Hitachi C43-FD2000 Service Manual page 54

SIG-POWER failure:
Sub-Power check flow
While the startup,
V>0.5V at I903(1)
transiently
POWER-SUP
No
PWB
F902 blown?
POWER-SUP PWB
No
V < 5V at I901(3)?
(Vin pin)
POWER-SUP PWB
No
15V
0V
While the startup
V > 20V at I901(3)
transiently
No
POWER-SUP PWB
20V
0V
Check D931, D932, C934, E903,
E904 and short-circuit of
SIG-POWER cold side.
POWER-SUP PWB
Over voltage of STBY5V
Shutdowned by PROTECTION:
Yes
Check I905 and short-circuit of STBY5V with
higher voltage.
0.8V
0V
Yes
Over current in live side.
Check I901, T901 and circuit connected to I901(3)
Yes
No power for I901,
Check I901, D907, R907, R908 and etc.
POWER-SUP PWB
become higher than 10V once
I901(3)
5V
power on
Yes
SIG-POWER Feedback circuit not function.
Check D930, I902, D933, E905 and etc.
15V
power on
POWER-SUP PWB
I903(1)
power on
POWER-SUP PWB
Note: Vin also becomes less than 5V if shutdowned by protection.
Check I905(5) first!
POWER-SUP PWB
10V