Troubleshooting) Other Problems - Panasonic NN-ST681S Service Manual

8.2.

(Troubleshooting) Other problems

SYMPTOM
1. Oven is dead.
Fuse is OK.
No display and no operation at all.
2. No display and no operation at all.
Fuse is blown.
3. Oven does not accept key input
(Program)
4. Fan motor turns on when oven is
plugged in with door closed.
5. Timer starts count down but no
microwave oscillation.
(No heat while oven lamp and fan
motor turn on)
6. Oven can program but timer does not
start countdown.
7. Microwave output is low. Oven takes
longer time to cook food.
8. Fan motor turns on and turntable
motor rotates when door is opened.
9. Oven does not operate and return to
plugged in mode as soon as [Start]
pad is pressed.
10. Loud buzzing noise can be heard.
11. Turntable motor does not rotate.
12. Oven stops operation during cooking.
NN-SD691S / NN-ST681S / NN-SD671S / NN-ST671S / NN-ST661S / NN-ST661B / NN-ST661W / NN-ST651B / NN-ST651W
CAUSE
1. Open or loose lead wire harness
2. Open thermal cutout / thermistor
3. Open low voltage transformer
4. Defective DPC
1. Shorted lead wire harness
2. Defective primary interlock switch (NOTE 1)
3. Defective monitor switch (NOTE 1)
4. Defective Inverter Power Supply (U)
NOTE 1:
All of these switches must be replaced at the same time.
Check continuity of power relay RY1 contacts (between 1 and 2) and if it has continuity, replace
power relay RY1 also.
1. Key input is not in proper sequence
2. Defective DPC or defective membrane switch Refer to DPC troubleshooting.
1. Misadjustment or loose wiring of secondary
interlock switch
2. Defective secondary interlock switch
3. Door switch CN4
1. Off-alignment of primary interlock switch
2. Open or loose connection of high voltage
circuit especially magnetron filament circuit
NOTE:
Large contact resistance will cause lower
magnetron filament voltage and cause
magnetron to have lower output and/or be
intermittent.
3. Defective high voltage component
H.V. Inverter Power Supply (U)
Magnetron
4. Open or loose wiring of power relay RY1
5. Defective primary interlock switch
6. Defective DPC or power relay RY1
1. Open or loose wiring of secondary interlock
switch
2. Off-alignment of secondary interlock switch
3. Defective secondary interlock switch
1. Decrease in power source voltage
2. Open or loose wiring of magnetron filament
circuit.(Intermittent oscillation)
3. Aging change of magnetron
1. Low voltage transformer on DPC.
1. Defective DPC
1. Loose fan and fan motor
1. Open or loose wiring of turntable motor
2. Defective turntable motor
1. Open or loose wiring of primary and
secondary interlock switch
2. Operation of thermal cutout
23
CORRECTIONS
Check thermal cutout is defective.
Check adjustment of primary, secondary
interlock switch and monitor switch including
door.
Refer to operation procedure.
Adjust door and interlock switches.
Adjust door and interlock switches.
Check high voltage component according to
component test procedure and replace if it is
defective.
Refer to DPC troubleshooting
Consult electrician
Check grounding connector on escutcheon
base.
Adjust door and interlock switches.