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ELECTRICAL TROUBLESHOOTING GUIDE
1. Power Circuit
• Input Voltage : 90V - 135V
• It is possible to malfunction, if the unload condition is left for a long time when power is on.
(More than Dummy load 100mA)
• A Primary side is abnormal when the fuse is short, secondary side is abnormal when the IC103 oscillates
intermittently.
• The resistor value of both terminal is measured with DVM crossing each other to check the each element is
normal or abnormal. (It is normal when the numerical value is different each other.)
Check the GND of C901 and
IC901 Pin
3
with oscilloscope.
When IC901
oscillating
Does oscillate
continuously when
the CON903 is
disconnected ?
YES
Secondary side
is abnormal.
Front Circuit
Board is
abnormal
Are D908, D909,
D907, D910, D906
and D905 normal?
YES
Replace Q908
and Q909.
NO
Is CON903 Pin
3
5.2V?
YES
Replace
IC902.
Check Q904
Replace
and ZD903.
defective
parts.
END
START
Is F901 normal?
YES
Is IC901 Pin
3
NO
switching normally?
<Fig.3-1>
In condition of DC140V.
YES
(Feedback is abnormal)
Is CN903 Pin
3
5.2V?
YES
After connect
CON903
Pin
1
(A)
Are CON902
NO
Pin
5
,
6
and
9
YES
NO
Is CON904 Pin
3
YES
NO
Is CON902 Pin
3
YES
Are CON903 Pin
-24V, Pin
7
-20V and
Pin
8
-16V?
YES
NO
A primary side is abnormal.
NO
Is IC905
normal?
YES
Check or
NO
replace
D908.
Are R922, C927,
R921 and R918
,
3
short.
normal?
5V?
8V?
12V?
To (A).
5
NO
3-2
Is voltage of BD901 140V?
YES
Are R907, D902,
D903 and R902
normal?
YES
Are D901, R904,
R905 and R906
normal?
YES
NO
Is PC901 normal?
YES
END
Replace defective
parts.
(Fig. 3-1) IC901 Pin
Normal switching waveform on the
stand-by mode at the AC110V
NO
NO
NO
NO
3
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