, a fuse will just die of old age or be zapped by a power surge that caused no damage to the rest of the TV. However, it must be an EXACT replacement (including sloblow if that is what was there originally). Else, there could be safety issues (e.g., fire hazard or equipment damage from too large a current rating) or you could be chasing a non-existent problem (e.g., if the new fuse is not slo-blow and is blown by the degauss circuit inrush current but nothing is actually wrong). If the fuse really blows absolutely instantly with no indication that the circuits are functioning (no high pitched horizontal deflection whine (if your dog hides under the couch whenever the TV is turned on, deflection is probably working).) then this points to a short somewhere quite near the AC power input. The most common places would be:      

Degauss Posistor - very likely. Horizontal output transistor. Power supply regulator if there is one. Power supply chopper (switchmode) transistor if there is one. Diode(s) in main bridge Main filter capacitor(s).

You should be able to eliminate these one by one. Unplug the degauss coil as this will show up as a low resistance. First, measure across the input to the main power rectifiers - it should not be that low. A reading of only a few ohms may mean a shorted rectifier or two or a shorted Posistor.  Test the rectifiers individually or remove and retest the resistance.  Some sets use a Posistor for degauss control. This is a little cubical (about 1/2" x 3/4" x 1") component with 3 legs. It includes a line operated heater disk (which often shorts out) and a PTC thermister to control current to the degauss coil. Remove the posistor and try power. If the monitor now works, obtain a replacement but in the meantime you just won't have the automatic degauss. If these test good, use an ohmmeter with the set unplugged to measure the horizontal output transistor. Even better to remove it and measure it.  

C-E should be high in at least one direction. B-E may be high or around 50 ohms but should not be near 0.

If any readings are under 5 ohms, the transistor is bad. The parts sources listed at the end of this document will have suitable replacements. Fuse blows or TV blows up when sync is disrupted This is a problem which is not going to be easy to identify. One possibility is a drive problem. The messed up sync resulting from swtiching channels, or changing input connections might be resulting in an excessively long scan Date Developed:

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time for just one scan line. However, this may be enough to cause a current spike in the horizontal output circuit or an excessive voltage spike on the collector of the horizontal output transistor. Normally, the HOT current ramps up during scan. During flyback, the current is turned off. This current is normally limited and the voltage spike on the collector of the HOT is also limited by the snubber capacitors to a safe value. If scan time is too long, current continues to increase. At some point, the flyback core saturates and current goes way up. In addition, the voltage spike will be much higher - perhaps destructively so. Troubleshooting these sorts of problems is going to be tough. However, a likely area to investigate would be:  Drive circuitry for the HOT including the coupling components.  The chip that generates takes the sync input and generates the horizontal drive signal.  A bad low voltage regulator might permit the B+ to rise to excessive levels during black scenes (i.e., video mute during channel changing). TVs usually have their own internal surge protection devices like MOVs (Metal Oxide Varistors) after the fuse. So it is possible that all that is wrong is that the line fuse has blown. Remove the cover (unplug it first!) and start at the line cord. If you find a blown fuse, remove it and measure across the in-board side of fuse holder and the other (should be the neutral) side of the line. The ohmmeter reading should be fairly high - well certainly not less than 100 ohms - in at least one direction. You may need to unplug the degaussing coil to get a reasonable reading as its resistance may be 25 or 30 ohms. If the reading is really low, there are other problems. If the resistance checks out, replace the fuse and try powering the TV. There will be 3 possibilities: 1. 2. It will work fine, problem solved. 3. It will immediately blow the fuse. This means there is at least one component shorted - possibilities include an MOV, line rectifiers, main filter cap, regulator transistor, horizontal output transistor, etc. You will need to check with your ohmmeter for shorted semiconductors. Remove any that are suspect and see of the fuse now survives (use the series light bulb to cut your losses - see the section: The series light bulb trick. 4. It will not work properly or appear dead. This could mean there are open fusable resistors other defective parts in the power supply or elsewhere. In this case further testing will be required and at some point you may need the schematic. If the reading is very low or the fuse blows again, see the section: TV blows fuse.

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Fuse replaced but TV clicks with power-on but no other action The click probably means that the power relay is working, though there could be bad contacts. Since the fuse doesn't blow now (you did replace it with one of the same ratings, right?), you need to check for: 

Other blown fuses - occasionally there are more than one in a TV. Replace with one of exactly the same ratings.

Open fusable resistors. These sometimes blow at the same time or in place of the fuses. They are usually low values like 2 ohms and are in big rectangular ceramic power resistor cases or smaller blue or gray colored cylindrical power resistors. They are supposed to protect expensive parts like the HOT but often blow at the same time.

If any of these are bad, they will need to be replaced with flameproof resistors of the same ratings (though you can substitute an ordinary resistor for testing purposes). Before applying power, check: Rectifier diodes, horizontal output transistor, regulator pass or chopper transistor (if present), and main filter capacitor for shorts. An initial test with an ohmmeter can be done while in-circuit. The resistance across each diode and the collector to emitter of the transistors should be relatively high - a few hundred ohms at lest - in at least one direction (in-circuit). If there is a question, unsolder one side of each diode and check - should be in the Megohms or higher in one direction. Removed from the circuit, the collector-emitter resistance should be very high in one direction at least. Depending on the type, the base-emitter resistance may be high in one direction or around 50 ohms. If any reading on a semiconductor device is under 10 ohms - then the device most likely bad. Assuming that you do not have a schematic, you should be able to locate the rectifiers near where the line cord is connected and trace the circuit. The transistors will be either in a TO3 large metal can or a TOP3 plastic package - on heat sinks. The filter capacitor should eventually measure high in one direction (it will take a while to charge from your ohmmeter). It could still be failing at full voltage, however. If you find one bad part, still check everything else as more than one part may fail and just replacing one may cause it to fail again. Assuming everything here checks out, clip a voltmeter set on its 500 V scale or higher across the horizontal output transistor and turn the power on. Warning - never measure this point if the horizontal deflection is operating. it is ok now since the set is dead. If the voltage here is 100-150, then there is a problem in the drive to the horizontal output circuit. If it is low or 0, then there are still problems in the power supply or with the winding on the flyback transformer. Other possible problems: bad hybrid voltage regulator, bad startup circuit, bad standby power supply (dried up filter capacitor, etc.) bad relay contacts as mentioned above. However, these probably would not have blown the fuse in the first place so are less likely. Date Developed:

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Power-on tick-tick-tick or click-click-click but no other action A variety of power supply or startup problems can result in this or similar behavior. Possibilities include: 

 

Lack of startup horizontal drive - see the section: Startup problems nothing happens, click, or tick-tick-tick sound. The main regulator is cycling on overvoltage due to lack of load. Excessive load or faulty power supply cycling on its overcurrent protection circuit. High voltage shutdown, or some other system detecting an out of regulation condition. However, in this case, there should be some indication that the deflection and HV is attempting to come up momentary whine, static on the screen, etc. A dried up main filter capacitor or other filter capacitor in the low voltage power supply that is producing an out-of-regulation condition until it warms up. A bad filter capacitor on the output of a series regulator may result in excessive voltage and subsequent shutdown. A problem with the microcontroller, relay or its driver, or standby power supply.

One possible test would be to vary the line voltage and observe the set's behavior. It may work fine at one extreme (usually low) or the other. This might give clues as to what is wrong. Also see the section: Dead TV with periodic tweet-tweet, flub-flub, or low-low voltage. No picture or raster and no sound The screen is blank with no raster at all. There are indications that the channel numbers are changing in the display. This indicates that some of the low voltages are present but these may be derived from the standby supply. Assuming there is no deflection and no HV, you either have a low voltage power supply problem, bad startup circuit, or bad horizontal output transistor (HOT) or other bad parts in the horizontal deflection. Check for bad fuses. (If you have HV as indicated by static electricity on the front of the screen and you hear the high pitched whine of the horizontal deflection when it is turned on, then the following does not apply). 1. Use an ohmmeter to test the HOT for shorts. If it is bad, look for open fusable resistors or other fuses you did not catch. 2. Assuming it is good, measure the voltage on the collector-emitter of the HOT (this is safe if there is no deflection). You should see the B+ probably between 100 and 150 V. Date Developed:

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3. If there is no voltage, you have a low voltage power supply problem and/or you have not found all the bad/open parts. 4. If there is voltage and no deflection (no high pitched whine and no HV), you probably have a startup problem - all TVs need some kind of circuit to kick start the horizontal deflection until the auxiliary power outputs of the flyback are available. Some Zeniths use a simple multivibrator for this - a couple of transistors. Others power the horizontal osc. IC from a special line-derived voltage. The multivibrator type are sometimes designed to fail if someone keeps turning the set on and off (like kids playing) since the power rating is inadequate. Test the transistors if it is that type with an ohmmeter. If one is shorted, you have a problem. The usual way a TV service person would test for startup problems is to inject a signal to the base of the HOT of about 15.75 kHz. If the TV then starts and runs once this signal is removed, the diagnosis is confirmed. This is risky - you can blow things up if not careful (including yourself). See the section: Bypassing the Startup Circuit for details. If you hear the high pitched whine of the deflection and/or feel some static on the scree, confirm that the horizontal deflection and high voltage are working by adjusting the SCREEN control (probably on the flyback). If you can get a raster then your problem is probably in the video or chroma circuits, not the deflection or high voltage. Reduced width picture and/or hum bars in picture and/or hum in sound The most likely cause is a dried up main filter capacitor. Once the effective capacitance drops low enough, 120 Hz (or 100 Hz in countries with 50 Hz power) ripple will make its way into the regulated DC supply (assuming full wave rectification). Another likely cause of similar symptoms is a defective low voltage regulator allowing excessive ripple. The regulator IC could be bad or filter capacitor following the IC could be dried up. Either of these faults may cause: 1. A pair of wiggles and/or hum bars in the picture which will float up the screen. For NTSC where the power line is 60 Hz but the frame rate is 59.94 Hz, it will take about 8 seconds for each bar to pass a given point on the screen. (On some sets, a half wave recitifier is used resulting in a single wiggle or hum bar). 2. Hum in the sound. This may or may not be noticeable with the volume turned down. 3. Possible regulation problems resulting in HV or total shutdown or power cycling on and off.

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The best approach to testing the capacitors is to clip a good capacitor of approximately the same uF rating and at least the same voltage rating across the suspect capacitor (with the power off). A capacitor meter can also be used but the capacitor may need to be removed from the circuit. Once the capacitors have been confirmed to be good, voltage measurements on the regulator should be able to narrow down the problem to a bad IC or other component. Excessive B+ from fixed regulator like STR30123/STR30130/STR30135 These are fixed regulators that do fail but the problem may be elsewhere. If the B+ goes to high, the X-ray protection circuitry may kick in and shut down the horizontal deflection. If there is little or no load (horizontal deflection not running at all), all bets are off as well the resistor that is likely across input-output will dominate and boost the voltage above the proper output for the regulator chip. Use a Variac to bring up the voltage to the TV. If the deflection does not start up at any voltage even with the B+ ramping up past its normal value, the problem is probably in the horizontal deflection/startup circuitry, not the regulator. Some of these may go out of regulation if the output electrolytics are dried up. There might a a 10 uF 200 V or so electrolytic across the output to ground. Test it or substitute a known good one of about the same uF rating and at least equal voltage rating. If you can get the TV to work at reduced voltage using a Variac (but possibly with hum bars in the picture and hum in the audio), check the output capacitor. Otherwise, it could be the regulator or one of its biasing components (sets current to B input the voltage at this input should be close to the output voltage value). Also check to be sure the input voltage is solid - main filter capacitor is not dried up. TV power cycling on and off The power light may be flashing or if you are runing with a series light bulb it may be cycling on and off continuously. There may be a chirping or clicking sound from inside the set. (Note: using too small a series light bulb load during testing for the size of the TV may also result in this condition.) If there is a low voltage regulator or separate switching supply, it could be cycling on and off if the horizontal output, flyback, or one of its secondary loads were defective. Does this TV have a separate low voltage regulator and/or switching power supply or is it all part of the flyback circuit? For the following, I assume it is all in one (most common). Some simple things to try first: Verify that the main filter capacitor is doing its job. Excessive ripple on the rectified line voltage bus can cause various forms of shutdown behavior. An easy test is to jumper across the capacitor with one of at least equal voltage rating and similar capacitance (make connections with power off!). Date Developed:

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Use a Variac, if possible, to bring up the input voltage slowly and see if the TV works at any point without shutting down. If it does, this could be an indication of X-ray protection circuit kicking in, though this will usually latch and keep the set shut off if excessive HV were detected. Dead TV with periodic tweet-tweet, flub-flub, or low-low voltage A TV which appears to be dead except for a once a second or so tweet or flub usually indicates an overload fault in the power supply or a short in one of its load circuits. In some cases, the low voltage (including B+) will just be reduced to a fraction of their normal value as a result of an overload on one of the outputs - usually the main B+. This may be caused by a shorted rectifier in the power supply, flyback, or even the yoke, but check the the loads first. Wait a few minutes for the filter caps to discharge (but stay away from the CRT HV connector as it may retain a dangerous and painful charge for a long time), use an ohmmeter across the various diodes in the power supply. Using an ohmmeter on the rectifier diodes, the resistance in at least one direction should be greater than 100 ohms. If it is much less (like 0 or 5 ohms), then the diode is probably bad. Unsolder and check again - it should test infinite (greater than 1M ohms) in one direction. Summary of possible causes:       

Bad solder connections. Other shorted components like capacitors. Other problems in the power supply or its controller. Bad flyback. Short or excessive load on secondary supplies fed from flyback. Short in horizontal yoke windings. Problem with startup drive (cycling on overvoltage).

Bypassing the Startup Circuit Where the TV is dead and a startup problem is suspected, a TV service person would test for startup problems by injecting a signal into the base of the HOT of about 15.75 kHz. If the TV then starts and runs once this signal is removed, the diagnosis is confirmed. This is risky - you can blow things up if not careful (including yourself). A 555 timer based circuit will work fine as a signal source for this. WARNING: be careful if you do this. The HOT circuit may be line-connected and it is possible to destroy the HOT and related components if this is not done properly. I once managed to kill not only the HOT but the chopper transistor as well while working in this area. An expensive lesson. You can reduce the risk somewhat (to the TV at least) by using a series light bulb load and/or running on reduced line voltage. The most important thing to avoid is putting in an excessively long drive pulse which will result in the flyback transformer saturating, huge amounts of current, and likely a dead HOT and possibly other parts if there is nothing to limit the current. For NTSC/PAL, it is fairly safe to assume that a 50 percent duty cycle 15 to 16 Date Developed:

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kHz drive signal will not result in fireworks as long as there aren't other problems (like a shorted flyback/LOPT). If after a second or so, the TV fires up (not literally!) and stays happy until it is turned off, a startup problem is almost certain. It could be the standby supply (if used) or a dedicated startup circuit that has failed. But, don't push your luck - if the TV starts after a second or so of your drive signal but doesn't continue to run when it is removed, don't be tempted to leave your circuit connected it could still be stressing other parts. Find out why the normal horizontal drive is not being generated - possibly a power supply or horizontal oscillator problem. If nothing happens, either startup is not the problem or there are other components that have failed preventing the HOT drive signal from having any effect. Shorted Components A failure of the horizontal output transistor or power supply switchmode transistor will blow a fuse or fusable resistor. Look for blown fuses and test for open fusable resistors in the power circuits. If you find one, then test the HOT and/or switchmode transistor for shorts. Other possibilities: rectifier diodes or main filter capacitor. While you are at it, check for bad connections - prod the circuit board with an insulated stick when the problem reoccurs - as these can cause parts to fail. Startup problems - nothing happens, click, or tick-tick-tick sound TVs and monitors usually incorporate some kind of startup circuit to provide drive to the horizontal output transistor (HOT) until the flyback power supply is running. Yes, TVs and monitors boot just like computers. There are two typical kinds of symptoms: power on click but nothing else happens or a ticktick-tick sound indicating cycling of the low voltage (line regulator) but lack of startup horizontal drive. Check the voltage on the horizontal output transistor (HOT). If no voltage is present, there may be a blown fuse or open fusable resistor - and probably a shorted HOT. However, if the voltage is normal (or high) - usually 100-150 V, then there is likely a problem with the startup circuit not providing initial base drive to the HOT.

The startup circuits may take several forms: 1. Discrete multivibrator or other simple transistor circuit to provide base drive to the HOT. 2. IC which is part of deflection chain powered off of a voltage divider or transformer. Date Developed:

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3. Other type of circuit which operates off of the line which provides some kind of drive to the HOT.

TV turns off after warming up If you can turn it back on with the s momentary key or power button: When it shuts off, do you need to push the power button once or twice to get it back on? Also, does anything else about the picture or sound change as it warms up? 1. If once, then the controller is shutting the TV down either as a result of a (thermally induced) fault in the controller or it sensing some other problem. Monitoring the voltage on the relay coil (assuming these is one) could help determine what is happening. The controller thinks it is in charge. 2. If twice, then the power supply is shutting down as the controller still thinks it is on and you are resetting it. A couple of possibilities here would be low voltage or high voltage regulation error (excessive high voltage is sensed and causes shutdown to prevent dangerous X-ray emission). A partially dried up main filter capacitor could also cause a shutdown but there might be other symptoms like hum bars in the picture just before this happened. Clipping a good capacitor across the suspect (with power off!) would confirm or eliminate this possibility. If it uses a pull-knob (or other hard on/off switch), then this may be like pulling the plug and would reset any abnormal condition. TV doesn't power up immediately The TV may do nothing, cycle on and off for a while, power up and then shutdown in an endless cycle - or at least for a while. Then it comes on and operates normally until it is turned off. A couple of possibilities: 1. The main filter capacitor or other filter capacitors in the low voltage power supply is dried up and this can cause all kinds of regulation problems. 2. The power supply regulator is defective (or marginal) allowing excessive voltage on its output and then the X-ray protection circuitry shuts you down.

TV shuts down with bright picture or when brightness is turned up This is probably a protection circuit kicking in especially if turning power off or pulling the plug is required to restore operation. Date Developed:

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The detection circuit could be in the power supply or horizontal deflection output circuit. It may be defective or the current may be too high for some other reason. A couple of tests can be performed to confirm that it is due to beam current: 

Determine if behavior is similar when adjusting the user brightness control and the screen (G2) pot (on the flyback) or master brightness control. If the TV quits at about the same brightness level, overcurrent protection is likely. Disconnect the filaments to the CRT (unsolder a pin on the CRT socket) and see if it still shuts down under the same conditions. If it is overcurrent protection, shut down should now *not* take place since there is no beam current.

Relays in the Power Circuitry of TVs Where power on or power off is erratic or only seems to work part way (e.g., the picture goes off but not the sound), it may just be a sticking or dirty relay. Of course, general on/off problems could also be relay related but could also be a lot of other things. For erratic on/off problems, gently tapping on the relay when the problem occurs will confirm that the relay is at fault - if the set then switches on or off properly, it's almost certainly the relay and replacing it will fix the problem. But double check its solder connections to make sure it isn't a simple bad connection to the relay or in its vicinity. What is a posistor? A posistor is a combination of a PTC (positive temperature coefficient) resistor and another resistor-element to heat it up and keep it hot. Sometimes, these will go by the name posister or thermistor. The heater is a disk shaped resistor across the power line and the themister is a disk shaped device in series with the degauss coil. They are in clamped together to be in close contact thermally. You can pry off the lid and see for yourself. The most common failure mode is for the part to short across the line. Its function is to control degauss, so the only thing you lose when you remove one of these is the degauss function on power-on. When you turn the TV or monitor on, the PTC resistor is cold and low resistance. When heated, it becomes very high resistance and turns off the degauss coil but gradually - the current ramps down to zero rather than being abruptly cut off.. Computer Component Source stocks a wide variety, I believe but it may be cheaper to go direct to the manufacturer if they will sell you one. Flameproof Resistors Flameproof Resistor or Fusable Resistor are often designated by the symbol 'FR'. They are basically the same. The designation "Flameproof" means that if they fail due to excessive current, there will be no chance of, well, them Date Developed:

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going up in flames. :) They will also have a power rating and thus can act as a protective device, though a specific circuit may not depend on a precise fuse rating, rather that the resistor will open with massively excessive current. if you find one bad part - many components can fail or cause other components to fail if you don't locate them all. Check resistors as well, even if they look ok. Since they function as fuses, flameproof resistors should not be replaced with higher wattage types unless specifically allowed by the manufacturer. These would not blow at the same level of overload possibly resulting in damage to other parts of the circuitry and increasing the risk of fire. Then, with a load on the output of the power supply use a Variac to bring up the voltage slowly and observe what happens. At 50 VAC or less, the switcher should kick in and produce some output though correct regulation may not occur until 80 VAC or more. The outputs voltages may even be greater than spec'd with a small load before regulation is correct. Width and height change with warmup Since both width and height are affected, this points to something common like the low voltage power supply. If there are any indications of hum bars, first check the main filter capacitor(s) or substitute a known good one. There might even be other symptoms like faint retrace lines on at least part of the screen. Start by monitoring the B+ to the flyback (feeding the HOT) to see if this drifts at all. If it does, then there is probably a low voltage regulator problem - bad capacitor, resistor, or chip. Use freeze spray to narrow it down. If this is solid, then there could be a high voltage drift but this would be somewhat unusual without other symptoms (like arcing) since the HV is nearly always tracks the low voltage supply. Problems with SCR based regulators Here are typical symptoms: "Sharp TV has a short blast of high voltage and sound then shuts down. All components in regulator area test good. I have two of these sets." Is there a good sharp tech out there thats seen this problem?" (From: Mr. Caldwell ([emailprotected]).) There is a bulletin from Sharp on troubleshooting *any* SCR regulated TV, this can easily be adapted to RCA, GE, Emerson and Panasonic sets that have similar circuits given a little thought but the technician. You are going to need to figure part of this out as I no longer have the schematics available. All this will do is allow you to rule out either the regulator or the horizontal section. Don't plug this in until you've read the whole list. Date Developed:

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Figure out how to bypass the turn on circuit from the microprocessor (unless it's a manual one). This is usually just jumpering the relay but sometimes Sharp puts a horizontal Vcc turn on transistor that also must be jumpered. Next jumper across the SCR anode to cathode. Now using an *variable isolation transformer* turn the voltage on it down and plug the set in. Bring the voltage up slowly, if you can bring the AC up so that the DC on the jumper across the SCR is within the regulated voltage you should have a picture and this rules out the horizontal section as the culprit. If the set shuts down prior to getting the DC up enough then you've got problems in the horizontal section. Either you have something wrong with the high voltage transformer or the tuning caps or there is a problem with the x-ray protect pick off voltage to the deflection IC. If it's the horizontal section you can set the AC at approx. 25v and look at the waveforms in the horizontal output section for defects like ringing. I've never gotten a good troubleshooting technique down for the regulator since it's an active circuit the waveforms and voltages are not stable when it's failed. A good diode, transistor and capacitor checker will help. It would help to get the service manual for that set, the training manual for that chassis and the bulletin dealing with troubleshooting SCR regulators. TV shuts down with dark picture or when changing channels This may happen at any time or possibly after being on for awhile in which something heats up and drifts out of spec. The low voltage regulator may be letting the voltage rise excessively. Then, a dark picture or video muting during a channel change triggers the X-ray or power supply overvoltage protection. Monitor the output of the low voltage power supply B+ to see if it is stable as the brightness/scene changes.

