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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
for R-22AT  and R-24AT
Check indicators after the oven
starts to confirm the oven is oper-
ating 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 SLEVEL 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

DISPLAY AND INDI-
CATORS for R-23AM
Check indicators after
the oven starts to con-
firm the oven is operat-
ing as desired.

1. Cook indicator

This indicator shows
cooking in progress.

2. Time display
3. Microwave power level

display

4. HIGH

100%

5. MEDIUM

50%

6. MED LOW 20%
7. DEFROST 10%
8. TIME CONTROL

Rotate the control to en-
ter cooking time.

9. START button

MICROWAVE
POWER LEVEL
buttons

START

HIGH

MEDIUM

MED LOW

DEFROST

TIME 
CONTROL

4

5

6

7

8

9

2
1

3

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/

REHEAT

STOP / CLEAR

POWER LEVEL

START

SET

CHECK

VOLUME

DOUBLE

QUANTITY

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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
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 (for R-22AT/24AT)/ RY2+RY3
(for R-23AM) 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
stirrer 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)

1st latch switch

COM-NO

Closed

  Open

Monitor switch

COM-NC

Open

  Closed

2nd latch switch

COM-NO

Closed

  Open

Stop switch

COM-NO

Closed

  Open

3rd latch switch

COM-NO

Closed

  Open

The circuits to the high voltage transformers T1+T2 are
cut off when the 1st latch, 2nd latch, 3rd latch and stop
switches SW1+SW2+SW3+SW5 are made open. The
blower motor BM, stirrer motors and oven lamp  re-
mains 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 remain-
ing time, but the program is cancelled if the oven is not
started within 3 minutes.

6. MONITOR SWITCH CIRCUIT

The monitor switch SW4 is mechanically controlled by
oven door, and monitors the operation of the 1st latch
switch SW1.

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

cycle of a cooking program, the 1st, 2nd, 3rd latch and
stop switches SW1+SW2+SW3+SW5 must open their
contacts first. After that the contacts (COM-NC) of the
monitor switch SW4 can be closed.

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

NC) of the monitor switch SW4 must be opened first.
After that the contacts (COM-NO) of the 1st, 2nd, 3rd
latch and stop switches SW1+SW2+SW3+SW5 must
be closed.

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

1st latch switch SW1 remain closed, remains closed,
the fuse F2 F6.3A will blow, because the monitor
switch is closed and a short circuit is caused.

When the microwave oven is preset for variable cooking

Closing the door activates all door interlock switches (1st
latch switch, 2nd latch switch, 3rd latch switch 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 point A5+A7 in the control panel
through the noise filter.

1. The digital display shows      .

When the door is opened, the contacts of the 1st. latch
switch SW1, 2nd. latch switch SW2, 3rd. latch switch SW3
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
stirrer 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 stirrer motors.

When the door is closed, the contacts of the 1st. latch
switch SW1, 2nd. latch switch SW2, 3rd. latch switch SW3
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/ Stirrer motors

RY1

High voltage transformer T1

RY3

High voltage transformer T2

RY4

Enter a desired cooking time with the turning TIME
CONTROL knob. And then push STARTbutton.

CONNECTED COMPONENTS

RELAY

Oven lamp/ Blower motor/ Stirrer motors

RY1

High voltage transformer T1

RY2

High voltage transformer T2

RY3

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

5

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.

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.

When the microwave oven is preset for variable cooking
power, the line voltage is supplied to the high voltage
transformers intermittently within a 48 second time base
through the contacts of the relays RY2+RY3.
The following levels of microwaves power are given.

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.

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

48 sec. ON

100% 

26sec. ON

50%

12 sec. ON

20%

8 sec. ON

10%

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

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.

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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 switch SW4 is activated (the contacts opened)
the upper latch head and switch lever A while the door is
closed. The switch is intended to render the oven inopera-
tive by means of blowing the fuse F2 F6.3A when the
contacts of the 1st latch switch SW1 fail to open when the
door is opened.

Function
1. When the door is opened, the monitor switch SW4

contacts close (to the ON condition) due to their being
normally closed. At this time the 1st latch switch SW1
is 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

switch SW4 contacts are opened and 1st latch switch
SW1 contacts are closed (On opening the door, each
of these switches operate inversely.)

3. If the door is opened and the 1st latch switch SW1

contacts fail to open, the fuse F2 F6.3A blows simulta-
neously with closing of the monitor switch SW4 con-
tacts.

CAUTION:BEFORE REPLACING A BLOWN FUSE F2

F6.3A TEST THE 1ST LATCH SWITCH SW1,
MONITOR SWITCH SW4 AND MONITOR
RESISTOR R1 FOR PROPER OPERATION.
(REFER TO CHAPTER “TEST PROCE-
DURE”).

The monitor resistor R1 prevents the fuse F2  F6.3A 250V
bursting when the fuse F 2 F6.3A 250V blows due to the
operation of the monitor switch SW4.

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

If the wire harness or electrical components make a short-
circuit, this fuse F1 (F13A) blows to prevent an electric
shock or fire hazard.

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 F2 also blows when 1st latch switch SW1

remains closed with the oven door open and when the
monitor switch closes.

If the wire harness or the high voltage transformers T1, T2
are short-circuited, these fuses F3 and /or F4 blow 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 TF4, 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

Latch head

SW4: Monitor switch

Latch hook

SW1: 1st. latch switch

SW2: 2nd. latch switch

SW5: Stop switch

SW3: 3rd. latch switch

Latch head

Joint lever

Door release
lever

Head lever