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R22AMM

4 – 1

R22AMM

Service Manual

 

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

IMPORTANT

                                    Figure O-1 on page 12-1 

1. The digital display shows “  .  0”.

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

                                     Figure O-2 on page 12-1

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-ener-

gizes 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 select-
ing and pressing the desired touch pads. A 60 second IDLE condition
will also follow the end of each cook cycle.

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

NOTE: The programme and the check are canceled when any keys

are not touched for more than 3 minutes during programming.

Function sequence 

                           Figure O-3 on page 12-2

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 approxi-
mately 2000 volts A.C. on the secondary winding.

2. The filament winding voltage (3.3 volts) heats the magnetron fila-

ment and the high voltage (2000 volts) is sent to the voltage dou-
bling circuit, where it is doubled to negative voltage of
approximately 4000 volts D.C.. 

3. The 2450 MHz microwave energy produced in the magnetron gen-

erates 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.

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, 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).

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.

2) When the oven door is closed, the contacts (COMNC) 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.

3) When the oven door is opened and the contacts of the interlock

switch (SW1 or SW2) remain closed, remains closed, the fuse
F10A (F1 or F2) 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) inter-
mittently 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 correspond to the

percentage of microwave power, because approx. 3 seconds
are needed for heating 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 according to the frequency of the power supply.
Refer to the Figure B-1 and B-2.

CONNECTED COMPONENTS

RELAY

Oven lamp/ Blower motor/ Antenna motors 

RY1

High voltage transformer T1 

RY3

High voltage transformer T2 

RY4

CONDITION

SWITCH CONTACT 

DURING 

COOKING

DOOR OPEN 

(NO COOKING)

Interlock switches 

COM-NO

Closed

Opened

Monitor switch   

COM-NC

Opened 

Closed

Stop switch        

COM-NO

Closed 

Opened

48 sec. ON

100%

26 sec. ON

50%

12 sec. ON

20%

8 sec. ON

10%

R22AMM

4 – 2

Figure B-1. High Voltage Circuit

Figure B-2. Operation of Magnetron

T1: HIGH VOLTAGE

TRANSFORMER

H. V. RECTIFIER

C1:
H.V.

C

APACITOR

MG1: MAGNETRON (UPPER)

(REAR)

H. V. RECTIFIER

H. V. FUSE

H. V. FUSE

C2:
H.V.

C

APACITOR

MG2: MAGNETRON (LOWER)

T2: HIGH VOLTAGE

TRANSFORMER

(FRONT)

COMMERCIAL

FREQUENCY

(50HZ)

POWER OUTPUT

BY MAGNETRON T1

POWER OUTPUT

BY MAGNETRON T2

OPERATION OF

MAGNETRON