Deflection Problems Deflection fundamentals Note: the following is just a brief introduction. For more detailed deflection system theory of operation and sample circuits, see the document: TV and Monitor Deflection Systems. The electron beams in the CRT need to be scanned horizontally and vertically in a very precise manner to produce a raster - and a picture. For NTSC and PAL, the horizontal scan rates are 15,734 and 15,625 Hz respectively. Date Developed:

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For NTSC and PAL, the vertical scan rates are 60 and 50 Hz (approximately) respectively. The deflection yoke includes sets of coils for horizontal and vertical scanning oriented at 90 degrees with respect to each other. Additional coils are needed to correct for pincushion and other geometric defects. The deflection circuits must be synchronized and phase locked to the incoming video signal. Therefore, we have the following functions: 1. Sync separator to obtain horizontal and vertical synchronization pulses. 2. Horizontal oscillator which locks to horizontal sync pulses. 3. Horizontal drive followed by horizontal output which feeds deflection yoke (and flyback for HV and other voltages), Yoke requires a sawtooth current waveform for linear horizontal deflection. Horizontal output in all but the smaller TVs is a large discrete power transistor, most often an NPN bipolar type. 4. Vertical oscillator which locks to vertical sync pulses. Yoke requires sawtooth waveform for linear vertical deflection. 5. Vertical drive/output which feeds vertical deflection yoke. Newer TVs use ICs for vertical drive and output. 6. Various additional deflection signals to correct for the imperfections in the geometry of large angle deflection CRTs. These may be fed into the normal deflection coils and/or there may be separate coils mounted on the neck of the CRT. About the vertical scan rate Some people believe that the TV scan rate is locked to the local power line. TVs never ever used the line frequency for vertical rate. The vertical rate is not even equal to line frequency, actually 59.94 Hz (NTSC). It was set originally to 60 Hz to minimize the visibility of interference between the deflection and power transformer. When NTSC added color, it changed to 59.94 Hz for highly technical reasons. And, TVs no longer have power transformers. Picture squeezed in then died You were watching 'Knight Rider' reruns and all of a sudden, the picture "squeezed in" slowly from the right hand side. It "squeezed in" about 2 inches or so when the entire picture went dead - has remained like this since. Sound is fine, but no activity at all from the tube. Has it died? How much time, effort, and expense to fix? No, it's not dead, at least it certainly is not the picture tube. Your set probably didn't like Knight Rider - at least that episode!

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Seriously, how old is the set? Is it a totally solid state chassis or are there tubes in the deflection circuits? Is there any indication of light on the screen? Any indication of the 15735 Hz horizontal running at all? (You would normally hear the high pitch sound). Newer TVs almost always derive voltages for the sound circuits from the horizontal deflection but older hybrids may run the sound off of its own power. In any case, there is a problem in the horizontal deflection and you probably have no high voltage as well assuming no light on the screen. The fact that it squeezed in first indicates that a partial short or other fault may have developed in the horizontal deflection circuits - possibly the deflection yoke or flyback transformer. It could also have been a bad connection letting loose. Once it failed completely, the horizontal output transistor may have bought the farm or blown a fuse. TV non-linearity Most modern TVs are nearly perfect with respect to linearity. There are never any user adjustments and there may not even be any internal adjustments. See the sections: Horizontal position, size, and linearity adjustment and/or Vertical position, size, and linearity adjustment. A sudden change in linearity or a TV that requires a warmup period before linearity becomes acceptable may have a bad component - probably a capacitor in the horizontal deflection circuits. For the latter, try some cold spray or a heatgun to see if you can locate the bad part. Horizontal deflection shutting down Confirm that the horizontal deflection is shutting down (along with the high voltage since it is derived from horizontal deflection: listen for the high pitched deflection whine, test for static on the screen, see if the CRT filaments are lit, turn up the brightness and/or screen control to see if you can get a raster) and then why: 1. Power is failing to the horizontal output transistor - this could be due to a low voltage power supply problem, bad connection, etc. 2. Base drive to the horizontal output transistor is failing - could be a fault in the horizontal oscillator or bad connection. 3. Problem with the flyback transformer or its secondary loads (flyback may provide other power voltages). 4. X-ray protection is activating - either due to excess HV or due to a fault in the X-ray protection circuitry. If the problem comes and goes erratically it sounds like a bad connection, especially if whacking has an effect. If it comes and goes periodically, then a component could be heating up and failing, then cooling, etc.

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TV will not sync There are a wide variety of causes for a TV that will not display a stable or properly configured picture. Among the symptoms are: 

Lack of sync horizontal - drifts smoothly horizontally. Depending on the difference between the video horizontal rate and the free-run frequency of the horizontal oscillator, the picture may be torn left or right (as shown in Symptoms of Some Common Deflection Problems or have multiple images superimposed horizontally. The situation where the picture is neatly split horizontally (which is what you might expect) is a special case where the frequencies are virtually the same. The key symptom common to all these is that there IS vertical lock (no blanking bar visible) AND there is no evidence that the deflection is even attempting to lock horizontally. This may mean that the horizontal sync signal is missing due to a sync separator problem or that there is some other fault in the sync processing circuitry.

 

Incorrect lock horizontal - a more-or-less stable torn picture. This means that the sync signal is reaching the deflection system but that it is having problem locking to it. The horizontal oscillator free-run frequency may be too far from what it is supposed to be (15,734 or 15,625 for NTSC and PAL, respectively). Lack of sync vertical - rolls smoothly vertically. This may mean that the vertical sync signal is missing or the deflection system is ignoring it. Lock not stable vertical - jumps or vibrates vertically. This may be a fault in the vertical sync circuitry. Multiple or repeated images horizontally or vertically. Problems in sync processing circuitry. Additional comments on some of these problems follow in the next few sections.

Horizontal lock lost A TV which loses horizontal lock when changing channels, momentarily losing the signal, or switching inputs may have a horizontal oscillator that is way out of adjustment or has drifted in frequency due to aging components. Note that the characteristics of this are distinctly different than for total loss of sync. In the latter case, the picture will drift sideways and/or up and down while with an off frequency oscillator, the torn up picture will try at least to remain stationary. This could be a capacitor or other similar part. Or, the oscillator frequency may just need to be tweaked (particularly with older sets). There may be an internal horizontal frequency adjustment - either a pot or a coil - which may need a slight tweak. If a coil, use a plastic alignment tool, not metal to avoid cracking the fragile core.

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Vertical lock lost This indicates a picture that is correct but rolling vertically. If the picture is rolling down the screen the frequency of the vertical oscillator is incorrect too high - and this may be the problem. Generally, the free run frequency of the vertical oscillator should be a little below the video rate (of around 50 or 60 Hz depending on where you live). If it is rolling continuously without jumping, then there is a loss of sync from the sync separator or faulty components in the vertical oscillator causing it to totally ignore the sync pulses. If it is rolling up rapidly and not quite able to remain locked, the free run frequency may be too low or there could be a fault in the sync circuits resulting in an inadequate vertical pull-in range. On older sets, there was actually a vertical hold (and possibly even a separate vertical frequency) control. On anything made in the last decade, this is unlikely. There may be Vertical Frequency and Vertical Pull-in Range adjustments (and others) accessible via the service menu. However, if any of these ever change, it indicates a possible problem with the EEPROM losing its memory as component drift is unlikely. As with everything else, bad connections are possible as well. You will need a schematic and possibly setup info to go beyond this. Vertical squashed This is a vertical deflection problem - possibly a bad capacitor, bad connection, flyback/pumpup diode, or other component. None of these should be very expensive (in a relative sort of way). If the symptoms change - particularly if they become less severe - as the set warms up, a dried up electrolytic capacitor is most likely. If they get worse, it could be a bad semiconductor. Freeze spray or a heat gun may be useful in identifying the defective component. It is often easiest to substitute a good capacitor for each electrolytic in the vertical output circuit. Look for bad connections (particularly to the deflection yoke), then consider replacing the vertical output IC or transistor(s). A defective deflection yoke is also possible or in rare cases, a bad yoke damping resistor (e.g., 500 ohms, may be mounted on the yoke assembly itself). Where the entire top half or botton half of the picture is squashed into into the center (i.g., only half the picture shows), a missing power supply voltage, defective vertical output IC, or a component associated with it is likely bad. A bad connection or blown fusable resistor may be the cause of a missing power supply voltage.

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The following are NOT possible: CRT, flyback (except possibly where it's the source for a missing voltage but this is more likely just a bad solder connection at a flyback pin), tuner (except for the famous RCA/GE/Proscan or Sony models where the controller is at fault - see the sections on these specific brands). I am just trying to think of really expensive parts that cannot possibly be at fault :-). Note that some movies or laser karaoke discs are recorded in 'letterbox' format which at first glance looks like a squashed vertical problem. However, the picture aspect ratio will be correct and turning up the brightness will reveal a perfectly normal raster above and below the picture. Part of picture cut off The following applies if the part of the picture is missing but not otherwise squashed or distorted. For example, 85% is missing but the portion still visible is normal size.

CAUTION: To prevent damage to the CRT phosphors, immediately turn down the brightness so the line is just barely visible. If the user controls do not have enough range, you will have to locate and adjust the master brightness or screen/G2 pots. Since you have high voltage, the horizontal deflection circuits are almost certainly working (unless there is a separate high voltage power supply - almost unheard of in modern TVs and very uncommon in all but the most expensive monitors). Check for bad solder connections between the main board and the deflection yoke. Could also be a bad horizontal coil in the yoke, linearity coil, etc. There is not that much to go bad based on these symptoms assuming the high voltage and the horizontal deflection use the same flyback. It is almost certainly not an IC or transistor that is bad. Single Horizontal Line CAUTION: To prevent damage to the CRT phosphors, immediately turn down the brightness so the line is just barely visible. If the user controls do not have enough range, you will have to locate and adjust the master brightness or screen/G2 pots. A single horizontal line means that you have lost vertical deflection. High voltage is most likely fine since there is something on the screen. This could be due to: 1. Dirty service switches contacts. There is often a small switch located inside on the main board or perhaps accessible from the back. This is used during setup to set the color background levels. (On some sets, this is located on the CRT neck board and may be a jumper plug or other means of selecting service mode - not an actual switch.) Date Developed:

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When moved to the 'service' position, it kills vertical deflection and video to the CRT. If the switch somehow changed position or got dirty or corroded contacts, you will have this symptom. Flip the switch back and forth a couple of times. If there is some change, then replace, clean, resolder, or even bypass it as appropriate. 2. Bad connection to deflection yoke or other parts in vertical output circuit. Bad connections are common in TVs and monitors. Check around the pins of large components like transformers, power transistors and resistors, or connectors for hairline cracks in the solder. Reseat internal connectors. Check particularly around the connector to the deflection yoke on the CRT. 3. Bad vertical deflection IC or transistor. You will probably need the service manual for this and the following. However, if the vertical deflection is done with an IC, the ECG Semiconductor Master Substitution guide may have its pinout which may be enough to test it with a scope. 4. Other bad parts in vertical deflection circuit though there are not that many parts that would kill the deflection entirely. 5. Loss of power to vertical deflection circuits. Check for blown fusable resistors/fuses and bad connections. 6. Loss of vertical oscillator or vertical drive signals. The most likely possibilities are in the deflection output stage or bad connections to the yoke. Keystone shaped picture This means that the size of the picture is not constant from top to bottom (width changes) or left to right (height changes). Note that some slight amount of keystoning is probably just within the manufacturing tolerance of the deflection yoke and factory setup (geometry magnet placement, if any). On a TV, this is only noticeable with scenes having straight edges (e.g., video games) in relationship to the CRT bezel. Loss of Horizontal Sync (also applies to vertical) after Warm-up The problem lies either in the horizontal oscillator or in the sync system. If it really is a problem with sync pulses not reaching the oscillator, the picture will move around horizontally and can be brought to hold momentarily with the hold control. If the picture breaks up into strips, there is a problem in the horizontal oscillator. Rotate the hold control: if the frequency is too far off, the picture will not settle into place at any adjustment of the hold control. Look around the horizontal oscillator circuit: all of the oscillator parts will be right there, or check on the horizontal oscillator module. Another horizontal problem can occur if the set is an RCA made from around 1972-1980: these sets are designed to slip very far off sync if the high voltage is too high, to protect against radiation. Turning up the brightness will decrease the number of bars if this system is in question, as the high voltage is decreasing. In this case, check around the high-voltage Date Developed:

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regulation system on the deflection systems board. I've had 2 1970's RCA's with this problem. Intermittent jumping or jittering of picture or other random behavior This has all the classic symptoms of a loose connection internal to the TV or monitor - probably where the deflection yoke plugs into the main PCB or at the base of the flyback transformer. TVs and monitors are notorious for both poor quality soldering and bad connections near high wattage components which just develop over time from temperature cycling. The problem may happen any time or more when cold or hot. The following is not very scientific, but it works: Have you tried whacking the TV when this happened and did it have any effect? If yes, this would be further confirmation of loose connections. What you need to do is examine the solder connections on the PCBs in the monitor, particularly in the area of the deflection circuits and power supply. Look for hairline cracks between the solder and the component pins - mostly the fat pins of transformers, connectors, and high wattage resistors. Any that are found will need to be reflowed with a medium wattage (like 40W) or temperature controlled soldering iron. It could also be a component momentarily breaking down in the power supply or deflection circuits. One other possibility is that there is arcing or corona as a result of humid weather. This could trigger the power supply to shut down perhaps with a squeak, but there would probably be additional symptoms including possibly partial loss of brightness or focus before it shut down. You may also hear a sizzling sound accompanied by noise or snow in the picture, static in the sounds, and/or a smell of ozone. Horizontal output transistors keep blowing (or excessively hot) Unfortunately, these sorts of problems are often difficult to definitively diagnose and repair and will often involve expensive component swapping. You have just replaced an obviously blown (shorted) horizontal output transistor (HOT) and an hour (or a minute) later the same symptoms appear. Or, you notice that the new HOT is hotter than expected: Would the next logical step be a new flyback (LOPT)? Not necessarily. If the set performed normally until it died, there are other possible causes. However, it could be the flyback failing under load or when it warms up. I would expect some warning though like the picture shrinks for a few seconds before the poof. Other possible causes: 1. Improper drive to horizontal output transistor (HOT). A weak drive might cause the HOT to turn on or (more likely) shut off too slowly Date Developed:

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2. 3. 4. 5. 6.

(greatly increasing heat dissipation. Check driver and HOT base circuit components. Dried up capacitors, open resistors or chokes, bad connections, or a driver transformer with shorted windings or broken or loose core can all affect drive waveforms. Excessive voltage on HOT collector - check LV regulator (and line voltage if this is a field repair), if any. Defective safety capacitors or damper diode around HOT. (Though this usually results in instant destruction with little heating). New transistor not mounted properly to heat sink - probably needs mica washer and heat sink compound. Replacement transistor not correct or inferior cross reference. Sometimes, the horizontal deflection is designed based on the quirks of a particular transistor. Substitutes may not work reliably. CRT shorting internally. If this happens only once in two weeks, it may be diffuclt to track down :-(.

The HOT should not run hot if properly mounted to the heat sink (using heatsink compound). It should not be too hot to touch (CAREFUL - don't touch with power on - it is at over a hundred volts with nasty multihundred volt spikes and line connected - discharge power supply filter caps first after unplugging). If it is scorching hot after a few minutes, then you need to check the other possibilities. It is also possible that a defective flyback - perhaps one shorted turn - would not cause an immediate failure and only affect the picture slightly. This would be unusual, however. See the section:Testing of flyback (LOPT) transformers. Note that running the set with a series light bulb may allow the HOT to survive long enough for you to gather some of the information needed to identify the bad component. Horizontal output transistors blowing at random intervals The HOT may last a few months or years but then blow again. These are among the hardest problems to locate. It could even be some peculiar combination of user cockpit error - customer abuse - that you will never identify. Yes, this should not happen with a properly designed TV though newer horizontal processor chips are quite smart about preventing HOT killing signals from reaching the horizontal driver. However, a combination of channel changing, loss of sync when switching video sources, and frequent power cycles, could test the TV in ways never dreamed of by the designers. It may take only one scan line that is too long to blow the HOT. On the other hand, the cause may be along the lines of those listed in the section: Horizontal output transistors keep blowing (or excessively hot) and just not as obvious - blowing in a few days or weeks instead of a few seconds but in this case, the HOT will likely be running very hot even after only a few minutes.

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Another possible cause for random failures of the HOT are bad solder connections in the vicinity of the flyback and HOT (very common due to the large hot high power components) as well as the horizontal driver and even possibly the sync and horizontal oscillator circuits, power supply, or elsewhere. Vertical fold over The picture is squashed vertically and a part of it may be flipped over and distorted. This usually indicates a fault in the vertical output circuit. If it uses an IC for this, then the chip could be bad. It could also be a bad capacitor or other component in this circuit. It is probably caused by a fault in the flyback portion of the vertical deflection circuit - a charge pump that generates a high voltage spike to return the beam to the top of the screen.

Test components in the vertical output stage or substitute for good ones.

In particular, this sounds like a pincushion problem - to correct for pincushion, a signal from the vertical deflection that looks something like a rectified sinewave is used to modify width based on vertical position. There is usually a control to adjust the magnitude of this signal and also often, its phase. It would seem that this circuit has ceased to function. If you have the schematics, check them for 'pincushion' adjustments and check signals and voltages. If not, try to find the 'pincushion' magnitude and phase adjustments and look for bad parts or bad connections in in the general area. Even if there are no adjustment pots, there may still be pincushion correction circuitry. If the internal controls have absolutely no effect, then the circuit is faulty. With modern digital setup adjustments, then it is even tougher to diagnose since these control a D/A somewhere linked via a microprocessor. Pincushion adjustment adds a signal to the horizontal deflection to compensate for the geometry of the CRT/deflection yoke. If you have knobs, then tracing the circuitry may be possible. With luck, you have a bad part that can be identified with an ohmmeter - shorted or open. For example, if the pincushion correction driver transistor is shorted, it will have no effect and the picture will be too wide and distorted as shown above. However, without a schematic even this will be difficult. If the adjustments are digital this is especially difficult to diagnose since you don't even have any idea of where the circuitry would be located. Faulty capacitors in the horizontal deflection power supplies often cause a similar set of symptoms.

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Deflection yoke testing A faulty deflection yoke can affect the geometry (size and shape) of the raster, result in insufficient high voltage and/or other auxiliary power problems, and blow various components in the low voltage power supply or elsewhere. 

A simple test to determine if the yoke is at fault for a major geometry problem (e.g., a keystone shaped picture) is to interchange the connections to the yoke for the axis that is not affected (i.e., the vertical coils if the width is varying from top to bottom). If the raster/picture flips (indicating that you swapped the proper connections) but the shape of the raster remains the same - the geometry is unchanged, the problem is almost certainly in the deflection yoke. Where high voltage (and other flyback derived voltages) are reduced and other problems have been ruled out, unplugging the deflection yoke (assuming no interlock) may reveal whether it is likely at fault. If this results in high voltage and a relatively clean deflection waveform or returns the power supply or deflection chip load to something reasonable, a defective yoke is quite possible. CAUTION: powering a TV or monitor with a disconnected yoke must be done with care for several reasons: o

o

o

The CRT electron beam(s) will not be deflected. If it turns out that the yoke is the problem, this may result in a very bright spot in the center of the screen (which will turn into a very dark permanent spot quite quickly) :-(. Disconnecting only the winding that is suspect is better. Then, the other direction will still scan resulting in a very bright line instead of a super bright spot. In any case, make sure the brightness is turned all the way down (using the screen/G2 control on the flyback if necessary). Keep an eye on the front of the screen ready to kill power at the first sign of a spot or line. Disconnecting the CRT heater as an added precaution would be even better unless you need to determine if there is a beam. Removing the yoke (which is effectively in parallel with the flyback) increases the inductance and the peak flyback voltage on the HOT. In the extreme, this may blow the HOT if run at full line voltage/normal B+. It is better to perform these tests using a Variac at reduced line voltage if possible. The deflection system will be detuned since the yoke inductance plays a very significant role in setting the resonance point in most designs. Don't expect to see totally normal behavior with respect to high voltage. However, it should be much better than with the faulty yoke. Date Developed:

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o

Resistance check - This may be possible without removing the yoke from the CRT if the terminal block is accessible. Disconnect the individual windings from each other and determine if the resistances are nearly equal. Check for shorts between windings and between the horizontal and vertical windings as well. Typical resistance of the intact windings (at the yoke connector assuming no other components): TV or NTSC/PAL monitor - a few ohms (3 ohms typical), SVGA monitor - less than an ohm (.5 ohms typical).

