Backlight Can't Be Turned On - Samsung 920NW - SyncMaster - 19" LCD Monitor Service Manual

4 Troubleshooting

4-4 Backlight can't be turned on

No backlight
Yes
LED lamp is OK
Yes
Is there 14V
voltage on pin 3,4
of T501, T502
Yes
Is there PWM
signal on pin 4 of
IC501
Yes
Is there High level
voltage on pin10 of
IC501
Yes
Vsense voltage
2.9V
No
Are there PWM
signal on pin1,
pin15 of IC501
Yes
Pin 5 of IC501
voltage is Low level
Yes
Pin 3 of IC501
voltage is high level
voltage
END
4-4
No
No power supply to
inverter
No
U501, U502 fail
No
Check I/F BD
No
Check I/F BD
No
Lamp connector opened
No
IC501 failure
Yes
Feedback circuit failure
Yes
IC501 protected
Yes
Check the cable that from
I/F BD to P/I BD is ok
No
Check power supply
Replace U501, U502
Yes
Check C524,R528, R533,
D507
Yes
Check D505, D511,
D512, R513, R520, C520