Service manual

5. Backlight can’t be turned on
No raster?
LED Green?
Yes
Yes
Yes
Backlight can’t be
turned on.
No
Check power
supply
Is there high-level voltage
on pin10 of IC501?
No
Is Ok R526?
Check I/F
board
Yes
R526 open
No
Yes
Is there instantaneously pulse wave on
pin1, pin3, pin15 of IC501 at the
moment
of restart?
No
Is Ok IC501?
Yes
U501, U502 fail
No
IC501 fail
Yes
Is ok T501, T502?
T501, T502 fail
Are connected rightly
CN501, CN502, CN503 and
CN504?
No
Connecting the
output connector
again
No
Check feedback circuit
Isen,Vsen.(D503,D504,D501,D502..)
Yes
Yes
END
Is there 5Vdc
voltage on pin2of
IC501?
Yes
Yes
42
ViewSonic Corporation Confidential - Do Not Copy VA503b-2_VA503m-2