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6. Door seals sealing surfaces
7. Coupling
8. Control panel
9. Waveguide cover

10. Power supply cord

1. Ventilation openings
2. Oven lamp
3. Door hinges
4. Door safety latches
5. See through door

11. Turntable
12. Roller stay

9

2

5

4

4

7

11

3

6

8

12

13

10

1

COOKING CONTROL

COOK & DEFROST GUIDE

TIMER (0 - 30 minutes)

4

1. When the timer knob is at "0", the oven is OFF condi-

tion.

2. Closing the oven door activates the monitored latch

switch, the latch switch and the monitor switch).

IMPORTANT
When the oven door is closed, the contacts (COM-NC) of
the monitor switch must be open.
When the microwave oven is plugged in a wall outlet, rated
voltage is supplied to the noise filter and the control unit.

HIGH COOKING
Set the variable cooking control to HIGH and then set the
timer.

1. Following components are energized.

High voltage rectifier

High voltage transformer

High voltage capacitor

High voltage fuse

Turntable motor

Timer motor

Fan motor

Magnetron

Oven lamp

Control unit

CONNECTED COMPONENTS

RELAY

High voltage transformer

RY1

2. Rated voltage is supplied to the primary winding of the

high voltage transformer. The voltage is converted to
about 3.3 volts A.C. output on the filament winding and
high voltage of approximately 2000 volts A.C. on the
secondary winding.

3. The filament winding voltage (3.3 volts) heats the

magnetron filament and the high voltage (2000 volts) is
sent to the voltage doubling circuit, where it is doubled
to negative voltage of approximately 4000 volts D.C..

4. The 2450 MHz microwave energy produced in the

magnetron generates a wave length of 12.24 cm. This
energy is channelled through the waveguide (transport
channel) into the oven cavity, where the food is placed
to be cooked.

5. When the cooking time is up, the timer returns to "0",

the bell rings and the contacts of the timer are opened.
The following components are turned off.

High voltage rectifier

High voltage transformer

High voltage capacitor

High voltage fuse

Turntable motor

Timer motor

Fan motor

Magnetron

Oven lamp

Control unit

6. When the oven door is opened during a cook cycle, the

switches come to the following position and they are
common to the other cooking conditions too.

          CONDITION

DURING

DOOR OPEN

SWITCH

CONTACT

COOKING

(NO COOKING)

Monitored latch switch COM-NO

Closed

  Open

Latch switch

COM-NO

Closed

  Open

Monitor switch

COM-NC

Open

  Closed

The circuits to the high voltage transformer, turntable
motor, timer motor, fan motor, oven lamp and control
unit are cut off when the contacts (COM-NO) of the
monitored latch switch and latch switch are made
open.
The timer stops to indicate how much cooking time
remains.

7. MONITOR SWITCH CIRCUIT

The monitor switch is mechanically controlled by oven
door, and monitors the operation of the monitored latch
switch.

7-1 When the oven door is opened during or after the

cycle of a cooking program, the monitored latch
switch and latch switch must open their contacts
(COM-NO) first. After that the contacts (COM-NC) of
the monitor switch can be closed.

7-2. When the oven door is closed, the contacts (COM-

NC) of the monitor switch must be opened first. And
then the contacts (COM-NO) of the monitored latch
switch and the latch switch are closed.

7-3. When the oven door is opened and the contacts

(COM-NO) of the monitored latch switch and con-
tacts of the timer switch remain closed. The fuse
T6.3A will blow, because the monitor switch is closed
and a short circuit is caused.

When the microwave oven is preset for variable cooking
power, rated voltage is supplied to the power transformer
intermittently within a 32-second time base through the
relay contact which is coupled with the current-limiting
relay. The following levels of microwave power are given.

SETTING;

NOTE: The ON/OFF time ratio does not exactly corre-

spond to the percentage of microwave power,
because approx. 3 seconds are needed for heat-
ing up the magnetron filament.

1. If the oven is set for more than 20 minutes at HIGH

(100%) power level, after the first 20 minutes the power
level will automatically adjust itself to 70% power to
avoid overcooking.

2. If the oven is operated for more than 90 minutes

continuously (at any power levels), the relay RY1
opens. And the circuit to the high voltage transformer
will be cut off.

HIGH

32 sec. ON

MEDIUM HIGH

Approx. 70%

100%

24 sec. ON

8 sec. OFF

14 sec. OFF

20 sec. OFF

26 sec. OFF

MEDIUM

Approx. 50%

18 sec. ON

MEDIUM LOW

Approx. 30%

12 sec. ON

LOW

Approx. 10%

6 sec. ON

5

closed. However, when abnormally high temperatures are
reached within the oven cavity, the thermal cut-out will
open at 125˚C, causing the oven to shut down. The
defective thermal cut-out must be replaced with a new
one.

