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• The low voltage transformer supplies the necessary

voltage to the micom controller when power cord is
plugged in.

• When the door is closed, the primary switch is ON, the

secondary switch is ON, and  the monitor switch opens
(contact COM and NO).

• The micom controller memorizes the function you set.
• The time you set appears in the display window.
• Each indicator light turns on to indicate that the stage

has been set.

• The coil of the relay is energized by the micom

controller.

• Power input is supplied to the high voltage transformer

through the fuse to the primary switch and relay 2.

• Turntable rotates.

• The fan motor rotates and cools the magnetron by

blowing the air (coming from the intake on the
baseplate).

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

vapor in the oven through the upper plate.

• Cooking time starts counting down.
• 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 high
voltage diode and charging of the high voltage
capacitor.

• The negative 4,000 Volts DC is applied to the filament

of the magnetron.

• The micom controller controls the ON-OFF time of 

relay 2 by the applied signal to vary the average output 

power of microwave oven as POWER LEVEL. 

(refer to page 1-1)

• One complete cycle of relay 2 is 22 seconds.

• Both the primary switch and relay 2 are cut off primary

winding voltage of the high voltage transformer.

• ON-OFF of relay 2 is coupled electrically with opening

and closing of the secondary switch.

• When the door is opened, the secondary switch is

opened and when the door is closed, the secondary
switch is closed.

• The cooking time stops counting down.
• Relay stops functioning.
• As the door is opened, if the contact of primary switch

fails 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 primary switch and the secondary

switch close the circuit.

• A.C. voltage is applied to the grill heater through grill

thermostat as shown by the solid line.

• Turntable rotates.
• The fan motor rotates.
• The air is also directed into the oven to exhaust the

vapor in the oven through the base plate and upper
plate.

4-4

L

FUSE

H.V.

TRANS-

FORMER

RELAY 2

MICOM CONTROLLER

SECONDARY
SWITCH

PRIMARY

SWITCH

N

MONITOR

SWITCH

L

FUSE

H.V.

TRANS-

FORMER

RELAY 2

MICOM CONTROLLER

SECONDARY
SWITCH

PRIMARY

SWITCH

N

MONITOR

SWITCH

RELAY 3

L

N

GRILL 

HEATER

GRILL 

THERMOSTAT

L

G -Y

N

E

and should

repair any unit found to have excessive emission levels
at no cost to the owner and should ascertain the cause
of the excessive leakage. The service personnel
should instruct the owner not to use the unit until the
oven has been brought into compliance.

• The service personnel should check all surface and

vent openings for microwave leakage.

• Check for microwave leakage after every servicing.

The power density of the microwave radiation leakage
emitted by the microwave oven should not exceed 
4 mW/cm

2

. Always start measuring of an unknown field

to assure safety for operating personnel from radiation
leakage.

5-1

Tools normally used for TV servicing are sufficient.
Standard tools are listed below.

• Diagonal pliers
• Long nose pliers
• Phillips screwdriver
• Flat blade screwdriver
• Wrench (size 5mm)
• Nutdriver (size 5mm)
• Adjustable wrench
• Soldering iron
• Solder
• Vinyl insulation tape
• Polishing cloth

• TESTER(VOLTS-DC, AC., Ohmmeter)
• Microwave survey meter

- Holaday HI-1500

HI-1501

- Narda     8100

8200

• Inch scale
• 600 cc non conductive material beaker (glass or plastic),

inside diameter: approx. 8.5 cm(3

1

/2

in.)

• Cylindrical and made of borosilicate glass vessel.

max. thickness: 3 mm
outside diameter: approx. 190mm
height: approx. 90mm

• Glass thermometer: 100°C or 212°F (1 deg scale)

• When you replace the magnetron, measure for

microwave energy leakage before the outer case is
installed and after all necessary components are
replaced or adjusted.

Special care should be taken in measuring the

following parts. (Circled area of below Fig.)

- Around the magnetron
- The waveguide

• After all components, including the outer case, are fully

assembled, measure for microwave energy leakage
around the door viewing window, the exhaust opening,
and air inlet openings.

• Microwave energy leakage must not exceed the values

prescribed below.

NOTE: Leakage with the outer case removed less than

5 mW/cm.sq. Leakage for a fully assembled
oven (Before the latch switch (primary) is
interrupted) with the door in a slightly opened
position-less than 2 mW/cm.sq.

• Do not  exceed meter full scale deflection.
• The test probe must be removed no faster than  

1 inch/sec (2.5 cm/sec) along the shaded area,
otherwise a false reading may result.

• The test probe must be held with the grip portion of the

handle.

A false reading may result if the operator's hand is

between the handle and the probe.

• When testing near a corner of the door, keep the probe

perpendicular to the surface making sure the probe
horizontally along the oven surface, this may possibly
cause probe damage.

• After adjustment and repair of any microwave energy

interruption or microwave energy blocking device,
record the measured values for future reference. Also
enter the information on the service invoice.

• The microwave energy leakage should not be more

than 4 mW/cm.sq. after determining that all parts are in
good condition, functioning properly and genuine
replacement parts which are listed in this manual have
been used.

• At least once a year, have the electromagnetic energy

leakage monitor checked for calibration by its
manufacturer.

5-2

• Microwave power output measurement is made with

the microwave oven supplied at its rated voltage and
operated at its maximum microwave power setting
with a load of (1000 ± 5)g potable water.

• The water is contained in a cylindrical borosilicate

glass vessel having a maximum material thickness
of 3 mm and an outside diameter of approximately
190 mm.

• The oven and the empty vessel are at ambient

temperature prior to the start of the test.

• The initial temperature (±1) of the water is (10±2)°C.

It is measured immediately before the water is
added to the vessel. After addition of the water to
the vessel, the load is immediately placed on the
center of the shelf which is in the lowest position and
the microwave power switched on.

• The time T for the temperature of the water to rise

by a value 

∆

T of (10±2)°K is measured, where T is

the time in seconds and 

∆

T is the temperature rise.

The initial and final water temperatures are selected
so that the maximum difference between the final
water temperature and the ambient temperature is
5°K.

• The microwave power output P in watts is calculated

from the following formula:

P =

is measured while the microwave generator is
operating at full power. Magnetron filament heat-up
time is not included.

• The water is stirred, to equalize temperature

throughout the vessel, prior to measuring the final
water temperature.

• Stirring devices and measuring instruments are

selected in order to minimize addition or removal of
heat.

WATER LOAD

TURNTABLE

1) Disconnect the power supply cord from the outlet.
2) Remove the screws from the rear and along side

edges of the case.

The outer case must be moved backward to be lifted

off.

1) Remove the outer case.
2) Disconnect two terminals, and remove one screw of

the earth terminal.

(refer to page 2-1)

1) Disconnect the leadwire from the PCB SUB ASS’Y.
2) Remove the screws for the earth and securing the

control panel.

3) Lift control panel ASS’Y from the oven by the tab

unhooked.

5-3

4187 X (

∆

T) + 0.55 X (T

2 

- T

0

) X M

T

• T

2

: Temperature after heating

• T

0

: Temperature of bowl

• M: Weight of bowl