NN-SM220W, NN-SM220WZPE - Panasonic Home Appliance Service Manual (repair manual). Page 10

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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 

 

. 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 “HIGH”)

• The contacts of primary and secondary switch close the

circuit.

•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

and secondary 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.

SWITCH

PRIMARY 

FILTER ASS'Y

H.V.T

SECONDARY SWITCH 

MONITOR

SWITCH 

TIMER

SWITCH

GE

GE

L

N

FUSE

COM

V.P.C

SLOW

 

RELAY

 

ACTING

ASS'Y

SWITCH

PRIMARY 

FILTER ASS'Y

H.V.T

SECONDARY SWITCH 

MONITOR

SWITCH 

TIMER

SWITCH

GE

GE

L

N

FUSE

COM

V.P.C

SLOW

 

RELAY

 

ACTING

ASS'Y

transformer and the microwave oven begin to operate.  

 

 Electricty apply to the high voltage

 

connect the circuit

the low acting relay assy works and

s

.

.

   Input Volts AC.

• 

oor hook

d