6. Troubleshooting
6-1 Electrical Malfunction
SYMPTOM
CAUSE
CORRECTIONS
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 Ass’y PCB
Check fan motor when thermal
cutout is defective.
Check Ass’y PCB when LVT is
defective.
No display and no operation at all.
Fuse is blown.
1. Shorted lead wire harness
2. Defective primary latch switch
(NOTE 1)
3. Defective monitor switch (NOTE1)
4. Shorted HVCapacitor
5. Shorted HVTransformer (NOTE2)
Check adjustment of primary,
interlock monitor,
power relay, door sensing switch.
NOTE 1: All of these switches must be replaced at the same time.
(refer to adjustment instructions)
Check continuity of power relay contacts and if it has
continuity, replace power relay also.
NOTE 2: When HVTransformer is replaced, check diode and
magnetron also.
Oven does not accept
key input (Program)
1. Key input is not in-Sequence
2. Open or loose connection of
membrane key pad to Ass’y PCB
3. Shorted or open membrane panel
4. Defective Ass’y PCB
Refer to operation procedure.
Replace PCB main.
Timer starts countdown but no
microwave oscillation.
(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 lower output
and/or intermittent oscillation.
3. Defective high voltage
components H.V.Transformer H.V.
Capacitor H.V.Diode, Magnetron,
H.V Fuse
4. Open or loose wiring of power relay
5. Defective primary latch switch
6. Defective power relay or Ass’y PCB
Adjust door and latch switches.
Check high voltage component
according to
component test procedure and
replace if it is
defective.
Replace PCB main.
PRECAUTION
1. CHECK GROUNDING BEFORE CHECKING FOR TROUBLE.
2. BE CAREFUL OF THE HIGH VOLTAGE CIRCUIT.
3. DISCHARGE THE HIGH VOLTAGE CAPACITOR.
4. WHEN CHECKING THE CONTINUITY OF THE SWITCHES OR TRANSFORMER, DISCONNECT
ONE LEAD WIRE FROM THESE PARTS AND THEN CHECK CONTINUITY WITHOUT THE
POWER SOURCE ON. TO DO OTHERWISE MAY RESULT IN A FALSE READING OR DAMAGE
TO YOUR METER.
5. DO NOT TOUCH ANY PART OF THE CIRCUIT OR THE CONTROL CIRCUIT BOARD, SINCE
STATIC DISCHARGE MAY DAMAGE IT.
ALWAYS TOUCH GROUND WHILE WORKING ON IT TO DISCHARGE ANY STATIC CHARGE
BUILT UP.