Inspection - Look for charring or other evidence of insulation breakdown due to arcing or overheating. For the horizontal windings, this will require removing the yoke from the CRT since little if any of the windings are visible from the outside. However, even then, most of the windings are hidden under layers of wire or behind the ferrite core. o Ring test. See the document "Testing of Flyback (LOPT) Transformers". This deals with flyback transformers but the principles are the same. Disconnecting the windings may help isolate the location of a fault. However, for windings wound on the same core, the inductive coupling will result in a short anywhere on that core reducing the Q. Vertical - The vertical section is usually manufactured as a pair of windings wired in parallel (or maybe in series) though for high vertical scan rate monitors, multiple parallel/interleaved windings are also possible. o

The vertical windings will be oriented with the coil's axis horizontal and wound on the outside of the yoke. The wire used for the vertical winding may be thinner than that used for the horizontal windings. o

Resistance check - This may be possible without removing the yoke from the CRT if the terminal block is accessible. Disconnect the individual windings from each other and determine if the resistances are nearly equal. Check for shorts between windings and between the horizontal and vertical windings as well. Typical resistance of the intact windings (at the yoke connector assuming no other components): TV or NTSC/PAL monitor - more than 10 ohms (15 ohms typical), SVGA monitor - at least a few ohms (5 ohms typical).

o

Inspection - Look for charring or other evidence of insulation breakdown due to arcing or overheating. The accessible portions of the vertical windings are mostly visible without removing the Date Developed:

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o

yoke from the CRT. However, most of the windings are hidden under layers of wire or behind the ferrite core. Ring test - Since the vertical windings have significant resistance and very low Q, a ring test may be of limited value.

Deflection yoke repair So you found a big black charred area in/on one of the yoke windings. What can be done? Is it possible to repair it? What about using it for testing to confirm that there are no other problems before ordering a new yoke? If the damage is minor - only a few wires are involved, it may be possible to separate them from each other and the rest of the winding, thoroughly clean the area, and then insulate the wires with high temperature varnish. Then, check the resistances of each of the parallel/interleaved windings to make sure that you caught all the damage. Simple plastic electrical tape can probably be used for as insulation for testing purposes - it has worked for me - but would not likely survive very long as a permanent repair due to the possible high temperatures involved. A new yoke will almost certainly be needed. Testing of fly back (LOPT) transformers How and why do fly back transformers fail? Fly backs fail in several ways: 1. Overheating leading to cracks in the plastic and external arcing. These can often be fixed by cleaning and coating with multiple layers of high voltage sealer, corona dope, or even plastic electrical tape (as a temporary repair in a pinch). 2. Cracked or otherwise damaged core will effect the flyback characteristics to the point where it may not work correctly or even blow the horizontal output transistor. 3. Internal shorts in the FOCUS/SCREEN divider network, if present. One sign of this may be arcover of the FOCUS or SCREEN sparkgaps on the PCB on the neck of the CRT. 4. Internal short circuits in the windings. 5. Open windings. More than one of these may apply in any given case. First, perform a careful visual inspection with power off. Look for cracks, bulging or melted plastic, and discoloration, Look for bad solder connections at the pins of the flyback as well. If the TV or monitor can be powered safely, check for arcing or corona around the flyback and in its vicinity, Horizontal or vertical flipped picture The picture is flipped left-to-right or is upside-down or both. This cannot happen as a result of a failure. For a CRT-based TV or monitor, it almost Date Developed:

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certainly means that the wires to the horizontal or vertical deflection yoke have been swapped to enable the picture to appear correct when viewed via a mirror (horizontal only) or if the unit were mounted base-up to a ceiling (both). The remedy is simply to swap the two wires to the relevant deflection yoke(s). There may even be obvious splices to guide you. There is usually a connector with 4 relatively fat wires that go to the deflection yoke on the CRT neck (NOT the PCB attached to the tube base). If you don't have a schematic, trace these on the main PCB back to their origin. The horizontal will originate somewhere in the vicinity of the flyback transformer. It may be possible to disengage the wires from the connector shell and swap them there. If not, cut, splice, and solder. Adjustment of the appropriate centering controls may be needed. For flat panel displays, it is even more unlikely this would happen as a result of a hardware failure. Most likely, there is a mode setting in the one of the setup menus for the TV or monitor itself. It could also be in the receiver for the TV, or the driver or application software of the PC. If the source is a video projector, the menu setting is likely there, to select between front and rear projection (horizontal) or table or ceiling mount (both). So, don't bother to open up the flat panel TV or monitor. The problem is not there! :)

High Voltage Power Supply Problems HV power supply fundamentals Most, if not all, TVs derive the high voltage for the CRT second anode, focus, and (sometimes) screen (G2) from the horizontal deflection system. This technique was developed quite early in the history of commercial TV and has stuck for a very simple reason - it is very cost effective. A side effect is that if the horizontal deflection fails and threatens to burn a (vertical) line into the CRT phosphors, the high voltage dies as well. Most TV high voltage supplies operate as follows: 1. Horizontal output transistor (HOT) turns on during scan. Current increases linearly in primary of flyback transformer since it appears as an inductor. Magnetic field also increases linearly. Note: flyback is constructed with air gap in core. This makes it behave more like an inductor as far as the primary drive is concerned. 2. HOT shuts off at end of scan. Current decreases rapidly. Magnetic field collapses inductively coupling to secondary and generates HV pulse. Inductance and capacitance of flyback, snubber capacitors, and parasitic capacitance of circuitry and yoke form a resonant circuit. Ideally, voltage waveform across HOT during flyback (retrace) period will be a single half cycle and is clamped by damper diode across HOT to prevent undershoot. 3. Secondary of flyback is either a single large HV winding with HV rectifiers built in (most often) or an intermediate voltage winding and a

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voltage multiplier built in or a separate unit (see the section: What is a tripler?. The output will be DC HV pulses. 4. The capacitance of the CRT envelope provides the needed filtering to adequately smooth the HV pulses into a DC voltage. 5. A high resistance voltage divider provides the several kV focus voltage and sometimes the several hundred volt screen (G2) voltage as well. Often, the adjustments for these voltages are built into the flyback. Sometimes they are mounted separately. The focus and screen are generally the top and bottom knobs, respectively. What is a tripler? In some TVs, the flyback transformer only generates about 6-10 kV AC which is then boosted by a diode-capacitor ladder to the 18-30 kV needed for modern color CRTs. The unit that does this is commonly called a tripler since it multiplies the flyback output by about 3 times. Some TVs use a quadrupler instead. However, many TVs generate the required HV directly with a winding with the required number of turns inside the flyback transformer. Triplers use a diode-capacitor ladder to multiply the 6-10 kV AC to 18-30 kV DC. Many triplers are separate units, roughly cubical, and are not repairable. Some triplers are built in to the flyback - it is probably cheaper to manufacture the HV diodes and capacitors than to wind a direct high voltage secondary on the flyback core. In either case, failure requires replacement of the entire unit. For external multipliers, the terminals are typically marked:     

IN - from flyback (6-10 kV AC). OUT - HV to CRT (20-30 kV DC). F - focus to CRT (2-8 kV). CTL - focus pot (many megohm to ground). G, GND, or COM - ground.

Symptoms of tripler failure are: lack of high voltage or insufficient high voltage, arcing at focus protection spark gap, incorrect focus voltage, other arcing, overload of HOT and/or flyback, or focus adjustment affecting brightness (screen) setting or vice-versa. Where there is overloading, if you disconnect the tripler and everything else comes back to life (obviously, there will be no HV or picture), then it is very likely bad. High voltage shutdown due to X-ray protection circuits A TV that runs for a while or starts to come on but then shuts down may have a problem with the X-ray protection circuitry correctly or incorrectly determining that the high voltage (HV) is too great (risking excessive X-ray emission) and shutting everything down. A side effect of activation of this circuitry is that resetting may require pulling the plug or turning off the real (hard) power switch. Date Developed:

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Was there anything else unusual about the picture lately that would indicate an actual problem with the HV? If this is the case, then there may be some problem with the HV regulation. If not, the shutdown circuit may be overly sensitive or one of its components may be defective - a bad connection of leaky cap (or zener). If the horizontal frequency is not correct (probably low) due to a faulty horizontal oscillator or sync circuit or bad horizontal hold control (should one exist!), HV may increase and trigger shutdown. Of course, the picture won't be worth much either! Modern television receivers and video monitors are all equipped with a safety circuit to shut down the high voltage feeding the anode of the picture tube if that high voltage becomes excessive. (This is to prevent dangerous x-rays emitted when electrons with too much energy strike the metal shadow mask just inside the TV screen.) Unfortunately, high voltage shutdown problems can be very difficult to diagnose because, once shutdown has occurred, the horizontal pulses used to generate the high voltage are turned off, and with them the high voltage itself. In many cases I have encountered, the high voltage is not excessive, but the shutdown circuit itself has failed and falsely triggers. A common cause of this is failure of the circuitry that samples the high voltage and feeds a portion back to the input of the shutdown circuit. Typically, a tap from the flyback transformer feeds a diode and a filter capacitor to produce a sample DC voltage proportional to the high voltage. As the high voltage increases, so does this sample. It is usually further reduced by a voltage divider, then sent through a series zener diode to the "horizontal shutdown" input of a video processor chip, so that, if the divided down voltage exceeds the rating of the zener diode, the latter will conduct and trigger the shutdown input, which then latches off the horizontal pulses. Now if the bottom resistor in the voltage divider opens, or increases above its nominal value (common for high value carbon resistors), the sampled voltage will increase, possibly enough to falsely trip the shutdown input. Check it with an ohmmeter. Incidentally, if you don't have a schematic, you can still attempt to diagnose and repair your shutdown problem. Start with the video processor IC, a huge chip that controls most of the TV functions. Get the pinout from this web site, the ECG semiconductor replacement guide, or data sheet archives on the Internet. Find the horizontal output and horizontal shutdown pins, and attach oscilloscope probes to verify that you have a shutdown problem. If you do, you will see horizontal pulses for a brief instant on power up, but suddenly disappearing as the shutdown input voltage goes up and turns them off. (This is a latching circuit, so the shutdown voltage will normally stay high until the power is turned off.) the voltage back up where it belongs. But that raises all the other output voltages as well, making them higher than they should be, including the one powering the high voltage supply! And that will trip the shutdown circuit. When replacing filter capacitors, be sure to use good ones rated for 105 (not 85) degrees C, and able to withstand the high frequency pulses they are getting hammered by in these circuits.

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Low or no high voltage Most of these problems are due to faults in the horizontal deflection system shorted HOT, shorted windings or HV rectifiers in the flyback, defective tripler, or other bad parts on the primary side of the flyback. However, if you discover an inch layer of filth inside the TV, the HV could simply be shorting out - clean it first. In most cases, these sorts of faults will put an excessive load on the horizontal output circuits so there may be excessive heating of the HOT or other components. You may hear an audible arcing or sizzling sound from internal shorts in the flyback or tripler. Either of these may bet hot, crack, bulge, or exhibit visible damage if left on with the fault present. Most modern TVs do not regulate HV directly but rather set it via control of the low voltage power supply to the HOT (B+), by snubber capacitors across the HOT, and the turns ratio of the flyback. The HV is directly related to the B+ so if this is low, the HV will be low as well. Faulty snubber capacitors will generally do the opposite - increase the HV and the X-ray protection circuits may kick in. However, low HV is also a possibility. The only way the turns ratio of the flyback can change is from a short which will manifest its presence in other ways as well - excessive heating and load on the horizontal output circuits. While a shorted second anode connection to the CRT is theoretically possible, this is quite unlikely (except, as noted, due to dirt). Excessive high voltage Any significant increase in HV should cause the X-ray protection circuits to kick in and either shut down the set or modify the deflection in such a way as to render it harmless. Symptoms include arcing/sparking of HV, smaller than normal picture, and under certain scenarios, possible excessive brightness. Causes of the HV being too high are: 1. Excess B+ voltage to the HOT. The likely cause is to a low voltage regulator failure. 2. Open snubber capacitors across the HOT. These are under a lot of stress and are located near hot components so failure is possible. 3. Incorrect excessively long scan drive to HOT caused by failure of horizontal oscillator/sync circuits. However, other things like the HOT will probably blow up first. The picture will definitely be messed up. 4. Failure of HV regulator (tube sets and a few solid state sets - actual HV regulators are relatively uncommon today.) This may result in an underscanned (smaller than normal) picture. Snaps, crackles, and other HV breakdown Various problems can result in occasional or sustained sparking or arcing sounds from inside the monitor. Note that a static electricity buildup is Date Developed:

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common on the front of the screen. It is harmless and there iss nothing you can do about it anyhow. The following may result in occasional or sustained sounds not commonly associated with a properly working TV or monitor. There may or may not be flashes or blanking of the screen at the same time as the audible noise. See the same-named sections that follow for details.     

Arcing, sparking, or corona from CRT HV anode (red wire/suction cup). Arcing at CRT sparkgaps. Arcing from flyback or vicinity. Arcing due to bad connections to or disconnected CRT return. Flashovers inside the CRT.

Arcing, sparking, or corona from CRT HV anode (red wire/suction cup) Symptoms could include a sizzling corona or more likely, an occasional or rapid series of sharp snaps - possibly quite loud and quite visible - from the anode connection (at the suction cup) on the CRT to the grounded coating on the outside of the CRT or a chassis ground point (or any other conductor nearby). Corona is a high resistance leakage through the air without total breakdown. The snapping is caused by the sudden and nearly complete discharge of the CRT anode capacitance through a low resistance ionized path similar to lightning. There are two likely causes: 1. Dirt, dust, grime, around and under the suction cup on the CRT are providing a discharge path. This may be more severe in humid weather. Safely discharge the HV and then remove and thoroughly clean the HV suction cup and the area under it and on the CRT for several inches around the HV connection. Make sure there are no loose wires or other possible places for the HV to discharge to in the vicinity. 2. The high voltage has gone through the roof. Usually, the X-ray protection circuitry should kick in but it can fail. If cleaning does not help, this is a likely possibility. See the sections: "High voltage shutdown due to X-ray protection circuits" and "Excessive high voltage". Arcing from flyback or vicinity Arcing may be visible or audible and result in readily detectable levels of ozone. Note that very slight traces of ozone may not indicate anything significant but if the TV smells like an office copier, there is probably some discharge taking place. WARNING: It is possible for arcing to develop as a result of excessive high voltage. Symptoms might be a smaller than normal excessively bright picture but this may not be able

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to be confirmed until the flyback is repaired or replaced. See the section: Excessive high voltage. 

On the HV output, it will probably be a loud snapping sound (due to the capacitance of the CRT) with associated blue/white sparks up to an inch or more in length. If the arc length is short enough, this may turn into a nearly continuous sizzling sound with yellow/orange arc and melting/burning plastic. Prior to the HV rectifier, it will likely be a continuous sizzle with orange/yellow/white arc and melting/burning plastic or circuit board material. Internal arcing in the flyback may be audible and eventually result in a bulging and/or cracked case (if some other component doesn't fail first as this would take some time to develop). A corona discharge without actual sparks or a visible well defined arc is also possible. This may be visible in a totally dark room, possibly more likely when the humidity is high. A thorough cleaning to remove all dust and grime may be all that is needed in this case. If the arc is coming from a specific point on the flyback - a crack or pinhole - this may be patched well enough to confirm that the rest of the TV is operational and a new flyback is worth the money. Otherwise, there is no way of knowing if the arcing may have damaged other circuitry until a replacement flyback - possibly money wasted arrives. To attempt a repair, scrape off any dirt or carbon that is present along the path of the arcing and its vicinity. Then, clean the area thoroughly with alcohol and dry completely. Otherwise, the dirt and carbon will just act as a good conductor and the arcing will continue under your repair! Several layers of plastic electrical tape may be adequate for testing. Multiple coats of high voltage sealer or non-corroding RTV silicone (if it smells like vinegar - acetic acid - as it cures, this may get in and affect the windings) would be better if the objective is an actual repair. A thick layer of Epoxy may be even better and affected less by possible HV corona. Either of these may prove to be a permanent fix although starting the search for a source for a new flyback would not hurt just in case. The arc most likely did damage the insulation internally which may or may not be a problem in the future. Procedure for repair of an arcing flyback

First I clean the afflicted area with Electromotive spray from Autozone. It's for cleaning alternators. On Z-line I remove the focus control and wash with the alternator cleaner and a tooth brush until all dirt and carbon deposits are removed. Then I take an xacto knife and carve out the carbonized hole where the arcing broke through. Then take your soldering iron and close the hole by melting adjacent plastic into it. (clean any solder off your iron with solder-wick first). Then cut some plastic off of some other part off the flyback where it wont be needed and use this to plastic weld (with your iron) a hump of a patch into and over the arc Date Developed:

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hole. Smooth and seal with iron. Next apply as thick a layer of silicone rubber as you can and let dry overnight. Arcing at spark gaps and gas discharge tubes on CRT neck board or elsewhere These are protective devices intended to breakdown and divert excessive voltage away from the CRT (usually). This is rarely due to a defective sparkgap or gas discharge tube but rather is a safety mechanism like a fuse designed to protect the internal electrodes of the CRT if the focus or screen voltage should become excessive. The sparkgap breaks down first and prevents internal arcing in the CRT. These sparkgaps may be built into the CRT socket as well. Arcing at a sparkgap or a glowing or flashing discharge tube may be accompanied by total loss of picture or bad focus, brightness or focus fluctuations, or any of a number of similar symptoms. A common cause is a breakdown inside the focus divider (usually part of the flyback or tripler) but could also be due to excessive uncontrolled high voltage due to a failure of the B+ regulator or HOT snubber capacitor, or (ironically) even a short inside the CRT.  

Spark gaps may be actual two or three pin devices with seemingly no insides, part of the CRT socket, or printed on the circuit board itself. Gas discharge tubes look like small neon lamps (e.g., NE2) but could be filled with some other gas mixture to provide a controlled higher breakdown voltage.

Therefore, like a fuse, don't just replace or disable these devices, locate and correct underlying problem. The CRT makes an expensive fuse! Arcing due to bad connections to or disconnected CRT return The Aquadag coating on the outside of the CRT is the negative plate of the HV filter capacitor. If this is not solidly connected to the HV return, you will have your 25 kV+ trying to go where it should not be. There should be a wire solidly attached to the CRT neck board or chassis. Without this, voltage will build up until it is able to take some other path - possibly resulting in damage to sensitive solid state components in the process. Therefore, is is important to rectify the situation. Warning: If you find this disconnected, don't just attach it anywhere. You may instantly kill ICs or other solid state components. It must be connected to the proper return point on the CRT neck board or chassis.

Ozone smell and/or smoke from TV Smoking is just as bad for TVs as for people and usually more quickly terminal. White acrid smoke may indicate a failed electrolytic capacitor in the power supply probably in conjunction with a shorted rectifier. Needless to say, pull the plug at once.

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Blooming or breathing problems There are several symptoms that are basically similar: 

Blooming is defined as an expansion of the raster or horizontal sections of the raster with bright material. For example, switching between dark and light picture causes the size of the picture to expand by 10%. A slight change in size is unavoidable but if it is greater than 1 or 2 percent from a totally black image to a full white one, this is either an indication of a defective TV or one that is badly designed. The cause is poor low or high voltage regulation. Check the B+ to the horizontal deflection. This is usually well regulated. If it is varying in sympathy to the size changes, trace back to determine why the low voltage regulator is not doing its job. The reason for the size change is that the high voltage is dropping and reducing the stiffness of the electron beam.

Expansion of the raster width in areas of bright imagery is an indication of short term regulation problems. The video drive may be interacting with the other power supplies. Check for ripple - this would be at the vertical scan rate - in the various regulated power supplies. The cause may be a dried up electrolytic capacitor - once you locate the offending voltage, test or substitute capacitors in that supply.

In both these cases, if this just started after some work was done to the TV, the brightness limiter and/or video drive may simply be set so high that the TV cannot supply enough current to the high voltage. If the brightness is acceptable with these turned down slightly and still have acceptable brightness, then there may be nothing wrong. 

Breathing is defined as a periodic change in the size of the raster which may be independent of what is displayed or its severity or frequency may be related to the brightness or darkness of the image. This is another type of regulation problem and may be caused by bad electrolytic capacitors or other components in the low voltage power supplies. If the TV uses a switchmode power supply or low voltage regulator separate from the horizontal deflection, first check its output(s) for a variation in voltage at the breathing rate. Test with a light bulb or resistor load to confirm that the problem is here and not the deflection or other subsystem of the TV.

