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3

1.

Control panel

2.

Hole for safety door latches

3.

Ceramic floor

4.

Splash cover

5.

Oven light

6.

Air intake filter

7.

Air intake openings

8.

Oven cavity

9.

Door seals and sealing surfaces

10. Door hinges
11. Oven door with see-through window
12. Door safety latches
13. Door handle.
14. Outer cabinet
15. Removable cover over oven light bulb
16. Air vent openings
17.  Power supply cord
18 Mounting plate
19 Screw for mounting plate

DISPLAY AND INDICATORS
Check indicators after the oven starts to
confirm the oven is operating as desired.

1.

Heating indicator
This indicator shows cooking in progress.

2.

Memory number indicator

3.

Express defrost

4.

Check mode indicator

5.

Power level display

6.

Time display

7.

Filter indicator

8.

Double quantity mode indicator

9.

3rd. stage indicator

10. 2nd. stage indicator
11. 1st. stage indicator

12. DOUBLE QUANTITY key
13. EXPRESS DEFROST key
14. NUMBER keys
15. MANUAL/ REPEAT key
16. STOP/CLEAR key
17. POWER LEVEL key
18. START key
19. SET key
20. VOLUME key
21. CHECK key

When this commercial  microwave oven is installed near other commercial electrical appliances, connect a lead wire to
each equivalent potential terminal with equipotential marking between them (insert a lead wire between a washer and
an earth angle, and screw them), as shown in Fig. A-1, to make sure that they are at equivalent potential.
If any lead wire is not connected between them, when person touch them he/she will get a electric shock.

COMMERCIAL MICROWAVE OVEN

OTHER COMMERCIAL 
ELECTRICAL APPLIANCE

Lead wire

Equipotential marking

Earth angle
(Equivalent potential terminal)

Equivalent 
potential terminal

Screw

Washer

Lead wire

DEF CHECK

POWER

%

DOUBLE

ON

NUMBER

1

2

3

16

18

20

13

5

2
1

12

15

17

19

21

11

10

FILTER

3 4

6

7
8
9

1

2

3

4

5

6

7

8

9

0

11

12

13

14

15

16

17

18

19

20

14

EXPRESS
DEFROST

MANUAL/

REPEAT

STOP / CLEAR

POWER LEVEL

START

SET

CHECK

VOLUME

DOUBLE

QUANTITY

4

to negative voltage of approximately 4000 volts D.C..

3. 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.

4. When the cooking time is up, a signal tone is heard and

the relays RY3+RY4 go back to their home position.
The circuits to the high voltage transformers T1+T2.
The relay RY1 remains and oven lamp, blower motor
and antenna motors work for 1 minute.

5. When the door is opened during a cook cycle, the

switches come to the following condition.

            CONDITION
DURING

DOOR OPEN

SWITCH

CONTACT

COOKING

(NO COOKING)

Interlock switches COM-NO

Closed

  Open

Monitor switches

COM-NC

Open

  Closed

Stop switch

COM-NO

Closed

  Open

The circuits to the high voltage transformers T1+T2
are cut off when the interlock and stop switches
SW1+SW2+SW5 are made open. The blower motor
BM, antenna motors and oven lamp  remains on even
if the oven door is opened after the cooking cycle has
been interrupted, because the relay RY1 stays closed.
Shown in the display is the remaining time, but the
program is cancelled if the oven is not started within 1
minute.

6. MONITOR SWITCH CIRCUIT

The monitor switches SW3+SW4 are mechanically
controlled by oven door, and monitors the operation of
the interlock switches SW1+SW2.

6-1. When the oven door is opened during or after the

cycle of a cooking program, the interlock switches
SW1+SW2 and stop switches SW5 must open their
contacts first. After that the contacts (COM-NC) of the
monitor switches SW3+SW4 can be closed.

6-2. When the oven door is closed, the contacts (COM-

NC) of the monitor switches SW3+SW4 must be
opened first. After that the contacts (COM-NO) of the
interlock switches SW1+SW2 and stop switch SW5
must be closed.

6-3. When the oven door is opened and the contacts of the

interlock switch SW1 (or SW2) remain closed, re-
mains closed, the fuse F1 F10A (or F2 F10A)  will
blow, because the monitor switch SW3 (or SW4) is
closed and a short circuit is caused.

When the microwave oven is preset for variable cooking
power, the line voltage is supplied to the high voltage
transformers T1+T2 intermittently within a 48 second time
base through the contacts of the relays RY3+RY4.
The following levels of microwaves power are given.

Closing the door activates all door interlock switches
(interlock switches and stop switch).

When the oven door is closed, the monitor switch contacts
COM-NC must be open. When the microwave oven is
plugged in a wall outlet (230 - 240 volts, 50Hz), the line
voltage is supplied to the control unit through the noise
filter.

1. The digital display shows      .

When the door is opened, the contacts of the interlock
switches SW1+SW2 and stop switch SW5 open, initiating
the following:

1. A signal is input to the control unit energizing the coil of

shut-off relay RY-1.

2. The shut-off relay RY-1 contacts close completing

circuits to turn on the oven lamp, blower motor and
antenna motors.

3. If the door remains open, 60 seconds later the control

unit de-energizes shut-off relay RY-1 turning off the
oven lamp, blower motor and antenna motors.

