R-222T(W)
5 – 1
R200K
Service Manual
CHAPTER 5.
OPERATION SEQUENCE
[1] OFF CONDITION
Closing the door activates all door interlock switches (1st. latch switch,
2nd. interlock relay control switch).
IMPORTANT
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, rated voltage is
supplied to the noise filter and the control unit.
Figure O-1 on page 12-1
1. The display will show flashing “88:88”.
2. To set any programmes or set the clock, you must first touch the
STOP/CLEAR key.
3. “ : “ appears in the display.
[2] MICROWAVE COOKING CONDITION
1. HIGH COOKING
Enter a desired cooking time by touching the NUMBER pads and start
the oven by touching START pad.
Function sequence
Figure O-2 on page 12-1
1. Rated voltage is supplied to the primary winding of the power trans-
former. 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 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
(RY1+RY2) go back to their home position. The circuits to the oven
lamp, power transformer, fan motor and turntable motor are cut off.
5. When the door is opened during a cook cycle, the switches come to
the following condition
The circuits to the power transformer, fan motor, turntable motor and
oven lamp are cut off when the 1st. latch switch and 2nd. interlock
relay control switch are made open.
6. MONITOR SWITCH CIRCUIT
The monitor switch is mechanically controlled by oven door, and
monitors the operation of the 1st. latch switch and the 2nd. interlock
relay (RY2).
1) When the oven door is opened during or after the cycle of a
cooking program, the 1st. latch switch and 2nd. interlock relay
control switch must open their contacts first. After that the con-
tacts (COM-NC) of the monitor switch can be closed.
2) When the oven door is closed, the contacts (COM-NC) of the
monitor switch must be opened. After that the contacts of the
1st. latch switch and 2nd. interlock relay control switch are
closed.
3) When the oven door is opened and the contacts of the 1st. latch
switch and the 2nd. interlock relay (RY2) remain closed. The
fuse (T6.3A) will blow, because the monitor switch is closed and
a short circuit is caused.
2. MEDIUM HIGH, MEDIUM, MEDIUM LOW, LOW
COOKING
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 correspond to the
percentage of microwave power, because approx. 3 seconds
are needed for heating up the magnetron filament.
[3] POWER OUTPUT REDUCTION
After 100% power cooking mode is carried out for more than 20 min-
utes, the power out-put is automatically reduced to 70%. Even if the
cooking time is shorter than for 20 minutes, the power output is
reduced to 70% after total cooking time over 20 minutes when the
oven is started in 100% power cooking mode again within 1 minute
and 35 seconds.
CONNECTED COMPONENTS
RELAY
Oven lamp, Fan motor, Turntable motor
RY1
2
Y
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CONDITION
SWITCH
CONTACT DURING
COOKING
DOOR OPEN
(NO COOKING)
1st. latch switch
COM-NO
Closed
Open
2nd. interlock relay
control switch
COM-NO
Closed
Open
Monitor switch
COM-NC
Open
Closed
100P (HIGH)
32 sec. ON
70P (MEDIUM
HIGH)
Approx. 70%
100%
24 sec. ON
8 sec. OFF
14 sec. OFF
20 sec. OFF
26 sec. OFF
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5
18 sec. ON
30P (MEDIUM
LOW)
Approx. 30%
12 sec. ON
%
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W
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1
6 sec. ON
