Panasonic NNS252BF - MICROWAVE OVEN/OTR, Service Manual

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SYMPTOM CAUSE CORRECTIONS
13. Oven returns to plugged in mode after
18 seconds elapses on the Auto
sensor cooking mode.
1. Open or loose wiring of sensor terminal from
DPC
2. Open steam sensor
3. Defective DPC
13.1. Trouble related to digital programmer circuit
SYMPTOM STEP CHECK RESULT CAUSE/CORRECTIONS
No display when oven is first plugged
in. Oven is dead. 1 Fuse pattern of DPC Normal
→
STEP 2
Open (NOTE) Shorted Circuit of ZNR,L.V.T.,
Oven Lamp etc.Replace DPC
2 Low voltage transformer (LVT)
secondary voltage Abnormal 0V LVT
Normal
→
Step 3
3 IC-1 pin 47 voltage Abnormal IC-10
Normal = 5V IC-1, CX320, Display
NOTE
Procedure of fuse pattern repairing is as follows:
1. When the fuse pattern (PF2) opens.
(1) Remove the jumper wire (PF1).
(2) Insert the removed jumper wire (PF1) to “(PF2)” position and solder it. If both “PF1” and “PF2” fuse patterns are open, please replace
DPC.
2. When the fuse pattern (PF4) opens.
(1) Remove the jumper wire (PF3).
(2) Insert the removed jumper wire (PF3) to “(PF4)” position and solder it. If both “PF3” and “PF4” fuse patterns are open, please replace
DPC.
NOTE:* At the time of these repairs, make visual inspection of the varistor for burning damage and examine the transformer with tester for
the presence of layer short-circuit (check primary coil resistance).
If any abnormal condition is detected, replace the defective parts.
No key input
1 Membrane switch continuity Abnormal Membrane switch
Normal IC-1
No beep sound 1 IC-1 pin 8 voltage Abnormal IC-1
Normal BUZZER, Q224
Power relay A(RY-1) does not turn
oneven though the program has been
setand the start pad is tapped 1 IC-1 pin 41 voltage while
operation Abnormal IC-1
Normal = 5V
→
Step 2
2 Short circuit between pin 8
and pin13 of IC-220 Still not turn on RY-2
RY-2 turns on IC-220
No microwave oscillation at any
powersetting 1 IC-1 pin 22 voltages while
operation at high power Abnormal IC-1
Normal
→
Step 2
22---5V
2 Q220 transistor Abnormal Q220
Normal RY-1
Dark or unclear display 1 Replace display and check
operation Normal DISPLAY
Abnormal IC-1
Missing or lighting of
unnecessarysegment 1 Replace IC-1 and check
operation Normal IC-1
Abnormal DISPLAY
H97/H98 appears in window and
ovenstops operation. Program High
powerfor 1 minute and conduct
following testquickly, unless H97/H98
appears andoven stops. NEW H.V. 1 Unplug CN702(2 pin)
connector and measure
voltage between terminals 0V 1. Latch Switch
2. DPC/Power Relay
AC line voltage of
120V
→
Step 2
2 Unplug CN701(3 pin)
connector and measure pin 1
voltage 0V DPC
Approx. AC 3V Magnetron
24
NN-S262SF / NN-S262BF / NN-S262WF / NN-S252BF / NN-S252WF