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MICROWAVE OVEN
SERVICE MANUAL

BEFORE SERVICING THE UNIT, READ THE
SAFETY PRECAUTIONS IN THIS MANUAL.

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•  As the door is closed, the contact of MONITOR

SWITCH opens. This switch creates the short circuit to
blow fuse during operation under abnormal condition.
(ie, should the contacts of primary and secondary
switch fail to open the circuit)

•  The latches are secured by latch board. The oven light

turns on while the oven is in operation.

•  The contacts of the timer switch changes to ON

position when the timer knob is rotated.
(While power control knob is set at “Full Power”)

•  The contacts of primary and secondary switch close

the circuit.

•  Input Volts AC. is applied to the high voltage

transformer through power control switch as shown by
the solid line.

•  Turntable rotates.
•  The fan motor rotates and cools the magnetron by

blowing the air (coming from the intake holes on the
baseplate) over the magnetron.

•  The air is also directed into the oven to exhaust the

vapor in the oven through the upper plate.

•  Timer starts rotating.
•  3.2 volts AC is generated from the filament winding of

the high voltage transformer. This 3.2 volts is applied
to the magnetron to heat the magnetron filament
through two noise preventing choke coils.
A high voltage of approximately 2100 volts AC is
generated in the secondary of the high voltage
transformer which is increased by the action of the
diode and charging of the high voltage capacitor.
The negative DC voltage is then applied to the filament
of the magnetron.

•  Both primary switch and secondary switch open to cut

off the primary winding voltage to the high voltage
transformer to stop microwave oscillation.

•  Timer, turntable and fan motor stop.
•  As the door is opened, if the contact of primary switch

fail to open, the fuse opens due to the large current
surge caused by the monitor switch activation which in
turn stops magnetron, oscillation.

•  The contacts of the timer switch change to ON

position.

•  The contacts of the grill select switch close the circuit.
•  Input volts AC is applied to the grill heater through

thermostat-grill as shown by the solid line.

•  The fan motor and turntable rotates.

FUSE

PRIMARY

SWITCH

SECONDARY

SWITCH

MONITOR

SWITCH

L

N

H.V.T

RELAY

TIMER

SWITCH

POWER

CONTROL

SWITCH

FUSE

PRIMARY

SWITCH

SECONDARY

SWITCH

L

N

H.V.T

RELAY

TIMER

SWITCH

POWER

CONTROL

SWITCH

MONITOR

SWITCH

PRIMARY

SWITCH

TIMER

SWITCH

GRILL

SELECT
SWITCH

L

N

THERMOSTAT

GRILL

GRILL 

HEATER

L

G -Y

N

E