LG CJ87 Service Manual page 30

ONE POINT REPAIR GUIDE ............................................................................................................................ 3-2
1. NO POWER ............................................................................................................................................ 3-2
2. NO BOOTING WHEN POWER ON THE SET........................................................................................ 3-4
3. NO BOOTING IN CD/USB FUNCTION .................................................................................................. 3-5
4. NO OPERATION OF MD ...................................................................................................................... 3-10
5. NO SOUND IN THE USB FUNCTION .................................................................................................. 3-15
6. AUDIO OUTPUT IS SMALL OR NO AUDIO OUTPUT ........................................................................ 3-16
7. NO POWER ON (STANDBY LED IS BLINKING) ................................................................................. 3-17
8. SPEAKER NO AUDIO .......................................................................................................................... 3-18
9. NO SOUND ........................................................................................................................................... 3-19
10. VFD IS NOT DISPLAYED WHEN POWER ON THE SET ................................................................... 3-24
ELECTRICAL TROUBLESHOOTING GUIDE ................................................................................................. 3-25
1. POWER SUPPLY ON SMPS BOARD .................................................................................................. 3-25
2. SYSTEM PART ..................................................................................................................................... 3-28
3. NO AUDIO CHECK ............................................................................................................................... 3-29
WAVEFORMS OF MAJOR CHECK POINT .................................................................................................... 3-34
1. DSP (IC501) .......................................................................................................................................... 3-34
2. PWM (IC600) ........................................................................................................................................ 3-35
3. SERVO (IC401) ..................................................................................................................................... 3-36
4. MOTOR DRIVER (IC400) ..................................................................................................................... 3-37
5. ADC ....................................................................................................................................................... 3-38
6. USB ....................................................................................................................................................... 3-38
7. BLUETOOTH ........................................................................................................................................ 3-39
WIRING DIAGRAM .......................................................................................................................................... 3-41
BLOCK DIAGRAM .......................................................................................................................................... 3-43
CIRCUIT VOLTAGE CHART ........................................................................................................................... 3-45
1. CAPACITOR VOLTAGE ....................................................................................................................... 3-45
PRINTED CIRCUIT BOARD DIAGRAMS ....................................................................................................... 3-47
1. SMPS P.C.BOARD DIAGRAM ............................................................................................................. 3-47
2. MAIN P.C.BOARD DIAGRAM .............................................................................................................. 3-51
3. FRONT P.C.BOARD DIAGRAM ........................................................................................................... 3-55
4. JACK P.C.BOARD DIAGRAM .............................................................................................................. 3-59
SECTION 3
ELECTRICAL
CONTENTS
3-1