LG CM4550 Service Manual page 38

AUDIO ELECTRICAL TROUBLESHOOTIHG GUIDE
No 12 V
YES
Is Vcc (15 V)
supplied to IC931?
YES
IC931 Pin4 "H"?
YES
Check or replace IC931.
No VFD
YES
D931 normal?
YES
ZD931 normal?
YES
Q501 / Q502 normal?
YES
Check or replace VFD.
NO
Check or replace D935.
NO Check P-CTRL "H" signal
NO
Check or replace D931.
NO
Check or replace ZD931.
NO
Check or replace Q501 / Q502.
3-19
from MCS.