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7

CONVECTION

MOTOR

THERMISTOR

Sensing 

Voltage

ON

OFF

ON

OFF

ON

OFF

0 2 3

28

31

32 (sec.)

64 (sec.)

3 sec.

Sensing the voltage across temperature measurement circuit.

3 sec.

The LSI also stops counting down and closes the
damper door so that no fresh air will enter the oven
cavity.

4. Once the fire sensor feature has shut the unit down, the

programmed cooking cycle may be resumed by
pressing the "START" pad or the unit may be reset by
pressing the "CLEAR" pad.

The door is opened by pulling the door handle down and
forward, referring to the figure D-1. When the door handle
is pulled down, the latch heads are moved upward. And
then when the door handle is pulled forward, the latch
heads are released from the latch hooks right and left.
Now, the door will open.

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 secondary interlock switch and the relay RY2 fail
to open, the fuse F10A blows simultaneously with
closing the contacts (COM-NC) of the monitor switch .

CAUTION: BEFORE REPLACING A FUSE TEST THE

SECONDARY INTERLOCK SWITCH, RELAY
RY2 AND MONITOR SWITCH   FOR PROPER
OPERATION. (REFER TO CHAPTER "TEST
PROCEDURE".)

1. The fuse F10A blows when the contacts (COM-NO) of

the secondary interlock switch and relay RY2 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 F10A 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 noise filter prevents the radio frequency interference
that might flow back in the power circuit.

The thermistor is a negative temperature coefficient type.
The temperature in the oven cavity is detected through the
resistance of the thermistor, and then the control unit causes
the heater relay to operate, thus the current to the heating
elements is turned ON/OFF. If the convection cooking or
some cooking modes which use the top / side heating
elements is started and the oven temperature does not rise
above 37.8˚C, the control unit will stop the oven after 10
minutes. In this case, the thermistor may be opened.

Monitor switch

Latch hook left

Latch 
head

3rd. latch 
switch

Latch hook right

Latch 
head

Door handle

Secondary
interlock switch
(Monitored latch switch)

Door
sensing switch
(Primary interlock
relay control switch)

8

The temperature fuse located on the waveguide flange is
designed to prevent damage to the magnetron if an over
heated condition develops in the magnetron due to cooling
fan failure, obstructed air guide, dirty or blocked air intake,
etc. Under normal operation, the temperature fuse remains
closed. However, when abnormally high temperatures are
reached within the magnetron, the temperature fuse will
open at 150˚C causing the oven to shut down.

The thermal cut-out located on the thermal cover upper is
designed to prevent damage to the top heating element
unit if an over heated condition develops in the top heating
element unit due to convection fan failure, thermistor
failure, obstructed air ducts, dirty or blocked air intake, etc.
Under normal operation, the thermal cut-out remains
closed. However, when abnormally high temperature are
reached within the top heating element unit, the thermal
cut-out will open at 170˚C causing the oven to shut down.
When the thermal cut-out has cooled, the thermal cut-out
closes at 155˚C.

The thermal cut-out located on the thermal cover left is
designed to prevent damage to the side heating element
unit if an over heated condition develops in the top heating
element unit due to convection fan failure, thermistor
failure, obstructed air ducts, dirty or blocked air intake, etc.
Under normal operation, the thermal cut-out remains
closed. However, when abnormally high temperature are
reached within the side heating element unit, the thermal
cut-out will open at 150˚C causing the oven to shut down.
When the thermal cut-out has cooled, the thermal cut-out
closes at 130˚C.

The top heating element is located at the top of the oven
cavity. It is intended to heat air driven by the convection
fan. The heated air is kept in the oven and force-circulated
and reheated by the top heating element.

The side heating element is located at the left side of the
oven cavity. It is intended to heat air driven by the convec-
tion fan. The heated air is kept in the oven and force-
circulated and reheated by the top heating element.

The turntable motor rotates the turntable located in the
bottom of the oven cavity, so that the food on the turntable
is cooked evenly during cooking. The turntable may turn in
either direction.

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

The fan motor drives a blade which draws external cool air.
This cool air is directed through the air vents surrounding
the power transformer and cools the power transformer.
This air is channelled through the oven cavity to remove
steam and vapors given off from the heating foods. It is
then exhausted through the exhausting air vents at the
oven cavity.

This oven is designed with a hot air heating system where
food is not directly heated by the heating element, but is
heated by forced circulation of the hot air produced by the
heating elements. The air heated by the heating elements is
circulated through the convection passage provided on the
outer casing of the oven cavity by means of the convection
fan which is driven by the convection motor. It then enters the
inside of the oven through the vent holes provided on the top
and left sides of the oven. Next, the hot air heats the food on
the turntable and leaves the oven cavity through the vent in
the center of the oven cavity back side wall. Without leaving
the oven, this hot air is reheated by the heating elements,
passes through the convection passage and enters the
inside of the oven cavity again, in a continuing cycle. In this
way, the hot air circulates inside the oven cavity to raise its
temperature and, at the same time, comes into contact with
the food being cooked. When the temperature inside the
oven cavity reaches the selected temperature, the heating
elements are de-energized. When the temperature inside
the oven cavity drops below the selected temperature, the
heating elements are energized again. In this way, the inside
of the oven cavity is maintained at approximately the se-
lected temperature. When the convection time reaches 0,
the heating elements are de-energized and the convection
fan stops operating and the oven shuts off.

The rotation direction of the convection motor is controlled
by relay RY6. When the convection fan rotates clockwise,
the hot air from the oven cavity left side wall blows stronger
than one from the oven cavity top wall. ( This mode is
called “Convection mode”.) When the convection fan
rotates counterclockwise, the hot air from the oven cavity
top wall blows stronger than one from the oven cavity left
side wall. (This mode is called “JET mode”.)

