Panasonic NN-GF668M - Digital Programmer Circuit Troubleshooting; Simple Inverter;Magnetron Troubleshooting

9.4. 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. or Fuse
Pattern
2 Low voltage transforment (L.V.T.)
secondary voltage
Abnormal 0V L.V.T.
Normal →Step3
3 IC10 pin5 voltage Abnormal IC10
Normal=5V IC1, CX320, Display
No key input 1 Touch switch continuity Abnormal Touch switch
Normal IC1
No beep sound 1 IC1 pin 33 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 IC200 pin13 voltage Abnormal IC200
Normal 0.7V RY2
No microwave oscillation at any power 1 IC1 pin 38 voltages while operation at high
power
Abnormal IC1
Normal=5V →Step2
2 Collector of Q222 voltage Abnormal Q222 and/or Q225
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
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=230V →Step2
2 Unplug CN701 (3 pin) connector and
measure pin3 voltage of CN11
Abnormal=0V D.P.C.
Approx. AC 3V Magnetron
9.5. SIMPLE WAY OF H.V. INVERTER/MAGNETRON TROUBLESHOOTING
Purpose:
Simple way (3/23 seconds rule) of identifying whether it’s Magnetron, Inverter or others.
Set-up:
The unit under question is connected through the Ammeter as shown below.
Procedure:
Follow the matrix table below to identify the problem source.
Note:
Do not replace both Inverter board and Magnetron simultaneously and automatically without going through this
procedure.
Power will: Ammeter reading is: To do: Remedy:
Shut off in 23 seconds
after “Start”.
1. Between 0.5A and 1.0A. Check and repair open magnetron circuit
CN703.
Open magnetron wiring between Inverter
and magnetron terminal.
2. Between 1.0A and 2.0A. Check continuity of D702 in Inverter PCB.
1. D702 shorted Replace H.V.Inverter(Z606Y6Y40BP)
2. D702 is OK Replace magnetron
Shut off in 3 seconds
after “Start”.
1. Less than 0.5A Check open circuit: Latch Switch, DPC,
Power Relay, CN701 and CN702.
Replace defective component(s), or
correct switch, cables and connectors.
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NN-GF668M