LG CM9750 Service Manual page 20

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. D-PROTECTION IS DISPLAYED ........................................................................................................... 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. SMPS BLOCK DIAGRAM ..................................................................................................................... 3-45
3. POWER BLOCK DIAGRAM ................................................................................................................. 3-47
CIRCUIT DIAGRAMS ...................................................................................................................................... 3-49
1. SMPS - POWER #1 CIRCUIT DIAGRAM ............................................................................................ 3-49
2. SMPS - POWER #2 CIRCUIT DIAGRAM ............................................................................................ 3-51
3. MAIN - CD DSP CIRCUIT DIAGRAM ................................................................................................... 3-53
4. MAIN - ADC/ PWM CIRCUIT DIAGRAM .............................................................................................. 3-55
5. MAIN - RF SERVO CIRCUIT DIAGRAM .............................................................................................. 3-57
6. MAIN - EXP/ VISENSE CIRCUIT DIAGRAM ....................................................................................... 3-59
7. MAIN - AMP CIRCUIT DIAGRAM......................................................................................................... 3-61
8. MAIN - MIC/ AUX CIRCUIT DIAGRAM ................................................................................................ 3-63
9. FRONT CIRCUIT DIAGRAM ................................................................................................................ 3-65
10. FRONT_CTRL CIRCUIT DIAGRAM ..................................................................................................... 3-67
CIRCUIT VOLTAGE CHART ........................................................................................................................... 3-69
1. CAPACITORS ....................................................................................................................................... 3-69
2. CONNECTORS ..................................................................................................................................... 3-70
PRINTED CIRCUIT BOARD DIAGRAMS ....................................................................................................... 3-71
1. SMPS P.C.BOARD ............................................................................................................................... 3-71
2. MAIN P.C.BOARD ................................................................................................................................ 3-75
3. FRONT P.C.BOARD ............................................................................................................................. 3-79
4. FRONT_CTRL P.C.BOARD .................................................................................................................. 3-83
SECTION 3 ELECTRICAL
CONTENTS
3-1