6. Troubleshooting
6-1 Electrical Malfunction
SYMPTOM
CAUSE
CORRECTIONS
Oven is dead.
Fuse is OK.
No display and
no operation.
1. Open or loose lead wire harness
2. Open thermal cutout (Magnetron, cavity)
3. Open low voltage transformer
4. Defective Ass’y PCB
Check fan motor when thermal cutout
is defective.
Check Ass’y PCB when L.V.T is
defective.
No display and no
operation Fuse is blown.
(10A, 1.6A)
1. Shorted lead wire harness
2. Defective primary latch switch(NOTE 1)
3. Defective monitor switch (NOTE1)
4. Shorted H.V.Capacitor
5. Shorted H.V.Transformer (NOTE2)
Check adjustment of primary, interlock
monitor, 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 H.V.Transformer is replaced, check diode and
magnetron also.
Oven does not accept
key input (Program)
(CM1929/1629/1329)
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. 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.
2. Defective high voltage
components H.V.Transformer
H.V. Capacitor
H.V.Diode, H.V.Fuse
Magnetron
Adjust door and latch switches.
Check high voltage component
according to component test
procedure and replace if it is
defective.
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
LEAD WIRES 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.
