Troubleshooting and Repairing Consumer Electronics This page intentionally left blank Troubleshooting and Repairing Consumer Electronics Third Edition Homer L. Davidson McGraw-Hill New York Chicago San Francisco Lisbon London Madrid Mexico City Milan New Delhi San Juan Seoul Singapore Sydney Toronto Copyright © 2004, 1997, 1994 by The McGraw-Hill Companies, Inc. All rights reserved. Except as permitted under the United States Copyright Act of 1976, no part of this publication may be reproduced or distributed in any form or by any means, or stored in a database or retrieval system, without the prior written permission of the publisher. ISBN: 978-0-07-178208-1 MHID: 0-07-178208-7 The material in this eBook also appears in the print version of this title: ISBN: 978-0-07-142181-2, MHID: 0-07-142181-5. All trademarks are trademarks of their respective owners. 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Contents Introduction xv Acknowledgments xvii 1 Servicing methods without a schematic 1 Locating critical components 2 Just listen, man 3 Hands on 3 Too, too bright 4 Audio pops and cracks 5 Smoke and fire 7 Under those eyes 8 Keep at it 9 Same chassis, different model 9 The same train tracks 10 Lines down the road 11 Identify part numbers 11 Resistor color codes 13 Flat capacitor color codes 14 Foreign capacitors 14 Dogs of all kinds 14 Cool nights and hot days 16 Double trouble 18 Lightning damage 19 Down below 19 Outside the chassis 20 Do it today, not tomorrow 20 Intermittent problems 21 Time is precious 22 Test points 23 v vi Contents Say it isn’t so 23 Ten points of servicing 25 Safety measures 28 2 How to locate, test, and repair 31 With only a DMM 31 Correct electronic test equipment 32 Who’s on first? 35 Case histories 36 Isolation 38 Location, location 38 Out of bounds 41 Lightning damage in a TV chassis 43 Burned and damaged 43 Ac input hot grounds 44 TV SMPS hot grounds 44 Running warm 45 Red hot—do not touch 45 Same circuits, another chassis 46 Resistance in-circuit test measurements 47 Continuity tests 48 Leaky or shorted transistor resistance tests 49 IC resistance tests 50 Sams Photofacts 51 Electronic Servicing and Technologyschematics 52 The various waveforms 52 Signal injection 53 Troubleshooting with an external amp 55 Transistor in-circuit tests 55 Digital transistor tests 57 NPN or PNP 57 DMM diode tests 58 Safety transistor replacement 59 Signal in and out tests of IC components 59 Voltage injection 60 Removing and replacing a defective IC 61 Here today and gone tomorrow 62 Component replacement 64 Low and behold 65 SMD components 65 Flat or round 66 Removing SMD parts 67 SMD replacement 68 ESD FCC ID numbers 68 Cleanup 69 Contents vii 3 Troubleshooting and repairing audio amps, large and small 71 List of audio test equipment 71 Required test equipment 72 Listen, listen 75 The dead chassis 75 Only a whisper 75 Repairing the audio amp 76 Stereo IC amp repairs 78 Repairing the cassette amp 79 Auto radio amp problems 85 Large stereo amp repairs 88 Troubleshooting CD player audio circuits 90 Servicing the TV audio amp 93 Extremely high-powered amps 96 4 Servicing auto receivers 103 Required test instruments 103 The power supply 104 The front-end radio section 104 The rear section 106 Variable-capacitor tuning 107 Inductance tuning 107 Varactor tuning 108 Keeps blowing the fuse 108 Common auto radio failures 109 New FM circuits 113 SMD components 114 Silent listening 115 Early car radio audio output circuits 116 Auto radio hookup 120 High-powered amps 120 Dismantling high-powered amps 122 Locating the correct components 123 Transistor high-powered amps 124 IC high-powered amps 124 Troubleshooting high-powered power supplies 126 Servicing high-powered amps 127 Bridged amp outputs 128 Two-channel amp hookup 128 Matching impedance 129 High-powered speaker hookup 130 Auto radio speakers 130 Speaker problems 133 viii Contents 5 Servicing cassette players 135 Required test equipment 135 Pocket cassette player layout 136 The portable cassette player 136 Auto radio/cassette player 136 Check out that cassette 138 Slow speeds 138 Will not eject 139 Dead, no sound 140 Poor tape motion 140 No fast-forward or rewind 141 Tape everywhere 142 Jammed tape 142 Squealing noises 143 Too much oil 143 Poor erase 144 Poorly soldered connections 145 Dead left channel 145 Intermittent operation 146 Under that magnifying glass 146 Locating and replacing bad transistors 146 Locating and replacing a bad IC 148 Recording problems 149 The boom-box cassette player 154 The auto cassette player 158 6 Troubleshooting CD players 167 Laser diode circuits 168 Digital-to-analog (D/A) converter 173 CD power supplies 173 Check those electrolytics with an ESR meter 175 Focus amp problems 176 Battery focus coil check 178 Tracking amp problems 178 Loading motor problems 178 Disc and SLED motors 180 Intermittent skipping 181 No play, dead operation 182 Noisy sounds 183 The portable CD player 183 Boom-box CD circuits 185 Similar diagrams 186 The defective CD motor 187 Motor drive circuits 189 SMD components 189 Troubleshooting D/A circuits 190 Contents ix Defective mute system 190 The CD changer 191 Servicing headphone circuits 194 Troubleshooting servo circuits 195 Loading problems 196 Actual CD case histories 196 Critical waveforms 197 7 Troubleshooting the TV chassis 201 TV chassis components 201 The most troubled sections 202 Locating TV components 203 Relay problems 203 Horizontal circuits 204 Horizontal circuit problems 205 What keeps destroying the horizontal output? 207 Old faithful replacement 209 Horizontal output problems 209 Horizontal voltage injection 209 Safety first 210 Pulled in on the sides 211 Flyback problems 211 Red-hot output transistor 213 Yoke problems 214 Intermittent shutdown 216 High-voltage shutdown 217 TV chassis shutdown 218 High-voltage problems 219 The bow and arrow 219 Critical horizontal waveforms 220 Vertical problems 220 System control 230 Tuner on the side 232 No raster or a bright raster 234 Color symptoms 235 Green with envy 236 Surface-mounted components 237 The “tough dog” 237 On-screen display 237 EEPROM problems 238 Audio problems 239 8 Servicing power supplies 241 Half full 241 The damaged bridge 242 Transistor regulators 243