consumer electronics troubleshooting and repair handbook

7/22/2019 Consumer Electronics Troubleshooting and Repair Handbook

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CONSUMERELECTRONICSTROUBLESHOOTING &

REPAIR HANDBOOK


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CONSUMERELECTRONICSTROUBLESHOOTING &REPAIR HANDBOOK

HOMER L. DAVIDSON

New York h n rancisco Washington, D.C. Auckland Bog&Caracas U s h n London Yadrld MexlcoCIty MllanMontreal New Delhl San Juan Singapore

Sydney Tokyo Toronto


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Library of Congress Cataloging-in-Publication DataDavidson, Homer L.Consumer etectronics troubleshooting and repair h a n d h k / HomerDavidson.p. cm.ISBN 0-07-015809-6I . Electronic appar atus and appliance+Maintenance andrcpair-Handbaaks, man uals, etc. I. Title.

TK7870.2.D375 19996 2 1 . 3 8 1 5 ' ~ ~ 2 1 99- 19660CIP

CopyrightO 1999by The McG raw-Will Comp anies, Inc. All rights reserved. Printed in theUnited States of Am erica. Excep t as permitted under the United States Copyright Act of1976, no part of this publication may lx reproduced w distributed in any form or by anymeans, or stored in a data base or retrieval system, without the prior written permission ofthe publisher.

ISBN 0-07-015809-6The sponsoring edito r for this hook WKFScott G rillo, the edm ng supervisor w as AndrewYoder, and thep roduction sup ervlsar war T ~ n a ameron. It was set In Times NewRoman hy Lisa M. Mellott through the service-P f Barry E. Brown (Broker-Editing,Design and ProductionJ .Printed and bound by R. R. Donnelley & Sons CompanyMcGraw-Hill books are available at special quantity discounts to use as premiums andsales promotions, or for use in corporate training programs. For more information, pleasewrite to the Director of Special Sales, McGraw-Hill, 1 E West 19th Street, New York, NY1001 1 . Or contact yo ur local bookstore.This h k as printed on acid-free paper.


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DedicationI dedicate this book to the thousands of electronic technicians who trou-bleshoot and repair millions of consum er electronic products every year. Agreat deal of thanks goes to those electronic manufacturers who provide theworld with electronic entertainment throughout every day of our lives. Isalute those who place the e lectronic product in the hands of the consumer,and the electronic technician who stands at the service bench each day andbrings the product back to life.


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Introduction

PART I Getting StartedChapter 1 Practical Troubleshooting Techniques

Precious Time 4The Symptom 5The Three S's 5Isolation 6Service Literature 8

Substitute Another Schematic 8Chassis Comparison 9Spilled Liquid 10Basic Test Equipment I I

BasicTV Test lnstruments 13Requirad Audio Test Instruments 13Basic Audio Test Equipment 13RequiredCD Test Equipment 14Required Microwave Oven Test Instruments 36Crucial Voltage Tests 36Transistor Voltages and Resistance Tests 17Dicde Tests 21IC Voltage and Resistance Tests 22Crucial Resistance Amplifier Tests 23SCR Resistance Measuramants 24Transistor And lC Replacements 24Crucial Waveforms 26TV Surface-Mounted Components (SMD) Tests 28HOW o Read SMD Values 30CD Surface-Mounted IC Chips 31CD Surface-Mounted Devices (SMD) 32Removing Surface-MountedComponents 33Replacing Surface-Mounted Components 34Double-Sided Boards 34

Read And Study 36Case Histories 3 7Preventative Maintenance 37

xxxi

vi i


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rlll CONTEWTS

Chapter 2 Play It SafeSafety Lessons 40TV Safety Capac~tors43Fire Damage 42HotTV Chassis $3Keeps Blowing he Fuse 44TV High-Voltage Shutdown 44TV High-Voltage Adjustments 46

TV Star Components 46CD Player Safety Precautions 47CD Laser Safety 49Handle With Care 49CD Transport Screw Removal 49Safety CD Interlocks 50

Safe Microwave Usage 52Basic Microwave Repair Safety Tips 55Basic Microwave Oven Precautions 57Checking The Power Outlet 60Dangerous HV Tests 60Oven Leakage Tests 61

Conclusion 63

PART 2 Troubleshooting and Repairing Solid State TVs 65Chapter 3 Servicing The Low-Voltage Power Supply 67

Low-Voltage Power-Supply Symptoms 68Isolation Transformer 69The Half-Wave Rectaier 70Full-Wave Rectifier Circuits 72Bridge Rectifier Circuits 75Hot Chassis 76The Vanable-Frequency Switching and Switched-Mode Power Supplies 77Regulator Circuits 79Chopper Power Supplies 81Flyback Transformer Low-Voltage Circuits 83Servicing the Low-Voltage Circuits 84Blowing 'Fuses 85Intermittent Power Supply 87B+ Voltage Adjustment Problems 89Lightning Damage 8sHum Bars 8gChassis And High-Voltage Shutdown MShutdown Horizontal Lines 91Excessive Line Voltage 92Insufficient ImageWidth 92Unusually Low Voltages 93'"rough Dog" Power Supply 93Standby Power Suppl~es94


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CONTENTS Ix

Servicing Standby Circuits 95Five New Low-Voltage Power Supply Problems 95

Conclusion 98Chapter 4 Troubleshooting The Horizontal Sweep Circuits J00

HorizontalOscillator Problems I 0 2Horizontal Osc~llator frcults 102

RCA CTC130C Horizontal Countdown Clrcuit 104Horizontal Oscillator IC Tests 105Poor Hor~mntal ync 105Crucial Horimntal Waveforms 107Horizontal Off-Frequency Problems 10gThe Horizontal Output Transistor 112The Flyback Transformer 116Basic Horizontal Circuits 118Holddown Capacitors 120The Damper Dicde 120Crucial Safety Components 122The Dead Chassis 122Intermittent Raster 131Keeps Blowing The Fuse 132Keeps Destroying The Output Trans~stors 134Red-Hot Output Transistors 136Checking the Flyback in an RCA CTCl 11L Chassis 136A GE 1906 Chassis Trans~stor lows 738Additional Damaged Parts 138

Varfac Transformer Tests 139High Voltage Too High 139High-Voltage Shutdown 140High-Voltage Shutdown C~rcuits 141RCA CTC101A High-Voltage Shutdown 142Sanyo SIC64 High-Voltage Shutdown 142RCA CTC97 Blast-on Shutdown 142Tic-Tic Noise 142Defechve Deflection Yoke 143Chassis Shutdown 144PmrFocus 145Poorwidth 146Excessive Width 146Poor High-Voltage Regulator 146Improper B+ or H~gh-Voltage djustments I46Flash~ng orizontal P~ctures 148Vertical White Line 148Horizontal Foldover Problems 148Pecul~arHor~mntal olses 149Noise Llnes In the Raster 151Arcover and Firing 151RCA CTC9PL Dark Llnes In Picture 151Jail Bars 152Pie-Crust Lines 152


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Horizontal Motorboating 153Poor Board Connections 153Soldering lC Terminals 154SCR Horizontal Circuits 154High-Voltage Problems 157Fire Damage 159SIX Actual Horizontal Sween Problems 160Chapter 5 High-VoAage Tests

Problems with HVCircuits 164Flyback Transformer Problems 166The High-Voltage Probe 167Remov~ng nd Replacing he Flyback 168Picture-Tube Filament Circuit 170Tripler Problems 171Keeps Blowing Fuses 17.2Loading Down-Magnavox T995-02 172Poor Focus 173High-Voltage Arc~ng 175Arcing In The Focus Control 176Secondary Flyback Circuits 176Quick High-Voltage Circuit Checks 178Voltage Supplies to CRT 179Check Components Before Replacing Flyback 1 8 0Five Actual Case Histories 181Overloaded Secondary Circuits 185Conclusion 186

Chapter 6 Repairing The Vertical CircuitsVertical Circult Problems 187Crucial Test Points 189TypesOf Vertical Circuits 189Vertical Frequency-Counter C 1mVertical Output Circuits 19fVertical Output lC 195Hor~mntalWhite Llne 195Vertical Oscillator IC Problems 198White L i nMu tp u t Circuits 199Crucial Vertical Waveforms 2 WVertical Voltage lnlect~on201Servicing Directly Coupled Vertical Circuits 202Insufficient Vertical Sweep 204IntermittentVertical Sweep 207

Vertical Pincushion Problems ,209Vertical Foldover 209Vertical Rolling 210Vertical Crawling 210Black Top Half 21 1Shutdown After Horizontal White Line 212Bunching Vertical Llnes 214Vertical-Related Problems 214


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CONTENTS XI

Troubleshooting Vertical IC circuits 218Five Actual Case Histones 219

Conclusion 221Chapter 7 How To Check IF And Video Circuits

IF Cfrcults 225IF ICs 226Saw Filter Network 2 6IF Trouble Symptoms 2 BTroubleshooting the IFStages 230Troubleshooting Saw Filter Circuits 230Latest IF Video Circuits 234IF Alignment 235

