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Troubleshooting - Samsung MW7490W Service Manual

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6. Troubleshooting

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.
6-1 Electrical Mulifunction
SYMPTOM
Oven is dead.
Fuse is OK.
No display and no operation at all.
No display and no operation at all.
Fuse is blown.
Oven does not accept
key input (Program)
Timer starts countdown but no
microwave oscillation.
(No heat while oven lamp and
fan motor turn on.)
Samsung Electronics
PRECAUTION!
CAUSE
1. Open or loose lead wire harness
2. Open thermal cutout (Magnetron)
3. Open low voltage transformer
4. Defective Ass'y PCB
1. Shorted lead wire harness
2. Defective primary latch switch (NOTE 1)
3. Defective monitor switch (NOTE1)
4. Shorted HVCapacitor
5. Shorted HVTransformer (NOTE2)
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.
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
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
4. Open or loose wiring of power relay
5. Defective primary latch switch
6. Defective power relay or Ass'y PCB
CORRECTIONS
Check fan motor when thermal cutout is defective.
Check Ass'y PCB when LVT is defective.
Check adjustment of primary, interlock monitor,
power relay, door sensing switch.
Refer to operation procedure.
Replace PCB main.
Adjust door and latch switches.
Check high voltage component according to
component test procedure and replace if it is
defective.
Replace PCB main.
6-1

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