Lenovo 9220-HB1 Service Manual page 35

20" LCD Color Monitor
8.2.2 Power Board
1.) No power
Check CN903 pin1, 2 = 12V
NG
Check AC line volt 110V or 220V
OK
Check the voltage of C905 (+)
OK
Check start voltage for the pin3 of IC901
OK
Check the auxiliary voltage is bigger than
10V and smaller than 20V
OK
Check IC901 pin8 PWM wave
OK
Check Q902, T901, D910, D911, IC902、IC903
NG
Check AC input
NG
Check bridge rectified circuit and F901 circuit
NG
Check R906, R907 and Change IC901
NG
1) Check IC901, D904, D902, R908
2) Check IC904, C903 OVP circuit
NG
Check R909, R914, Q901, IC901
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Lenovo 9220-HB1