Panasonic NN-ST681S Service Manual page 26

NN-SD691S / NN-ST681S / NN-SD671S / NN-ST671S / NN-ST661S / NN-ST661B / NN-ST661W / NN-ST651B / NN-ST651W
8.4.2. EXCEPT NN-SD691S & NN-SD671S
SYMPTOM
No display when oven is first plugged
in
No key input
No beep sound
Power relay RY2 does not turn on
even though the program had been
set and the Start pad is tapped
No microwave oscillation at any
power
Dark or unclear display
Missing or lighting of unnecessary
segment
H95/H97/H98 appears in window and
oven stops operation.Program High
power for 1 minute and conduct
following test quickly, unless
H95/H97/H98 appears and oven
stops
STEP CHECK
1 Fuse pattern of D.P.C.
2 Low voltage transforment (L.V.T.)
secondary voltage
3 IC1 pin 13 voltage
1 Membrane switch continuity
1 IC1 pin 61 voltage
1 IC1 pin 21 voltage while operation
2 Collector of Q223 voltage
1 IC1 pin 27 voltages while operation at high
power
2 Collector of Q220 voltage
3 Short circuit between collector of Q220
and emitter of Q225
1 Replace display and check operation
1 Replace IC1 and check operation
1 Unplug CN702 (2 pin) connector and
measure voltage between terminals
2 Unplug CN701 (3 pin) connector and
measure pin1 voltage of D. P. C. CN3
RESULT
Normal
Open
Abnormal 0V
Normal
Abnormal
Normal=5V
Abnormal
Normal
Abnormal
Normal=5V
Abnormal
Normal=5V
Abnormal
Normal 0.7V
Abnormal
Normal=5V
Abnormal
Normal 0.7V
Still not turn on
RY1 turns on
Normal
Abnormal
Normal
Abnormal
Abnormal=0V
Normal=120V
Abnormal=0V
Approx. AC 3V
26
CAUSE/CORRECTIONS
→Step2
Replace D.P.C. or Fuse Pattern
L.V.T.
→Step3
Q10, ZD10
IC1, Display
Membrane switch
IC1
IC1
BZ210, Q210
IC1
→Step2
Q223
RY2
IC1
→Step2
Q220 and/or Q221, Q222, Q225
→Step3
RY1
Q220 and/or Q221, Q222, Q225
Display
IC1
IC1
Display
1. Latch Switch
2. D.P.C. /Power Relay
→Step2
D.P.C.
Magnetron