R-465 (serv.man9). Complete - Sharp Home Appliance Service Manual (repair manual). Page 6

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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.

1. The display will show flashing "88:88".
2. To set any programmes or set the clock, you must

first touch the STOP/CLEAR pad.

3.        :        appears in the display.

NOTE: When the oven door is opened, the oven lamp

comes on at this time.

HIGH COOKING
Enter a desired cooking time with the touching TIME keys
and start the oven with touching STARTkey.

CONNECTED COMPONENTS

RELAY

Oven lamp, Fan motors, Turntable motor

RY1

High voltage transformer

RY2

1. Rated voltage is supplied to the primary winding of the

high voltage transformer. 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 channeled 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, high voltage transformer,
fan motors and turntable motor are cut off.

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. interlock switch

COM-NO

Closed

  Open

2nd. interlock relay
control switch

COM-NO

Closed

  Open

Monitor switch

COM-NC

Open

  Closed

The circuits to the high voltage transformer, fan motors
and turntable motor are cut off when the 1st. interlock
switch  and 2nd. interlock relay control switch are made
open. The 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.

6.

MONITOR SWITCH CIRCUIT
The monitor switch is mechanically controlled by
oven door, and monitors the operation of the 1st.
interlock switch and the relay RY1.

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

cycle of a cooking program, the 1st. interlock switch
and 2nd. interlock relay control switch must open their
contacts first.
After that the contacts (COM-NC) of the monitor
switch can be closed.

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

NC) of the monitor switch must be opened. After that
the contacts of the 1st. interlock switch and 2nd.
interlock relay control switch are closed.

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

the1st. interlock switch and the relay RY1 remain
closed, the fuse F10A will blow, because the monitor
switch is closed and a short circuit is caused.

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 RY2. 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.

After 100% power cooking mode is carried out for more
than 40 minutes, the power out-put is automatically re-
duced to 70%.  Even if the cooking time is shorter than for
40 minutes, the power output is reduced to 70% after total
cooking time over 40 minutes when the oven is started in
100% power cooking mode again within 1 minute and 35
seconds.

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

50P (MEDIUM)

Approx. 50%

18 sec. ON

30P (MEDIUM 

LOW)

Approx. 30%

12 sec. ON

10P (LOW)

Approx. 10%

6 sec. ON