Philips NN-SA631B, Service Manual

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8.4. Trouble related to Digital Programmer Circuit
8.4.1. NN-SD681S
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 pin 13 voltage Abnormal Q10, ZD10
Normal=5V IC1, Display
No key input 1 Touch switch continuity Abnormal Touch switch
Normal IC1
No beep sound 1 IC1 pin 1 voltage Abnormal IC1
Normal=5V BZ210, Q210
No microwave oscillation at any
power 1 IC1 pin 27 voltages while operation at high
power Abnormal IC1
Normal=5V
→
Step2
2 Collector of Q220 voltage Abnormal Q220 and/or Q221, Q222, Q225
Normal 0.7V
→
Step3
3 Short circuit between collector of Q220
and emitter of Q225 Still not turn on RY1
RY1 turns on Q220 and/or Q221, Q222, 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=120V
→
Step2
2 Unplug CN701 (3 pin) connector and
measure pin1 voltage of D. P. C. CN3 Abnormal=0V D.P.C.
Approx. AC 3V Magnetron
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NN-SD681S / NN-SN671S / NN-SN661S / NN-SA661S / NN-SA651S / NN-SN651B / NN-SN651W / NN-SA631B / NN-SA631W