A condition with somewhat similar symptoms is bad focus - fuzzy picture - but only with bright (high beam current) scenes. This could be just a matter of adjusting the focus control but may also indicate sub-optimal filament voltage due to bad connections or components in the filament circuit, or a tired worn CRT. You won't get high beam Date Developed:

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current without some serious spot blooming (a fat beam because too much cathode area is used) and you will get cathode 'poisoning' after prolonged use. Visually inspect the neck of the CRT for the normal orange glow of the filaments and check for bad connections and bad parts. Erratic focus or screen (G2) voltage and/or controls on flyback Symptoms may include fluctuating focus or brightness. In extreme cases, the result may be a too bright or dark picture or other behavior caused by breakdown in the Focus/Screen(G2) divider network. Usually, this will require flyback replacement to repair reliably. Sometimes, the section with the controls can be snapped apart and cleaned but this is not common. First, just try rotating the screen (G2) control back and forth a few times. This may clean up the contacts and eliminate the erratic behavior. Possibly, positioning it a bit to one side of the original location will help. Then, use the individual or other master background/bias adjustments to compensate for the improper brightness. Focus/Screen divider bypass surgery This is kludge number 41256 but may be the difference between a bit more life and the dumpster. If the previous extreme measures don't help, then it may be possible to simply substitute a good divider network externally. Note that if there is evidence of internal breakdown in the divider of the original flyback (hissing, cracks, overheating, bulging case, etc.), this will not work unless you can disconnect it from its HV connection. There are two issues: 1. Is this a stable situation? Even if you provide an external substitute, the parts inside the flyback may continue to deteriorate eventually resulting in other more total failure of the flyback or worse. 2. If you provide an external focus/screen divider, it must be done is such a manner (including proper mounting and super insulation) such that it cannot be called into question should there be a fire where the monitor is even the slightest bit suspect. Various size external focus/screen divider networks can be purchased but whether this is truly a cost effective solution is not obvious. Decaying or erratic focus or screen (G2) voltages The following applies to both CRT focus voltage (which should be a few kV) and screen or G2 voltage (which should be several hundred V). Date Developed:

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"The screen voltage will come up to normal after sitting over night, 400 V or so. After approximately 5 minutes or slightly longer, I hear a slight arcing. From that point on, the screen voltage will wander anywhere from 75 V up to maybe 150 V. Adjustment of the screen control on the flyback has only a small effect and is not permanent. Removing the CRT pcb results in the screen voltage returning to normal." This is very likely a short between electrodes inside the CRT unless there is something on the neck board that is breaking down as a result of some connection to the CRT. The flyback should largely not know the difference with the socket plugged into the CRT. However, on rare occasions, there is contamination within the 'plastic alignment base' on the end of the CRT neck. (It is possible to *carefully* remove the plastic piece and clean the CRT glass/pins. Reinstall the plastic piece if it is still intact or leave it off - just take care in replacing the CRT neck board.) One possibility is that glue used to hold components down on some circuit boards has deteriorated and turned conductive. Check for tan to brown stuff shorting traces on the CRT neck board. If this is present on the focus or screen traces or wires, it may just be your problem. Scrape off all of the old glue and then clean thoroughly. Repair any damaged traces. What happens to the HV? A HV breakdown possibly inside the CRT would result in all the voltages being dragged down. What happens to the picture? If you connect a charged HV capacitor (guessing a couple hundred volts, a couple microfarads) between G2 and G1 or focus, you **will** know if tapping the neck results in a momentary short! I cannot predict whether this will be a temporary cure or permanent killer. See the section: Rescuing a shorted CRT. Here is another thing to try: put a 100 M ohm or so resistor between SCREEN and the CRT socket. This should not affect the behavior much until the failure occurs. Then, check the voltage on both sides with a high impedance voltmeter (1000 M). If the CRT is arcing, it will be much lower on the CRT side and will probably fluctuate. You can play similar games with focus voltage. Disconnecting flyback wire(s) from CRT driver board In some cases, there may be one or more separate wires running to directly to the CRT socket. These are typically for focus which has a relatively high voltage so better insulation is needed but there may be no obvious means of removal should flyback replacement be needed. One alternative is simply to cut the wire(s) in a location that is well away from any place to short out, solder, and then do a most excellent job of insulating the splice. If there is more than one wire, make sure to label them first if they aren't color coded. However, you may find that the cap on the CRT socket snaps off using a thin knife blade or screwdriver. The wire may be soldered or just pressed in place in such a way that pulling it Date Developed:

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out is difficult or impossible without removing the cover. If there is more than one wire, label them before removal unless the locations are clearly marked. Sometimes the color is stamped on the plastic but there may just be a designation like "A" and "B".

Raster, Color, and Video Problems No color - black and white picture This means absolutely no color - equivalent to a black and white picture. Not even a hint of color. First, confirm that the source is actually in color - try another channel or input device. Next, check the settings of the color control - it may have accidentally been turned down. If your TV has some kind of automatic picture mode, try turning if off and adjusting the color control. Try adjusting fine tuning if you have such a control and the problem is with a broadcast or cable transmission. At this point with a confirmed color signal source, there is a problem with the chroma circuitry. Note that to the average person, the obvious question becomes: is my color picture tube bad? The answer is a definitive NO. It is virtually impossible for a defective CRT to cause a total loss of color. A defective CRT can cause a lack of a primary color - R, G, or, B or a short between two colors which will mess up the color but is not likely to result in a black and white picture. Some possibilities in no particular order: 1. 2. 3. 4. 5.

Weak signal or defect in tuner/IF causing loss of signal strength. Coler killer set too high (internal control) if it has one. Defective part around the chroma chip/circuit. Faulty color oscillator. Bad connections in area of chroma chip/circuit. Defective chroma chip (don't suspect this first just because it is probably very expensive).

A service manual or Sams', DMM, and scope will help greatly in attempting to troubleshoot this unless it is an obvious bad connection. Try prodding the main board around the chroma chip with an insulated tool to see if you can make the color come and go. I had one set where a $.02 resistor decided to open up causing just this problem - perfect BW picture, no color. Another had a coil with a broken wire. Saturated color but almost no brightness This means you have lost the luminance input to the chroma decoder or final video chip. A failure of the brightness limiter may result in similar symptoms. A few common causes are: Date Developed:

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 

Check the service switch (if any). Its contacts may be dirty and moving it back and forth a few times or using contact cleaner may be all that is needed. Check for open high value resistors around the chroma decoder IC. Check for open high value resistors in the brightness limiter circuit.

With a scope and schematic (or even just a pinout for the chip), you should be able to trace the luminance signal to see where it is getting lost. I have had several TVs and monitors where the delay line in the luminance circuitry has failed. Usually it's made out of glass, and inherently is fragile. Sometimes whacking the monitor would make it come back, leading to the thought of connectoritis or a cold solder joint -- where in fact it was the delay line (long rectangular unit with two to four leads). Replacing the delay line was the solution, but to check it first it'd be a good idea to look for 'in' and 'out' on the line and short the pins. The picture may be shifted, colours may not line up, but it'll tell you that it's the delay line if the picture comes back at all. It's better than looking at a saturated picture with no luminance! :)

Brightness control has no effect The following assumes that the picture is fine but the brightness is fixed probably at too high a level. However, there could be several interrelated problems if a common supply voltage were missing, for example. If it is a knob, then it should be varying the control grid (G1) voltages relative to the cathodes (K) of the CRT. This is not likely to be a very complex circuit. If you do not have a schematic, I would start by tracing from the control, check continuity and solder connections. Check the control itself for proper operation with an ohmmeter. A power supply going to one side of the control (negative probably) may be missing. Tbe control grid voltage will end up on the little board on the neck of the CRT - check there as well for bad solder connections or open resistors. If brightness is a digital control, then you will need a schematic unless there is an obvious bad connection.

One color is too weak or too strong If the problem is slight and/or has gradually gotten worse, this may just require an adjustment of the color brightness/background/bias and/or color gain/drive controls inside the TV. See the section: Color balance adjustment. Note that if it is possible to obtain a good black and white picture with the user color control set to its minimum, then this is not likely a problem with one of the primary color channels (red, green, or blue) but with the chroma decoding circuitry. Or, perhaps, you are just watching MTV! Even if it appears as though there is an excess, this may actually be a reduction in one of the primary colors. For example, a magenta tinge is represents a reduction in the strength of the green signal. Date Developed:

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   

Too high an intensity for one of the color channels will result in a tint of one of the primaries: red, green or blue. Too low an intensity for one of the color channels will result in a tint of the complement of one of the primaries: yellow, cyan, or magenta. Problems mainly in the shadows or dark areas of the picture usually represent a fault with brightness/bias/background. Problems mainly in the highlights or bright areas of the picture usually represent a fault with the gain/drive.

Once these have been eliminated, you are left with the following possibilities: 1. Defective part around the chroma chip/circuit. Misadjusted color oscillator. 2. Bad connections or short circuit in area of chroma chip/circuit. 3. Defective chroma chip (don't suspect this first just because it is probably very expensive). 4. Bad degauss circuit resulting in lack of degauss or abrupt termination of degauss current rather than smooth tail off. The CRT is not being properly demagnetized and color purity is totally messed up. 5. Bad CRT - the shadow mask has been damaged and it is impossible to properly adjust purity No picture/dark picture/erratic picture Where the picture is erratic - coming and going entirely or changing brightness suddenly, with power off, remove the picture tube socket (carefully!) and clean the pins with fine sandpaper and use contact cleaner on the socket. This source of bad connections can result in a variety of erratic symptoms. Check for bad solder connections on the CRT neck board. TV and monitor manufacturing quality and cold solder joints Any intermittent problems with monitors that cause random sudden changes in the picture brightness, color, size, or position are often a result of bad connections. Strategically placed bad connections can also cause parts to blow. For example, a bad connection to the SCR anode in a phase controlled power supply can result in all the current passing through the startup resistor, blowing it as well as other components. I had a TV like this - the real problem was a bad solder joint at a pin on the flyback. Thus, erratic problems, especially where they are power or deflection related, should not be ignored!

Why can't TV manufacturers learn to solder properly? I can think of several potential reasons - all solvable but at higher manufacturing cost. 1. Mass of large component leads (like shields) does not get adequately heated during manufacture leading to latent cold solder joints. While they may look ok, the solder never actually 'wetted' the heavy pins and therefore did not form a good mechanical or electrical bond. Date Developed:

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2. Thermal cycles and differential thermal coefficients of circuit boards, traces, and solder. While it is not easy to do anything about the material properties, using plated through-holes or a similar mechanical via would greatly increase the surface area of the joint and prevent the formation of cracks. 3. Vibration. This is also directly related to the single sided circuit boards without plated through-holes to strengthen the joints. 4. Lack of adquate mechanical support (single sided circuit boards without plated through-holes (vias). I believe that the single most significantimprovement would come about by using plated trhough-holes but this would add to the cost and apparently the consumer is not willing to pay more for better quality and reliability! Some designs have used rivlets - mechanical vias instead of plated ones. While this is good in principle, the execution has often been flawed where cold solder joints resulted between the rivlets and the circuit board traces due to lack of adequate process control. The Sony and RCA/GE tuner shield problem is interesting because this could have been solved years ago at essentially no additional cost as other manufacturers - and their own repair procedures - have proven. Intermittent or missing colors This is a catch-all for some of the most common TV and monitor problems. Note that due to the additive color scheme used in all emissive color displays like CRT or flat panel TV sets and video monitors, a single missing primary color (red, green, or blue) will result in the following appearance (for a white screen): Missing Color Appearance -----------------------------------------------Red Cyan (blue-green) Green Magenta (reddish-purple) Blue Yellow

Which color is affected may be even more obvious if the set has a color on-screen display for which you recall the proper colors. 

If gently whacking the set can make the color(s) come and go suddenly, then bad connections are probable. The most likely place for these are solder pads on the little circuit board on the neck of the CRT or even dirty CRT socket pins that are not making solid contact. Try prodding the CRT neck board with an insulated stick to see if you can affect the colors. Although not impossible, this is not likely to be a CRT problem.

If the color fades in and out with a delay of about 10-15 seconds, it is probably intermittent power to the CRT filament for that color and probably means a bad CRT since the three filaments are wired in Date Developed:

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parallel inside the CRT. One of the internal connections has come loose. Look in the neck of the CRT to make sure all three filaments are glowing orange. If one is out or goes on and off, toss the set. Replacing the CRT is probably not worth it. However, if they all go on and off together (all colors would be fading in and out though perhaps not quite in unison), then bad connections for the CRT filaments on the CRT neck board are indicated. To narrow down the problem: 

 

Locate the output for the bad color on the video driver board on the neck of the CRT. This will probably read a significantly higher voltage than the corresponding pins for the good colors. A circuit problem is likely - probably on this board. Test components on this board for the good and bad color channels. A shorted transistor or open resistor can kill one channel. Swap parts between good and bad colors to confirm. Gently pull the CRT neck board off of the CRT and replace it. This will tend to clean the contacts. Connect an output of the video/chroma circuit/chip that is working (i.e., a color that appears on the screen) to *all* three color drivers on the CRT neck board. o If you now get a more-or-less black and white picture (there may be a moderate color tint as the relative intensities of R,G,B may not be balanced), the problem is likely with the chroma decoder or its support circuitry. Note: the picture will be the intensity of only one color channel so it will not be quite *normal* in any case. o

If you still have missing or messed up colors, the problem is on the CRT neck board or with the CRT.

Retrace lines in picture During the time the electron beam is returning from right to left at the end of a line and bottom to top (over the course of multiple lines), it is supposed to be result in no visible light on the screen. However, a number of faults can result in visible retrace lines. The appearance will likely be a general reduction in contrast from the visible horizontal retrace on every scan line and two dozen or so diagonal lines lines (lower left to upper right) resulting from the vertical retrace. The retrace lines may be either white or gray (possibly with a slight color tint due to unequal settings of the color adjustments) or a primary color - red, green, or blue. Anything in between is also possible but less likely. Date Developed:

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White/gray retrace lines Where all colors are involved - the lines are essentially white or gray (or with a slight tint due to slight unequal settings of the color adjustments), look for something common like an incorrectly adjusted screen (G2) or master brightness/background/bias control or a problem in one of these circuits, a defective power supply or a problem in the blanking circuitry: 

Screen (G2) or master brightness/background/bias control - mark setting and then see if a slight adjustment removes the retrace lines. See the chapter: "TV Adjustments". Of course, if this happened suddenly, the problem is not due to a misadjusted control though a dirty pot is possible - turn it back and forth - this might clean it and restore normal operation. Power supply or connection to CRT neck board - insufficient voltage will result in the CRT never totally blanking. Check (usually scan derived) power supply components (from flyback). General power supply - check B+ for correct value and ripple. A main power supply fault might result in these symptoms (and usually many others). Blanking circuit - this may be a part of the video/chroma chip or separate. Check waveforms to determine if the blanking pulses are making it to the video output.

Red, green, or blue retrace lines Where only one color is showing, suspect an incorrectly adjusted individual background/bias control or bad part on the CRT neck board for that color. There is a slight possibility that a bad CRT may result in visible retrace lines. To eliminate this possibility: 

Disconnect the filament - all evidence of a picture, raster, and retrace lines should disappear once the filaments/cathodes have cooled (15 seconds or so. If there are still visible retrace lines, the CRT is suffering from cold or field emission from someplace (may not even be the cathode). Turn down the screen (G2) control on the flyback (usually). If one color remains no matter how you set the control, again there is some kind of weird emission from the CRT. However, if white/gray retrace lines remain, the problem may be in the screen supply.

The TV which I bought last started developing retrace lines after a month or so of use. I took it back to the lab for warranty (special deal) and had it examined by the real experts. They found that even with the filament supply disconnected and VG2 at 0V the screen would still light up. They could even see that the electrons weren't even coming from the cathode. That was with only the picture tube in a test rig. So in this case the obvious conclusion had to be that the tube was bad, and it was replaced (32" 16:9 SF, very $$). It had something to do with processing problems during manufacturing of the electron guns. Date Developed:

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So even if this was a rare case, it *can* happen that retrace lines are due to a bad picture tube. It's more usual to suspect the VG2 (screen voltage) or a defect somewhere in the RGB video path.

Providing isolation for a CRT H-K short This procedure will substitute a winding of your own for the one that is built in to the flyback to isolate the shorted filament from the ground or voltage reference. Note that if you have a schematic and can determine where to disconnect the ground or voltage reference connection to the filament winding, try this instead. The flyback is the thing with the fat red wire coming out of it (and perhaps a couple of others going to the CRT board or it is near this component if your set has a separate tripler) and may have a couple of controls for focus and screen. It should have some exposed parts with a ferrite core about 1/2-3/4" diameter. The filament of the CRT is the internal heater for each gun - it is what glows orange when the set is on. What has happened is that a part of the fine wire of the bad color's filament (assuming this is indeed your problem) has shorted to the cathode - the part that actually emits the electrons. Normally, the heater circuit is grounded or tied to a reference voltage so when it shorts to the cathode, the cathode voltage level is pulled to ground or this reference. You will need some well insulated wire, fairly thick (say #18-22). Find a spot on the flyback where you can stick this around the core. Wrap two turns around the core and solder to the CRT filament pins after cutting the connections to the original filament source (scribe the traces on the board to break them). Make sure you do not accidentally disconnect anything else. This winding should cause the filaments to glow about the same brightness as before but now isolated from ground. If they are too dim, put another turn on the flyback to boost the voltage as this will result in low emission, blooming, and possible damage to the cathodes after awhile. (Don't go overboard as you may blow the filament totally if you put too many turns on the core - you then toss the TV.) Rescuing a shorted CRT If the short is filament-cathode (H-K), you don't want to use the following approach since you may blow out the filament in the process. If this is the case, you may be able to float the filament and live with the short (see the section on: "Red, green, or blue full on - fog over picture". Shorts in the CRT that are between directly accessible electrodes can be dealt with in a more direct way than for H-K shorts. At this point you have nothing to loose. A shorted CRT is not real useful. If the fault is intermittent, you will, of course, need to catch the CRT with the socket disconnected and the short still present. Try some gentle tapping if necessary. If you do this with the charged capacitor across the suspect electrode, you **will** know when the short occurs! Date Developed:

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Also see the section: High voltage to focus short. Picture tube replacement It is possible to replace the picture tube. However, this is likely to be both expensive and possibly time consuming with respect to adjustments like purity and convergence. When replacing:  

Discharge both the old and new tubes before you start to be sure you won't have any unpleasant surprises. Take extreme care when handling - at the very least, a slip can result in a broken neck and a bad and expensive day.

"The 25VCXP22 picture tube of my RCA Accutouch XL-100 CCU-942 TV start fading. Its 100% transistorized, everything still works perfectly after about 20 years service. But:   

Can I still buy new RCA 25VCXP22 picture tube? What is the approximate cost? Any equivalent tube for direct replacement? Cost? If no replacement picture tube is available, what is other option?"

(From: Chris Jardine ([emailprotected]).) The important thing here is that the tube begins with 25V. If it does it should work in your set. The only thing you have to know is whether the tube has 'ears' attached permanently. The 25V comes both with and without these mounting ears permanently attached. I know that you can still get one of these from any of a number of suppliers. I know that Channel Master and RCA (Thomson, whatever!) still make them available as well as any of a number of local CRT rebuilders. High voltage to focus short Symptoms would be (with the unit powered and high voltage present):  

With the CRT neck board plugged into the CRT, the focus spark gap is likely arcing. With the socket unplugged, putting anything connected to ground (or any other circuitry) near the focus pin would result in a juicy spark or arc. WARNING: Removing the CRT socket and powering the set may destroy the CRT on some models. See the section: Warning about disconnecting CRT neck board.

If the CRT is gassy or up to air, forget it - it might make a decent fish tank :-). In this case, there would be visible arcing INSIDE the CRT probably not confined to a single location. However, if there is just a metal whisker between the F and HV, that might be able to be cleared by careful tapping or a charged capacitor. You may even be able to see it if you were Date Developed:

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to remove the yoke - the gap is pretty large, about 1-2 mm - the last gap between electrodes before the start of the internal (Dag) coating. See the section: Rescuing a shorted CRT. Note that other damage may have been done as Other components including the flyback, HOT, and parts on the CRT neck board and beyond, may have been damaged as a result of the short. Zapping the CRT may be just the beginning of what is required to repair it all. Dark picture A TV or monitor with a picture that is too dark may have a fault or the CRT may just be near the end of its useful life. First, confirm that your video source - computer, camera, etc. - is producing a proper signal. Is the brightness at all erratic? Does whacking the monitor have any effect? If so, then you may have bad connections on the CRT driver card or elsewhere. If the brightness tends to fade in and out over a 10 to 20 second period, a bad filament connection is likely. Check for the normal orange glow of the filaments in the neck of the CRT. There should be 3 orange glows. If they are excessively reddish, very dim, or fade in and out, you have located a problem. See the section: Picture fades in and out.

Common causes of brightness problems: 1. Dirty CRT faceplate or safety glass. Don't laugh. It sounds obvious, but have you tried cleaning the screen with suitable screen cleaner? It is amazing how dirty screens can get after a few years - especially around smokers! Wipe gently with a slightly dampened cloth - not soaking or you may end up with real problems when the water drips down inside and hits the electronics! On TVs with a separate protective faceplate, clean both the front and rear surfaces of this plate as well as the CRT itself. 2. Old CRT. The brightness of the CRT deteriorates with on-time. It does not matter much how bright your run your TV. An indication of a weak CRT would be that turning up the SCREEN (G2) or master brightness control only results in a not terribly bright gray raster before the retrace lines show up. There may be indications of poor focus and silvery highlights as well. A CRT brightener may help. See the section: Brightening an old CRT.