Video Test Eqvipment 236Video Problems 236Video IF Circuits 236Comb Filter Circuits 236No Video, Normal Sound 236No Video, No Raster 237Weak or Washed-Out Picture 2'38Weak P~cture,Red Outline 238Washed-Out Picture, Retrace Lines 239Loss of Picture and Sound 240Intermittent Video 240lntermittent Black Screen 240Intermittent Vldeo, Audio Ok 242Fuzzy Pictures 242Very Little Brightness 24.2No Brightness, Normal High Voltage 243Can't Turn Down The Brightness 243Brightness With Retrace Lines 243CannotTurn Down Brightness 244No Brightness Control 245No Control of the Luminance IC 245Video IC Replacement 245Very Low Brightness 247Faint Picture with No Contrast 247Intermittent Brightness 247No Brightness After One Hour 248Very Bright Screen And Shutdown 248Brightness Shutdown 249Smeary Plctures 249An Unusual Video Problem 249Five Actual V~deo ase Histories 251

Conclusion 255Chapter 8 AGC And Sync Circuit Problems

AGC Controls 259AGC Problems 260

AGC Clamping Tests 261


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AGC and Tuner 261Poor AGC Action 261

AGC Circuits 262ICs And AGC 264Electrolyt~cCapacitors And AGC 265F~ ve ctual AGC Problems 267

AGC Circuits Conclusion 269Servicing Sync Circuits 270

The Sync Separator 273The Latest IC Sync Circu~ts272Troubleshooting he Sync Separator 273SIX Actual Sync Problems 274

Conclusion 278Chapter 9 Tuner Repairs

About the Tuner 280No Picture, No Sound, White Raster 282Snowy Picture 283Intermittent Picture 283

C'FeaningThe Tuner 284Three Quick Tuner Tests 285The Tuner-Subber 286Defective Antenna Balun Coils 287Typesof Tuners 287

The Conventional Mechanical Tuner 287UHFTuner 288The Varactor Tuner 290

Frequency-Synthesis Tuner Servicing 294RCA CTCl57 Tuner Control 294The Electronic Tuner Keyboard 2%Scan Tuning 297Tuner Control Or Tuner Module 298Electronic Tuner Repair 299Seven Actual Tuner Problems 300

Conclusion 305Tuner Repair Centers 306

Chapter f 0 Color Circuit ProblemsUslng the Correct Test Equipment 308

Color-Dot-Bar Generator 3OgColor Waveform Test Points 310

Color IC Circuits 314Color Matnx Circuits 316Color Circuits or CRT 317No Color 321Weak Color 322Intermittent Color 322No Red 323No T~nt ontrol 325


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CONTEMTS xl l l

All-Blue Raster And Shutdown 326Crucial Color Waveforms 327Troubleshooting The RCA CTC108 Color Chassis 328

Difficult Color Problems 332Unusual Color Problems 332Five Actual Color Case Histories 333Troubleshooting With The Color-Dot-Generator 3%

Conclusion 336Chapter I f Testing The Remote-Control Circuits

Basic Rem ote Transmitters 339Testing Supersonic Remote Transmitters 341Servicing The Sonic Transmitter 341lnfrared Remote Transmitter 343Testing The Infrared Transmitter 344lnfrared Remote-ControlTester 345RF Remote-Control Receivers 346Standby Power Circuits 347

In-TV Rem ote-Control Circuits 34$lnfrared Remote Receiver 349Simple Remote-Control Receiver 349RCA CTC157 lnfrared Receiver Circuits 350TV Control Modules 55.2OnlCmCircuit Tests 353TV Relay Problems 354Five Actual Remote Case Histories 355Troubleshooting Interface Circuits 360

Troubleshooting The Keyboard Interface 360Universal Remote Controls 361Conclusion 362

Chapter 12 Sewicing The Sound CircuitsRequired Servicing Instruments 364Transistorized Sound Stages 365

Transistorized Sound Circuits Are Back 367IC Sound Stages 368

Latest ICSound Circuits 369Signaltracing Sound Circuits 369

Stereo Sound 370Servicing The Sound Circuits 370

No Sound 371No Sound in IC Circuits 372Weak Sound 372DistortedSound 374Extreme Distortion 375Intermittent Sound 376Motorboating Noises 377Sound and Picture Do Not Track 378Servicing RCA CTClO9 Sound Circuits 379


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xlw CONTEWTS

Five Actual Sound Case Histories 379Practical Sound Hints 382

Chapter 63 Troubleshooting Picture-Tube ProblemsPicture-Tube Components 386

Larger Picture Tubes 387CRT Bias and Driver-Board Circuits 388Visual Symptoms 389

No Raster 389No Picture 390Weak Picture 391No Br~ghtness391No Control of Brightness 391Washed-Out Picture 392Negative Picture 392Blotchy or Shiny P~cture392Poor Focus 392Intermittent Raster 394Retrace Lines 395All-Red Raster 395One Missing Color 397Intermittent Color Line 398

Other High-Voltage Problems 398Chassis Shutdown 398Yoke Problems 398High-Voltage Arc~ng 400Firing Lines in the Picture 400Defective CRT Harness 401

Testing The CRT 403CRTRepairs 403IHVT-DerivedVoltages for the CRT 404Spark Gaps 405CRT Voltages 406P~cture-Tube rotwt~on407Discharging he Picture Tube 107P~cture ube Replacement 407P~cture ube Removal 407An On-Screen Display Problem 409Five Actual Picture-Tube Problems 470

Conclusion 413

Part 3 TROUBLESHOOTING AND REPAlRlNG AUDIOAND VIDEO CASSETTE PLAYERSChapter 4 4 Basic Cassette Player Tests

Required Test Instruments 419Soldering Equipment 421Battery Problems 42.2Tests Tapes and Tension Gauges 423


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CONTENTS xv

Troubleshooting with Voltage and Resistance Measurements 42 4Transistor Tests 426Transistor Junction-Diode Tests 428

IC Tests 429Transistor and IC Replacement 430

Troubleshooting Without the Exact Schematic 43 4Signaltracing With a Cassette 435

Build Your Own Test Equipment 436Sine-ISquare-Wave Generator 436IC Audio Signal Tracer 438White-Noise Generator 439Head Azimuth And Current Tests $42Tape and Erase Head Problems 444Demagnetize Tape Heads 445Speed Adjustments 445

Conclusion 446Chapter 15 Repairing Tag-Along AndPersonal Cassette Players

Player Only 448Cassette Tapes 448VAS, VOX, or VOR Systems 451Head and Cabinet Cleaning 451Head Demagnetization 452The Cassette Mechanism 452Slow Speed 453Disassembling The Covers 454No Sound/No tape movement 455No Fast Fotward 455Poor Rewind 458No Automatic Shut Off 458Belt-Drive Systems 460Cassette Switches 460Early Aud~oCircu~ts 462Surface-Mounted Components 466Dead Playback 466DistortedSound 467Removing the Small Cassette Lid or Cover 468Repairing Headphones 468Stereo Features $70Erratic Play 471Rad~o r Cassette Switching 474Single Stereo IC 475Poor Rewind 477Dead Cassette Player 478Defective Motor 479Replace Defwtive Motor 479Tape Spill Out 480No Fast Forward 4B.2Noisy IC or Transistor 482


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xvl CONTEWTS

The Personal Portable Cassette Player 483Pushbutton Problems 483Dirty Function Switch 485No Playback Lock In 485No Tape Action 485Muffled or Distorted Sound $87Errat~c ounter 489Flywheel Thrust Adlustment 491

Chapter 16 Troubleshooting Boom-Box Cassette Players 495Continuous Tape Playback 496Three-Band G raphic Equalizer 497Oscillator Switch 498Variable Monitor 498Dubbing 498

Dubbing From Tape Deck 2 to Tape Deck 1 499The Erase Head 500Erratlc Switch~ng501AccidentalErase 502

Broken Soft Eject 503No Action on Deck 2IDeck 1 Okay 504Power-Supply Circuits 5504

Bridge Rectifier Circuits 506Recording Circuits 508

IC Recording Circuits 510Dead Right Speaker 513Defective Record~ngMeters 513

LED Meter Circuits 515Chapter 17 Troubleshooting Portable

AMISM CassetteE D 'PlayersThe Power Supply 518Head Cleaning 519Erratic Play 520

Fast-Foward Torque Adjustment 520Take-Up Torque Adjustment 520Rewind Torque Adjustment 521

Pinch-Roller Adjustment 521No Fast Forward 522

Binding Buttons 522No Take-Up R eel Action 523Removing Covers 523Block Diagram 524Stereo Amp Circuits 525Improper Audio Balance 526Garbled Recording 527Cassette Door Will Mot Ope n 529CTeaning The Optic al Len s 531


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CONTEtlTS xvll

CD Motors 532Disc Motor 532Sled Motor 533

CD Block Diagram 535CD Low-Voltage Power Supply 537No Sound From The CD Player 537Conclusion 540

