Sharp Carousel R-350F Service Manual - Page 6

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R-350F

OFF CONDITION

Closing the door activates all door interlock switches

(1st. latch switch and 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 25

1. The display shows "SHARP , MICRO-WAVE and

OVEN".

2. To set any programmes or set the clock, you must

first touch the STOP/CLEAR pad.

appears in the display.

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

comes on at this time.

MICROWAVE COOKING CONDITION

HIGH COOKING

Enter a desired cooking time with the touching NUMBER

pad and start the oven with touching START pad.

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

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 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 switch

COM-NO

2nd. interlock relay

COM-NO

control switch

Monitor switch

COM-NC

The circuits to the power transformer, fan motor and

turntable motor are cut off when the 1st. latch switch

and 2nd. interlock relay control switch are made open.

The oven lamp remains on even if the oven door is

OPERATION SEQUENCE

RELAY

RY1

RY2

CONDITION

DURING

DOOR OPEN

COOKING

(NO COOKING)

Closed

Open

Closed

Open

Closed

opened after the cooking cycle has been interrupted,

because the relay RY1 stays closed. Shown in the

display is the remaining time.

MONITOR SWITCH CIRCUIT

The monitor switch is mechanically controlled by

oven door, and monitors the operation of the 1st. latch

switch and 2nd. interlock relay.

6-1 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 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. latch switch and 2nd. interlock

relay control switch are closed.

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

1st. latch switch and 2nd. interlock relay remain

closed. The fuse F10A 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 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;

HIGH

MEDIUM HIGH

MEDIUM

MEDIUM LOW

LOW

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.

POWER OUTPUT REDUCTION

After 100% power cooking mode is carried out for more

than 40 minutes, the power out-put is automatically re-

duced to 70%.

32 sec. ON

8 sec. OFF

24 sec. ON

Approx. 70%

18 sec. ON

14 sec. OFF

Approx. 50%

12 sec. ON

20 sec. OFF

Approx. 30%

6 sec. ON

26 sec. OFF

Approx. 10%