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3. Bad component in filament circuit or bad connection reducing filament voltage. This should be easy to check - there are only a few parts involved. If it is erratic, bad connections are likely. 4. Brightness control faulty - bad pot, bad connections, or problem with its power supply. Depending on specific problem, control may or may not have any effect. If digitally adjusted, there could be a problem with the logic or control chip. If the button or menu item has no effect at all, then a logic or control problem is likely. 5. Improperly set SCREEN (G2) voltage (usually on flyback) or faulty divider network. See the section: Adjustment of the internal SCREEN and color controls. 6. Improperly set video bias (background) levels or fault in video drive circuitry. See the sections starting with: "Optimal procedure for setting brightness/background and screen adjustments". 7. Fault in video amplifiers. With all three color affected equally, this would most likely be a power supply problem. A video amplifier problem is likely if turning up the SCREEN (G2) or master brightenss control results in a very bright raster before the retrace lines appear. Cheack signals out of the video/chroma(IC. 8. Fault in beam or brightness limiter. Many TVs and monitors measure the beam current (possibly indirectly) and limit the maximum to a safe value. The purpose of this may be to protect the CRT phosphors, and/or to assure that the power supply does not go out of regulation, and/or to limit X-ray emission. If this circuit screws up, a dark picture may result. Checking the signals and voltages at the CRT socket should determine if this is the problem. 9. High voltage is low. However, this would likely result in other symptoms as well with focus, size, and geometry. Brightening an old CRT If performing adjustments of the internal background and/or screen controls still results in a dark picture even after a long warmup period, the CRT may simply be near the end of its useful life. In the old days of TVs with short lived CRTs, the CRT brightener was a common item (sold in every corner drugstore, it seemed!). You can try a similar approach. Caution: this may shorten the life of the CRT - possibly quite dramatically (like it will blow in a couple of seconds or minutes). However, if the monitor or TV is otherwise destined for the scrap heap, it is worth a try. The approach is simple: you are going to increase the voltage to the filaments of the electron guns making them run hotter. Hopefully, just hotter enough to increase the brightness without blowing them out. Voltage for the CRT filament is usually obtained from a couple of turns on the flyback transformer. It is usually easy to add an extra turn or two which will increase the voltage and thus the current making the filaments run hotter. This will also shorten the CRT life - perhaps Date Developed:

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rather drastically. However, if the TV or monitor was headed for the dumpster anyhow, you have nothing to lose. Picture tube brightener Try a CRT brightener from MCM Electronics about $20. It boosts the filament voltage a volt or two. I have used them before and they help. You can also try running a power supply on the filament with the monitor OFF. Set the supply at the filament voltage and slowly bring the voltage up. If the filament is 6.3 volt bring it up gradually to 10 -12 volts for about a half hour. This will brighten it up some. Be careful because too much voltage can open the filament ! Before doing this did you check the screen voltage setting and the RGB settings for drive and background ? There are also commercial CRT rejuvenators that supposedly zap the cathodes of the electron guns. A TV repair shop may be able to provide this service, though it is, at best, a short term fix. More drastic measures to brighten CRT As a start, I crank the brightness control all of the way up. I then turn the color control all of the way up. I let the set run with a bright screen for around 15 min. This procedure cleans up the cathode surfaces so that they can emit more electrons. Now turn the controls back to normal and see if any improvement took place. If not, Wrap 2 or 3 turns of around 18 gauge insulated wire around the flyback and add this extra power in series with existing filament leads from flyback. You can experiment with the number of turns etc. to get brighter filaments. do not run the filaments white - just a brightened yellow. This will probably turn out to be around 8-9v in most cases. I had to do this on two different Sanyo replacement flybacks as they had low filament voltage from the factory. (flakey replacement parts). I`ve been running one of these Sanyos for around 4 years now with a nice bright picture (13") Left portion of screen is dark or faded "I've got an old TV where the left 1/3 of the screen is 'faded'. It is especially noticable when a dark picture is showing (like a night time scene)." This is normally caused by a bad filter capacitor on the power supply line (typically 200 V) that feeds the RGB output transistors. It is usually a scan derived voltage off of the flyback. Look for an electrolytic capacitor of around 4.7 to 10 uF, 160 to 250 V fed from a rectifier diode on this supply. Color balance changes across screen from left to right The characteristics are that a solid white screen will tend to be blue tinted on one side and red tinted on the other. This is usually a subtle effect and may be unavoidable with some designs. There are several possibilities: 1. Purity - this means the beams are landing on the wrong phosphor dots. This is what would be affected by moving from one location to Date Developed:

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another or even rotating the TV on its base without degaussing. If the problem just appeared, degaussing may be needed. What do you have near the TV or monitor? Loudspeakers or other devices which generate magnetic fields can easily cause all sorts of color purity problems. Relocate the offending device(s) or the TV or monitor and then degauss it. See the section: Degaussing (demagnetizing) a CRT. If the problem still persists, purity adjustment may be needed. However, this isn't likely to have changed so look for other causes before tackling these adjustments. 2. Unequal electron gun to shadowmask/screen distance - the electron beams for the red and blue video travel slightly different distances on the left and right sides of the screen so their intensity (due to focus not being optimal and other factors) in each case may differ slightly affecting color balance. 3. Doming - This would only happen in very bright areas and causes the shadow mask to expand and distort. (Doming should not be a problem with Trinitron CRTs which use tensioned wires in their aperture grill.) This would also not really affect left-right color balance in particular. I don't really know how much of a problem (2) is in practice or whether some manufacturers compensate for it. Bleeding highlights On very bright areas of the picture, one or more colors may bleed to the right resulting in a trail of those colors. The difference between this problem and the section: Trailing lines in one or more colors is that in this case, only highlights are affected. One cause of this is that the color gain, contrast, or intensity controls (whatever they are called on your set) are set too high. See the section on: "Color balance adjustment". Check the settings of any brightness limiter controls as well. Trailing lines in one or more colors Assuming this is not a form of ghosting resulting from poor reception conditions, then it could be any of the following: 

Poor decoupling in the power supplies for the video drive circuits probably on the CRT neck board. Check for bad (low uF or high ESR) filter capacitors (electrolytic mostly) on this board or the power supplies feeding it. Insufficient CRT filament voltage. This could be a result of bad connections or a bad component in the filament power supply (probably from the flyback). Check to see if the filaments are glowing bright orange and check the voltage if possible (though this can be Date Developed:

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tricky since it is often fed from a winding on the flyback and is a pulse waveform, not DC or a sinusoid. The service manual (or Sams' Photofact) will probably have info and waveforms. Bad CRT (more likely if only one color is affected). A weak electron gun can result in this behavior. Swap it with one that work properly. If the same color is still bad, that CRT gun is weak. The CRT will need rejuvenation or need to be replaced (more likely, the entire TV will be tossed into the dumpster).

One simple test would be to swap two of the color outputs to the CRT pins. If the behavior moves with the swap (i.e., from red to blue), then it is likely an electronic problem. If it is still the same colors, it is probably the CRT. Brightness changes from left-to-right across screen Slight variations in brightness across the face of the CRT are not unusual. In fact, if you used a photometer to actually measure the brightness, you might be amazed at the actual variance even with the best monitor or TV you just don't notice it. However, a major variation - usually a decay from left to right but could be the other way indicate a component failure. Of course, make sure the face of the screen is clean! 

A fault in the power supplies to the video amplifier and/or video output circuits. Most likely, an electrolytic capacitor has dried up and is not adequately filtering the power derived from the flyback which then has ripple at the horizontal scan rate and thus locked to the screen. The voltage decays from left-to-right between horizontal flyback pulses. The most likely location for these capacitors is in the vicinity of the flyback transformer on the mainboard or on the CRT neck board. Check the capacitors with capacitor tester or ESR meter and/or take a look at the power right at the video amplifier and video output drivers.

Horizontal linearity is bad - this may actually be a horizontal geometry problem and not a brightness problem. See if objects on left side of the screen are stretched compared to those on the right (or vice-versa). If they are, the problem is in the horizontal deflection circuits possibly a bad S correction capacitor or linearity coil.

Inoperative degauss circuit, TV moved or rotated without degaussing, or magnetic field from some other device (like a permanent magnet) is affecting CRT - slight amounts of magnetization may reduce brightness (by moving the beams into the black space between phosphor dots) before affecting color purity (where the beams land on the wrong phosphor dots). Date Developed:

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Try deguassing manually. See the section: Degaussing (demagnetizing) a CRT. Picture fades in and out If the picture faded away on the order of 10-20 seconds (and if it comes back, also comes up to full brightness in same time frame - possibly with the persuasion of some careful whacking) AND with NO other significant changes such as size, focus, etc., then take a look in the back of the tube for the filament to be lit - the orange glow near the CRT socket. If there is none, then you probably have a bad solder connection on the circuit board on the neck of the CRT. Look for fine cracks around pins on that board. Try prodding it with an insulating stick to see if the picture comes back. Resolder if necessary. Dirty or corroded CRT pins/socket contacts can also do this - remove, inspect, clean, and replace the neck board. It is probably not a bad CRT as the filaments are usually wired in parallel and all would not likely go bad at the same time. However, if only a single color fades in and out, then a bad connection inside the CRT is a distinct possibility - look for only one of the filament's glow to be coming and going. This is probably not worth fixing. If the picture faded away with other symptoms, then there is probably a fault in the video amplifier/output one of its power supplies - still probably a loose connection if you are able to get it back by whacking. Occasional brightness flashes These may last only a fraction of a scan line or much much longer. This could mean an intermittent fault in a variety of places including the video circuitry and SCREEN power supply: 

Brightness circuitry - SCREEN, master background or its power supply. Could be in or around flyback or focus/screen divider. Could perhaps be in the CRT, but probably less likely. Video amp before or at chroma demodulator - since after this point, you would most likely get colored flashes since only one of the RGB signals would likely be effected.

If you get it from all sources, then tuner/IF is ruled out. Suppose you just have no signal to a direct video input. What do you get? If you still get flashes, it should be real easy to monitor either the video outputs or SCREEN supply (with a HV divider on your scope) for noise. Then trace back to power or noise source.

Bad focus (fuzzy picture) Focus voltage on the CRT is usually in the range of 2-8 kV DC and should be controllable over a fairly wide range by the focus pot - usually located on the flyback or a little panel in its vicinity: Date Developed:

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 

If adjusting the pot results in a position of acceptable focus, you may be done. It is not unusual for the focus setting to drift a over time. If the setting is already as good as possible but not really good enough, the CRT may be tired. Alternatively, the filament voltage may be too low. Check for bad connections in the filament circuit. If the optimal setting is out of range of the focus pot, the problem is likely leakage in the focus divider in the flyback or one of the components on the CRT neck board.

Also see the sections: "Focus adjustment" and "Focus drifts with warmup". The focus wire usually comes from the flyback or if the general area or from a terminal on a voltage multiplier module in some cases. It is usually a wire by itself going to the little board on the neck of the CRT. If a sparkgap (a little 2 terminal device with a 1/8" gap in the middle) is arcing with power on, then the resistive divider has shorted inside the flyback, focus board, or HV multiplier whatever you TV has - and the this unit will need to be replaced. Ditto if the SCREEN control affects focus and/or vice-versa. Using a suitable high voltage meter (range at least 10 kVDC, 1000 M ohm or greater input impedance), you should be able to measure it connected and disconnected. The ground return will be the outside coating of the CRT which may or may not be the same as the metal chassis parts. If the voltage is very low (less than 2 kV) or too high and the pot has little effect: 

When measured right off of the source disconnected from the CRT neck board, then the problem is probably in the focus network in the flyback (or wherever it originates). Sometimes these can be disassembled and cleaned or repaired but usually requires replacement of the entire flyback or voltage multiplier. Note: you may need to add a HV (10 kV) capacitor between the focus wire and DAG ground to provide filtering so you get a DC level for your meter. When measured with the focus wire attached to the CRT neck board with the CRT connected but reasonable with the CRT unplugged, there is probably a short between the focus and another electrode inside the CRT. See the section: Rescuing a shorted CRT. When measured with the focus wire attached to the CRT neck board with the CRT unplugged, there is likely a component on the CRT neck board that is leaky or breaking down. Also, check for decayed (tan or brown) glue which may turn leaky with age.

Focus drift with warmup This could be due to a problem with the focus voltage power supply, components on the CRT neck board, or a tired worn CRT.

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Focus is controlled by a voltage of 2-8 kV DC usually derived from the flyback transformer and includes some resistors and capacitors. One of these could be changing value as it warms up. (assuming nothing else changes significantly as the unit warms up - e.g., the brightness does not decrease.) Focus voltage is derived from a subset of the high voltage winding on the flyback using a resistive voltage divider which includes the focus pot. These are extremely high value resistors - 200 M ohm is common - and so leakage of any kind can reduce or increase the focus voltage. All other things being ok - i.e., the picture is otherwise fine - I would suspect this type of failure rather than the CRT. The connection to the CRT is usually a separate wire running from the flyback or its neighborhood to the CRT neck board. Look for components in this general area. Use cold spray or a heat gun to isolate the one that is drifting. If you have access to a high voltage meter, you should be able to see the voltage change as the TV or monitor warms up - and when you cool the faulty part. If it is in the flyback, then sometimes the part with the adjustments clips off and can be repaired or cleaned. Most often, you will need to replace the flyback as a unit. 

If the optimal adjustment point of the focus control doesn't change that much but the best focus is simply not as good as it should be, the CRT is probably the problem. However, if the optimal point produces acceptable focus but it changes (and possibly moves off of one end of the adjustment knob range) as the unit warms up, the flyback or one of the components on the CRT neck board are likely drifting. If you have a high voltage meter, you can measure the focus voltage to determine if it is being changed by the focus pot and if it is in the ball park (2-8 kV typical). Sometimes, the part of the flyback with the focus pot can be snapped off and cleaned or parts replaced but usually you need to replace the whole unit. There may a capacitor or two on the PCB on the neck of the CRT that could have increased leakage as well thus reducing the focus voltage. To determine if the CRT is the problem, for sharp focus after the unit has warmed up. Power-off for an hour or so and carefully pull the CRT neck board off of the CRT. Then, power up the unit. Let it run long enough such that there would have been a detectable focus drift. Now, power-down, plug the CRT neck board back in, and power-up. Watch the image as it appears on the screen: o If the focus starts out fuzzy and sharpens up as the image appears and gradually becomes sharper as the CRT warms up the CRT is likely tired. The only catch here is that plugging the CRT neck board into the CRT results in an additional load on the flyback due to the picture beam current which heats it more as well. Thus, if the problem takes a few minutes to appear, keep

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the brightness turned down except to check the appearance of the picture from time to time. You can set the focus control for optimum when warmed up and just turn the TV on in well in advance of your favorite shows or add a user focus adjustment by drilling a hole in the plastic case for an *insulated* screwdriver or flyback focus knob extender :-). The CRT may continue to function for quite a while so this is not impending doom. o

o

If the focus is relatively stable as the image appears and increases in brightness *and* is about as sharp as it would be with the TV warmed up, the problem is most likely in the flyback. However, also check for bad components or decayed (tan or brown) glue on the CRT neck board. A drifting flyback will need to be replaced as it will probably get worse and fail completely. Clean the surface of the circuit board and CRT socket in the vicinity of the focus and screen terminals and traces. Contamination or just dirt and grime can easily cause problems especially on humid days since the resistance of these circuits is extremely high (100s of M ohms). If the focus is relatively stable as the image appears and increases in brightness *and* is similar to what it would be with the monitor cold, you have a very strange situation where some load on the high voltage power supply, perhaps, is causing a thermal problem. This would be rare.

Bad focus and adjustment changes brightness This is the classic symptom of a short between the focus and screen supplies - probably in focus/screen divider which is part of the flyback or tripler. If you have a high voltage meter, measuring the focus voltage will show that (1) it is low and (2) it is affected by the SCREEN control Similarly, the SCREEN voltage will be affected by the FOCUS control (which is what is changing the brightness. Blank picture, good channel tuning and sound Since the tuner and sound are ok, horizontal deflection which usually generates power for most of the set is also working. Does 'blank picture' means a totally black screen with the brightness and contrast controls having no effect whatsoever? Or, is there is no picture but there is a raster - scan lines on the screen? The direction in which troubleshooting should proceed differ significantly depending the answer. Here are some questions:

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1. As above, is there any light on the screen at any settings of the brightness and contrast controls, and/or when switching channels? Can you see any raster scanning lines? 2. Can you hear the high pitched (15735 Hz) of the horizontal deflection? 3. Looking in the back of the set, can you see the glow of the CRT filament? 4. Do you get that static on the front of the tube that would indicate that there is high voltage? Any cracking or other normal or abnormal sounds or smells?

Possible causes of no raster:    

No or low high voltage (low voltage, deflection, or high voltage power supply failure). Fault with other voltages like G1 or screen (G2) to CRT. Filament to CRT not getting powered. Drive to CRT bad/shut off as a result of fault elsewhere. For example, failure of the vertical deflection may disable HV or blank the screem to protect the CRT from burn-in due to the very bright horizontal line that would result. With some sets, it is possible that the X-ray protection circuitry will blank the screen without affecting tuning or audio.

Color TV only displays one color I assume that now you have no other colors at all - no picture and no raster. Let us say it is red - R. It is probably not the CRT. Do you have a scope? Check for the R, G, and B video signals at the CRT. You will probably find no signals for the defective colors. This is almost certainly a chroma circuit problem as any failure of the CRT or a video driver would cause it to lose a single color - the other two would be ok. Therefore, it is probably NOT the CRT or a driver on the little board on the neck of the CRT. Try turning up the SCREEN control to see if you can get a G and B raster just to confirm that the CRT is ok. Locate the video drive from the mainboard for the good and a bad color. Interchange them and see if the problem moves. If so, then there is a video signal problem. If not, it is on the little CRT board. It could be a defective chroma IC or something else in the chroma decoder. Disappearing Red (or other color) Problem: I have been given an old colour TV. The reception is good, but very often, when the contrast and brightness of the TV image is low (e.g. when a Date Developed:

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night scene is shown), the red colour slowly disappears, leaving behind the green and blue image and many red lines. The remaining red retrace are the giveaway that this is most likely not a CRT problem. (If there were no red lines, it could be the filament for the red gun of the CRT going on and off due to a bad connection inside the CRT - bad news.) How is a black and white picture? (Turn down the color control). If B/W picture is good, then the problem is somewhere back in the chroma decoder circuitry. Check the video input to the CRT video driver board and signals on that board. If B/W picture is also bad, then you can compare red and green signals to determine where they are becoming different. The red lines in your description sounds like the red video output circuit is drifting and messing up the background level, blanking, screen, or other setting. Could be a capacitor or other component.

Vertical brightness or color bars These are typically more or less equally spaced possibly more evident at the left side of the screen. They result only in brightness or color variations, not deflection speed. Diagonal lines are straight and not squiggly. Note that the appearance of these bars differs from those caused by ringing in the deflection circuits where diagonal lines will show a squiggling stair-step appearance. The most likely cause is a dried up electrolytic capacitor in the scan derived power supply for the video or chroma circuits or video output. Check for this ripple with a scope or test/replace any suspect capacitors.

Tuner, AGC, and Sync Problems No reception from antenna or cable Make sure your source is providing a signal and that the cable connectors are good (center pin not broken or bent). Try another TV if possible. Make sure you source select switch or mode is set correctly. Someone may have accidentally set it to direct video or AUX input. Are all bands affected? If so, the tuner or IF is faulty. If there is a lot of snow, then it is probably toward the front (circuitry wise) of the tuner. If it is just a black screen, then it could be in the IF or video amplifier. If only certain bands are bad - channels 2-6 for example, then certain parts of the tuner circuitry are faulty. However, make sure the CATV mode is set correctly as this affects reception on a band-by-band basis.

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The problems may be due to bad solder connections of the tuner shields, connectors, coils, and other components. Try prodding the tuner to see if you can make the problem come and go or at least change.

Picture is overloaded, washed out, or noisy This indicates an Automatic Gain Control (AGC) problem often caused by a dried up capacitor. You will probably need a schematic to go much further. This could be a problem in the tuner, IF, or video amplifiers. The following assumes you are sure the signal source is strong - try a VCR or other local one (channel 3/4, not the RCA jacks). (From: Glenn Watkins ([emailprotected]).) Substitute a variable voltage source for the tuner's AGC voltage. Most of the time the range of AGC is from 1 to 7 volts. If you can get a decent snow free picture with an external AGC source, then the tuner is probably OK.

Jumping picture on white scenes This could be an AGC problem if the picture appears overloaded. However, if the picture is normal except unstable, the sync separate is the place to look: White screens are a worst case video pattern for sync separators, and will cause an erratic shift in the vertical multivibrator trigger level unless the horizontal and video information is filtered out [integrated] prior to driving the vertical sync input of the processor IC. This will show up with a scope as high frequency noise going into the vertical sync input. Look for a small electrolytic [in fact, all of them], around 1-10 uF or so near the deflection/sync processor IC. Often simply increasing the value of this cap will help. Interference when using VCR RF connection (Some of these comments also apply to use of LaserDisc players, satellite receivers, video games, or other sources with RF modulator (Channel 3/4) outputs). This may consist of patterns or lines in the picture. If this only happens on the antenna or cable, it may be a problem with these sources or the tuner in the VCR rather than the TV. As a test, try the connecting the TV directly to the antenna or cable. If it only happens on cable, there may be a (temporary) problem with cable transmission contact your cable company. If it happens on playback of good quality (commercial) recordings, then it could be a compatibility problem between the VCR and TV. Make sure your patch cable connections are secure and that the cables are not damaged - in particular that the center pin is intact. Date Developed:

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1. Do these bars show up on other TV's connected to the same cable? 2. Is your TV connected to anything else? A/V receiver? VCR? If so, unplug *all* the equipment and plug it in one-at-a-time until the hum appears. If you have an AV receiver in the system, try running a jumper wire from the incoming CATV ground at the TV to the receivers chassis ground (usually the "phono ground screw"). If you have any devices with un-polarized plugs, unplug them and rotate them 180 degrees, and plug them back in. 3. If you connect a temporary antenna and view "off-the-air" signals, are the bars still there? If you still cannot eliminate the hum, try building a simple "ground isolator" out of two 75300 ohm baluns, as described in the link below:

Place it as close to the TV as possible. Missing or noisy channel or block of channels If you are unable to receive certain channels or blocks of channels, this is a tuner problem - could be as simple as bad connections - or even simpler:. First, check to see that the tuning mode is correct - TV, CATV, as this is the most common cause of channels 'disappearing'.

