9.3. Digital programmer circuit troubleshooting guide
SYMPTOM STEP CHECK RESULT CAUSE/CORRECTION
S
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 Emitter of Q10 Abnormal ZD10, Q10
Normal = 5V 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, 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, 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 29 voltage Abnormal IC-1
(For NN-S453WF/S553WF) Normal BZ, Q224
No beep sound 1 IC-1 pin 8 voltage Abnormal IC-1
(For NN-K593MF/K573MF/K573WF/K543WF) Normal BZ, Q224
Power relay A(RY-2) does not turn on even
though the program has been set and the
start pad is tapped
1 IC-1 pin 9 voltage while
operation
Abnormal IC-1
Normal = 5V
→
Step 2
2 Short circuit between collector
and Emitter of Q223.
Still does not turn on RY-2
(For NN-S453WF/S553WF) RY-2 turns on Q223
Power relay A(RY-2) does not turn on even
though the program has been set and the
start pad is tapped
1 IC-1 pin 41 voltage while
operation
Abnormal IC-1
Normal = 5V
→
Step 2
2 Short circuit between collector
and Emitter of Q223.
Still does not turn on RY-2
(For NN-K593MF/K573MF/K573WF/K543WF) RY-2 turns on Q223
No microwave oscillation at any power setting 1 IC-1 pin 7 and pin 34 voltages
while operation at high power
Abnormal IC-1
Normal=18V
→
Step 2
(For NN-S453WF/S553WF) 2 Q220 transistor Abnormal Q220
Normal RY-1
No microwave oscillation at any power setting 1 IC-1 pin 39 and pin 45
voltages while operation at
high power
Abnormal IC-1
Normal=18V
→
Step 2
(For NN-K593MF/K573MF/K573WF/K543WF) 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 incorrect segment 1 Replace IC-1 and check
operation
Normal IC-1
Abnormal DISPLAY
H97/H98 appears in window and oven stops
operation. Program High power for 1 minute
and conduct following test quickly, unless
H97/H98 appears and oven 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 230-
240V
→
Step 2
2 Unplug CN701(3 pin)
connector and measure pin 3
voltage
0V DPC
Approx. AC 3V Magnetron
CONTINUED FOR SENSOR MODELS
Auto sensor cooking does not operate
normally.
(Steam Sensor cooking does not
detect steam from foods.)
1 Steam sensor terminal voltage
by using high impedance
tester (20k
Ω
/ V),while
breathing on metal surface of
sensor
Abnormal = 0V Steam sensor
Normal>10-30mV IC-1
22
NN-S453WF
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