9.3. Trouble related to Digital Programmer Circuit (NN-ST340M, ST340W)
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 IC1 pin23 voltage Abnormal Q11, ZD11, Q10, ZD10
Normal=3.3V IC1, CX320, Display
No key input 1 Membrane switch continuity Abnormal Membrane switch
Normal IC1
No beep sound 1 IC1 pin 1 voltage Abnormal IC1
Normal=3.3V BZ210, Q210
Power relay RY2 does not turn on
even though the program had been set
and the start pad is tapped
1 IC1 pin 2 voltage while operation Abnormal IC1
Normal=3.3V →Step2
2 Collector of Q223 voltage Abnormal Q223
Normal 0.7V RY2
No microwave oscillation at any power 1 IC1 pin 20 voltages while operation at high
power
Abnormal IC1
Normal=3.3V →Step2
2 Collector of Q220 voltage Abnormal Q220 and /or Q221, Q222,
Q225, Q227
Normal 0.7V →Step3
3 Short circuit between collector and emitter
of Q220
Still not turn on RY1
RY1 turns on Q220 and /or Q221, Q222,
Q225, 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
9.4. How to check the semiconductors using an OHM meter
21
NN-ST340M / NN-ST340W / NN-SM330M / NN-SM330W / NN-SM320M
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