LG CMS9540F Service Manual page 49

ELECTRICAL TROUBLESHOOTING GUIDE
No AMP output
Is the
C904, C905 voltage
about 380 V?
YES
F911 normal?
NO
Replace F911.
NO
Q911 ~ Q914 OK?
NO
Replace Q911 ~ Q914.
NO
PFC P.CTL OK?
Is the
VCC 12 V supplied to
IC904 Pin16?
Check or replace
IC904, Q907 ~ Q910.
YES
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).
3-28
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.