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1

This Manual has been prepared to provide Sharp Corp. Service
engineers with Operation and Service Information.

It is recommended that service engineers carefully study the
entire text of this manual, so they will be qualified to render
satisfactory customer service.

Service engineers should not be exposed to the microwave
energy which may radiate from the magnetron or other
microwave generating devices if it is improperly used or
connected. All input and output microwave connections,
waveguides, flanges and gaskets must be secured. Never
operate the device without a microwave energy absorbing
load attached. Never look into an open waveguide or
antenna while the device is energized.

Never operate the oven until the following points are ensured.
(A) The door is tightly closed.
(B) The door brackets and hinges are not defective.
(C) The door packing is not damaged.
(D) The door is not deformed or warped.
(E) There is not any other visible damage with the oven.

Servicing and repair work must be carried out only by trained
service engineers.

All the parts marked "*" on parts list are used at voltages more
than 250V.

Removal of the outer wrap gives access to potentials above
250V.

All the parts marked "

∆

" on parts list may cause undue micro-

wave exposure, by themselves, or when they are damaged,
loosened or removed.

PRODUCT SPECIFICATIONS

APPEARANCE VIEW

OPERATING SEQUENCE

FUNCTION OF IMPORTANT
COMPONENTS

SERVICING AND
TROUBLESHOOTING CHART

TEST PROCEDURE

TOUCH CONTROL PANEL
ASSEMBLY

COMPONENT REPLACEMENT
 AND ADJUSTMENT PROCEDURE

MICROWAVE MEASUREMENT

WIRING DIAGRAM

PARTS LIST

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1 Door opening handle
2 Control panel
3 Digital display
4 See through door
7 Door latches
6 Door hinges
7 Door seals and sealing surfaces
8 Coupling
9 Oven cavity
10 Oven lamp
11 Waveguide cover
12 Ventilation openings
13 Outer case cabinet
14 Power cord
15 Turntable
16 Turntable support

1. EXPRESS COOK keys

Use to cook 7 popular foods.

2. EXPRESS DEFROST keys

Use to defrost 3 popular foods.

3. INSTANT COOK keys

Use to cook 3 popular foods. menus. (See NOTE.)

4. DIGITAL DISPLAY
5. WEIGHT CONVERSION key

Use to change weight, e.g. Kg/g to Lb/oz.

6. KITCHEN TIMER key

Press to use as a minute timer, or to programme
standing time.

7. TIME key

Use to enter clocking time.

8. POWER LEVEL key

Press to select microwave power level.

9. START/ AUTO MINUTE key

Press to start a programme. Press to cook on 100P for
1 minute on or increase time during cooking in multiples
of 1 minute. (See NOTE.)

10.STOP/CLEAR key

Press once to stop a programme, twice to cancel a
programme.

11.LESS/ MORE keys

Press to shorten/ lengthen cooking time.

12.WEIGHT keys

Press up or down to select correct weight/ number of
pieces.
When the minimum (or maximum) weight/ number is
reached, the display will not change, even if you
continue to press the DOWN (or UP) key.

13.CLOCK SET key

Use to set the clock or display the time.

4

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 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

5

The thermal cut-out, located on the top of the oven cavity,
is designed to prevent damage to the oven by fire. If the
foods load is overcooked, by either error in cook time or
defect in the control unit, the thermal cut-out will open.
Under normal operation, the oven thermal cut-out remains
closed. However, when abnormally high temperatures are
reached within the oven cavity, the oven thermal cut-out
will open at 125˚C, causing the oven to shut down. The
defective thermal cut-out must be replaced with new one.

The thermal cut-out located near the magnetron is de-
signed to prevent damage to the magnetron if an over
heated condition develops in the tube due to cooling fan
failure, obstructed air guide, dirty or blocked air intake, etc.
Under normal operation, the thermal cut-out remains
closed. However, when abnormally high temperatures are
reached within the magnetron, the thermal cut-out will
open at 125˚C causing the oven to shut down.  The
defective thermal cut-out must be replaced with new one.

The thermostat protects the high voltage transformer
against over heating. If the temperature goes up higher
than 150˚C because the fan motor is interrupted or the
ventilation openings are blocked, the thermostat will cycle,
line voltage to the high voltage transformer will also cycle.
(If operated, check the magnetron for damage.)

The turntable motor drives the turntable roller assembly to
rotate the turntable.

The fan motor drives a blade which draws external cool air.
This cool air is directed through the air vents surrounding
the magnetron and cools the magnetron. This air is
channeled through the oven cavity to remove steam and
vapors given off from the heating foods. It is then ex-
hausted through the exhausting air vents at the oven
cavity

The noise filter prevents the radio frequency interference
that might flow back in the power circuit.

The door is opened by pulling the door, refer to the Figure
D-1.

1. When the oven door is closed, the contacts  (COM-NO)

must be closed.

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

NO) must be opened.

1. When the oven door is closed, the contacts (COM-NC)

must be opened.

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

NC) must be closed.

3. If the oven door is opened and the contacts (COM-NO)

of the 1st. interlock switch and the relay RY1 fail to
open, the fuse blows  simultaneously with closing the
contacts (COM-NC) of the monitor switch.

CAUTION: BEFORE REPLACING A BLOWN FUSE

TEST THE 1ST. INTERLOCK SWITCH,  RE-
LAY  RY1, MONITOR SWITCH AND MONI-
TOR RESISTOR FOR PROPER OPERA-
TION.

Ω

The monitor resistor prevents the fuse bursting when the
fuse blows due to the operation of the monitor switch.

The high voltage fuse blows when the high voltage rectifier
or magnetron is shorted.

1. The fuse blows when the contacts (COM-NO) of the

1st. interlock switch and the relay RY1 remain closed
with the oven door open and when the monitor switch
closes.

2. If the wire harness or electrical components are short-

circuited, this fuse blows to prevent an electric shock or
fire hazard.

Latch 
Heads

Door

Latch Hook

2nd. Interlock
Relay Control
Switch

1st. Interlock
Switch

Monitor Switch