Sharp Carousel II R-3A54 Service Manual - Page 6

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R -3A54

R-3E54

OPERATING

SEQUENCE

OFF CONDITION

Closing

the door activates

all door interlock

switches

(1 st latch switch,

2nd latch switch

and stop switch).

IMPORTANT

When

the oven

door

is closed,

the monitor

switch

contacts

(COM -

NC) rnust be open.

When the microwave

oven is plugged

in a wall outlet.

Rated voltage

is supplied

to the point A3+

A5 in the

control

unit.

3 L.

Figure

O-l

on page 29

The display flashes "88:88".

To set any programmes

or set the clock, you must

first touch the STOP/CLEAR

key.

11 . .

II appears in the display

and the time counts

up every minute.

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

key and start the oven with touching

START key.

Function

sequence

Figure

O-2 on page 29

CONNECTED

COMPONENTS

RELAY

Oven lamp, Fan motor, Turntable

motor

RYl

Power transformer

RY2

Rated voltage

is supplied

to the primary winding

the power transformer.

The voltage

is converted

about 3.3 volts A.C. output

on the filament

winding

and high voltage

of approximately

2000 volts A.C.

on the secondary

winding.

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..

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.

When the cooking

time is up, a signal tone is heard

and the relays RYI + RY2 go back to their home

position.

The circuits

to the oven

lamp,

power

transformer,

fan motor and turntable

motor are cut

off.

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 latch switch

COM - NO

Closed

Open

Monitor

switch

COM -NC

Open

Closed

2nd latch switch

COM - NO

Closed

Open

Stop switch

COM - NO

Closed

Open

The circuits to the power transformer,

fan motor and

turntable

motor

are cut

off

when

the

1st

latch

switch,

2nd latch switch

and stop switch

are made

open.

The oven lamp remains on even if the oven door is

opened

after the cooking

cycle

has been

inter-

rupted, because the relay RYI stays closed.

Shown

in the display

is the remaining

time.

6. MONITOR

SWITCH

CIRCUIT

The monitor

switch

is mechanically

controlled

oven door,

and monitors

the operation

of the 1 st

and 2nd latch switches.

6-l

When the oven door is opened during

or after the

cycle

of a cooking

program,

the 1 st latch,

2nd

latch and stop switches

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)

the

monitor

switch

must

opened.

After that the contacts

of the 1st latch,

2nd latch and stop switches

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

cook-

ing power,

240 volts

A.C. power

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

32 sec. ON

HIGH

MEDIUM

HIGH

MEDIUM

LOW

24 sec. ON

8 sec. OFF

18 sec. ON

14 sec. OFF

J-1

Approx.

50%

12 sec. ON

20 sec. OFF

6 sec. ON

26 sec. OFF

J-1

Approx

10%

NOTE: The ON/OFF

time ratio does not exactly

corre-

spond to the percentage

of microwave

power,

because

approx.

2 seconds

are needed

for

heating

up the magnetron

filament.