LG CM4540 - Section 3 Electrical

SECTION 3
ELECTRICAL
CONTENTS
ONE POINT REPAIR GUIDE ................................................................................................................... 3-2
1. NO POWER ............................................................................................................................................ 3-2
2. NO BOOTING WHEN POWER ON THE SET ....................................................................................... 3-4
3. VFD IS NOT DISPLAYED WHEN POWER ON THE SET ..................................................................... 3-5
4. NO OPERATION OF MD ....................................................................................................................... 3-6
5. NO SOUND .......................................................................................................................................... 3-11
AUDIO ELECTRICAL TROUBLESHOOTING GUIDE .................................................................. 3-17
1. POWER (SMPS) ................................................................................................................................... 3-17
2. MCS PART CHECK.............................................................................................................................. 3-20
3. IC504(M24C16) CHECK ....................................................................................................................... 3-20
4. FLD DISPLAY CHECK ......................................................................................................................... 3-21
5. PWM MODULATION CHECK .............................................................................................................. 3-22
6. POWER AMP PART CHECK ............................................................................................................... 3-24
7. TUNER / AUX FUNCTION CHECK ...................................................................................................... 3-25
8. TUNER FUNCTION CHECK ................................................................................................................ 3-26
CDP ELECTRICAL TROUBLESHOOTING GUIDE ....................................................................... 3-27
1. CD FUNCTION ..................................................................................................................................... 3-27
2. DOUBLE USB FUNCTION ................................................................................................................... 3-28
WAVEFORMS OF MAJOR CHECK POINT ..................................................................................... 3-29
1. SDRAM ................................................................................................................................................. 3-29
2. SERVO ................................................................................................................................................. 3-29
3. AUDIO PATH ........................................................................................................................................ 3-30
4. USB....................................................................................................................................................... 3-31
WIRING DIAGRAM ................................................................................................................................... 3-33
BLOCK DIAGRAMS ................................................................................................................................. 3-35
1. SYSTEM BLOCK DIAGRAM ................................................................................................................ 3-35
2. SMPS BLOCK DIAGRAM..................................................................................................................... 3-37
3. AUDIO PATH BLOCK DIAGRAM ......................................................................................................... 3-39
4. POWER DIAGRAM .............................................................................................................................. 3-41
CIRCUIT DIAGRAMS ............................................................................................................................... 3-43
1. SMPS CIRCUIT DIAGRAM .................................................................................................................. 3-43
2. MAIN - DSP CIRCUIT DIAGRAM ......................................................................................................... 3-45
3. MAIN - SERVO CIRCUIT DIAGRAM ................................................................................................... 3-47
4. MAIN - ADC/ PWM CIRCUIT DIAGRAM ............................................................................................. 3-49
5. MAIN - AMP CIRCUIT DIAGRAM ........................................................................................................ 3-51
6. FRONT CIRCUIT DIAGRAM ................................................................................................................ 3-53
CIRCUIT VOLTAGE CHART ................................................................................................................. 3-55
1. ICs......................................................................................................................................................... 3-55
2. CAPACITORS....................................................................................................................................... 3-57
PRINTED CIRCUIT BOARD DIAGRAMS ......................................................................................... 3-59
1. SMPS P.C.BOARD ............................................................................................................................... 3-59
2. MAIN P.C.BOARD ................................................................................................................................ 3-61
3. FRONT P.C.BOARD ............................................................................................................................. 3-63
3-1