Troubleshooting) Other Problems - Panasonic NN-CS894S Service Manual

7.2.

(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. Timer starts count down but no
microwave oscillation.
(No heat while oven lamp and fan
motor turn on)
5. Oven can program but timer does not
start countdown.
6. Microwave output is low. Oven takes
longer time to cook food.
7. Oven does not operate and return to
plugged in mode as soon as [Start]
button is pressed.
8. Loud buzzing noise can be heard.
9. Heater does not turn on.
10. Oven stops operation during cooking.
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 latch switch (NOTE 1)
3. Defective short 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. Open or loose connection of D.P.C. BU to
D.P.C. FU (Flat cable)
3. Defective D.P.C.
4. Defective touch screen
1. Off-alignment of primary latch 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 latch switch
6. Defective DPC or power relay RY1
1. Open or loose wiring of secondary latch switch
2. Off-alignment of secondary latch switch
3. Defective secondary latch switch
1. Decrease in power source voltage
2. Open or loose wiring of magnetron filament
circuit.(Intermittent oscillation)
3. Aging change of magnetron
1. Defective DPC
1. Loose fan and fan motor
1. Open or loose wiring of heater
2. Defective heater
3. Defective power relay
4. Defective DPC
1. Open or loose wiring of primary and
secondary latch switch
2. Operation of thermal cutout
31
CORRECTIONS
Check thermal cutout is defective.
Check adjustment of primary, secondary latch
switch and short switch including door.
Refer to operation procedure.
Adjust door and latch 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 latch switches.
NN-CS894S