Side heating
element unit

Top heating
element unit

Convection 
fan

Convection mode

JET 
mode

FRONT VIEW

9

Usually, the damper is in the open position except during
convection cooking, preheat, grill, dual1, dual2 or all
cooking modes which use the top / side heating elements.
Damper position is set automatically by damper motor,
damper switch, motor cam and damper shaft. These
components are operated by a signal that judges if
microwave cooking, convection cooking operation or
other cooking operation is selected by the control unit.

Microwave Cooking:
Damper is in the open position, because a portion of cooling
air is channelled through the cavity to remove steam and
vapors given off from the heating foods. It is then exhausted

Hot air

Hot air

Hot air

Convection
fan

Hot air

Oven cavity left side

Oven cavity   
top wall

Side heating
element unit

Side heating
element unit

Top heating element unit Top heating element unit

Turntable

at the top of the oven cavity into a condensation compart-
ment.

Convection, Preheat, Grill, Dual1, Dual2, or all cook-
ing modes which use the top / side heating elements:
Damper is in the closed position, so that no hot air will be
allowed to leak out the oven cavity.

Damper Operation
1. When power supply cord is plugged in:

1-1. When power supply cord is plugged in, a signal is

sensed in the control unit, and operates shut-off
relay (RY4).

1-2. Contacts of shut-off relay (RY4) close, the damper

motor is energized, opening the damper door.

1-3. When the damper is moved to the open position by

the damper cam the damper switch is opened
(OFF position).

1-4. The signal from damper switch is re-sensed in the

control unit and shut-off relay (RY4) is turned off.

1-5. The rated voltage to the damper motor is removed

and the motor turns off.

2. When oven is microwave cooking:

Damper is in the open position.

3. When oven is convection cooking:

3-1. Damper motor is energized by touching the CONV.

(˚C) and START keys.

3-2. When damper is in the closed position (damper

switch is ON), its signal is sensed by the control
unit, and shut-off relay (RY4) is de-energized.

3-3. The damper is held in the closed position during

the convection cooking operation.

3-4. At the end of the convection cooking, if the cavity

air temperature is below 121˚C, shut-off relay
(RY4) is energized, and the damper is returned to
the open position.

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 require that a
specific test be performed. These tests are given a proce-
dure letter which will be found in the "Test Procedure
"section.

IMPORTANT: If the oven becomes inoperative because

of a blown fuse F10A in the secondary
interlock swith - monitor switch - primary
interlock relay RY2 circuit, check the moni-
tor switch, relay (RY1), primary interlock
relay (RY2) and secondary interlock switch
before replacing the fuse F10A.

10

Home fuse blows when power cord is plugged into wall receptacle.

Fuse 20A blows when power cord is plugged into wall receptacle

PRESS STOP" does not appear in display when power cord is first

plugged into wall receptacle.

Display does not operate properly when STOP/CLEAR key is touched.

(The time of day should appear on the display with beep sound.)

Oven lamp does not light with door opened.

Oven lamp does not light in cook cycle. (It light when door is opened).

Cooking cycle runs 1 minute then shuts down.

Oven lamp light, but turntable motor does not operate.

Turntable motor operates normally but cooling fan motor does not

operate.

Oven does not go into a cook cycle, when START key is touched.

Low or no power is produced during microwave cooking (The food is

heated incompletely or not heated at all)

Extremely uneven heating is produced in oven load (food).

Function of variable cooking does not operate properly except HIGH

power.

Oven does not go into cook cycle when START pad is touched.

Heating elements do not heat.

Temperature in the oven cavity is lower or higher than preset.

Convection cycle runs for 10 minutes then shuts down.

Convection motor does not operate of all or properly.

A

MAGNETRON

B

HIGH VOLTAGE TRANSFORMER

C

H.V. RECTIFIER ASSEMBLY

D

HIGH VOLTAGE CAPACITOR

E

SECONDARY INTERLOCK SWITCH

E

3RD. LATCH SWITCH

E

DOOR SENSING SWITCH

E

MONITOR SWITCH

F

HIGH VOLTAGE FUSE

G

NOISE FILTER

H

FUSE 20A

J

MAGNETRON TEMPERATURE FUSE

K

THERMAL CUT-OUT (TOP)

M

TOP HEATING ELEMENT

O

THERMISTOR

P/U

DAMPER MOTOR

Q

DAMPER SWITCH

V

TOUCH CONTROL PANEL

W

TACT SWITCH

X

RELAY RY-1

X

RELAY RY-2

X

RELAY RY-3

X

RELAY RY-4

X

RELAY RY-5

X

RELAY RY-6

Z

FUSE1 ON PWB.

Y

SOLID-STATE RELAY (TOP)

Y

SOLID-STATE RELAY (SIDE)

Replace

OVEN LAMP

U

FAN MOTOR (MAGNETRON)

U

TURNTABLE MOTOR

S

CONVECTION MOTOR

Check

LOOSE WIRING

Check

SHORTED IN POWER CORD

Check

NO POWER AT OUTLET

Check

LOW VOLTAGE

L

THERMAL CUT OUT (SIDE)

N

SIDE HEATING ELEMENT

U

FAN MOTOR 

(HIGH VOLTAGE  TRANSFORMER)

Z

T/C TRANSFORMER

I

FUSE F10A

R

CONVECTION MOTOR CAPACITOR

Check

MISADJUSTMENT SWITCH

POSSIBLE CAUSE

AND

DEFECTIVE PARTS

TEST PROCEDURE

CONDITION

COOKING CONDITION

(MICROWAVE)

(CONVECTION/

GRILL/ DUAL)

OFF CONDITION

PROBLEM