LG OM7550 - SECTION 3 ELECTRICAL

SECTION 3 ELECTRICAL
CONTENTS
ONE POINT REPAIR GUIDE ................................................................................................................................................ 3-2
1. NO POWER ............................................................................................................................................................... 3-2
2. NO AMP POWER....................................................................................................................................................... 3-3
3. NO BOOTING WHEN POWER ON THE SET ........................................................................................................... 3-4
4. VFD IS NOT DISPLAYED WHEN POWER ON THE SET ........................................................................................ 3-5
5. AUDIO OUTPUT IS SMALL OR NO AUDIO OUTPUT ............................................................................................. 3-6
6. NO POWER ON (STANDBY LED IS BLINKING) ...................................................................................................... 3-7
7. SPEAKER NO AUDIO................................................................................................................................................ 3-8
8. NO BOOTING IN CD/USB FUNCTION ..................................................................................................................... 3-9
9. NO OPERATION OF MD ......................................................................................................................................... 3-14
10. NO SOUND .............................................................................................................................................................. 3-19
ELECTRICAL TROUBLESHOOTING GUIDE .....................................................................................................................3-25
1. POWER SUPPLY ON SMPS BOARD ..................................................................................................................... 3-25
2. SYSTEM PART ........................................................................................................................................................ 3-28
3. NO AUDIO CHECK .................................................................................................................................................. 3-29
4. NO LIGHTING (SPEAKER LED) ............................................................................................................................. 3-34
WAVEFORMS OF MAJOR CHECK POINT ........................................................................................................................3-35
1. DSP (IC501) ............................................................................................................................................................. 3-35
2. PWM (IC202) ............................................................................................................................................................ 3-36
3. SERVO (IC401) ........................................................................................................................................................ 3-37
4. MOTOR DRIVER (IC400) ........................................................................................................................................ 3-38
5. ADC (IC201) ............................................................................................................................................................. 3-39
6. USB (CN502) ........................................................................................................................................................... 3-39
7. BLUETOOTH (CN504) ............................................................................................................................................. 3-40
WIRING DIAGRAM .............................................................................................................................................................. 3-41
BLOCK DIAGRAMS ............................................................................................................................................................ 3-43
1. SYSTEM BLOCK DIAGRAM.................................................................................................................................... 3-43
2. POWER BLOCK DIAGRAM ..................................................................................................................................... 3-45
CIRCUIT DIAGRAMS .......................................................................................................................................................... 3-47
1. SMPS_POWER #1 CIRCUIT DIAGRAM ................................................................................................................. 3-47
2. SMPS_POWER #2 CIRCUIT DIAGRAM ................................................................................................................. 3-49
3. MAIN_CD DSP CIRCUIT DIAGRAM ....................................................................................................................... 3-51
4. MAIN_ADC/PWM CIRCUIT DIAGRAM.................................................................................................................... 3-53
5. MAIN_RF SERVO CIRCUIT DIAGRAM .................................................................................................................. 3-55
6. MAIN_AMP CIRCUIT DIAGRAM ............................................................................................................................. 3-57
7. MAIN_AUX OUT/ VFD PWR CIRCUIT DIAGRAM .................................................................................................. 3-59
8. FRONT CIRCUIT DIAGRAM.................................................................................................................................... 3-61
9. VFD/RMC1 CIRCUIT DIAGRAM.............................................................................................................................. 3-63
10. TOP CIRCUIT DIAGRAM ......................................................................................................................................... 3-65
CIRCUIT VOLTAGE CHART ............................................................................................................................................... 3-67
1. ICs ............................................................................................................................................................................ 3-67
2. CAPACITORS .......................................................................................................................................................... 3-68
3. CONNECTORS ........................................................................................................................................................ 3-69
4. ZENER DIODES ...................................................................................................................................................... 3-70
PRINTED CIRCUIT BOARD DIAGRAMS ........................................................................................................................... 3-71
1. SMPS P. C. BOARD (TOP VIEW) ........................................................................................................................... 3-71
2. SMPS P. C. BOARD (BOTTOM VIEW) ................................................................................................................... 3-73
3. MAIN, VFD/RMC1 P.C.BOARD (TOP VIEW) .......................................................................................................... 3-75
4. MAIN, VFD/RMC1 P.C.BOARD (BOTTOM VIEW) .................................................................................................. 3-77
5. FRONT P.C.BOARD (TOP VIEW) ........................................................................................................................... 3-79
6. FRONT P.C.BOARD (BOTTOM VIEW) ................................................................................................................... 3-79
7. TOP(VOLUME_FR1) P.C.BOARD (TOP VIEW) ...................................................................................................... 3-81
8. TOP(VOLUME_FR1) P.C.BOARD (BOTTOM VIEW) .............................................................................................. 3-83
3-1