Troubleshooting - Samsung MD800WC Service Manual

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 Malfunction
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.)
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 Secondary latch switch
(NOTE 1)
3. Defective monitor switch (NOTE1)
4. Shorted H.V.Capacitor
5. Shorted H.V.Transformer (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 H.V.Transformer 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 Secondary latch switch
6. Defective power relay or Ass'y PCB
- 13 -
CORRECTIONS
Check fan motor when thermal
cutout is defective.
Check Ass'y PCB when L.V.T is
defective.
Check adjustment of , Secondary
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.