Loss of Channel after Warmup If there is a general loss of picture and sound but there is light on the screen, then most likely the tuner or IF stage is pooping out. With both no sound and no picture but a raster and static, it is most likely a problem in the tuner, power to the tuner, or its controller (if non-knob type). If it recovers after being off for a while, then you need to try a cold spray in the tuner/controller to identify the component that is failing. Take appropriate safety precautions while working in there! If it stays broken, then most likely some component in the tuner, its controller, or its power supply as failed. There is a slight chance that it could be a bad solder connection - I have seen these in the tuner modules of RCAs on several occasions (and many other manufacturers apparently not a solved manufacturing problem even after 40+ years!

Channel tuning drifts as set warms up This may be a slight drift - like someone is messing with the fine tuning or such a substantial change in tuning frequency that the channels go by as though you are surfing. Possible causes depend on tuner type: Date Developed:

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1. Quartz tuner (10 button direct access digital synthesizer) - For a slight drift, a component is probably changing value, possibly the crystal in the reference oscillator. For gross changes - flipping through channels - it is more likely to be a digital control problem - the microcontroller is misdirecting the synthesizer to change frequency. 2. Varactor tuner (buttons but not direct channel access) - If only a single pushbutton selection is the problem, the the varactor tuning diode for that button is probably changing capacitance. If all channels in a band (Vl, Vh, U) are having a problem, it is more likely to be a drifting D/A or faulty AFT (Automatic Fine Tuning) circuit or power supply. 3. Turret or switch tuner (Knobs) - A component like a capacitor is changing value. You will have to get in there with a heat gun or cold spray and track it down the old fashioned way. At least, the problem is almost certainly localized to the tuner box (and possibly the controller if applicable). As noted, gradual slight changes in tuning are likely due to frequency determining components drifting. Uncontrolled channel surfing is probably a logic problem. For the quartz tuner, this could still be marginal connections causing the microprocessor to misdirect the synthesizer to change channels. For the latter case, particularly, the cause may still be bad connections resulting in loss of channel memory and/or erratic behavior. Noise in picture and sound due to bright scene When a bright scene comes, the screen flashes and there is a lot of noise in the sound. When a dark scene comes, there is no flash or noise. Changing channel does not help. The noise persists even when the sound is muted. (The following is from: [emailprotected] (Sam Lattuca)) When the video detector level is adjusted too high, you will get noise in the sound while screen contains a lot of white information (i.e. letters) but won't when only dark scenes are present. The video level adjust is usually a small coil normally located near the IF section. Since your set is several years old, this wouldn't be uncommon. It can be adjusted while watching the picture and listening to the sound. Internal interference - switchmode power supplies and digital circuitry On virtually all newer televisions and in particular Mitsubishi televisions there is a problem with interference being emitted by the switched mode power supply. The common symptom of this 'fault' is snake like dotted 'S' lines on channels 2-6. It doesn't matter if it's cable, antenna or satellite(channel 3/4), this symptom can occur. Date Developed:

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The common cause of this interference being allowed into the tuner is cabling. The super cheap 'suitable for garbage tie' cable that comes with even the most expensive VCR's is the culprit in most cases. The second is a set of rabbit ears the least common is an open or high resistance to ground connection (usually at a connector) on the incoming cable line. To fix this there is only one reliable solution. All cabling must be hand made RG-6 cable. Make as follows: 1. Strip the outer sheath of the cable to expose the braid and *fold the braid* away from the end so that it covers the unstripped outer braid. 2. Strip the inner conductor to it's proper length. 3. Install a good quality RG-6 connector *over the folded* braid. 4. Crimp with the proper RG-6 attachment to the cable crimpers, don't use a set of pliers or other -crushing- device. If the cable company doesn't waterproof the outside connectors, Radio Shack sells a 'sealing tape' just for this purpose. Most cable companies use self sealing 'o-ring' connectors. There is also interference from internal microprocessors and digital text generators (on-screen display, close captioning, teletext). And with 100 Hz digital television there is a wealth of sources... Using only high quality shielded cable as described above seems like really good advise, FWIW I'd like to second that. I wish that everyone would take antenna cables as seriously as you. Generally, double-braided cable (using copper foil for second shield) and coaxially constructed connectors are recommended. But I think that the hand-mountable F-type connectors (Radio Shack) would be equally good, though less robust, if mounted properly. As far as antennas go, a decent rooftop antenna should always be better than whatever rabbit ear construction you might think of. In this case, distance counts too, the antenna WILL pick up interference. Those darn rabbit ears So you bought a high performance TV and a set of $20.00 rabbit ears and there are lines on channels 2 to 6. Go buy a set of rabbit ears that has *only* a coax connector on the back, throw the cable supplied with it in the bin for 'twist ties'. Also buy an inexpensive surge suppressor that has a cable protector, enough RG-6 cable and connectors for two cables.   

Make one cable long enough to get the antenna away from the set (12ft) and the other to connect the antenna to the surge suppressor. Connect the long cable to the set and the other end to the surge suppressor. Find an outlet away from the set and plug the surge suppressor in (pick the most sane order for all of this.) Date Developed:

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Connect the shorter cable to the surge suppressor and connect the other end to the antenna.

You're done and if you thought carefully you would have put the antenna near your easy chair so you can adjust the picture or put the antenna where you'll get the best reception and prevent interference. The surge suppressor was needed to ground the other end of the coax so as not to make the outer shield an antenna for the interference from the TV's power supply. This method can also help allevate 'dead spots' when using rabbit ears.

Audio Problems Picture fine, no audio First check that any muting control is not activated. This might be a button on the remote or set itself. If you have a headphone jack, it may have dirty contacts as plugging in a headphone usually mutes the speaker. If the set is mono or only one channel of a stereo set is out, then check for bad connections to the loudspeaker. Test the loudspeaker by disconnecting one of the wires (with the power off!) and measuring its resistance with an ohmmeter (it should be less than 100 ohms - probably less than 8 ohms). Or momentarily touch a 1.5 volt battery to the speaker terminals - you should get a click or pop from the speaker. Next, trace back from the speaker output terminals to the circuit board and look for bad solder connections or a loose or dirty connector. If these tests do not reveal anything, you probably need a scope (or audio signal tracer) and schematic. Or at least the part number off of the chip. Is the final amp a chip also or just a transistor? Have you tested the transistor? If there is little or no buzz from the speaker, that would indicate a problem fairly near the output. If the tuner/if were bad, I would expect some noise/humm pickup from the low level audio stages. Get the part number off of the chip. If it is in a socket, check the contacts for corrosion or looseness. Weak or distorted audio Assuming you are not attempting to play it at ear shattering levels, this may be due to an alignment problem in the IF/audio demodulator, a bad audio IC or other circuitry, bad connection, or a defective speaker. If your TV has an earphone or audio line out jack, try this to see if it is clear. If so, then your problem is in the final audio amp or speaker(s). If only one channel of a stereo TV is affected, it is almost certainly the audio amp or speaker for that channel. Interchange connection to the two speakers temporarily and see if the problem moves. If the problem is at all intermittent - try gently whacking the TV - then it is likely a bad connection - either a cold solder joint or a dirty or tired IC socket. Date Developed:

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The audio amplifiers in newer TVs are almost always ICs and replacements are usually readily available. If the IC is in a socket, remove the IC, clean the pins and socket contacts and reinstall it. Sometimes, the contacts on old socket lose their springiness and do not provide solid connections. Such a socket will need to be replaced. If your TV is fairly old - 10 years or so - this may be an alignment problem requiring tweaking of a coil in the sound IF. See your service manual. It may be possible to have similar problems with newer TVs but this is relatively rare. There could also be bad electrolytic capacitors, probably in the power supply area. Even though you might think this would result in hum and there is none (even when there is no audio in the program or the sound is turned down) dried up caps can result in distorted sound that may sound like a sort of clipping. An ESR meter is best for testing (with power off!) but carefully jumpering known good caps across suspect ones (again with power off, then turn on the set and check), will eventually find the bad one(s). High pitched whine or squeal from TV with no other symptoms First, make sure it is not coming from the loudspeaker itself. If it is, then we are looking at an unusual electronic interference problem rather than simply mechanical vibration. If it is a new set and think the sounds will drive you insane, returning it for a refund or replacement may be best alternative. However, you may get used to it in time. I don't know about returning a set to a store that doesn't take refunds (I won't even ask about that!). In most cases, this sound, while annoying, does not indicate an impending failure (at least not to the set - perhaps to your mental health) or signify anything about the expected reliability of the set though this is not always the case. Intermittent or poor connections in the deflection or power supply subsystems can also result in similar sounds. However, it is more likely that some part is just vibrating in response to a high frequency electric current. There are several parts inside the TV that can potentially make this noise. These include the horizontal flyback transformer, deflection yoke, other transformers, even ferrite beads in the horizontal deflection circuits. In addition, transformers or chokes in the switching power supply if this is distinct from the horizontal deflection circuitry. Or even a portion of the sheetmetal used for shielding if in close proximity to a magnetic component. You have several options before resorting to a 12 pound hammer: 

As much as you would like to dunk the TV in sound deadening insulation, this should be avoided as it will interfere with with proper cooling. However, the interior of the entertainment center cabinet can be lined with a non-flammable sound absorbing material, perhaps acoustic ceiling tiles. Hopefully, not a lot of sound energy is coming from the front of the set. Move the TV out of a corner if that is where it is located - the corner will focus sound energy into the room. Date Developed:

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Anything soft like carpeting, drapes, etc. will do a good job of absorbing sound energy in this band. Here is your justification for purchasing those antique Persian rugs you always wanted :-).

If you are desperate and want to check the inside of the set: 

Using appropriate safety precautions, you can try prodding the various suspect parts (flyback, deflection yoke, other transformers), even lowly ferrite beads, with an insulated tool such as a dry wooden stick. Listen through a cardboard tube to try to localizing the source. If the sounds changes, you know what part to go after. Once you have located the guilty party, some careful repositioning, a strategically wedged wooden toothpick, or a dab of RTV silicone or hot-melt glue may keep it quiet. Where the yoke is the guilty party, see the section: Reducing/eliminating yoke noise. It is possible to coat the flyback transformer, but this is used mostly when there a loose core or windings and you are getting not only the 15,735 Hz horizontal (NTSC) but also various subharmonics of this. This is probably acceptable but may increase the temperature of the flyback. A replacement flyback (or whatever part) may cure the problem unless it is a design flaw or manufacturing quality problem. However, the replacement part could be noisier. You really do not want to replace the yoke (aside from the cost) as convergence and other service adjustments would need to be performed. Other transformers can be replaced.

Note that the deflection frequency - just over 15 kHz for NTSC and PAL - is on the border of audible for adults but will likely be loud to younger people possibly to the point of being terribly annoying - or worse. If you are over 40 (men more so than women), you may not be able to hear the fundamental at all (at least you can look forward to silence in the future!). So, even sending the TV back for repair may be hopeless if the technician cannot hear what you are complaining about! BTW, if you have a really old tube type TV, the power tubes (damper and horizontal output) can also whine but these sets are few and far between these days :-). Reducing/eliminating yoke noise Carefully look under vertical core next to plastic liner, on top and bottom is a plate called the astigmatism shunt, it has come loose. Work RTV, epoxy, or service cement onto it to glue it down and noise should quit. yokes by removing the yokes and using motor armature spray sealant. If you carefully mark the EXACT position of everything (yoke, purity magnets), and slide the yoke off the CRT, then once the yoke has been sealed with motor armature spray sealant and Date Developed:

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has dried thoroughly, put the yoke back EXACTLY where it was, there should be no problems. The only thing I have had to do was set the purity on one set, but it was off a little to begin with. Whining when off? Many TVs actually run their switchmode power supplies even when off to power the standby stuff like the remote control receiver, real time clock or timer, and channel memory. Depending on the design of the regulator, the power supply may be running at a low chopper frequency due to the light load. Some people, dogs, and rodents are then annoyed. It could also be an indication of a fault like a bad capacitor or loosened transformer core if this symptom just developed - your hearing isn't likely improving :-(. There is so much running nowadays in 'off' electronics!

Miscellaneous Problems General erratic behavior You press VOLUME UP and the channel changes or a setup menu appears all by itself just at the climax of your mystery story. Before you break out the screwdriver (or 12 pound hammer), cover up the IR remote sensor. Some types of electronic ballasted fluorescent lights may confuse the remote control receiver. Someone or something may be sitting on the remote hand unit or it may be defective and continuously issuing a bad command. Or, the kids across the street may have nothing better to do than to drive your TV (and you) nuts with their remote! Assuming this is not the source of the problem: Check for bad connections - see if gently whacking the TV makes any difference or triggers the errant behavior. Bad connections in the power supply, system controller, or tuner, may result in this sort of behavior. See the section: TV and monitor manufacturing quality and cold solder joints. See the sections and separate documents on problems with RCA/GE/Proscan and Sony TVs if yours is made by one of these companies. A microcontroller or other electronic problem is also possible. If the symptoms only develop after the set warms up, it may be heat related (though simple bad connections are more likely). Use 'circuit chiller' or a heat gun to identify the bad part. Wiring transmitted interference The power that comes from the wall outlet is supposed to be a nice sinusoid at 60 Hz (in the U.S.) and it probably is coming out of the power plant. However, equipment using electric motors (e.g., vacuum cleaners), fluorescent lamps, lamp dimmers or motor speed controls (shop tools), and other high power devices, may result in a variety of effects. Date Developed:

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SELF-TEST EXAMINATION 1. Television Diagnoses (20)

2. TV. Parts at least

Defective section _____________

1._________________

Defective parts_______________ 2._________________ ______

3._________________ Defective section _____________4._________________ Defective parts_______________ 5._________________ 6._________________ Defective section _____________7.________________ Defective parts_______________ 8.________________ 9.________________ Defective section _____________10._______________ Defective parts_______________ 11._______________ Defective section _____________12._______________ Defective parts_______________ 13._______________ 14._______________ Defective section _____________15._______________ Defective parts_______________ 16._______________ 17._______________ Defective section _____________18._______________ Defective parts_______________ 19._______________ 20._______________

PARTS AND FUNCTION OF POWER SUPPLY Date Developed:

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The power supply is the heart of all electronic equipment or appliances. It supplies the electronic equipment all the voltages and current needed foe each operations. Functions of each parts: AC. Plug- with the plug we can easily plug in and plug out our converter from the supply voltages source. Switch- with the switch we can conveniently connect and disconnect the converter to or supply source. The types of switch is slide or single pole single throw switch (spst) . Fuse- the fuse protects the converter or power supplies the amplifier, radio, television or computer device. Types of converter 1. 2. 3. 4.

Half-wave converter Full-wave converter Split type converter Multiple converter

Types of transformer 1. Step-down – input AC. 220v, 110v, 0v and output 12v DC. 2. Step- up- input DC. 12v or 24v 0v and output 100v AC.,110v, or 220v AC. 3. Multiple output transformer- input 0vAC. 220vAC, and 110v AC. And output 3vdc,4.5vdc 6v, 7.5v, 9v, and 12v dc. Parts list to build converter 1. Fuse 2. Switch 3. Rotary switch 4. Step-down or step up transformer 5. Rectifier diode 6. Filter capacitor or electrolytic 7. Resistor 8. Hook-up wire 9. Line cord or AC. Cord 10. And basic tools and equipment TROUBLE SHOOTING OF GUIDE Symptom 1. No voltages output. Date Developed:

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Possible causes: 1. No contact or loose connection in the selector switch. Solder all wires at the selector adjusted. 2. Open diode, check the diode for the possible problem a. Leaky b. Open c. Shorted d. Loose contact 3. Test transformer.

and

verify

the

components

and

primary

winding

of

4. Double check the ac cord and other possible trouble and possible cause and remedies are the same as in project one.

Symptom2. Very low output voltages Possible causes: 1. Loose contact points in the selector switch. Remedy. Clean the contact point of the selector switch with contact cleaner or fluid. 2. Loose connection from selector switch to secondary winding of the transformer. Remedy resolders all connection from selector switch to the secondary winding. 3. Check and verify the components and circuit. 4. Replace the possible components defect and shorted.

Symptom3. Output voltage is present only in the range of 12 and 9v but no voltage output 6volt ranges. Possible cause: 1. Loose connection or loose contact of the selector switch at 6v range check the contact points and apply necessary remedies. 2. Check all components for circuit connection. Date Developed:

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Symptom4. Humming sound but the voltages is ok Possible causes: 1. Check the connection for no shortage circuit 2. Check the filter capacitor 3. Check the diode

TASK SHEET AND INSTRUCTION Title: CONSTRUCTION

OF

SWITCH

MODE

POWER

SUPPLY (SMPS) Performance Objectives: 1. To identify the electronic components used in a regulated power supply. 4. To learn how to make an etching printed circuit board for the regulated power supply projects and new switch mode device. 5. To assemble the power supply, and then measure its output voltage Materials Needed: PCB-printed circuit board UNIVERSAL POWER SUPPLY: SMPS Date Developed:

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Etching solution with PCB board SOLDERING AND DESOLDERING TOOLS Measuring equipments: VOM

Steps/Procedure: 1. Your instructor will give you a simple project and schematic diagram study then draw the circuit diagrams in the PCB layout labels all parts. 2. Make an etching printed circuit board for mounting the electronic components 3. Disassembly and transfer all components to the new PBC circuit check and verify. 4. In the following assembly steps, the components will be installed on the components side of the board the leads passed through the corresponding holes, and the board turned to solder the components terminals to the printed side. Solder each component immediately after it has been installed on the board. 5. Verify and check the connection of the circuit and testing for measuring tools. Assessment Method: 2. Check and verify every procedure during the testing process of training or students. 3. We will collect the papers on the right answer after measured value of the training or students. 4. Practical testing and direct observation and follow up questions. 5. Test and review exercises.

Radio Receiver set Two type of radio receiver set 1. Amplitude modulation 2. Frequency modulation Basic parts 1. Antenna- to receive and collect radio signals coming from radio broadcasting network 2. Tuning condenser or tuning capacitor-to select and collect the signal coming from antenna

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3. Mixer converter- to covert audio information or also called demodulator 4. Detector- to detect audio information and voltage signals 5. Local oscillator-

Two parts of AM/FM 1. Audio amplifier section 2. Tuning section 

As seen in the previous section, it is incredibly easy to transmit with static. All radios today, however, use continuous sine waves to transmit information (audio, video, data). The reason that we use continuous sine waves today is because there are so many different people and devices that want to use radio waves at the same time. If you had some way to see them, you would find that there are literally thousands of different radio waves (in the form of sine waves) around you right now -- TV broadcasts, AM and FM radio broadcasts, police and fire radios, satellite transmissions, cell phone conversations, GPS signals, and so on. It is amazing how many uses there are for radio waves today (see How the Radio Spectrum Works to get an idea). Each different radio signal uses a different sine wave frequency, and that is how they are all separated.

Any radio setup has two parts:

 o

Tuning: Broadband tuning is applied to the RF stage. The purpose of this is to reject the signals on the image frequency and accept those on the wanted frequency. It must also be able to track the local oscillator so that as the receiver is tuned, so the RF tuning remains on the required frequency. Typically the selectivity provided at this stage is not high. Its main purpose is to reject signals on the image frequency which is at a frequency equal to twice that of the IF away from the wanted frequency. As the tuning within this block provides all the rejection for the image response, it must be at a sufficiently sharp to reduce the image to an acceptable level. However the RF tuning may also help in preventing strong off-channel signals from Date Developed:

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entering the receiver and overloading elements of the receiver, in particular the mixer or possibly even the RF amplifier. o

Amplification: In terms of amplification, the level is carefully chosen so that it does not overload the mixer when strong signals are present, but enables the signals to be amplified sufficiently to ensure a good signal to noise ratio is achieved. The amplifier must also be a low noise design. Any noise introduced in this block will be amplified later in the receiver.

Mixer / frequency translator block: The tuned and amplified signal then enters one port of the mixer. The local oscillator signal enters the other port. The performance of the mixer is crucial to many elements of the overall receiver performance. It should eb as linear as possible. If not, then spurious signals will be generated and these may appear as 'phantom' received signals.

Local oscillator: The local oscillator may consist of a variable frequency oscillator that can be tuned by altering the setting on a variable capacitor. Alternatively it may be a frequency synthesizer that will enable greater levels of stability and setting accuracy.

Intermediate frequency amplifier, IF block : Once the signals leave the mixer they enter the IF stages. These stages contain most of the amplification in the receiver as well as the filtering that enables signals on one frequency to be separated from those on the next. Filters may consist simply of LC tuned transformers providing inter-stage coupling, or they may be much higher performance ceramic or even crystal filters, dependent upon what is required.

