LG FH6 Service Manual page 40

ELECTRICAL TROUBLESHOOTING GUIDE
SYSTEM POWER SUPPLY ON SMPS BOARD
No PVDD (50 VA / 40 VA)
Is the P-CTRL normal?
Is the VCC
(18 V ~ 25 V) supplied to IC931
pin4?
Is IC931 normal?
Is Q921 normal?
Is D981 normal?
Is C981, C982 normal?
Power line of MAIN PCB is short.
YES
YES
YES
YES
YES
YES
YES
NO
Check IC501 (MLC3730S) IC on MAIN board.
NO
Check or replace Q901.
NO
NO
NO
NO
Replace C981, C982.
3-21
Is Q901 normal?
Replace IC931.
Replace Q921.
Replace D981.