LG CM2460, Service Manual

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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
ELECTRICAL TROUBLESHOOTING GUIDE ................................................................................................. 3-16
1. POWER (SMPS) ................................................................................................................................... 3-16
2. MCS PART CHECK .............................................................................................................................. 3-19
3. FLD DISPLAY CHECK ......................................................................................................................... 3-20
4. PWM MODULATION CHECK ............................................................................................................... 3-21
5. POWER AMP PART CHECK ............................................................................................................... 3-22
6. TUNER / AUX FUNCTION CHECK ...................................................................................................... 3-23
7. TUNER FUNCTION CHECK................................................................................................................. 3-24
8. CD FUNCTION CHECK ........................................................................................................................ 3-25
9. DOUBLE USB FUNCTION ................................................................................................................... 3-26
WAVEFORMS OF MAJOR CHECK POINT .................................................................................................... 3-27
1. SDRAM ................................................................................................................................................. 3-27
2. SERVO .................................................................................................................................................. 3-27
3. AUDIO PATH ........................................................................................................................................ 3-28
4. USB ....................................................................................................................................................... 3-29
WIRING DIAGRAM .......................................................................................................................................... 3-31
BLOCK DIAGRAMS ........................................................................................................................................ 3-33
1. SYSTEM BLOCK DIAGRAM ................................................................................................................ 3-33
2. SMPS BLOCK DIAGRAM ..................................................................................................................... 3-35
3. POWER BLOCK DIAGRAM ................................................................................................................. 3-37
CIRCUIT DIAGRAMS ...................................................................................................................................... 3-39
1. SMPS CIRCUIT DIAGRAM .................................................................................................................. 3-39
2. MAIN - POWER CIRCUIT ..................................................................................................................... 3-41
3. MAIN - SERVO CIRCUIT DIAGRAM .................................................................................................... 3-43
4. MAIN - MPEG CIRCUIT DIAGRAM ...................................................................................................... 3-45
5. MAIN - AUDIO CIRCUIT DIAGRAM ..................................................................................................... 3-47
6. MAIN - AMP CIRCUIT DIAGRAM......................................................................................................... 3-49
7. DISPLAY/ KEY CIRCUIT DIAGRAM .................................................................................................... 3-51
CIRCUIT VOLTAGE CHART ........................................................................................................................... 3-53
1. ICs ......................................................................................................................................................... 3-53
2. CAPACITORS ....................................................................................................................................... 3-54
PRINTED CIRCUIT BOARD DIAGRAMS ....................................................................................................... 3-55
1. SMPS P.C.BOARD ............................................................................................................................... 3-55
2. MAIN P.C.BOARD ................................................................................................................................ 3-59
3. DISPLAY P. C. BOARD ........................................................................................................................ 3-63
4. KEY P. C. BOARD ................................................................................................................................ 3-67
3-1