Chapter 18 Sewicing Microcassette andProfessional RecordersMicrocassettes 546

To Record With Built-In Microphone 546Playback Mode 548

VOR Recording 548Circuit Block Diagram 548Surface-Mounted Components 550Disassembly 550Removing the PC Board 551Removing the Cassette Deck 551

Only One Speed 553Weak Batteries 554Rechargeable Batteries 555Slow Speed 556Damaged Cassettes 556No Review Or Cue 556Noisy Headphone Jack 557Accidental Erase 558Works With Batteries, But Not With Ac 558IntermittentVOR Operahon 559No Playback 560No Record~ng561Defective Microphone 562No Sound 563Muffled or Tinny Sound 565Weaksound 566Head Azimuth Adlustment 566Microcassette Conclusion 567

Professional Recorders 57310Precautluns 573Cassette Features 575Block Diagram 575Regular Maintenance 576Disassembly 577Mechanical Adjustments 577Pinch Roller Adjustment 578Toque Adjustment 578Erratic Fast 'Forward 580Only One Speed 580Uneven Pressure Roller 581


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xvlli CONTENTS

No Tape Motion 582Excessive Wow 583No Speed Control 585No Left Mic Channel Operation 585Poor Left-Channel Sound 587Poor Hgh-Frequency Response 588No SpeakerlMonitor 588No Erase 589Poor Recording 589No Pitch Control 590NoVU Movement 59.2

Troubleshooting 593Chapter f 9 Troubleshooting Auto StereoCassette and CD Players

Blows Fuses 595Pilot Lamp Replacement 598Erratic Speed 598High Speeds 600Works On RadiotNo Tape Action 601Will Not Load 603Jammed Tape 603Erratic Or Intermittent Audio 604Auto Stereo Channels 605Distorted Right Channel 608Preamp and Dolby Regulator Circuits 608Noisy Volume Control 609Hot lC 609Dead Left Channel 610Keeps Reversing Direction 610No Auto Reverse 617Auto Head Azimuth Adjustment 613Motor Problems 614Low Speaker Hum 614Speaker Problems 616Auto Cassette/CD Players 617Surface-Mounted Components 619Block Diagram 621Removing Covers 622Safety Precautions 623Laser Head Cleaning 624Tape Player and Tuner OperatestNO CD 624

No Soundffaully Output Circuits 624No Line-Output Signal 626Ungrounded Speaker Outputs 628Cassette Player Normaltintermittent CD Audio 628Weak Sound in Left Channel 628


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COMTEMTS xl x

Dead Dc-Dc Converter 629No +5-V Source 631No +8-V Source 632Erratic Loading 632Disc-Select Motor Problems 633No S pindle Or Disc Rotation 633No Feed-Motor R otation 635Wiring Diagram 635Improper Search 635External Wiring 638

Chapter 20 Repairing Stereo Cassette DecksCassette Features 647Cassette Problems 648Can't Open Door 648

Cassette Will Not Load 649Dead Cassette Deck 649Keeps Blowing Fuses 650Stops After A Few Seconds 650Smobng Transformer 652Noisy Operation 654No Rew~nd r Fast Farward 654Erratic Tape SpeedlUneven Pressure Roller 655JumbledorBad Recording 655Reverse Side Of the Tape Does Not Play 657Single-Motor Fast Forward 657No Record on Left Channel 658No High-Speed Dubbing 658Lineoutput Decks 659Line-Output Power Circuits 659No Automatic Stop 659Both Stereo Channels Dead 660Dead Left Channel 661Dead RigM Channel 663Intermittent Left Channel 663Weak Right Channel 665

Speake rs and Speaker Connections 666Chapter 21 VCR Repairs You Can Make

The Video Cassette 670ToolsNeeded 672How to Operate the Machine 672To Prevent Accidental Erasure 673Recording 673Recording One Program While Watching Another 675Playing 675Features and F unctions 675How to Connect the VCR to the TV 676


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Head Cleaning 678Before Calling For Professional Service 683Demagnetizing he Tape Head 684

Several Cassettes Will Not Record 685Check the Belts 685Visual Inspection 685Erratic Operation 685Burned Components 686Tape Head Continuity 686No Tape Action 686Keeps Blowing Fuses 687Mechanical Problems 688Squeaky Noises 688Sound Problems 688Poor PC Board Connections 688

Take I t to the E xpert 689

PART 4 TROUBLESMOOTlNG ANDREPAIRING COMPACT DlSC PLAYERSChapter 22 Handling and Care of the Compact: Disc

Record Versus Disc 696Compact Disc Construction 698Handle With Care 699

Wet and Dry Claanets 700Loading The Disc 702The Test Disc 703

The Test Disc EFM Signal 7U3Sony YEDS-1 Demo Test Disc 705Philips CC Test Set 705The Ultimate Test Disc 705

Disassembly 705Chapter 23 The Laser Disc Pickup Assembly

Photodetector Diodes 708Laser 'Pick-Up Precautions 709The Laser Diode 710

The Optical Pickup 713Laser Action 716

Differences in One- and Three-Beam Lasers 716Focus and Tracking Coils 71Latest Optical Systems 718Pickup T~anS polt ystems 718Laser Head Connections 720Testing The Laser Assembly 721

Infrared Detectorllnd~cator722


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COMTEMTS xx l

Power Meter Tests 724Laser Diode Optical Light Meter Measurements 725

CTeaning The Optical Lens 726Protection Of Laser Diodes 726Handling The Pick-Up Assembly 727

Defective Laser Assembly-Shutdown 727Replacing The Pickup Laser Assembly 728

Laser Warnings 729Chapter 24 Low-Voltage Power Supplies

The Black Diagram 732The Main Low-Voltage Power-Supply Circuits 733The Power Transformer 735Dead Chassis: Power Supply 738CD Boom-Box Power Circuits 738

Bridge Rectif ier Circuits 740Zener D ~ d eegulators 740Transistor Regulators 742IC Voltage Regulators 744Dc-Dc Converter 745

Auto CD Regulation Circuits 746Overloaded Power-Supply Circuits 747Several Low-Voltage Sources 747Low-Voltage Problems 748

Filter Capacitor Problems 748No Operahon: Defective Filter Capacitor 751Universal Capacitor Replacement 751Lightning Damage 752Intermittent Power-Supply Sources 752Checking The OnlOfI Smtch 752Transformer Replacement 753Universal Replacement Parts 754Quick Low-Voltage Test Points 755Dead Chassis 756Immobile Tray (No Loading) 757No Disc Rotation 758

Low-Voltage Troubleshooting Sources 758Chapter 25 The RF Signal Paths

Signal Path Block Diagram 761ReplacingLS I or IC Signal Processors 763Surface-Mounted RF Components 765

The RF or HE Sensor Preamp 765Signal Processor or Modulator 766

AF (Auto Focus) and Focus-Error Circuits 768Tracbng-Error Circuits 771Defect Circuits 772

RF And EFM Waveforms 774


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xx i i CONTENTS

Chapter 26 The Servo And 'Motor CircuitsBlock Diagram 77QServo lC 779

The Focus Servo Circuits 783Focus Coil Drive Circuits 785Tracking Servo Circuits 785Servo Problems 790

The Various Motor Circuits 7Q3Tabletop Changer Motors 7grfVarious Motor Troubles 797The Tray Or Loading Motor 799lntermittent Loading 801Slide, Sled, or Feed Motor 8U3Removing The Def&ive Slide Motor 805The Spindle, Disc, or Turntable Motor 8U5Tray Motor Control Circuits BY17Motor Control ICs 808Slide Motor-Control Circuits 808Spindle Or Turntable Motor Circuits 810The Different CD Changer Motors 814

Conclusion 815Chapter 27 Digital Audio DlA Circuits

Boom -Box CD/Cassette Player 818TheSoundCircuit 82.2DlA Converter 823SamplelHold (SM) Circuits 823Low-Pass Filter Network 824Muting Systems 825Audio Line Output 826Headphone Sound Circuits 828Audio Output Voltage M ICD Audio Hookup 832

Troubleshooting The Sound Circuits 832Troubleshooting Audio Distortion 832CD Player Or External Amplifier? 833How To Locate A Defective Audio Channel B34

Signaltracing the Sound Circuits 835Signaltracing With an External Amp 835Locating Defective Transistors or ICsWith the DMM El36IC Resistance Measurements 837Replacing he Transistor or ICs 837Locating Defective Muting Relays and Transistors 838Dead RigMor Left Channel 839One Dead and One Weak Channel 839Distorted Channel 840lntermittent Sound 841Troubleshooting he Headphone Circuits 841


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Chapter 28 CD Player AdjustmentsRequired Test Equipment 845Test Points 847

Laser Power Adjustments 849PLL-VCO Adjustments 850RF Signal Adjustments 85Focus and Tracking Offset Adjustments 853Tracking Gain Adjustments 854Auta Radio Electrical Electronic Adjustments 859

