Sharp Carousel R-210D Service Manual - Page 6

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R-210D

OFF CONDITION

Closing the door activates all door interlock switches

(1st. latch switch, 2nd. latch switch and stop 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 25

MICROWAVE COOKING CONDITION

HIGH COOKING

Select the power level HIGH by pressing the power level

button until the power level indicator indicates "HIGH".

And set the cooking time by rotating the Light Up Dial.

Function sequence

Figure O-2 on page 25

CONNECTED COMPONENTS

Oven lamp, Fan motor, Turntable motor

Power transformer

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

power 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 sec-

ondary 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 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.

SWITCH

CONTACT

1st. latch switches COM-NO

2nd. latch switch

COM-NO

Monitor switch

COM-NC

Stop switch

COM-NO

The circuits to the power transformer, fan motor, turn-

table motor and the oven lamp are cut off when the 1st.

latch switch, 2nd. latch switch, and stop switch are

made open.

6. MONITOR SWITCH CIRCUIT

The monitor switch is mechanically controlled by oven

door, and monitors the operation of the 1st and 2nd.

latch switches.

OPERATION SEQUENCE

RELAY

RY1

RY2

CONDITION

DURING

DOOR OPEN

COOKING

(NO COOKING)

Closed

Open

Closed

Open

Closed

Open

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

cycle of a cooking program, the 1st. latch and stop

switch must open their contacts first. After that the

contacts (COM-NC) of the monitor switch can be

closed and the contacts (COM-NO) of the 2nd. latch

switch can be opened.

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

NC) of the monitor switch must be opened and the

contacts (COM-NO) of the 2nd. latch switch must be

closed. After that the contacts of the 1st. latch switch

and stop switch are closed.

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

1st and 2nd latch switches remain closed. The fuse

M8A will blow, because the monitor switch is closed

and a short circuit is caused.

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 27-second time base through the

relay contact which is coupled with the current-limiting

relay. The following levels of microwave power are given.

SETTING;

27 sec. ON

HIGH

21 sec. ON

MEDIUM HIGH

15 sec. ON

MEDIUM

9 sec. ON

MEDIUM LOW

5 sec. ON

LOW

NOTE: The ON/OFF time ratio does not exactly corre-

spond to the percentage of microwave power,

because approx. 2 seconds are needed for heat-

ing up the magnetron filament.

6 sec. OFF

Approx. 70%

12 sec. OFF

Approx. 50%

18 sec. OFF

Approx. 30%

22 sec. OFF

Approx. 10%