Detector / demodulator stage: Once the signals have passed through the IF stages of the superheterodyne receiver, they need to be demodulated. Different demodulators are required for different types of transmission, and as a result some receivers may have a variety of demodulators that can be switched in to accommodate the different types of transmission that are to be encountered. Different demodulators used may include:

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o

AM diode detector: This is the most basic form of detector and this circuit block would simple consist of a diode and possibly a small capacitor to remove any remaining RF. The detector is cheap and its performance is adequate, requiring a sufficient voltage to overcome the diode forward drop. It is also not particularly linear, and finally it is subject to the effects of selective fading that can be apparent, especially on the HF bands.

o

Synchronous AM detector: This form of AM detector block is used in where improved performance is needed. It mixes the incoming AM signal with another on the same frequency as the carrier. This second signal can be developed by passing the whole signal through a squaring amplifier. The advantages of the synchronous AM detector are that it provides a far more linear demodulation performance and it is far less subject to the problems of selective fading.

o

SSB product detector: The SSB product detector block consists of a mixer and a local oscillator, often termed a beat frequency oscillator, BFO or carrier insertion oscillator, CIO. This form of detector is used for Morse code transmissions where the BFO is used to create an audible tone in line with the on-off keying of the transmitted carrier. Without this the carrier without modulation is difficult to detect. For SSB, the CIO re-inserts the carrier to make the modulation comprehensible.

o

Basic FM detector: As an FM signal carries no amplitude variations a demodulator block that senses frequency variations is required. It should also be insensitive to amplitude variations as these could add extra noise. Simple FM detectors such as the Foster Seeley or ratio detectors can be made from discrete components although they do require the use of transformers.

o

PLL FM detector: A phase locked loop can be used to make a very good FM demodulator. The incoming FM signal can be fed into the Date Developed:

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reference input, and the VCO drive voltage used to provide the detected audio output. o

Quadrature FM detector: This form of FM detector block is widely used within ICs. IT is simple to implement and provides a good linear output.

Audio amplifier: The output from the demodulator is the recovered audio. This is passed into the audio stages where they are amplified and presented to the headphones or loudspeaker.

SELF-TEST QUESTIONS 1. What colors are commonly used to identify the following a. Local oscillator coil b. First intermediate frequency (IF) c. Second intermediate frequency (IF) d. Third intermediate frequency (IF) 2. What parts or components of the radio tuner to intercept and collect the signals 3. What are the common parts of the section in the radio tuner? 4. Name the components and each parts and functions. 5. Why is the intermediate frequency transformer important? 6. From the detector, where does the audio signal go? 7. What are the two type of receiver? 8. Draw the circuit diagram. Date Developed:

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Answer for Self-Test Question 1. 2. 3. 4. 3. 4. 5. 6. 7. 8.

Red color Yellow White Black The antenna intercepts and collects the radio signals. Antenna, mixer converter, intermediate frequency, detector, local oscillator Tuning section, and amplifier section The intermediate frequency transformer is important because it prevent interference. Amplitude modulation, frequency modulation diagram

AM-FM RECIEVER TROUBLE SHOOTING Trouble symptom1. No Radio signal, but the audio amplifier section is good. Possible causes: 1. disconnected components into the radio tuner section 2. open shorted detector diode of components or any wire connection 3. open or shorted IF transformer transistor 4. open or disconnected antenna coil 5. shorted coupling capacitor connected at the emitter of the mixer converter transistor. 6. Shorted ceramic capacitor 7. Shorted bypass capacitor at the base of the IF amplifier transistor. 8. Shorted tuning capacitor 9. Open primary winding of the local oscillator coil. 10. Open primary winding third IF transformer Date Developed:

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Trouble Symptom 2. Weak sound, but audio amplifier section is good. Possible causes: 1. Loose connection in the radio tuner section 2. Shorted emitter stabilizing of mixer converter transistor. 3. Shorted coupling capacitor connected at the emitter of the mixer converter transistor. 4. Shorted ceramic capacitor 5. Shorted bypass capacitor at the base of the IF amplifier transistor. 6. Shorted tuning capacitor 7. Open primary winding of the local oscillator coil. 8. Open primary winding third IF transformer Trouble symptom 3. No audio, No sound indicating no signals or no output at all Possible causes: 1. Loose connection and power supply is open. Check and verify 2. Open transformer and power transistor is shorted 3. Replace any components that connected to system board amplifier or tuner section. AUDIO AMPLIFIER CIRCUITS BY WATTS 4. 15 WATTS AMPLIFIER AMPLIFIER

2. 50 WATTS MONO

AUDIO MIXER WITH AMPLIFIER Date Developed:

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SERVICE PRODUCT ELECTRONIC GUIDE Guidelines for service 1. Observe and prepare the guidelines the trainers must be observe the situation and condition of any domestic appliances before start for repairing and diagnosis, possible question before start. a. What are the symptoms? b. What conditions existed at the time of failure? c. What action was in the progress? d. What functions still works? 2. Apply your planning- before start be plan for repair and condition a. Use the proper test and equipment b. Don’t panic or any action 3. Use your senses- look any smell. is there any odor present that suggest overheated components does any parts of electronic components.

Microprocessor Programming

The “vocabulary” of instructions which any particular microprocessor chip possesses is specific to that model of chip. An Intel 80386, for example, uses a completely different set of binary codes than a Motorola 68020, for designating Date Developed:

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equivalent functions. Unfortunately, there are no standards in place for microprocessor instructions. This makes programming at the very lowest level very confusing and specialized. When a human programmer develops a set of instructions to directly tell a microprocessor how to do something (like automatically control the fuel injection rate to an engine), they’re programming in the CPU’s own “language.” This language, which consists of the very same binary codes which the Control Unit inside the CPU chip decodes to perform tasks, is often referred to as machine language. While machine language software can be “worded” in binary notation, it is often written in hexadecimal form, because it is easier for human beings to work with. For example, I’ll present just a few of the common instruction codes for the Intel 8080 micro-processor chip: Hexadecimal

Binary

Instruction description

-----------

--------

-----------------------------------------

|

7B

01111011

Move contents of register A to register E

87

10000111

Add contents of register A to register D

1C

00011100

Increment the contents of register E by 1

D3

11010011

Output byte of data to data bus

| | | | | |

Even with hexadecimal notation, these instructions can be easily confused and forgotten. For this purpose, another aid for programmers exists called assembly language. With assembly language, two to four letter mnemonic words are used in place of the actual hex or binary code for describing program steps. For example, the instruction 7B for the Intel 8080 would be “MOV A,E” in assembly language. The Date Developed:

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mnemonics, of course, are useless to the microprocessor, which can only understand binary codes, but it is an expedient way for programmers to manage the writing of their programs on paper or text editor (word processor). There are even programs written for computers called assemblers which understand these mnemonics, translating them to the appropriate binary codes for a specified target microprocessor, so that the programmer can write a program in the computer’s native language without ever having to deal with strange hex or tedious binary code notation. Once a program is developed by a person, it must be written into memory before a microprocessor can execute it. If the program is to be stored in ROM (which some are), this can be done with a special machine called a ROM programmer, or (if you’re masochistic), by plugging the ROM chip into a breadboard, powering it up with the appropriate voltages, and writing data by making the right wire connections to the address and data lines, one at a time, for each instruction. If the program is to be stored in volatile memory, such as the operating computer’s RAM memory, there may be a way to type it in by hand through that computer’s keyboard (some computers have a mini-program stored in ROM which tells the microprocessor how to accept keystrokes from a keyboard and store them as commands in RAM), even if it is too dumb to do anything else. Many “hobby” computer kits work like this. If the computer to be programmed is a fully-functional personal computer with an operating system, disk drives, and the whole works, you can simply command the assembler to store your finished program onto a disk for later retrieval. To “run” your program, you would simply type your program’s filename at the prompt, press the Enter key, and the microprocessor’s Program Counter register would be set to point to the location (“address”) on the disk where the first instruction is stored, and your program would run from there. Although programming in machine language or assembly language makes for fast and highly efficient programs, it takes a lot of time and skill to do so for anything but the simplest tasks, because each machine language instruction is so crude. The answer to this is to develop ways for programmers to write in “high level” languages, which can more efficiently express human thought. Instead of typing in dozens of cryptic assembly language codes, a programmer writing in a high-level language would be able to write something like this . . .

Print "Hello, world!"

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How to Set Up Home Theater System (A Simple Guide) Miles of wires, acres of poorly-labeled connections, inputs, outputs, it can all be quite daunting. Setting up a home theater system doesn’t have to be, though. In fact, it can be quite easy. No matter what gear you have, this guide should help you get everything set up correctly. Even if your system is already connected, it’s probably worth skimming this article to make sure it’s connected right. You may not be getting the most out of your system and not even know it. Follow the signal The first thing to understand is something called signal flow. Wait, don’t click away! It’s not as tetchy as it sounds. The flow of the signal. If you can get this part, the rest is easy. The signal is the movie on your Blu-ray, the TV show from Netflix NFLX +2.18%, or the music from Pandora. Following the flow of the signal will help you figure out the right inputs and outputs on your gear. Note: I’m going to say “Blu-ray” as my source example, but the setup is the same if you’ve got a Roku, Apple AAPL -0.64% TV, Amazon Fire TV, or any cable/satellite box. Speaker Configurations Audio accounts for 50 percent of the cinema experience, and a surround sound system can create a complete audio environment around you. A good 5.1-channel system will give you a full surround sound experience. Most DVD and Blu-ray™ media, some Super Audio CDs (SACDs), broadcast TV, and many streaming sources are in 5.1channel format. Date Developed:

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Going to 7.1 channels improves the directionality of sound effects and adds to the audio ambience of 3D. Some Blu-ray Disc™ and premium streaming sources feature 7.1. (They will sound fine on a 5.1 system, too.) A 9.1-channel system adds front height speakers to take advantage of Dolby Pro Logic® IIz, which derives height information from the signal. Audio Video Setup

Audio setup

Application 1. Connect the identified connection coming from television to audio by using RF or RCA jack 2. Try to test the input video and input audio connection 3. Same color standard coding by polarity 4. The RED color is positive 5. The Black color is Negative Connectivity 6. Double check and verify to test audio video connection

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CCTV Installation and Wiring Options Today there are a lot of options when it comes to choosing a quality CCTV security system. You may decide to go with a traditional analog system, HD-SDI, HD-CVI or even an IP network based security products. One thing all of these options have in common is you will probably have to run some sort wire to the cameras. Yes, there are some “Wireless Security Camera” solutions available on the market today, but if you do some research you will find that there are a lot of limitations to wireless security cameras. Most CCTV professionals would probably not recommend a wireless system in an environment where up-time and security are critical.

I do want to mention that it is possible to reliably transmit video wirelessly using a device such as the TP-LocoM5 – Wireless Access Point/Bridge But even then you would still need to have a power wire run to the camera or a local power source near the camera and it only works with IP Cameras. That being said, we will be talking about a fully-wired system in conjunction with a storage device such as a DVR (Digital Video Recorder) or NVR (Network Video Recorder).

NEWINSTALLATION when installing a completely new security system you may want to have the video and power wires come from a single location located near the storage device (DVR or NVR) as shown below. Date Developed:

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ANALOG SYSTEMS Analog, HD-SDI and HD-CVI cameras will need two wires run to them. One for video transmission and a set of power wires in order to power the camera. You could run a coax wire and separate power wires but most CCTV professionals choose to use “Siamese Cable”. Siamese Cable is a manufactured coax cable with a set of power wires attached to it. The power wires can be split off from the coax in cases where your power source may not be in a close proximity to your recording device.

NETWORK IP SYSTEMS IP cameras use digital video transmission over CAT5 or CAT6 cable. In most cases you run your video and power to and from the camera on the same CAT5 or CAT6 wire, assuming you are using a POE (Power Over Ethernet) power source such as a POE injector or POE Switch. Some NVRs come with built in POE, but in most cases it is recommended to use an external POE switch like the POEDate Developed:

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8MB1G from SecurityCameraKing.com. When using an external POE switch all of your CAT5 or CAT6 will run directly from each camera to a POE switch that is connected to your local network. Then you simply connect your NVR to the network and you are all set.

Most IP cameras also come with an additional power wire if you choose not to use POE and power them with 12v or 24v power as shown below.

If you are going to power your IP camera with 12v /24v power you will still run all of your CAT5 or CAT6 from the camera to a Non-POE switch (usually significantly less expensive than a POE switch) but you will run an extra set of power wires from a power source to each camera.

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RUNNING YOUR CABLES Now it’s time to run your cable. The following will cover 2 popular scenarios. Scenario 1: Running your cable through your attic and mounting your cameras to the soffit. This is a common installation option, provided you have access to your attic and your soffits are also accessible. First you have to choose the placement of you recorder and power supply. Some people simply have them located in an office or a room within their home. Others prefer having them in a more secure location such as in a lockbox, hidden in a closet, or even in the attic itself. The image below shows the recorder and power supply inside a room of the home. Power and video wires run up the wall into the attic to the location where the camera will be located and out a small hole in the soffit were the camera will be mounted. Date Developed:

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Scenario 2: Another option is to run your cable through an exterior wall and then use conduit on the exterior of your structure to run your cables from one camera to another. This is a great option for those who do not have an attic or limited access to one.

Mounting Your Cameras Once you have run your wires to the desired location you can connect your camera. In some cases where the cables are coming out of the soffit it is possible to connect your wires together and tuck the connections up into the hollow area of the soffit, then mount the camera directly to the soffit.

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In situations where you’re running your wires through a solid concrete or brick wall that the connections cannot be tucked into, it is common to mount a junction box.

Junction Boxes and Conduit Junction boxes are particularly useful when running your cable through conduit on the exterior of your structure as they serve as a weather proof container protect your power and video connections from the elements and also provide you with a flat surface to mount your cameras to.

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First you will pull your wires through the access hole on the back of the junction box. Then mount the junction box to the wall. You may have to drill a hole in the junction box cover big enough to feed your camera connections through. Next, connect the camera to the power and video connection(s). Then screw the cover on to the junction box. Now you can mount you camera to the junction box. See the diagram below.

CCTV Cables | BNC | RG59 Siamese Coax CCTV Camera Pros provides every type of cable that you will need for a professional security camera system installation. Please choose from the below cable categories to jump to the page that you need or browse this page for all cables that we offer. All of our cables are professional grade and easy to use for installation.

Plug & Play CCTV Cables

RG59 Siamese Cable

BNC Jumper Cables

RG59 Cable &BNC Connector Kits

Audio Cable and Connectors

Power Cable & Power Leads

Application Tools needed: Date Developed:

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        

RG-59 BNC connectors RG-59 crimping tool RG-59 stripping tool RG-59 Siamese wire BNC barrel Wire cutter Standard wire crimp tool 22-16 AWG insulated butt splice connectors Electrical tape CCTV Training Training is generally a fairly dull and uninspiring process you have to go through to satisfy your bosses. This was the process I was tasked with! However we choose Tavcom Training and their Foundation CCTV course – designed to be a good introduction to CCTV. That’s exactly what I needed to improve me knowledge of CCTV from the bottom up. Day 1 After travelling down from Leeds the night before I was a little out of sorts, but on arrival I was greeted in the training building by many of the staff at Tavcom with a smile and a coffee. After signing in we were taken to a dedicated room crammed with equipment. I was handed a quick “light-hearted quiz” – well i couldn’t answer one question! Was hoping this was not a sign of things to come. The tutorage was led by a chap called Andy and he was very friendly and clear in how he taught. The process was generally theory and then practice – a process that suits me very well. Day 1 was basic stuff, but for myself and the other students it was quite a challenge. We set up a camera and used an oscilloscope. The practical side was very good – the equipment was modern and things were explained clearly. Looked at the “light hearted quiz” at the end of Day 1 and found I could now understand and answer all the questions. A good sign. For the evening we were set a task of using a Lens Calculator. Before tea and the bar of course! Day 2 After a quick revision session we moved onto Lighting, Ohms Law and Housings among other things. This was the session I enjoyed the most, as i am not so technical but enjoy the application side. We bounced through quite a lot of information in Day 2 – with any questions being answered at every stage. Date Developed:

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Day 3 The morning session was given over to the more modern cctv systems of IP and DVR technology. We built a 4 camera system, ran it though a DVR and learnt how to record, set up spot monitors and play with different recording setups. Then we built an IP Camera system which was an interesting experience seeing the differences between old and new technology – which isn’t always as good! After a brief revision session it was onto lunch. The afternoon was an exam which was difficult. I felt the training had covered more or less everything and it was obviously down to me whether I passed or now… update to come. Conclusion Tavcom are obviously well set up with masses of equipment, knowledge and friendly staff. The training centre is clean, modern and stocked with coffee and jelly babies. The course I went on was fun, but had a serious side – I learnt a lot and felt tired at the end of each day – a good sign you have worked hard.

Remote control A standard remote control symbol used on many TVs, video equipment and remote controls In consumer electronics, a remote control is a component of an electronic device such as a television set, DVD player, or other home appliance, used to operate the device wirelessly from a short distance. Remote control is a convenience feature[dubious – discuss] for the consumer, and can allow operation of devices that are out of convenient reach for direct operation of controls. Commonly, remote controls are Consumer IR devices which sends digitally-coded pulses of infrared radiation to control functions such as power, volume, tuning, temperature set point, fan speed, or other features. Remote controls for these devices are usually small wireless handheld objects with an array of buttons for adjusting various settings such as television channel, track number, and volume. For many devices, the remote control contains all the function controls while the controlled device itself has only a handful of essential primary controls. Earlier remote controls in 1973 used ultrasonic tones. The remote control code, and thus the required remote control device, is usually specific to a product line, but there areuniversal remotes, which emulate the remote control made for most major brand devices. Remote control has continually evolved and advanced over recent years to includeBluetooth connectivity, motion sensor-enabled capabilities and voice control.[1][2]

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Television remote controls[edit]

Remote controls for TV, VHS and DVD devices The first remote intended to control a television was developed by Zenith Radio Corporation in 1950. The remote, called "Lazy Bones", was connected to the television by a wire. A wireless remote control, the "Flashmatic", was developed in 1955 by Eugene Polley. It worked by shining a beam of light onto aphotoelectric cell, but the cell did not distinguish between light from the remote and light from other sources. The Flashmatic also had to be pointed very precisely at the receiver in order to work.[8]

The Zenith Space Commander Six hundred remote control

A Toshiba TV remote In 1956, Robert Adler developed "Zenith Space Command", a wireless remote.[9] It was mechanical and used ultrasound to change the channel and volume. When the user pushed a button on the remote control, it clicked and struck a bar, hence the term "clicker". Each bar emitted a different frequency and circuits in the television detected this sound. The invention of thetransistor made possible cheaper electronic remotes that contained a piezoelectric crystal that was fed by an oscillatingelectric current at a frequency near or above the upper threshold ofhuman hearing, though still audible to dogs. The receiver contained a microphone attached to a circuit that was tuned to the same frequency. Some problems with this method were that the receiver could be triggered accidentally by naturally occurring noises, and some people could hear the piercing ultrasonic signals. There was an incident in which a toy xylophone changed the channels on such sets because some of the overtones from the xylophone matched the remote's ultrasonic frequency.[citation needed] The impetus for a more complex type of television remote control came in 1973, with the development of the Ceefax teletext service by theBBC. Most commercial remote controls at that time had a limited number of functions, sometimes as few as three: next channel, previous channel, and volume/off. This type of control did not meet the needs of teletext sets, where pages were identified with three-digit numbers. A remote control to select teletext pages would need buttons for each numeral from zero to nine, as well as other control functions, such as switching from text to picture, and the normal television controls of volume, channel, brightness, colour intensity, etc. Early teletext sets used wired remote controls to select pages, but the continuous use of the remote control required for teletext quickly indicated the need for a wireless device. So BBC engineers began talks with one or two television manufacturers, which Date Developed:

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led to early prototypes in around 1977–1978 that could control many more functions. ITT was one of the companies and later gave its name to the ITT protocol of infrared communication.[10] In 1980, a Canadian company, Viewstar, Inc., was formed by engineer Paul Hrivnak and started producing a cable TV converter with an infrared remote control. The product was sold through Philips for approximately $190 CAD. At the time the most popular remote control was the Starcom of Jerrold (a division of General Instruments) which used 40-kHz sound to change channels. The Viewstar converter was an immediate success, the millionth converter being sold on March 21, 1985, with 1.6 million sold by 1989.[11] Some television manufacturers now include Bluetooth remotes to control the television without requiring line of sight, overcoming the limited range in IR-based remotes.

Other remote control] The Blab Off was a wired remote control created in 1952 that turned a TV's sound on or off.[12] In the 1980s Steve Wozniak of Apple started a company named CL 9. The purpose of this company was to create a remote control that could operate multiple electronic devices. The CORE unit (Controller Of Remote Equipment) was introduced in the fall of 1987. The advantage to this remote controller was that it could "learn" remote signals from different devices. It had the ability to perform specific or multiple functions at various times with its built-in clock. It was the first remote control that could be linked to a computer and loaded with updated software code as needed. The CORE unit never made a huge impact on the market. It was much too cumbersome for the average user to program, but it received rave reviews from those who could.[citation needed] These obstacles eventually led to the demise of CL 9, but two of its employees continued the business under the name Celadon. This was one of the first computer-controlled learning remote controls on the market.[13] In 2006, Hillcrest Labs introduced the Loop pointer, a remote control that used Hillcrest's Freespace motion control technology to allow users to control their televisions with natural gestures. The Loop had just four buttons and a scroll wheel.[14][15][16][17] Freespace-enabled remote controls use radio waves to communicate with a USB antenna connected to a computer that is also connected to the television, so they do not need to be pointed at the PC, or even have a direct line of sight.[18][19][20] In the 2010s, cars are increasingly sold with remote control door locks. These remotes transmit a signal to the car which locks or unlocks the door locks or unlocks the trunk. An aftermarket device sold in some countries is the remote starter. This enables a car owner to remotely start their car. This feature is most associated with countries with winter climates, where users may wish to start the car for several minutes before they intend to use it, so that the car heater and defrost systems can remove ice and snow from the windows.