Chapter 29 Remote-Control FunctionsRemo te-Control Operations 861

Auto Remote-Control Functions 861The Remote Transmitter 862

Remote-Control Problems 862Remote Transmitter Or Receiver 864Defective Infrared Transmitter 865Universal Central Control Remote 866Infrared Power Meter 867Infrared Remote Receiver 870Serv~cing he Control Sensor Unit 870

System-Central Clrcuits 870Typical Control Processor 873Troubleshooting Display Functions 874

Chapter 30 Servicing Portable CD And Boom-Box Players 877The Boom-Box CD Player 878Test Equipment And Tools 879Safety Requirements 881Tap Loading 881The B lack Diagram 882

Boom-Box CD Player Block Diagram 883SMD C omponents In Portable CD Players 884Battery Operation 885

12-V Car Battery 886The Power Supply 886

Boom-BoxCD Power-Supply Circuits 8LWPhone and Line Output 890Headphone Output Circuits 892Interlock Switch 893The Various Switches 896Remaving The Boom-Box Case 897Laser Optical Assembly 898Required Test Equipment 899

Infrared lnd~cator899Laser Power Meter Measurements 899Laser Optical Assembly Replacement 96J0


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xxiv CONTENTS

Signal Processing And Servo Circuits 9 3Focus And Tracking Coils 904Crucial Electronic Adjustments 908Trackfng Error Balance Adjustment 909

Focus Error Balance Adjustment 910Chapter 31 Repairing the Auto CD Player

Specifications or Three Auto CD Players 915Auto CD Precautions 916The Block Diagram 917

The Optical Pickup 917Laser Optical Pickup Assembly 977The Preamplifier 918FocuflrackingiSled Servo 919Troubleshooting he RF and Servo Sections 922The APC Circu~ts 922Interlock Circuits 923

Motor Operations 924The Sled or Carriage Motor 924Disc or Spindle Motor C~rcuits 925The Loading Motor Circuits 928

Troubleshooting The Motor Circuits 929PowerHook-Up 92gThe Power Supply 929

Chapter 32 Troubleshooting CD Player CircuitsGrrpclal Waveforms 936The Most Common Problems 937

Intermittent Power Source 941Defective Loading Circu~ts 944Drawer or Tray Does Not Move 945lnterrnittent Loading 947Tray Will Not Open 947Tray Will Not Close 948Poor Turntable Rotation: Magnavox CDC745 949Defective Display Section 949Defective EFM or Signal Section 950Laser Diode Not Lit 951Troubleshooting Opt~cal hutdown Circuits 953Defective Focus Mechanism 954Defective Tracking Mechanism 956Defective Carriage, Slide, or Sled Operation 959Player Skips 960Defective Spindle or Disc Operation 960Spindle Motor Won't Stop 961Disc Does Not Start After Loading 961Does the Spindle or Disc Motor Stop at Once? 962Spindle Motor Runaway 962Defective PLL Circuits 963


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CONTEtlTS xxv

Defective Audio Circu~ts 964Sound Check 965Major Wave f~n ns967Service Notes 969

Par#5 TROUBLESHOOTING ANDREPAIRING CAMCORDERSChapter 33 Camcorder Cassette Formats

New Features 976Beta 977VHS 877VHS-C 9788-mm 979Video Cassette Problems 980Camcorder Features g81Auto Focus 981Auto White Balance 982

CCD and MOS Sensor 982Automatic lris 982Zoom Lens 984Electronic Viewf~nder EVf ) 984Audio Dubbing 984HQ Technology 984Power Requirements 985Hookups 985New Weights 987

Black Diagram 987VHS 987VHS-C 9888 mm 988

The Camera Section 989CCD and MOS Image Sensor 990CCD or MOS Drive Pulse 99QDig~tal ignal Processing 990Sync Generator 991Slgnal Processing 9g1Preamplifier 992Matnx Color Circults 992Resampling Process 992Luminance Signal Processing 992Chroma Prbcessing 993Encoder 993AIC or lris Control 993Automatic White Balance 993Automatic Focus 993VTR or VCR Section 993


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xxv i CONTENTS

Service Notes 997Warn-Up Time 998Tab Lock 9%Write It Down 998Service Cloth 999Service Literature 999Wrist Strap 999Know When Not to Touch 999

Chapter 34 The Camera CircuitsVHSNHS-C Camera Circtllts 1001Canon 8-mrn Camera-Signal Circuits 7 0 0 7Pickups 1002CCD Pickups 1W3

MOS Pickups IOU3Typical (VHS-C) MOS Image Sensor 1003Typical(VHS-C) SyncGenerator Circuit 1004

Signal-Processing Circuits 1005Typical (VHS-C) Preamplifier Circuits 1005Luminance Signal Processing 1006Chroma Pmessing Circuits 1008Automatic Iris Control (AIC) 1009Automatic White Balance 1009Automatic Facus Control 101

The Electronic Viewfinder 1612Typical 8-mm EV F Circuits 1013TroubleshootingEVFCircuits 1015

Chapter 35 Video and System-Control CircuitsVideo Signal lnpuVOutput Circuits 1038Head-Switching Circuits 101$

Typical 8-mm Headswitching Circuits 1019Typical Video Record Circuits 1020

The 8-mm Y & C Record Mode 1020Operation In The Play Mode 1021Typical 8-mm Video Playback 1022

Typical 8-mm Flying Erase Head I022Chroma Signal Recording Circuits 1023Typical 8-mm Y/C Record Circuit 1023Luminance Playback Processing Circuits 1024AGC Circuit 1025Phase Equalizer 1025High-Pass Lim~ter 1026Main Reemphasis Circuit 1026Playback Equalizer 1026Noise Canceler 7026Sync Separator 1026Chroma Signal Playback Circuits 1026

System Control 1027System-Control Circults 1028Power-Control Circuits 1031


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COMTENTS xxvll

On-Screen Display Circuits 10328-rnm V~deo ight Hookup 10348-rnm Remote Control Module 1034Chapter 36 Servo and Motor Circuits

Tape-End Sensw 1037Typical 8-mm Tape-End Sensor 1WVHS-C End-Sensor Clrcuits 1038Samsung 8-rnm Tape-End Sensor 1039VHS-C Supply Reel and Take-Up Reel Sensors 11139Typlcal 8-mm Tape LEDTop Sensor 1047Take-Up Reel Detection Clrcuits 1040

Dew Sensor 1041Typlcal 8-mm Dew Sensor Circuits 1041Canon 8-mrn Dew-Condensation Clrcuit 1042

Cylinder Lock Circuits 1042VHS-C Cylinder Lock Circuit 1U42Typlcal 8-mm Cassette Holder Sensor 1043Typ~cal -mm Reel Sensor Circuits 1043Mode Switch 7044VHS-C Mechanism-State Switch Circuit 1044VHS-C Tape-Detection Circuit 1044Loading Motor Drive Circuits 1045Typical 8-mm Loading Motor Clrcuits 1045

Typical Load~ngMotor Circuits 1046Capstan Motor Drive Cirwits 10468-rnm Capstan Motor Circuit 1046Servo Circuits 1047Typlcal 8-mm Capstan Motor Circuits 1048

Typical 8-mm Servo Circu~ts 1048Typ~calVHS-C ervo Circuits 1 # BTyplcal8-mm Drum Servo Clrcuits 1049Servo Control signals 1050Motor Circuits 1052Loading Motors 1054Capstan Motors 1055Drum Motors 1056Autofmus Motors 1058Ins Motor Dr~ves 1060ZoomMotors 1061Conclusion 1062

Chapter 37 Camcorder Audio CircuitsCamcorder Audio Circuits 1063TyplcalVHS-CAudloCircuik 1064Typlcal 8-mm Audlo Circuits 1 W 5Microphones 1066Headphone Jack 1068Audio Control Heads 1069Audio Output Jacks 1070


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xxvi i i CONTEMTS

Chapter 38 Mechanical Problems and Adjustments to72General Head Description 1073Typlcal8-mm Video Head Cylinder 1074

Typical 8-mm Preamp Circuits 1075Mechanical Operations 1075

8-mm Stop-to-Play Tape Path 1075Typical VHS-C Impedance Roller 1076VHS-C Guide Rollers 1076Typical 8-mm Drum Assembly 1076Slant and Guide Poles 10788-mm Center Gear and FRP Gear I079Typical 8-mm Take-Up Reel Disk 1080VHS-C Main S Brake 1080Loading And Drive Mechan~sms IU&IO

Mechanical Adjustments 1081Important Precautions 1081Test Equipment 1083Preliminary Adjustment Steps 10&3

Conclusion 1090Chapter 39 Electrical Adjustments

List of Maintenance Tools and Test Equipment 7093Reflection Of Wall Charts 1095Tools and Fixtures 1095Typical 8-mm Camera Set-Up Procedure 1097Camera Setup 10g7

Typical 8-mm VAPIAF Adjustment 1U97Camcorder Breakdown 1098

Power-SupplyAdjustments log8Servo Adjustments 1100Typlcal8-mm Adjustment Sequence I101

