Panasonic NN-T259WB, Service Manual

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9. TROUBLESHOOTING GUIDE
Before troubleshooting, operate the microwave oven following the correct operating procedures in the instruction manual in order to
find the exact cause of any trouble, since operator error may be mistaken for the oven’s malfunction.
CAUTION
1. DO NOT try to REPAIR this H.V. Inverter power supply(U). Replace as whole H.V. Inverter(U) Unit. When returning H.V.
Inverter(U) make sure to pack as originally packed.
2. DO NOT RE-ADJUST PRESET VOLUME on the H.V. Inverter(U). It is very dangerous to repair or adjust without sufficient test
equipment because this circuit handles very large current with very high voltage.
3. Ensure proper grounding before checking for trouble.
4. Be careful of the high voltage circuitry, taking necessary precautions when troubleshooting.
5. Discharge the high voltage that remains in the Inverter(U).
6. When checking the continuity of the switches or the H.V. Inverter, disconnect one lead wire from these parts and then check
continuity with the AC plug removed. To do otherwise may result in a false reading or damage to your meter. When
disconnecting a plastic connector from a terminal, you must hold the plastic connector instead of the lead wire and then
disconnect it, otherwise lead wire may be open or the connector cannot be removed.
7. Do not touch any parts of the circuitry on the digital programmer circuit, since static electric discharge may damage this control
panel.
Ensure you are touching the ground while working on this panel to discharge any static charge in your body.
8. 240VAC is present on the digital programmer circuit (Terminals of power relay’s and primary circuit of low voltage transformer).
When troubleshooting, be cautious of possible electrical shock hazard.
SYMPTOMS CAUSE CORRECTIONS
1. Oven is dead.
Fuse is OK.
No display and no operation at all.
1. Open or loose lead wire harness.
2. Open thermal cutout (Magnetron)
3. Open low voltage transformer
4. Defective DPC AU or DPC DU
Check fan motor when thermal cutout is
defective.
2. No display and no operation at all.
Fuse is blown.
1. Shorted lead wire harness
2. Defective primary latch switch (NOTE 1)
3. Defective short switch (NOTE 1)
4. Defective Inverter power supply
(U)
Refer to component test procedure (Page 15)
Check adjustment of primary, secondary
latch switch and short switch including
door.
NOTE 1: All of these switches must be replaced at the same time.
(Refer to adjustment instructions.)
Check continuity of power relay B’s contacts (between 1 and 2) and if it has continu-
ity, replace power relay B also.
3. Oven does not accept key input (Program). 1. Key input is not in sequence.
2. Shorted push button on DPC AU.
3. Defective DPC AU.
Refer to operation procedure.
Refer to DPC troubleshooting.
4. Oven lamp and turntable motor turn on when
oven is plugged in with door closed
1. Misadjustment or loose wiring of secondary
latch switch.
2. Defective secondary latch switch
Adjust door and latch switches.
5. Timer starts countdown but no microwave oscil-
lation.
(No heat while oven lamp and fan motor
turn on)
1. Off-alignment of latch switches
2. Open or loose connection of high voltage
circuit especially magnetron filament circuit
NOTE: Large contact resistance will bring lower
magnetron filament voltage and cause
magnetron to have lower output and/or
be intermittent.
3. Defective high voltage component
H.V. Inverter Magnetron
4. Open or loose wiring of power relay B
5. Defective primary latch switch.
6. Defective power relay B or DPC
AU or DU.
Adjust door and latch switches.
Check high voltage component according
to component test procedure (Page 15)
and replace if it is defective.
Refer to DPC troubleshooting.
6 Microwave output is low.
Oven takes longer time to cook food. 1. Decrease in power source voltage
2. Open or loose wiring of magnetron filament
circuit. (Intermittent oscillation)
3. Aging change of magnetron.
Consult electrician
Refer to output test procedures by water
temperature raising test.
7 Turntable on when door is opened. 1. Shorted primary latch switch.
8 Oven does not operate and returns to plugged in
mode as soon as start pad is pressed. 1. Opened or loose wiring of temp sensor
2. Defective temp sensor
Check tighten screws on escutcheon base
bracket, D.P.C board and temp sensor.
NEW H.V.
NEW H.V.
NEW H.V.