The proliferation of remote controls

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used remote controls for sale in a market in Hong Kong. By the early 2000s, the number of consumer electronic devices in most homes greatly increased, along with the number of remotes to control those devices. According to the Consumer Electronics Association, an average US home has four remotes.[citation needed] To operate a home theater as many as five or six remotes may be required, including one for cable or satellite receiver, VCR or digital video recorder (DVR/PVR),DVD player, TV and audio amplifier. Several of these remotes may need to be used sequentially but, as there are no accepted interface guidelines, the process is increasingly cumbersome. One solution used to reduce the number of remotes that have to be used is the universal remote, a remote control which is programmed with the operation codes for most major brands of TVs, DVD players, etc. In the early 2010s, many smartphone manufacturers began incorporating infrared emitters into their devices, thereby enabling their use as universal remotes via an included or downloadable app.[21]

Technique The main technology used in home remote controls is infrared (IR) light. The signal between a remote control handset and the device it controls consists of pulses of infrared light, which is invisible to the human eye, but can be seen through a digital camera, video camera or a phone camera. The transmitter in the remote control handset sends out a stream of pulses of infrared light when the user presses a button on the handset. A transmitter is often a light emitting diode (LED) which is built into the pointing end of the remote control handset. The infrared light pulses form a pattern unique to that button. The receiver in the device recognizes the pattern and causes the device to respond accordingly.

Opto components, and circuits

The emission spectrum of a typical sound system remote control is in the near infrared.

The infrared diode modulates at a speed corresponding to a particular function. When seen through a digital camera, the diode appears to be emitting pulses of purple light. Most remote controls for electronic appliances use a nearinfrared diode to emit a beam of light that reaches the device. A 940 nm wavelength LED is typical. This infrared light is invisible to the Date Developed:

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human eye, but picked up by sensors on the receiving device. Video cameras see the diode as if it produces visible purple light. With a single channel (single-function, one-button) remote control the presence of a carrier signal can be used to trigger a function. For multi-channel (normal multi-function) remote controls more sophisticated procedures are necessary: one consists of modulating the carrier with signals of different frequency. After the receiver demodulates the received signal, it applies the appropriate frequency filters to separate the respective signals. One can often hear the signals being modulated on the infrared carrier by operating a remote control in very close proximity to an AM radio not tuned to a station. Today, IR remote controls almost always use a pulse width modulated code, encoded and decoded by digital computer: a command from a remote control consists of a short train of pulses of carrier-present and carrier-not-present of varying widths.

Consumer electronics infrared protocols Different manufacturers of infrared remote controls use different protocols to transmit the infrared commands. The RC-5 protocol that has its origins within Philips, uses, for instance, a total of 14 bits for each button press. The bit pattern is modulated onto acarrier frequency that, again, can be different for different manufacturers and standards, in the case of RC-5, the carrier is 36 kHz. Other consumer infrared protocols include the various versions of SIRCS used by Sony, the RC6 from Philips, the Ruwido R-Step, and the NEC TC101 protocol.

Infrared, line of sight and operating angle Since infrared (IR) remote controls use light, they require line of sight to operate the destination device. The signal can, however, be reflected by mirrors, just like any other light source. If operation is required where no line of sight is possible, for instance when controlling equipment in another room or installed in a cabinet, many brands of IR extenders are available for this on the market. Most of these have an IR receiver, picking up the IR signal and relaying it via radio waves to the remote part, which has an IR transmitter mimicking the original IR control. Infrared receivers also tend to have a more or less limited operating angle, which mainly depends on the optical characteristics of the phototransistor. However, it's easy to increase the operating angle using a matte transparent object in front of the receiver.

Radio remote control systems

The exterior and interior layout of the remote control for a garage door opener Radio remote control (RF remote control) is used to control distant objects using a variety of radio signals transmitted by the remote control device. As a complementary method to infrared remote controls, the radio remote control is used with electric garage door or gate openers, automatic barrier systems, burglar alarms and industrial automation systems. Standards used for RF remotes are: Bluetooth AVRCP,ZigBee (RF4CE), Z-Wave. Date Developed:

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Most remote controls use their own coding, transmitting from 8 to 100 or more pulses, fixed or Rolling code, usingOOK or FSK modulation. Also, transmitters or receivers can be universal, meaning they are able to work with many different codings. In this case, the transmitter is normally called Universal remote control duplicator because it's able to copy existing remote controls, while the receiver is called Universal receiver because it works with almost any remote control in the market.

Motor controller A motor controller is a device or group of devices that serves to govern in some predetermined manner the performance of an electric motor.[1] A motor controller might include a manual or automatic means for starting and stopping the motor, selecting forward or reverse rotation, selecting and regulating the speed, regulating or limiting the torque, and protecting against overloads and faults.[2] There are many types of starters: 1) Direct On Line (DOL) 2) Star delta starter 3) Auto transformer starter Servo controllers are a wide category of motor control. Common features are: 

precise closed loop position control

fast acceleration rates

precise speed control Servo motors may be made from several motor types, the most common being: 

brushed DC motor

brushless DC motors

AC servo motors

Light-emitting diode

Light-emitting diode

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Blue, green, and red LEDs in 5 mm diffused case Working

Electroluminescence

principle Invented

Oleg

Losev (1927)[1]

James

R.

Biard (1961)[2] Nick Holonyak (1962)[3] First

October 1962

production Pin

Anode and cathode

configuration Electronic symbol

Parts of an LED. Although unlabeled, the flat bottom surfaces of the anvil and post embedded inside the epoxy act as anchors, to prevent the conductors from being forcefully pulled out via mechanical strain or vibration.

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Appearing as practical electronic components in 1962,[6]the earliest LEDs emitted low-intensity infrared light. Infrared LEDs are still frequently used as transmitting elements in remote-control circuits, such as those in remote controls for a wide variety of consumer electronics. The first visible-light LEDs were also of low intensity, and limited to red. Modern LEDs are available across thevisible, ultraviolet, and infrared wavelengths, with very high brightness.

Types

LEDs are produced in a variety of shapes and sizes. The color of the plastic lens is often the same as the actual color of light emitted, but not always. For instance, purple plastic is often used for infrared LEDs, and most blue devices have colorless housings. Modern high-power LEDs such as those used for lighting and backlighting are generally found in surface-mount technology (SMT) packages (not shown).

The main types of LEDs are miniature, high-power devices and custom designs such as alphanumeric or multi-color.

Electric Fan Parts

of

the

Electric

Fan

Front Guard. It is a protective metal mesh wire used to prevent the fan blade from any physical contact with foreign objects. Power Controller. It is a circuit that controls the amount of power supplied to the motor. Sensor. It from

is

the

Manual Control. It operation

input

receiver that remote

is of

push

a

button the

detects

switch

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input

that controls electric

coming control. manually fan.

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signal

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Non-polarized Capacitor. A low reactance non-polar capacitor connected in series with the start winding of an electric fan. Timer. It is predetermined

used

to

switch

on

or

off

automatically

with time.

Comparator. It is a processing circuit that accepts the input signal coming from remote control, manual switch or timer switch. This circuit provides the triggering voltage to the power controller. AC Motor. It is rotating electrical energy or power AC Plug. It source 220 V.

is

a

electric machine which changes applied into mechanical output energy or power.

connector

intended

for

connecting

to

the

main

Washing Machine Parts of the Washing Machine and their Working 

Let us see the important parts of the washing machine; this will also help us understand the working of the washing machine. Please refer to the image below. 1) Water inlet control valve: Near the water inlet point of the washing there is water inlet control valve. When you load the clothes in washing machine, this valve gets opened automatically and it closes automatically depending on the total quantity of the water required. The water control valve is actually the solenoid valve. 2) Water pump: The water pump circulates water through the washing machine. It works in two directions, re-circulating the water during wash cycle and draining the water during the spin cycle. 3) Tub: There are two types of tubs in the washing washing machine: inner and outer. The clothes are loaded in the inner tub, where the clothes are washed, rinsed and dried. The inner tub has small holes for draining the water. The external tub covers theinner tub and supports it during various cycles of clothes washing. 4) Agitator or rotating disc: The agitator is located inside the tub of the washing machine. It is the important part of the washing machine that actually performs the Date Developed:

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cleaning operation of the clothes. During the wash cycle the agitator rotates continuously and produces strong rotating currents within the water due to which the clothes also rotate inside the tub. The rotation of the clothes within water containing the detergent enables the removal of the dirt particles from the fabric of the clothes. Thus the agitator produces most important function of rubbing the clothes with each other as well as with water.

TASK SHEET AND INSTRUCTION Title: Terminate the connection of the following Domestic appliances. Objective: 1. To learn about the basic connectivity and identify the connection. 2. To be able to learn and identifying the parts 3. To be able to diagnoses the possible defect and problem 4. And also learning for assembly and disassembly the system product Materials needed: 1 Set of screw driver 1 set of soldering material 1 set of wire striper VOM or meter Flat iron Electric fan and washing machine Date Developed:

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Procedure: 1. Disassembly the product identify the parts and list the basic components 2. Identify the connection and terminate the polarity or color coding of wires connection. 3. Assembly the system product and terminate the connection 4. Test and verify Assessment Method: 1. Check the instructor all products for functionally or good condition of each system product observe the connectivity of each task, each trainers individual perform list the name of trainers to the progress chart. 2. We will check the instructor before testing and verify the connection, check the achievement chart. 3. Direct observation and motivation

Electric Iron

The Invention of the Electric Iron The electric iron is one of the most important, extremely popular and widely used domestic electric appliance. The electric iron is based on the heating effect of electric current. Find out more about the invention of the electric iron and how it works. Date Developed:

Electronic Products Assembly and Servicing NC II

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Introduction There are various electrical inventions used for domestic purposes such as the electric fire, electric iron, and electric water heater that all depend on one common principle; when a current is passed through a piece of wire, the wire heats up and emits heat radiation. This heat is distributed and used for various purposes. Learn more about how this works with information on the electric iron invention. In this article, we will discuss about the various types, parts, and theory of operation.

The Electric Iron An electric Iron is a general household appliance used to press the wrinkles out of the clothes. This works on the basis that the combination of heat and pressure removes wrinkles. The principle of the electric iron is that when current is passed through a coil, the coil gets red hot and transfers the heat to the base plate of the electric iron through conduction. In the earlier days steam irons were used, but now the electric iron is preferred over the steam ones. Steam irons have some maintenance issues due to clogging. Steam irons usually have vents through which the water passes. As the steam iron gets used, slowly the minerals from the water accumulate at the vents and blocks the water from passing through. Thus the efficiency of the steam iron is compromised. So the steam iron has to be cleaned and maintained regularly to ensure its proper working. If you live in an area where hard water is used, then clogging is a major problem. This drawback is eliminated in electric iron as it uses a heating element and there are no vents in it. There is considerably less maintenance in an electric iron when compared to a steam iron.

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Electronic Products Assembly and Servicing NC II

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There are basically two types of electric irons: 

Automatic

Non-Automatic

There is not much difference between the two types. The former has one regulator to control the temperature of the element and in-turn the temperature of the iron. Now you may ask, why do we need to control the temperature of the iron?

Parts of an Electric Iron Sole Plate The sole plate is the thick, triangular-shaped slab of iron that forms the base over which the electric iron is built up. The bottom surface and edges are heavily chromium plated, to prevent it from rusting. The base plate should hold the iron pressure plate and cover plate in position. For this purpose we can see two or sometimes three studs in the base plate. These studs aid in holding the position of cover plate and pressure plate. Pressure Plate This plate is generally called the top plate as it follows the shape of sole plate. The pressure plate has some holes through which the studs form the base plate passes through. We should tighten the nuts on the studs in such a way that the pressure plate and sole plate are pressed tight against each other. In some iron the pressure plate is heavy and made of cast iron while in some other cases, it is a thin sheet of steel, about ¼ cm thick. In automatic type of electric iron, the pressure plate has a rectangular or circular hole for locating the thermostat.

Learn various facts and information about the electric iron invention including the working parts of an electric iron and a typical schematic. The various parts include heating element, pilot lamp, handle, cover plate, thermostat, capacitor, bimetallic switch, and others are explained. Learn these facts of the electric iron including diagrams and pictures. Date Developed:

Electronic Products Assembly and Servicing NC II

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Parts of electric Iron [contd...] The Heating Element The heating element is present between the sole plate and pressure plate. It is pressed hard between the two plates. The heating element consists of nichrome wire wound around a sheet of mica. The two ends of the nichrome wire are connected to the contact strips. The contact strips are connected to the terminals of the iron. There are two reasons for which mica is chosen in the heating material. Mica is a very good insulating material. Besides that mica can also withstand very high temperatures. The entire assembly of mica sheet, nichrome wire and contact strips are riveted together resulting in a mechanically sound and robust construction. There is an asbestos sheet, which separates and thermally insulates the top plate from the heating element.

The Cover Plate The cover plate is made of thin sheet of iron. It is placed on top of the base plate and it covers all the internal parts of the iron. The handle and connector are only attached to the cover plate. Handle The handle can be made either with wood or with plastic. The handle is attached to the cover plate with the aid of screws. Studs can also be used for this purpose. Pilot Lamp The pilot lamp is housed in the cover plate of the electric iron. One end of the pilot lamp is connected to supply, while the other end is connected to the heating element. A shunt resistance is provided across the pilot lamp which assists in providing a voltage drop. The shunt is designed to provide a voltage drop of 2-5 volts. Date Developed:

Electronic Products Assembly and Servicing NC II

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Thermostat When it comes to an automatic electric iron, the thermostat is the most important item. It uses a bimetallic strip to operate the switch which is connected in series with the resistance (or) heating element. The bimetallic strip is a simple element which converts a temperature change into mechanical displacement. A bimetallic strip consists of two different metals bonded together. The two metals should have a different coefficient of expansion. If such a strip is heated, it starts to curve towards the metal having the lower co-efficient of expansion. On cooling, it straightens and comes back to the normal position. Now we might wonder why such an element is used in iron. What is the purpose of this element in an electric iron? The bimetallic strip is attached to a contact spring through small pins. The contact point between the strip and contact points remains closed. When the temperature rises significantly, the unusual expansion causes the strip to curve and the contact between strip and contact spring opens. Thus the supply to heating element is temporarily stopped (until the temperature goes down to normal). A special device called the cam is placed is placed near the contact spring, with which we specify the amount of curving of bimetallic strip required to separate the contact. Thus using bimetallic strip the temperature is kept constant within certain limits.

Capacitor

Date Developed:

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The thermostat helps in maintaining the temperature within limits. But frequent making and breaking of circuit damages the contact points and it may also result in interference with radio reception. To avoid this, a capacitor of certain range is connected across the two contact points.

Working When a current is passed through the heating element which is placed between the sole plate and pressure plate, the element gets heated up and transfers its heat to the sole plate through conduction and in-turn the sole plate also gets heated up. Now to remove the wrinkles in clothing, we should apply heat and pressure. Heat is formed due to the coil and when we press the clothes with iron, the wrinkles are removed. For maintaining the optimum temperature, a thermostat is used along with pilot lamp which serves as an indicator.

Date Developed:

Electronic Products Assembly and Servicing NC II

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Electrical installation rules, standards    

Definition of voltage ranges Electrical regulations and standards Quality and safety of an electrical installation Environmental directives

Installed power loads - Characteristics  

  

Induction motors Resistive-type heating appliances (conventional or halogen) Fluorescent lamps Discharge lamps LED lamps & fixtures

and

incandescent

Power loading of an installation    

Installed power (kW) Installed apparent power (kVA) Estimation of actual maximum kVA demand Example of application of factors ku and ks Date Developed:

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lamps

 

Choice of transformer rating Choice of power-supply sources

Simple sequential lights

Sequential circuit (sequential machine) A logic circuit whose outputs at a specified time are a function of the inputs at that time, and also at a finite number of preceding times. In practice, any physically realizable sequential circuit will have a finite transit time, or delay, between the inputs changing and the outputs changing (one or more of these inputs may be clock signals); the intention of the term sequential is to include not only combinational circuits but also (explicitly) memory elements such as flip-flops. Analysis and synthesis of sequential circuits is facilitated by state diagrams.

Sequential Diagram

Date Developed:

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Solar Solar energy is a dynamic illumination and temperature from the Sun controlled by applying numerous ever-evolving alternative technologies similar to solar power heating system, photovoltaic, solar thermal electricity, solar architecture and manmade

photosynthesis.

It happens to be a significant method of obtaining sustainable energy and their concepts are widely epitomized as a choice between passive solar or vibrant solar determined by the means they harness and deliver solar power or process it into photo voltaic energy. Vigorous solar strategies can include the utilization of photovoltaic products, focused solar powered energy and solar water heating system to funnel the electricity. Passive solar approaches comprise of orienting a house to the Sunlight, deciding upon elements with preferred thermal volume or daylight dispersing characteristics, and developing spots that organically disperse air flow. Battery Chargers A battery charger, or recharger, is equipment accustomed to supply electric power into a supplementary cell or rechargeable battery pack by pressuring an electric current into it.The recharging decorum is determined by the specifications and nature of the battery getting charged. A number of battery categories possess large tolerance for overcharging which enables them to be recharged by attaching to a constant voltage supply or a constant current supply; ordinary chargers of this nature necessitate hand cut-off at the finish of the charge cycle, or perhaps might well have a timer device to discontinue charging current at a specified duration. Various other Date Developed:

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battery classes are not able to endure prolonged high-rate over-charging; the charger might need warmth or voltage sensing circuits and a microprocessor controller to regulate the charging current, establish the status of charge, and deactivate at the conclusion of charge. Inverters Some of the best square wave and sine wave inverter designs have been presented on, specifically designed and researched by me. But before that you may want to take a peek regarding what a sine wave inverter concept is all about from the following discussion, the later section walks you through the various sine wave inverter circuit links of your choice. The following link will take you to some most interesting and useful LED related circuits, such as LED drivers, LED formulas, LED hobby circuits and many more.

Flashing LED Battery Low Indicator Circuit The post explains a simple low/normal battery voltage status indicator circuit through a flashing and a constant LED, where the flashing LED indicates...

Battery Charger Circuit with 4 LED Indicator A universal current controlled automatic battery charger circuit with 4 LED indicators can be learned in the following post. The design also includes LED This page presents a huge collection of LED related circuit links, meticulously designed and compiled by me. Here we exclusively deal with the various LED driver circuits, consisting of articles explaining how to make LED drivers for high watt LEDs through SMPS concepts and also using capacitive power supplies. We also learn regarding the various safety related parameters essentially stipulated for these LEDs, this includes detailed instruction regarding how to make precise current control circuits and also regarding how to wire the LEDs correctly such that the SMPS and the LeDs become perfectly compatible with each other and render an optimal performance and maximum operating life span.

Date Developed:

Electronic Products Assembly and Servicing NC II

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SOLAR PANEL SETUP

Date Developed:

Electronic Products Assembly and Servicing NC II

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Tools Required ➢ Table Saw – Not an absolute requirement but will make the job of cutting the wood and acrylic a lot easier. Use a 60 tooth blade for the wood and an 80 tooth blade for the acrylic. ➢ Electric Drill – For drilling the panel frame, acrylic etc. ➢ Clamps Various - To hold the panel frame pieces together during construction ➢ Soldering Iron – You will need to experiment to find the soldering iron that works for you. See www.diypvsolarenergy.com for some recommendations. ➢ Multimeter – You will need a meter to measure DC voltage up to 24V and DC current up to 5A. Most meters won't measure high currents so you may need to borrow or purchase one that does. ➢ 3/16” drill bit for plastics – It is important to use a drill bit designed for drilling plastic. If you don't you will likely crack your sheet of acrylic. The drill has a distinctively different pitch and a pilot tip. Source – Aircraft Tool Supply P/N DDPD3/16 ➢ Philips screwdriver – Various screws ➢ Regular Screwdriver – Various screws ➢ Electrical side cutters – Small for delicate work, mid size for cutting 12 gage wire ➢ Electrical crimping toll – To crimp the #8 connectors in the junction box ➢ Electrical wire strippers – To strip the 12 gage wire

Date Developed:

Electronic Products Assembly and Servicing NC II

December 2015

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TASK SHEET AND INSTRUCTION

Title: Terminate the connection of solar panel Objective: 1. To identify the connection of each solar panel components 2. To learn basic function of the input voltage and output voltage from DC. To AC. Isolation 3. To perform and actual application of the following product assembly. Materials Needed: Set of screw driver Measuring tools and drill bit Wires striper and solar panel components VOM or meter Procedures: 1. Apply OHS before start the task list the components and prepare the system installation. 2. Connect each components verify the connectivity 3. Before testing try to verify the polarity and connectivity 4. Test and measure the output voltage. Assessment Method: 1. The instructor checks all components for a good condition and functionally good components. 2. List the actual demonstration of the trainers and check the progress chart. 3. Actual observe direct motivation the trainers.

Date Developed:

Electronic Products Assembly and Servicing NC II

December 2015

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CORE 2 CBLM Service Consumer Electronic Products and Systems - PDFCOFFEE.COM (2024)
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