CCD Drive Section 1 103Back-Focus Adjustment 11U3Camera Adjustments I-l#Electronic Viewfinder (EVF) Adjustments 1107

Chapter 40 Troubleshooting and Repairing the Camcorder t i OBefore Troubleshooting 1112Voltage Measurements 11 12Scope Waveforms 11 13Common Failures 1113

No Picture 1173No Audio 1114No or Improper Color 1114Fuzzy or Out-of-Fbcus Picture 1 1 14

Damaged Parts 11 14Cracked or Broken Boards 1 11Poorly Soldered Joints 1 115


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CONTENTS x x l x

Troubleshooting the Various Circuits 1115No Power 7115NO ~ u t oOCUS 1 laNo Pow er Zoom Operation 1119No Ins-Control C ir c u i 1120Capstan Does Not Rotate 1121Does Not Eject OrLoad 1121Cylinder Or Dru m Motor Does Not Op erate 1122Poor Drum M otor Rotation T 123Sensors Not Working 1123Detectots Not Working 1124Improper White Balance 1124No On-Screen Display 1124No Video Monitor 1725No Video Recording 1-125No Record Chroma 1126No Color Playback 1127No Video Playback 1128No Picture in Playback Mode 1128No Record Chroma 1129Sound D oes Not Operate 1129No Audio Playback 1130Noisy and Jittery P icture 1130White Balance Drifts 1 1 3No EV F Raster 1732No EVF Horizontal Def lM ion 1133No E VF Vertical Deflection 1133No EVF Or Weak Video 1135Infrared lnd~ca tor 1135ServolSystem Control Waveforms 1136The Pow er Supply 1137


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Se rv ici ng today's TV, audio and video, cassette and CD players, and C M C O ~ ~ ~ ~ Se-quires more knowledge, constant use of the oscilloscope, and crucial test instruments.Most of the latest consumer electronic products have crucial circuits with miniature surface-mounted components (SMD), requiring dedicated troubleshooting. The components mightbe crammed together and require removing different sections to access the defective com-ponent. Each section must be isolated, tested, and repaired. This book is crammed withservice data, electronic tips, and how to make those difficult repairs within its 1200pages.The purpose of this book is to provide practical service data on consumer audiohide0equipment. It can help the beginning college student, intermediate, and experienced elec-tronic technician further their howledge with practical service applications of test equip-ment. Examplesare aken from many case histories in the electronic field. Different methodsof servicing the electronic chassis are given because each year many changes and modifica-tions are included in TVs, audio equipment, cassette and CD players, and camcorders.This large book is broken down into five different parts with an introduction to basic andgeneral troubleshooting, and a safety chapter. Part 1explains "Getting St;trted." Part 11 is"Troubleshooting and Repiring Solid-State TVs." Part I I I provides service data in 'Trou-bleshooting And Repairing Audio And Video Cassette Players." Part I V explains how to"Troubleshoot And RepairCD Players." Last but not least, Part V winds up the book with"Troubleshooting And Repairing Camcorders."How to troubleshoot and service the circuits in the modern TV, such as SAW filters,comb filter, high-definition circuitry, chopper and switched-mode power supplies, start-upcircuits, scan-derived voltage, and stereo sound are included in "Troubleshooting And Re-pairing The Solid-State TV Chassis."A wealth of detailed illustrations and photographs help you learn how to service defec-tive horizontal and vertical sweep circuits, diagnose high-voltage circuit problems, iden-tify and cure tuner malfunctions, pe rfom AGC and sync circuit tests, maintain brightnessand picture tube problems, how to service remote-control transmitter and receiver circuits.This incredibly complete workbench reference gives you practical information on how totroubleshoot and repair the latest solid-state circuitry used by all major TV manufacturers.The cassette player is used in every room of the house or office, outdoors, in the car, andwhile running for more exercise. Inside the section "Troubleshooting and Repairing Audioand Video Cassette Players," you will find detailed coverage of a wide range of electronicaudio and video components, which includes personal and portable CD players, boom-boxand double cassette decks, home and car stereo cassette players, professional portable cas-sette and microcassette recorders, and VCRs.How to troubleshoot the cassette player without the exact schematic, and how to performspeed adjustments, fix tape and erase head problems, demagnetize the tape heads, the erase

xxxi


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xxxil INTRODUCTION

head, and repair erratic switching, accidental erasing, defective recording circuits, non-functional fast forwarding, weak stereo circuits, garbled recording, and noisy stereo chan-nels are only a few of the symptoms included in this section.

Just about anyone can make the most simple audio and cassette repairs in these chapters.Although certain cassette problems are provided in a given chapter, the same problemmight be included in another chapter and related to the cassette player you are now servic-ing. Cassette troubleshooting and servicing methods are all here, so you can bring that cas-sette player and recorder back to life.

The compact disc (CD) player has come a long way in the past 15 years. The little rain-bow-reflecting disc has brought clear, crisp, noise-fiee reproduction of music to our ears.The digital music source can now be reproduced with more depth, greater detail, and moreimaging than ever before. This new digital-to-analog technology has brought the ultimatein glorious sound.

"Troubleshooting and Repairing CD Players" covers the newest makes and models, ad-dresses te~hnologicaladvance, with troubleshooting charts throughout. You will findhands-on instructions on how to service servo systems, remove and replace the defectivelaser head, how to locate the defective optical assembly, how to service he signal and system-control circuits, and how to locate and replace the defective slide, load, spindle up-down,magazine, chucking, elevator, and changer motors.

Compact disc players are loaded with special components, such as surface-mountedparts (SMD), crucial large-scale integration (LSI) and integrated circuits (ICs), opticallens-and-laser assemblies, and many different motor circuits. You should obtain theseparts through the CD distributor, manufacturer, manufacture service depot, or a dealer thathandles CD players. Very few universal components are used in compact disc players. Al-ways replace these special parts with those that have the original part number.

All formats of today's camcorders (8 mm, Beta, VHS, and VHS-C) are covered in thesection "Troubleshooting And Repairing Camcorders." The various chapters include prac-tical service techniques, video circuits, servo circuits, control systems, motor circuits, me-chanical tape operations, mechanical adjustments, electrical adjustments, and camerapickup circuits.

Like today's compact disc player, the camcorder is loaded with special components,such as SMDs, integrated ICs, main MI-COM processors, COD and MOS image devices,and special optical components. Besides correct test equipment, the schematic diagramand service literature is a must-have item. Many manufacturers have special test equip-ment and jigs to provide quicker camcorder service.

In the many pages of this book, you will find how to troubleshoot and repair 90% of theelectronic products in the consumer electronics field. Actually, this is four complete booksin one large volume. Servicing electronic products can be a learning experience, a life-time job, and can be a lot of fun. This volume contains more than 40 years of practical ex-perience with repairing data makes an excellent reference for anyone involved inconsumer electronic repair, professionally, or as a hobby.


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GETTING ISTARTED


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4YIL-"4a,PRACTICAL -

TECHNIQUES

Precious TimeThe SymptomThe Three S'sIsolationService LiteratureSubstitute another schematic

Chassis ComparisonSpilled LiquidBasic Test Equipmen t

Baslc TV test instrumentsRequired audio test instrumentsBaslc audio test equipmentRequired CD test equipmentRequired microwave oven test

InstrumentsCrucial voltage testsTransistor voltages and reslstance

tests

Diode testsIC vdtage and reslstance testsCrucial reslstance ampllfler testsSCR reslstance measurementsTransistor and IC replacementsCrucial waveformsTV surface-mounted component(SMD) tests

How to read SMD valuesCD surface-mounted C chipsCD surface-mounted devices (SMD)Removing surface-mountedcomponents

Replacing surface-mountedcomponents

Double-sided boardsRead and StudyCase HistoriesPreventative Maintenance


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4 PRACTICAL TROUBLESH00TIMQ TECHNIQUES

T h e experienced electronic technician finds a symptom and ends up replacing the defec-tive component. Just by looking at the TV screen or listening to a speaker, you can isolatethe stage where the trouble appears (Fig. 1- 1). By using the three senses, you can some-times pinpoint the possible stage on the block diagram or schematic. Knowing how to b-cate, remove, and replace the defective part saves service time.

Precious TimeTime is one of the electronic technician's greatest factors. You can waste it or makemoney with it. The time servicing the difficult or intermittent problem will determineif the repair job is profitable. Any time that the experienced technician spends morethan one hour on a given electronics problem without locating the defective compo-nent, time is bs t. Lost time can also occur when a coffee break extends from 15 to 30minutes (or even longer).

Call backs or repeated repairs cost the electronic technician extra money. Doing a thor-ough repair job at the beginning eliminates repeated calls. Preventive maintenance can re-duce call backs. Of course, I must ad& that the electronic chassis does produce a lot ofservice problems that can happen after a repair. Always charge for repeated service whenthe original repair has nothing to do with the present prob1em. Remember, the doctor orauto mechanic charges for the additional call.

1-=Bychecklng the TV screen, you can note thesymptomand decide the location of the trouble.


