ViewSonic Corporation
Confidential - Do Not Copy
36
5. Backlight can’t be turned on
No raster?
Is there 14Vdc
voltage on pin13
Yes
Yes
Yes
No
Check power
supply
No
Check I/F
board
Yes
R526 open
No
Yes
No
Connecting the output
connector again
Yes
Yes
LED
Green?
Backlight cannot
be turned on.
Is R526
Ok?
Is there high-level
voltage on pin8 of
Check CN501,
CN502, CN503
No
Yes
U501, U502 fail
No
IC501 fail
Is Ok
IC501?
T501, T502 fail
No
Yes
Is ok
Yes
Check protected circuit Q501,
Q502, Q503, Q504
END
Is there pulse waveform
on pin1, pin3, pin15 and
pin16 of IC501 at the
moment of restart?
VA702-2_VA721-3_VA721b-3