Panasonic NN-CF770M CPH - Troubleshooting: Digital Programmer Circuit; D.P.C. Circuit Malfunctions

10.4. Trouble related to Digital Programmer Circuit
SYMPTOM STEP CHECK RESULT CAUSE/CORRECTIONS
No display when oven is first plugged
in
1 Fuse pattern of D.P.C. Normal →Step2
Open Replace D.P.C., L.V.T. or
Fuse Pattern
2 IC10 pin4 voltage Abnormal 0V L.V.T.
Normal=18V →Step3
3 IC1 pin9 voltage Abnormal IC10
Normal=5V IC1, CX320, Display
No key input 1 Touch switch Abnormal Touch switch
Normal IC1
No beep sound 1 IC1 pin 5 voltage Abnormal IC1
Normal=5V BZ310, IC200
Power relay RY2 does not turn on
even though the program had been set
and the [start] button is tapped
1 IC1 pin 78 voltage while operation Abnormal IC1
Normal=5V →Step2
2 Short circuit between pin 14 of IC200 and
ground
Still not turn on RY2
RY2 turns on IC200
No microwave oscillation at any power 1 IC1 pin 27 voltages while operation at high
power
Abnormal IC1
Normal=5V →Step2
2 Collector of Q222 voltage Abnormal Q222 and /or
Q225,Q226,Q227
Normal 0.7V →Step3
3 Short circuit between collector of Q222
and emitter of Q225
Still not turn on RY1
RY1 turns on Q222 and/or Q225,Q226,Q227
Dark or unclear display 1 Replace display and check operation Normal Display
Abnormal IC1
Missing or lighting of unnecessary
segment
1 Replace IC1 and check operation Normal IC1
Abnormal Display
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
1 Unplug CN702 (2 pin) connector and
measure voltage between terminals
Abnormal=0V 1. Latch Switch
2. D.P.C. /Power Relay
Normal=120V →Step2
2 Unplug CN701 (3 pin) connector and
measure pin1 voltage of CN3
Abnormal=0V D.P.C.
Approx. AC 3V Magnetron
29
NN-CF770M