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1IC501 22capstan 25 4 capstanICW1speed drivercont rolICFIGURE 1 The slow-speed symptomof a camcorder canp i n t to a defectlvespeed-circuitcapstandriverC motor or belt.

The SymptomOn a TV, a distorted picture and mushy sound point to a defective IF or tuner within thechassis. If the volume control is turned completely on and only weak sound within thespeaker of an audio amplifier can indicate that the transistor, IC, or coupling capacitor isdefective. Distorted and weak sound might indicate a d m ape head or output audio stagewithin the cassette player.A camcorder with slow speed might have a defective speed circuit or motor (Fig. 1-2).Improper or intermittent loading of the CD player or camcorder might result in a dirty or

defective switch, loose motor belt, dry ge ar hx , or a defective motor. The tape might notrotate in the camcorder or cassette player if the motor is defective, capstan is dirty or dry,or if the motor belt is loose. Just remember to watch, listen, and smell for the varioussymptoms, before tearing into the electronic chassis.

The Three S 'sThe three S's might be your most important tool. Sight, sound, and smell can help you tosolve a lot ofTV , cassette, camcorder, CD player, and microwave oven problems. You cansee burned resistors, fried flyback or power transformers, and lightning damage. A leakyelectrolytic capacitor might have a black or white substance oozing out at the buttom con-nections. Poor board connections might indicate an overheated solder connection. Crackedor overheated connections of a high-power resistor might indicate possible trouble. Defi-nitely, you can see a spark gap, tripler unit, or high-voltage lead arc over. Above all, youreyes identify the trouble symptoms from the front of a picture tube, overheated IC, or tran-sistor on the chassis.Insufficient or distorted audio suund might be traced to the sound stages. Arcover at thepicturetubeor high-voltage transformer within the TV chassis mightbe h e a d The ear mightpick up h e ic-tic sound of h e flyback transformer with high-voltage or chassis shutdown.SomeTV echnicians can hear the 15,750-Hz sound of the horizontal output transformer, in-dcating that the horizontd oscillator stages are performing (Fig. 1-3).Noisy sounds from ainterstage or output transformer might indicate loose particles within the component.


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FIGURE1-4he 15,750-Hz sound from the flyback can be heardby same people.You might smell an overheated voltage-droppingresistor or degaussing thermistor withintheTV chassis.The ozonesmellmight be traced to the flyback hamformer, trip1er unit, screen-fmus assembly,focuscontrols,or the anodeconnectionofthe picturetube.The sweet smell ofthe overheatedpower transformer in the cassette player might indicate lightningor power lineoutage damage. Not only can you smell an overheated transistor or diode, but you can feel

them. Overheated componentswithin the electronic chassis are always a source of trouble.

IsolationIsolate the symptom to a block diagram. Begin troubkeshooting procedures with the blockhagram. Upon checking the block diagram, you can quickly isolate the defective sectionsin the TV, cassette player, audio amplifier, and CD player. You can see where the signalpath goes from section to section (Fig. 1-4).The block diagram can further be broken downto show several blocks of one particular section. Not only does the block diagram illustratehow the different sections are tied together, but it can be used to show how the circuib o pera& in a given chassis.

After locating the defective section or circuits, locate the various components upon aschematic diagram that might cause the electronic chassis to not operate. The h s t look at aschematic of a TV or CD player might appear complicated, but if you break the schematicdown into various sections, servicing becomes more systematic. For instance, if the load-ing motor in the camcorder is not operating, go directly to the servo or system control ICand trace the signal back to the driver and loading motor (Fig. 1-5).Each functional pro-lem can be circuit-traced using the same logic.


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ISOWTION 7

A lot of the manufhcturers have the differentcircuits drawn in various colors, so they standout.Othersuse a variation of dotted lines to separate thevariouscircuits. MostCD schemat-ics have arrows or a thick color path of arrows, indicating the signal path throughout the var- Ious stages. Crucial voltages are found on the schematic or listed separately in a voltagechart. Some schematics have voltages listed in red or green. If not, mark them hrectly on thediagram before you start servicing procedures.After locating a defective component, circleit, and draw a line out to the side to the margin area to record the service problem.ha t ing the suspected component on the PC board chassis might be &fficult if a partslayout diagram is not handy. Sometimes the components are labeled and others are not.The electronic components are often mounted on one board and the mechanical parts arelocated on another assembly. Small components, such asmuis tors , capacitors, resistors,and diodes might be dificult to locate because many are not individually marked. If youdo not have a service manual or schematic, you must trace out wiring and components,which takes up a lot of valuable time.

T401C4Q1 Q401 driver Q402horiz-vert * horiz horizdeflection driver outputFlybackT4Q2

+I15 V+I15 V

~ I G U R Ediagram.

Isolate the symptom to a block dlagram and then use the clrcult

Loadingmotor

IC501servocontrol16

Trace the dead loadlng motor symptom to the system control IC,driverC,and loading motor.

21 I00 k3

23 I00 kw


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Service LiteratureSchematicsand service literature are a must for the electronic technician. Although manyTV echnicians might service a TV or camcorder without a schematic, it is not practicalover the long run (Fig. 1-6). You can lose a kot of valuable service time without a goodelectronic schematic. Several years back, the Japanese TV chassis was difficult to servicebecause wiring diagrams and par& were difficult to obtain.

This is not so today because most foreign imports are covered by schematics and serviceliterahe. Howard Sams Photofacts cover most TV chassis. Manufacturers Profaxschematics are found in the pages of Electronic Sewicing d Technology magazine.

Service literature, including detailed diagrams, is published by each electronics manu-facturer. Here, additional data as to how each stage operates might clear up the tough job.This service literature can be purchased yearly or for each individual electronic chassis.You will also receive important production and modification information for each chassis.Many electronic manufactures hold service clinics several times a year. Take a day offand attend these meetingsbecause they provide crucial servicing data. Besides, you mighttalk to a fellow electronics technician who has just licked the same service problem thathas you stumped.A day away from the shop might bring future rewards.

SUBSTITUTE ANOTHER SCHEMATICWhen the exact service manual or schematic is not available, use another manufacturer'sschematic diagram. Although the substitute is not exactly the same, it will give you differ-ent test points to hu bleshmt the circuit. Signal tracing audio circuits can be checked by

A schematic dlagram Isa must-haveItemwhentroubleshooting a difficull problem.


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CHASSIS COMPARISON 9

Fittercapacitor

C.YV" Lacate the low-voltagecircuits by ldentlfylng thelarge filter capacitor.

starting at the tape head winding and going from base to base of each transistor. The out-put stages can be checked by starting at the volume control.Usually, cassette audio stereo circuits are laid out on the PC board with the left channelon the left and the right channel on the right. You can start at the speaker and h c e he cir-cuit back to h a t e he output transistor$ or ICS. Some of these puwer output transistors andICs are located on heatsinks. The suppiy lead from the IC or transistor can be traced backto the power supply. The power suppiy can be identified with large filter capacitors,&odes, and bridge rectifiers (Fig. 1-7). The suspectedpart can be checked against the iden-tical one found in the good stereo channel.ORen the horizontal and verticd circuits within the TV chassis can be compared to an-other schematicwith very few changes. The different stages can be scoped with the sametype of waveforms as another chassis. Likewise, the voltage and resistance measurementsare quite common in the horizontal and vertical circuits.

Chassis ComparisonMany times the same chassis might be located in more than one different TV. This is es-pecially true if you are servicing chain-store merchandise. It's also pussible to have trou-ble with a new TV right out of the box.The newTV hassis might also be compared withthose in the showroom if you carry that certain brand of TV.


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10 PRACTICAL TROUBLESHOOTINO TECHNIQUES

If the correct schematic lo not handy,compare thedefective circuits with those in a comparable chassis.

If, by chance, you are stumped on a new circuit or do not have a schematic handy, com-pare the voltage and resistance measurements of the working chassis can help solve theproblem (Fig. 1-8). Many chain-store TVs are manufactured for them by another source,and many TV brands actually have the same equipment. Of course, comparison checkstake a lot of time and should only be made when you have no other choice.

Spilled LiquidAfter removing the back cover of a TV, you can quickly decide if some kind of liquid hasspilled down on the chassis. Besides being a big cleaning mess, the chassis might not berepairable if liquid has been spilled inside the back of the TV. It is very difficult to cleansmall resistors and capacitors that are soldered flat against the PC board. Ofken, the chas-sis is turned on, causing arcing in the horizontal and high-voltatage circuits.Sometimes when a voltage arc between components occurs, the arcbreaks down the PCboard and can cause burning of the board. The board can be saved by cutting out theburned area. Use a pocket knife or drill out the burned area, then replace burned compo-nents across the area. Place hookup wires around burned-out PC wiring connections. Thewiring schematic and component replacement charts can be handy with this procedure.If a beverage is spilled in the chassis, the PCboard and components become sticky andcan be difficult to repair. Place a fan near the chassis to dry the areas if water has beenspilled inside the TV. ARer cleaning and repairing the board, spray the entire area withcha r high-voltatage insolation spray after the chassis operates for severd hours. The chas-sis should then be operated for several days to be sure that no further breakdowns occur.Sometimes you will fmd that the TV cannot be repaired and must be replaced.


