LG CM9750 Service Manual page 46

ELECTRICAL TROUBLESHOOTING GUIDE
No AMP output
Is the
C903, C913 Voltage
about 395 V?
YES
Is F911 normal?
NO
Replace F911.
NO
Q911 ~ Q914 OK?
NO
Replace Q911 ~ Q914.
NO
Is the
PFC P.CTL OK?
Is the
VCC 12 V supplied to
IC904 pin16?
Check or replace
IC904, Q907 ~ Q910.
YES
Is the
AMP P.CTL OK?
Is the
VCC 12 V supplied to
IC902 pin8?
Check or replace IC902 and
Check Q911 ~ Q914 gate(pin2)
Components (Resistors, Diodes).
3-27
NO
YES
NO
YES
NO
YES
NO
YES
Check PFC P.CTL
from μ-com.
Replace D908, Q955, PC903.
Check AMP P.CTL
from μ-com.
Replace D908, Q956, PC902.
Check or replace D953 ~ D956.
Check line of MAIN PCB is short or not.