Panasonic Inverter NN-H275, Service Manual

Page: 79 / 92

13.1. Trouble related to digital programmer circuit
SYMPTOM STEP CHECK RESULT CAUSE/CORRECTIO
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 D
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 resistanc
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
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