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Basic Test EquipmentBack in the vacuum tube days, many TVs were repaired with a tube tester, a VTVM orVOM, and an oscilloscope (Fig. 1-9). Today, a digital multimeter (DMM), oscilbscope,CRT checker, color-dat-bar generator, and tube-test jig are the basic test equipment. Cru-cial voltage and resistance measurements can be made with the DMM. The DMM caneven check diodes and transistors in or out of the circuit. The osci lbscope is required tolook at waveforms in the various circuits. Most waveforms are checked with the color-dot-bar generator connected to the antenna terminals to provide a signal. A tube test jig is idealto monitor when servicing the pulled chassis. A good CRT tester eliminates guessingabout the status of the picture tube.

As new circuits arrive and old test equipment is replaced, an older oscilbscope shouldbe replaced with a dual-trace 40- or 100-MHz unit. An isolation variable line transformeris a must item when servicing a new integrated flyback chassis. A capacitance meter andCRT restorer-analyzer are handy test instruments to have around. A frequency counter andsweep-marker generator are required for TV-alignment purpases. To check high voltage atthe CRT, elect a good high-voltage probe (Fig. 1-10).

With the latest portable and console TVs, the chassis can be loosened, slid backwards,or tilted on edge or side for easy servicing. Ofken, the connecting lead wires and cablesfiom the TV chassis to other components mounted within the plastic purtable case can beuntied and extended so that the chassis can be slid backwards or actually removed from thecabinet (Fig. 1-11). Likewise, remove chassis bults and screws so that the small TV chas-sis inside the large TV onsole can be moved to test most parts within the wooden cabinet.

You might find that the busy electronics technician uses only three or four test instru-ments in his daily service routine. Many other test instruments are collecting dust on the

A dual-trace scope, DMM, FFT-VOM, and isolationtransformer are basic test instrumentsfar an electronic technician.


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Check the high voltage at the picture tube with ahlgh-voltageprobe.

Pull the portablelV chassis back or remove il foreasy access.

service bench andnot being used. Knowing how to use the basic test equipment is the se-cret toquick, efficient, and practical elecimnics servicing. One quick way to learn how thetest instruments operate is to attend the classes sponsored by many test instrument distributors and manufacturers. Check the list that follows for required basic test instruments.


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BAS#: TEST EQUIPMENT 19

IASIC TV TEST INSTRUMENTSI Digital multimeter (DMM)2 VOM, VTVM, or FET voltmeter3 Oscilloscope (at least 40MHz)4 Variable isolation transformer5 CRT ester and rejuvenator6 Diode, SCR, emiconductor tester7 Capacitance tester8 High-voltage probe9 Colordot-bar generatorREQUIRED AUDIO TEST INSTRUMENTSBesides several screwdrivers, a pair of long-nose pliers and side cutters do the bulk of au-&O work, combined with a VOM and DMM. The digital multimeter @MM) can checkvoltage, resistance, current, capacitance, diodes, and iransistors; some testers even have afrequency counter. A VOM or FET-VOM is ideal in audio alignment (Fig. 1-12). It'smuch easier to see the meter hand respund to the audio signal than the DMM. You willh d hat the same TV est equipment can be used to service audioequipment.

BASIC AUDIO TEST EQUIPMENT1 VOM and DMM2 FET-VOM3 Dual-trace uscikloscope4 Noise signal generator5 Audio generator6 Sine-squarewave generator

Amplifier

tape

FrequencycounterThe VOM, FET-VOM, and frequency counter are Ideal for t a p

head and audio-alignment praaedures In cassette players.


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7 Semiconductor tester8 Capacitance meter9 Audio signal tracer10 Test speaker11 Speaker loads12 Test discs andcassettes

For those technicians who specialize in troubleshooting audio equipment, the additionaltest equipmentmight speed up making crucial repairs and alignment:1 Frequency counter2 Function generator with counter3 Audio oscillator and frequency counter4 Distortion meter or analyzer5 Wow and flutter meter

REQUIRED CD TEST EQUIPMENTYou need several as t instruments to troubleshoot and make the necessary alignment ad-justments in the compact disc player. Most of these test instruments are already commonto the average electronics technician's service bench (Fig. 1-13).1 Dual-trace oscilloscope2 Optical power meter

Besides the test instruments found upon the TVbench, the optical power meter, frequency counter, and AF signalgenerator are essential for compact disc (CD) servicing.


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BASK TEST EQUIPMENT 1S

FIGU- The opticalpower meter and rpeclaladjustmenttools are n-ssary for CDservlclng.3 Digital Multimeter (DMM)4 Low-frequencyAF oscillatorS Signal generator6 Capacitance meter7 Frequency counter8 Test discs9 Special tools, filter adjustment circuits, wrist trap, manufacturer specid jigs, etc.

The optical power meter, test discs, special tools, filter circuits and special jigs pur-chased from the manufacturer for special adjustments are probabky the only devices thatthe estabkished repair shop might not have (Fig. 1-14).Special tools, such as a grating tool, feeker gauge, or special screwdrivers might be neededfor some adjustments. The focus and tracking, Ioopgain harness, and special manufhcturercircuits can be handmade. Special manufacturers jigs, monitor devices, and test cables canbepurchased for certain tests required by the manufacturer. Although, each manufacturermightrequire acertain test disc, the most common are the YEDS7, YEDS18, and SZZP1014F.The laser power meter is used to measure the laser diode output and infrared remote-control units.The laser meter is particularly suitable for the service of compact disc andlaser disc players because of its narrow, tillable probe. The meter can be used to check thefunction of cassette compartment LED in video recorders and transmitting diode in in-frared 04 remote cuntrols (Fig. 1-15).With the three measuring ranges of 0.3 mW, 1 mW,and 3 mW, aH laser light sources found in many CD players can be checked. The switch-able wavelength of 633 nm, 750 to 820 nm, has an accuracy of 5% .When measuring the laser light beam, do not look directly at the laser light. Rememberthat CD and LD players emit invisible, infrared light. You simply cannot see the infraredbeam. Keep your eyes at least 14 feet away from the laser beam.


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Besides checking the laser beam, the opticalpower meter can help you to check the LED, transmlttlng diode, andInfrared remote-control units.REQUIRED MICROWAVE OVEN TEST INSTRUMENTSSeveral different test equipment is required to service and maintain microwave ovens. Be-sides regular hand tools, torque and star screwdrivers, a microwave leakage tester andmap me t e r are must-have test instruments (Fig. 1-16). Many of the basic tools you'llneed are found in the shop or on a TV repair bench.I Torque and star screwdrivers2 DMM3 Microwave leakage tester4 Triac and SCR tester5 Magnameter6 Fuse saver7 Test bulb

CRUCIAL VOLTAGE TESTSNo doubt, crucial voltage and resistance tests have been used to find more defective com-ponents than any other tests. Most defective solid-state components, such as transistors,diodes, and ICs can be locatedwith crucial voltage tests. A quick voltage check across themain filter capacitor can help you to determine if the power supply of any electronic prod-uct is normal or has an improper voltage source (Fig. 1-17).A leaky or shorted audio out-put transistor or IC can be spottedwith a crucial voltage test.


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BASIC TEST EQUIPMENT 17

TRANSISTOR VOLTAGES AND RESISTANCE TESTSTaking crucial voltage measurements on the transistor element can determine if the tran-sistor is normal. Suspect that the transistor is open i f the collector voltage is much higherthan normal, with no voltage on the emitter terminal.An open emitter resistorcan producethe same voltage readings (Fig. 1- 18).

~ I G U R E f 61 The Magnametercan checkthe current,high-voltage,and magnetronoperation within the microwaveoven.

120Vac

( I - IGUH~-1 A quick voltagetest of the largefilter capacilors can indicate ifthe low-voltagesource Isnormal.


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18 PRACTICAL TROUBLESHOOTlNQ TECHNIQUES

AFAMP

C104.7 pFAudio in } (

An open emitter resistor can increase the voltage at the collectorterminal.

