Sharp Carousel R-880FS Service Manual - Page 6

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R-880F(S)

OFF CONDITION

Closing the door activates the 1st. latch switch and 2nd.

interlock relay control switch.

IMPORTANT:

When the oven door is closed, the contacts COM-NC

of the monitor switch must be open. When the mi-

crowave oven is plugged in a wall outlet (230 - 240V

50Hz), the line voltage is supplied to the noise filter

and the control unit.

Figure O-1 on page 33

1. The oven display will show " SHARP MICRO- WAVE

OVEN " .

2. Press the STOP/CLEAR pad. The oven display will

show " :

3. Set the clock as follows.

3-1. Press the CLOCK pad once.

3-2. Enter the time of day by perssing the number

pads.

3-3. Start the clock by pressing the CLOCK pad.

NOTE:

1. If you do not set the clock, " : " will appear on the

display. When the operation of the oven is finished, " :

" will appear on the display instead of the time of day.

2. The oven can be also used when the clock is not set.

3. When the oven door is opened, the oven lamp does not

come on.

MICROWAVE COOKING CONDITION

100% (HIGH) COOKING

Enter a desired cooking time by pressing the number pads

and start the oven by pressing START pad.

Function sequence Figure O-2 on page 33

CONNECTED COMPONENTS

Convection motor

High voltage transformer

Grill heater (Top)

Bottom heater

Fan motor,

Oven lamp, Turntable motor

1. The line 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 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 RY2 + RY5 + RY6 go back to their home

position. The circuits to the oven lamp, high voltage

transformer, fan motor and turntable motor are cut off.

5. When the oven door is opened during a cooking cycle,

the switches come to the following condition.

OPERATION SEQUENCE

Switch

1st. latch switch

2nd. interlock relay

control switch

Monitor Switch

The circuit to the high voltage transformer, fan motor, oven

lamp and turntable motor are cut off when the 1st. latch

switch and 2nd. interlock relay control switch are made

open. Shown in the display is remaining time.

6. MONITOR SWITCH CIRCUIT

The monitor switch is mechanically controlled by the

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

switch and the 2nd. interlock relay RY2.

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 RY2 remain

closed, the fuse F10A will blow, because the monitor

switch is closed and a short circuit is caused.

70% (MEDIUM HIGH), 50% (MEDIUM), 30% (ME-

DIUM LOW), 10% (LOW COOKING)

When the microwave oven is preset for variable cooking

power, the line voltage is supplied to the high voltage

transformer intermittently within a 32-second time base

through the relay contact which is coupled with the cur-

RELAY

rent-limiting relay RY2. The following levels of microwave

RY1

power are given.

RY2

RY3

SETTING

RY4

RY5

RY6

Note: The On/Off time ratio does not exactly correspond

GRILL COOKING CONDITIONS

The oven has three grill cooking condition. They are the

TOP HEATER mode, BOTTOM HEATER mode and TOP

AND BOTTOM HEATER mode.

TOP

In this mode, the food is cooked by the top heaters. Press

the GRILL pad once and then enter the cooking time by

pressing the number pads. When the START pad is

pressed, the following operations occur:

Contact

During

Cooking

COM-NO

Closed

COM-NO

Closed

COM-NC

Opened

32 sec. ON

100%

24 sec. ON

70%

18 sec. ON

50%

12 sec. ON

30%

6 sec. ON

10%

to the percentage of microwave power, because

approx. 3 seconds are needed for heating up the

magnetron filament.

HEATER

MODE

Figure O-3(a) on page 34

Condition

Oven Door

Open(No cooking)

Opened

Closed

100%

8 sec. OFF

Approx. 70%

14 sec. OFF

Approx. 50%

20 sec. OFF

Approx. 30%

26 sec. OFF

Approx. 10%