The thermal cut-out located on the top of the oven cavity
is designed to prevent damage to the magnetron if an over
heated condition develops in the tube due to cooling fan
failure, obstructed air guide, dirty or blocked air intake, etc.
Under normal operation, the thermal cut-out remains
closed. However, when abnormally high temperatures are
reached within the magnetron, the thermal cut-out will
open at  95˚C, causing the oven to shut down. When the
magnetron has cooled  to 75˚C, the thermal cut-out closes
and cook cycle will resume.

The turntable motor drives the roller stay to rotate the
turntable.

The fan motor drives a blade which draws external cool air.
This cool air is directed through the air vanes surrounding
the magnetron and cools the magnetron. This air is
channelled through the oven cavity to remove steam and
vapours given off from the heating foods. It is then ex-
hausted through the exhausting air vents at the oven
cavity.

1. When the timer switch is at "0" position, the switch of

the timer is opened.

2. When the timer is turned clockwise from "0" position,

the switch of the timer is closed.

The noise filter prevents the radio frequency interference
that might flow back in the power circuit.

The door is opened by pulling the door, refer to the Figure
D-1.

1. When the oven door is closed, the contacts (COM-NO)

must be closed.

2. When the oven door is opened, the contacts (COM-

NO) must be opened.

1. When the oven door is closed, the contacts (COM-NC)

must be opened.

2. When the oven door is opened, the contacts (COM-

NC) must be closed.

3. If the oven door is opened and the contacts (COM-NO)

of the monitored latch switch and timer switch contacts
fail to open, the fuse blows simultaneously with closing
the contacts (COM-NC) of the monitor switch.

CAUTION: BEFORE REPLACING A FUSE TEST THE

MONITORED LATCH SWITCH, TIMER
SWITCH AND MONITOR SWITCH FOR
PROPER OPERATION. (REFER TO CHAP-
TER "TEST PROCEDURE".)

1. The fuse blows when the contacts (COM-NO) of the

monitored latch switch remain closed with the oven
door open and when the monitor switch  closes.

2. If the wire harness or electrical components are short-

circuited, the fuse T6.3A blows to prevent an electric
shock of fire hazard.

The high voltage fuse blows when the high voltage rectifier
or the magnetron is shorted.

The thermal cut-out located on the top of the oven cavity
is designed to prevent damage to the oven if the foods in
the oven catch fire due to over heating produced by
improper setting of cook time or failure of control unit.
Under normal operation, the thermal cut-out remains

Latch Heads

Latch Hook

Door

Monitor
Switch

Monitored
Latch
Switch

Latch
Switch

6

IMPORTANT: If the oven becomes inoperative because

of a blown fuse T6.3A in the monitored
latch switch - timer switch  - monitor switch
circuit, check the monitored latch switch,
timer switch and monitor switch before
replacing the fuse T6.3A.

When troubleshooting the microwave oven, it is helpful
to follow the Sequence of Operation in performing the
checks. Many of the possible causes of trouble will re-
quire that a specific test be performed. These tests are
given a procedure letter which will be found in the "Test
Procedure"section.

MAGNETRON

POWER TRANSFORMER

H.V. RECTIFIER ASSEMBLY

HIGH VOLTAGE WIRE

HIGH VOLTAGE CAPACITOR

MONITORED LATCH SWITCH

LATCH

 SWITCH

MONITOR SWITCH

THERMAL CUT-OUT 125

˚C (OVEN)

THERMAL CUT-OUT 95

˚C (MG)

TIMER MOTOR

TIMER SWITCH

FAN MOTOR

TURNTABLE MOTOR

FUSE T6.3A

CONTROL UNIT

RELAY (RY-1)

FOIL PATERN ON P.W.B.

POWER SUPPLY CORD

SHORTED WIRE HARNESS

OPENED WIRE HARNESS

OVEN LAMP

WALL OUTLET

MISADJUSTMENT SWITCH

HOME FUSE OR BREAKER

BLOCKED COOLING FAN

BLOCKED VENTILATION

NOISE FILTER

H.V. FUSE

Home fuse blows when power
supply cord is plugged into wall
outlet.

FUSE T6.3A blows when
power supply cord is plugged
into wall outlet.

Oven does not start when the
timer is set.

Oven lamp does not light (Other
function is normal.)

Fan motor does not operate.
(Other function is normal.)

Turntable motor does not op-
erate. (Other function is nor-
mal.)

Oven or any electrical parts
does not stop.

Oven seems to be operating
but little or no heat is produced
in oven load. (Microwave
power level is set at HIGH)

Oven does not seems to be
operating properly when ME-
DIUM HIGH, MEDIUM, ME-
DIUM LOW or LOW is set.
(Oven operates properly at
HIGH.)

Oven goes into cook cycle but
shuts down before end of cook-
ing cycle.

OFF
CONDITION

PROBLEM

CONDITION

POSSIBLE CAUSE

AND

DEFECTIVE PARTS

TEST PROCEDURE

ON
CONDITION

CK = Check / RE = Replace

A B C

CK

D E E E   F  F G  G  H  H  I  L M N

RECKCKRE CKCKCK CK CK

J K