Trouble Related To Digital Programmer Circuit - Panasonic NN-C784MF Service Manual

7.3.

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 Low voltage transforment (L.V.T.)
secondary voltage
3 IC10 pin 9 voltage
1 Membrane switch continuity
1 IC1 pin 8 voltage
1 IC1 pin 41 voltage while operation
2 IC220 pin 12 voltage
1 IC1 pin 39 voltages while operation at high
power
2 IC220 pin 15 voltage
3 Short circuit between collector and emitter
of Q220
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 pin3 voltage
21
RESULT CAUSE/CORRECTIONS
→Step2
Normal
Open Replace D.P.C. or Fuse
Pattern
Abnormal 0V L.V.T.
→Step3
Normal
Abnormal IC10
Normal=12V IC1, CX320, Display
Abnormal Membrane switch
Normal IC1
Abnormal IC1
Normal=5V BZ210, IC220
Abnormal IC1
→Step2
Normal=5V
Abnormal IC220
Normal 0.7V RY2
Abnormal IC1
→Step2
Normal=5V
Abnormal IC220
→Step3
Normal 0.7V
Still not turn on RY1
RY1 turns on Q220
Normal Display
Abnormal IC1
Normal IC1
Abnormal Display
Abnormal=0V 1. Latch Switch
2. D.P.C. /Power Relay
→Step2
Normal=120V
Abnormal=0V D.P.C.
Approx. AC 3V Magnetron
NN-C784MF