Trouble Related To Digital Programmer Circuit - Panasonic NN-CF770M CPH Service Manual

10.4. Trouble related to Digital Programmer Circuit

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] button 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 IC10 pin4 voltage
3 IC1 pin9 voltage
1 Touch switch
1 IC1 pin 5 voltage
1 IC1 pin 78 voltage while operation
2 Short circuit between pin 14 of IC200 and
ground
1 IC1 pin 27 voltages while operation at high
power
2 Collector of Q222 voltage
3 Short circuit between collector of Q222
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 CN3
29
RESULT CAUSE/CORRECTIONS
Normal →Step2
Open Replace D.P.C., L.V.T. or
Fuse Pattern
Abnormal 0V L.V.T.
→Step3
Normal=18V
Abnormal IC10
Normal=5V IC1, CX320, Display
Abnormal Touch switch
Normal IC1
Abnormal IC1
Normal=5V BZ310, IC200
Abnormal IC1
→Step2
Normal=5V
Still not turn on RY2
RY2 turns on IC200
Abnormal IC1
Normal=5V →Step2
Abnormal Q222 and /or
Q225,Q226,Q227
→Step3
Normal 0.7V
Still not turn on RY1
RY1 turns on Q222 and/or Q225,Q226,Q227
Normal Display
Abnormal IC1
Normal IC1
Abnormal Display
Abnormal=0V 1. Latch Switch
2. D.P.C. /Power Relay
Normal=120V →Step2
Abnormal=0V D.P.C.
Approx. AC 3V Magnetron
NN-CF770M