37
VC-TA350/TA351/351W
VC-TA352W/TA355/TA356
FLOW CHART NO.1 POWER TROUBLESHOOTING(1)
No power
Unplug the AC power cord.
Replug it a few minutes later.
See FLOW CHART NO.2 POWER
TROUBLESHOOTING(2)
YES
YES
YES
YES
YES
NO
NO
NO
NO
NO
Is the fuse good?
Replace fuse.
Is AT 5V voltage line normal?
Check primary circuit.
Are AT 42V, AT 23V, AT 12.6V, AT -25V
and filament voltage lines normal?
Check each rectifier circuits and
short-circuit of secondary circuit.
Is "H" level applied at pin(1) of
IC701?
Check peripheral circuits of Q706
and P-FAIL (L) signal line etc.
Check system control circuit(IC701).
7. TROUBLESHOOTING
FLOW CHART NO.2 POWER TROUBLESHOOTING(2)
In case of Fuse(F901) blown out.
Replace F901, Q901 and
R904, check D901, D902, D903 and
D904. Replace where necessary.
Check short-circuit or leakage of
D921, D922, D923, D924, D925,
D926 and secondary circuit.
FLOW CHART NO.3 POWER TROUBLESHOOTING(3)
In case of abnormal noise(sound)
Check D921, D922, D923, D924,
D925 and D926.
The Check D921, D922, D923,
D924, D925 and D926. Replace
where necessary.
NO
FLOW CHART NO.4 POWER TROUBLESHOOTING(4)
No power is turned on
Does power control (H) signal at pin
(4) of IC701 change from "L" to "H"
level?
Check IC701.
YES
YES
YES
NO
NO
NO
Does the base of Q951 change from
about 5.0V to 4.5V?
Check IC701 and all the way up
through to Q951.
Is voltage of 5V sent out from
collector of Q951.
Check peripheral circuit of Q951
and PC 5V line.
Check peripheral circuit for poor
soldering.
FLOW CHART NO.5 POWER TROUBLESHOOTING(5)
No power is turned on from STANDBY mode.
Is AT 5V voltage line normal?
Check rectifier circuit of AT 5V and
short-circuit of secondary circuit.
YES
YES
YES
YES
NO
NO
NO
NO
NO
Does STBY CTL signal at pin(94) of
IC701 change from "L" to "H" level?
Check the operation of IC701.
Does the filament STBY SW. circuit
Q947 is turned on?
Check peripheral circuit of Q947,
Q948, Q949, D940.
Does the STBY -25V SW. circuit Q944 is
turned on?
Check peripheral circuit of Q944.
Does the STBY 5V SW. circuit Q945
is turned on?
Check peripheral circuit of Q945,
Q946, Q950.
