LG CMS9540F Service Manual page 47

ELECTRICAL TROUBLESHOOTING GUIDE
No -5 V
Is the
VCC -7 VA supplied to IC953
Pin2?
YES
Is there
'H' signal at Q953
Base?
YES
Check or replace Q953, Q957.
Or check line of MAIN PCB is short or not.
No output VFD
R968 normal?
YES
D957, D959 normal?
YES
ZD951, ZD952 normal?
YES
Check line of FRONT PCB is short or not.
NO
R965 normal?
Check or replace Q951.
NO
Check P_CTL from μ-com.
NO
NO
Replace D957, D959.
NO
Replace ZD951, ZD952.
3-26
NO
YES
Replace R968.
Check or replace R965 / D959.