4.2. (Troubleshooting) Other problems
SYMPTOM
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 / thermistor
Check fan motor if thermal cutout is defective.
3. Open low voltage transformer
4. Defective DPC
2. No display and no operation at all.
Fuse is blown.
1.
2.
Shorted lead wire harness
Defective primary latch switch (NOTE 1)
Check adjustment of primary, secondary latch
switch and short switch including door.
3. Defective short switch (NOTE 1)
4. Defective Inverter Power Supply (U)
NOTE 1:
All of these switches must be replaced at the same time.
Check continuity of power relay B (RY1)´s contacts (between 1 and 2) and if it has continuity,
replace power relay B (RY1) also.
3. Oven does not accept key
input(Program)
1. Key input is not in proper sequence
Refer to operation procedure.
2. Open or loose connection of membrane key
pad to DPC (Flat cable)
3. Shorted or open membrane key board
4. Defective DPC
Refer to DPC troubleshooting.
4. Fan motor turns on when oven is
plugged in with door closed.
1. Misadjustment or loose wiring of secondary
latch switch
Adjust door and latch switches.
2. Defective secondary latch switch
5. Timer starts count down but no
microwave oscillation.
(No heat while oven lamp and fan
motor turn on)
1.
2.
Off-alignment of latch switches
Open or loose connection of high voltage circuit
especially magnetron filament circuit
NOTE:
Large contact resistance will cause lower
magnetron
filament
voltage
and
cause
magnetron to have lower output and/or be
intermittent.
Adjust door and latch switches.
3. Defective high voltage component
H.V. Inverter Power Supply (u)
Magnetron
Check high voltage component according to
component test procedure and replace if it is
defective.
4. Open or loose wiring of power relay B (RY1)
5. Defective primary latch switch
6. Defective DPC or power relay B (RY1)
Refer to DPC troubleshooting
6. Oven can program but timer does not
start countdown.
1. Open or loose wiring of secondary latch switch
2. Off-alignment of secondary latch switch
3. Defective secondary latch switch
7. Microwave output is low. Oven takes
longer time to cook food.
1. Decrease in power source voltage
Consult electrician
2. Open or loose wiring of magnetron filament
circuit.(Intermittent oscillation)
3. Aging change of magnetron
8. Fan motor turns on and turntable
rotates when door is opened.
1. Shorted primary latch switch
9. Oven does not operate and return to
plugged in mode as soon as start pad
is pressed.
1. Defective DPC
Check grounding connector on escutcheon
base.
10. Loud buzzing noise can be heard.
1. Loose fan and fan motor
11. Oven stops operation during cooking.
1. Open or loose wiring of primary and
secondary latch switch
Adjust door and latch switches.
2. Operation of thermal cutout
10
NN-ST657S / NN-ST677M / NN-ST667W / NN-ST657W
Summary of Contents for NN-ST657S
Page 2: ...2 NN ST657S NN ST677M NN ST667W NN ST657W ...
Page 3: ...3 NN ST657S NN ST677M NN ST667W NN ST657W ...
Page 5: ...1 SCHEMATIC DIAGRAM 5 NN ST657S NN ST677M NN ST667W NN ST657W ...
Page 15: ...5 EXPLODED VIEW AND PARTS LIST 5 1 EXPLODED VIEW 15 NN ST657S NN ST677M NN ST667W NN ST657W ...
Page 23: ...6 DIGITAL PROGRAMMER CIRCUIT 6 1 NN ST657S ST657W 23 NN ST657S NN ST677M NN ST667W NN ST657W ...
Page 24: ...24 NN ST657S NN ST677M NN ST667W NN ST657W ...
Page 25: ...6 2 NN ST677M ST667W 25 NN ST657S NN ST677M NN ST667W NN ST657W ...