When the door is closed, the contacts of the interlock
switches SW1+SW2 and stop switch SW5 close. With the
closing of the stop switch SW5 contacts, an additional
circuit is provided which will permit the operation of the
oven when one of the touch pads is depressed. Since the
control is enabled through the stop switch SW5, the door
must be closed before the touch pads will be effective.
When the door is closed, a full 60 second IDLE condition
is always provided for selecting and pressing the desired
touch pads. A 60 second IDLE condition will also follow the
end of each cook cycle.

Touch MANUAL/REPEAT key and enter a desired
cooking time with the touching NUMBER key. And then
touch START key.

CONNECTED COMPONENTS

RELAY

Oven lamp/ Blower motor/ Antenna motors

RY1

High voltage transformer T1

RY3

High voltage transformer T2

RY4

1. The line voltage is supplied to the primary winding of

the two high voltage transformers. 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.

2. 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

5

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.

Two magnetrons MG1+MG2 are equipped in order to get
higher microwave power output. The primary windings of
the high voltage transformers T1+T2 are connected so
that each magnetron can be oscillated alternatively ac-
cording to the frequency of the power supply. Refer to the
Figure B-1 and B-2.

48 sec. ON

Number key   

44sec. ON

Number key 9

40 sec. ON

Number key 8

36 sec. ON

Number key 7

32 sec. ON

Number key 6

26 sec. ON

Number key 5

22 sec. ON

Number key 4

16 sec. ON

Number key 3

12 sec. ON

Number key 2

8 sec. ON

Number key 1

0 sec. ON

Number key 0

T1: HIGH VOLTAGE
      TRANSFORMER

 H. V. RECTIFIER

C1: H.V. CAPACITOR

MG1: MAGNETRON (UPPER)

(REAR)

 H. V. RECTIFIER

 H. V. FUSE

 H. V. FUSE

C2: H.V. CAPACITOR

MG2: MAGNETRON (LOWER)

T2: HIGH VOLTAGE
      TRANSFORMER

(FRONT)

COMMERCIAL
FREQUENCY
(50HZ)

POWER OUTPUT
BY MAGNETRON T1

POWER OUTPUT
BY MAGNETRON T2

OPERATION OF
MAGNETRON

6

1. The door release lever is pulled.
2. The upper latch head is lifted up by the linked door

release lever.

3. The head lever is lifted up by the door release lever.
4. The joint lever is lifted up by the head lever.
5. The lower latch head is lifted up by the joint lever.
6. Now both latch heads are lifted up, so they can be

released from the latch hook.

7. Now the door can be opened.

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.

The monitor switches SW3, SW4 are activated (the con-
tacts opened) the upper latch head and switch lever A
while the door is closed. The switch SW3 (or SW4) is
intended to render the oven inoperative by means of
blowing the fuse F1 F10A (or F2 F10A) when the contacts
of the interlock switch SW1 (or SW2) fail to open when the
door is opened.

Function
1. When the door is opened, the monitor switches SW3

+SW4 contacts close (to the ON condition) due to their
being normally closed. At this time the interlock switch
SW1+SW2 are in the OFF condition (contacts open)
due to their being normally open contact switches.

2. As the door goes to a closed position, the monitor

switches SW3+SW4 contacts are opened and inter-
lock switch SW1+SW2 contacts are closed (On open-
ing the door, each of these switches operate inversely.)

3. If the door is opened and the interlock switch SW1 (or

SW2) contacts fail to open, the fuse F1 F10A (or F2
F10A) blows simultaneously with closing of the monitor
switch SW3 (or SW4) contacts.

CAUTION:BEFORE REPLACING A BLOWN  FUSE F1

F10A (OR F2 F10A) TEST THE INTERLOCK
SWITCH  SW1 (OR SW2) AND MONITOR
SWITCHE SW3 (OR SW4)  FOR PROPER
OPERATION. (REFER TO CHAPTER “TEST
PROCEDURE”).

The noise filter assembly prevents radio frequency inter-
ference that might flow back in the power circuit.

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

circuited, this fuse blows to prevent an electric shock or
fire hazard.

2. The fuse F1 F10A (or F2 F10A) also blows when

interlock switch SW1 (or SW2) remains closed with the
oven door open and when the monitor switches SW3
(or SW4) closes.

If the wire harness or electrical components make a short-
circuit, this weak point F3 blows to prevent an electric
shock or fire hazard.

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

The temperature fuses TF1, TF2 located on the top of the
upper and lower waveguide, are designed to prevent
damage to the magnetrons MG1, MG2. If an over heated
condition develops in the tube due to blower motor failure,
obstructed air ducts, dirty or blocked air intake, etc., the
circuit to the magnetrons are interrupted. Under normal
operation, the temperature fuses remains closed. How-
ever, when abnormally high temperatures are generated
within the magnetrons, the temperature fuses will open at
150˚C causing the microwave energy to stop. The defec-
tive temperature fuses must be replaced with new rated
ones.

The temperature fuse TF3, located on the side of the
exhaust duct assembly, is designed to prevent damage to
the oven by fire. If the food load is overcooked, by either
error in cook time or defect in the control unit, the tempera-
ture fuse will open. Under normal operation, the oven
temperature fuse remains closed. However, when abnor-
mally high temperatures are generated within the oven
cavity, the oven temperature fuse will open at 120˚C,
causing the oven to shut down. The defective temperature
fuse must be replaced with new rated one.

Latch head

SW4: Monitor switch

(Oven side)

SW3: Monitor switch

Latch hook

SW1: Interlock switch

SW2: Interlock switch

(Oven side)

SW5: Stop switch

Latch head

Joint lever

Door release
lever

Head lever