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4-3

IMPORTANT SAFETY NOTE: THE SHADED AREAS ON THIS SCHEMATIC DIAGRAM INCORPORATE SPECIAL FEATURES

       

      IMPORTANT FOR PROTECTION FROM MICROWAVE RADIATION,  FIRE, 

ELECTRICAL SHOCK,  AND

                                                  HAZARDS. WHEN SERVICING IT IS ESSENTIAL THAT ONLY MANUFACTURER'S SPECIFIED PA

RTS 

                                                  BE USED FOR THE CRITICAL COMPONENTS IN THE SHADED AREAS OF THE SCHEMATIC DIAG

RAM.

NOTICE: SINCE THIS IS BASIC SCHEMATIC DIAGRAM, THE VALUES OF COMPONENTS AND

                SOME PARTIAL CONNECTIONS ARE SUBJECT TO CHANGE FOR IMPROVEMENT. 

NOISE FILTER

MONITOR 

RESISTOR

A.C RELAY

4-4

•  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 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.

FUSE

PRIMARY

SWITCH

SECONDARY

SWITCH

MONITOR

SWITCH

MONITOR

RESISTOR

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

MONITOR

RESISTOR

MICROWAVE OVEN
SERVICE MANUAL

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

5-9

1. DISCONNECT THE POWER SUPPLY CORD FROM THE OUTLET WHENEVER REMOVING THE

OUTER CASE FROM THE UNIT. PROCEED WITH THE TEST ONLY AFTER DISCHARGING THE HIGH
VOLTAGE CAPACITOR AND REMOVING THE WIRE LEADS FROM THE PRIMARY WINDING OF THE
HIGH VOLTAGE TRANSFORMER. (SEE PAGE 2-1)

2. ALL OPERATIONAL CHECKS WITH MICROWAVE ENERGY MUST BE DONE WITH A LOAD (1 LITER

OF WATER IN CONTAINER) IN THE OVEN.

HIGH VOLTAGE
TRANSFORMER
(Wire leads removed)

MAGNETRON
(Wire leads removed)

1. Measure the resistance.

(Ohm-meter scale: Rx1 and Rx100)
• Primary winding
• Secondary winding
• Filament winding

2. Measure the resistance.

(Ohm-meter scale: Rx1000)
• Primary winding to ground
• Filament winding to ground

1. Measure the resistance.

(Ohm-meter scale: Rx1)
• Filament terminal

2. Measure the resistance.

(Ohm-meter scale: Rx1000)
• Filament to chassis

Approx.: 2 ohm
Approx.: 125 ohm
Less than: 1 ohm

Normal: Infinite
Normal: Infinite

Normal: Less than 1 ohm

Normal: Infinite

PRIMARY  
TERMINAL

SECONDARY  
TERMINAL

FILAMENT 
WINDING
TERMINAL