LG LST-3100A Service Manual page 15

(4) No 12VA
Is there about 13V
at the IC155 pin1?
YES
NO
Is there about 3.3V~5V
at the IC155 pin4?
YES
NO
Check the IC155
and Replace
(5) No 30VA
No 30VA
YES
NO
Is The ZD110
Normal?
YES
Check and
Replace the D110
Check or Replace
the D109
Check the 'PWR CTL
"H"' signal from µ-com
Replace the ZD101
3-6
(6) No VFD
No VFD
YES
NO
Is The R123
Normal?
YES
NO
Is The D107
Normal?
YES
NO
Is The ZD102
Normal?
YES
Check and
Replace the D108
Replace the R123
Replace the R107
Replace the ZD102