Connect the voltmeter across the collector and emitter terminals and mark down thevoltage measurements. Remember, the DMM can read these low-voltage measurements.The collector terminal of a NPN transistor is positive, but a PNP transistor is negative.Now short the base to emitter terminals together and the voltage should increase if thetransistor is normal.Practically the same voltage measurements on all three terminals can indicate that thetransistor is leaky or shorted. The collector and emitter terminals become leaky in mosttransistors. The voltage measurement on both terminals can be quite close with a directcollector-to-emitter short. Discard transistors with any signs of leakage between any of theterminals.The transistor is usually good if normal base-emitter bias is found (fig. 1-19). The sili-con transistor will have a 0.6-V bias voltage between emitter and base, but a germaniumtransistor will have a bias voltage of 0.3Vbetween these same elements. You can quicklycheck the bias voltage of each transistor within the electronic chassis and possibly locatethe defective transistor circuit. Of course, with an improper or no voltage source, very lit-tle voltage is found on any transistor terminals.First, measure the voltage on all three elements to common ground. Then check thebase-emitter bias voltage. If you're not convinced of the legitimacy of the results, removethe transistor from the circuit and check it out of the circuit with a DMM or transistortester. Some technicians prefer to remove only the base terminal from the circuit and giveit another in-circuit test. Sometimes when the transistor is removed, or when the in-circuittester is applied to the transistor, the defective or intermittent transistor can test normal.Besides using the voltage and resistance methods, the transistor can be checked in or outof the circuit with any of the many different transistor testers on the market. The suspected


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BASK TEST EQUIPMENT 13

transistor can be checked out ofthe circuit with resistance measurements of theVOM orDMM (Fig. 1-20). Leaky or open transistors can be locatedwith the ohmmeter scale.A quick method to check a transistor in or out of the circuit is with the diode or transis-tor test of the &gital multimeter(Dm)Fig. 1-21).Comparableresistance measurementsof the diode junction from base to cullector and base to emitter will identify an NFW orPNP ransistor, and will indicate if a leakage or open junction occurs between the ele-ments. The leaky transistor resistance might be low between collector and emitter or base

Q644LDR amp

Open baseto collector

~ F ~ G U R E14 Check far anormal forward blasvoltage(0.6 Y) between the baseandemltter of an NPNtranslstor.

Leakybetween base andemitterHigh-resistancejunction betweenbase and collector

Check the suspectedtranslstor wlth a dlode-junctlon translstor testof DMM.


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GermaniumSilicon

DMMNormaltransistor

DMM DMMLeaky transistorbetween collector andemitter

Open junctionbetween collectorand base terminalsTransistors can be checked with the ohmmeter or diodejunc tion

test of a digital multimeter {DMM).

npntransistor

NormalLeaky betweencollector and base

Leaky betweenemitter and collector Reversedtest leadsThe leaky transistor might show low leakage between the base

and emitter or between the emitter and collector.and emitter in both directions (Fig. 1-22). Most transistors become leaky between theemitter and collector terminals.The transistor might be open between base and collector or base and emitter terminals,with no measurement on the DMM. A transistor with a high-resistance joint can cause a


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BASK TEST EQUIPMENT 21

weak or dead response when the leakage is greaterwithone set of transistor elements thanthe other set.A high-resistance joint exists when the measurement is differentby severalhundred ohms between two elements and not the other two. T m i s t o r s can be quicklycheckedwith the DM M diode or transistortests.

DIODE TESTSA quick voltage test with the positive terminal of voltmeter at the positive terminal of sus-pected diode and the negative termind to ground can help you to locate a defective diode.Likewise, a zener diode can be located in the same manner. The zener diode is used in acircuit to regulate the voltage at a certain level. Really low voltages at the positive termi-nal indicate that the diode is leaky or shorted.

The defective diode can be located with a low-resistance measurement. Low-voltage&odes can be checked for open or leaky conditions with the diode test of a DMM. Be surethat a power transformer winding, low-resishnce resistor, or transistor is not across thepath of the diode when making in-circuit tests. It's best to remove one end of the diode foraccurate leakage test (Fig. 1-23).

Check the suspected diode with the red probe of DMM to the anode terminal of the &odeand the black probe to the cathode terminal.You should get a reading. Now reverse the pro-cedure. No meawementor an nfmite measurement is noted on a normal diode. When mak-ing a diode test with the FET-VOM, start with the red or positive probe to the cathode and

Collectar Silicondiodenormaltest

Anode Reverseleadsnormal

Leaky Collectar IN34 Anadesilicon diodediode normal

FIGURE 1-23 Remove one end of dlodefrom the clrcult for accurate open or leakytests.


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black probe to the anode terminal. The normal diode will show a resistance measurement. Ifa low-resistance measurement is found in any direction, the diode is leaky or shorted.Most low-voltage and damper diodes can be checked for open or leaky conditions withan ohmmeter or DMM. The RF, ideo, and audio detector diodes can be checked withmohmmeter and DMM, but will have a higher resistance measurement. Some older boostrectifiers within the TV can only be checked for heavy leakage. The high-voltage rectifierstick found in the black-and-white TV chassis and microwave oven c m o t successfully bemeasured with the VOM or DMM tests.

IC VOLTAGE AND RESISTANCE TESTSThe defective IC c a n be traced with voltage and resistance measurements. Check the sig-nal in and out of the IC with the scope. The audio 1Ccan be signal traced with audio in andout tests of the suspected IC with an external audio amplifier. Very low voltage on severalterminals of the IC can indicate a leaky component.A low voltage at the IC erminal sup-plied directly from the low-power supply can indicate a leaky IC (Fig. 1-24).Remove the

Left spk

Right spk

A Iuw resistance at the voltagesup ply terminal d an IC m ightindicate that it is leaky.


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BASIC TEST EQUIPMEWT 29

JFIGURE 1.251 A leaky or open transistor mlghtappear to operateproperlyafter removlngIt from the chassls.terminal pin from the circuit and take another resistance measurement between the pin andthe chassis ground. Apply the soldering iron tip to the mesh material and suck up all sol-der around the voltage-supply pin. Flick the pin with a pocket knife or small screwdriverto be sure that the pin is free. Replace any IC that has a low-resistance measurement.

Internal open connections inside of the IC can cause it to be dead or intermittent. If thesignal is applied to the input and no signal or a low signal is at the output terminal, suspecta defective IC. Take accurate voltage measurements and check them against the schematicto determine if the IC is defective. Sometimes voltage and resistance measurements arenormal compared to the schematic; replacing the IC is the only way to solve the problem.Replace the suspected IC at once if it is a plug-in socket type.Sometimes, with ohmmeter tests, you can locate a change in a resistor or leaky capaci-tor from one pin to common ground. Be sure that IC is defective by taking signal-in andsignal-aut tests, with crucial voltage and resistance measurements. Always compare thesemeasurements with the good channel in the stereo audio amplifier. Replacing the IC re-quires a little more time than replacing a bnsistor.

CRUCIAL RESISTANCE AMPLIFIER TESTSIf the audio amplifier keeps blowing a fuse and the chassis shuts down, sometimes it is dif-ficult to take accurate voltage tests. Sometimes an IC or transistor will break down underload and test normal within the transistor tester (Fig. 1-25).You might find that in-circuittransistor tests with the DMM indicates that all transistors are normal. It is difficult in di-redy driven transistor or IC output circuits to locate the defective component without ac-curate voltage measurements.


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The best method is to take in-circuit resistance measurements of the transistors and ICs.Start at the speaker output terminals and take crucial resistance measurements to commonground. Now compare these resistance measurements with the normal stereo channel.Check each IC and transistor with resistance tests until you receive or have a different re-sistance measurement. Sometimes a leaky capacitor or a change in resistance can cause thearnp to shut down.A leaky 1C or transistor might be located with accurate resistance mea-surements to common ground.SCR RESISTANCE MEASUREMENTSThe SCR found in low-voltage power supply and high-voltage rectifier circuits can bechecked with resistance measurements (Fig. 1-26). A low-resistance measurement be-tween the gate (G) and cathode (K ) is normal. Replace the SCR if the measurement is be-low 50 ohms. If my resistance measurement is found between the anode (A) and cathode(K ) terminals, replace the leaky SCR. Like the transistor, the SCR can break down or be-come intermittent under load and should be replaced if you suspect that it is faulty.TRANSISTOR AND I C REPLACEMEMTSMost transistors and 1Cs can be replaced with original parts or universal replacements. Useoriginal transistors within the TV tuner, control, and IF stages. Large, crucial ICs shouldbe replaced with those that have the original part numbers (Fig. 1-27). Foreign transistorsmd ICs are found at most wholesale or mail-orderTV part establishments.After locating the defective transistor in the audio amplifier, the transistor must be re-moved and replaced. Most transistors found in audio and radio circuits can be replacedwith universal replacements if the original part is not available. For instance, the commonAF ransistor (2SC374) can be replaced with universal RCA SK3 124A or ECG289A. TheAF transistor (2N3904) can be replaced with a universal RCA SK3854 or ECG 123AP.Look up the transistor number within the RCA SK series, NTE, or with Sylvania's ECGseries replacement guide book (Fig. 1-28). Most universal solid-state transistors and ICscan be replaced with RC G GE, Motorola, NTE, Sylvania, Workman, or Zenith replace-ments. Simply look up the part number and replace it with an universal replacement. Testthe new transistor before installing it.After obtaining the correct replacement, remove the old transistor with iron and solderwick from the PC board. Remove the mounting screws on the power output transistors,then unsolder the emitter and base terminals. Be sure that you have the correct terminals in

SCR

Checkthe suspected SCR withresistance tests or upunan SCR tester.


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Check lCpart number

FIGURE-271 Replace large processors and E swlth those thathavethe orlglnalpart number.

)#Topof theWRe1976ReplncemsntGum

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