Sharp R-211A Service Manual

R-211A

TABLE OF CONTENTS

Page

CAUTION, MICROWAVE RADIATION .............................................................................................................. 1

WARNING............................................................................................................................................................1

PRODUCT SPECIFICATIONS........................................................................................................................... 2

GENERAL INFORMATION ................................................................................................................................. 2

APPEARANCE VIEW......................................................................................................................................... 3

OPERATION SEQUENCE ................................................................................................................................. 4

FUNCTION OF IMPORTANT COMPONENTS ................................................................................................... 5

SERVICING ........................................................................................................................................................ 6

TEST PROCEDURE .......................................................................................................................................... 8

COMPONENT REPLACEMENT AND ADJUSTMENT PROCEDURE............................................................. 13

MICROWAVE MEASUREMENT ...................................................................................................................... 19

WIRING DIAGRAM .......................................................................................................................................... 20

PICTORIAL DIAGRAM..................................................................................................................................... 21

PARTS LIST...................................................................................................................................................... 22

In interests of user-safety the oven should be restored to its original
condition and only parts identical to those specified should be used.

MODEL

R-211A

S5709R211APX/

MICROWAVE OVEN

SHARP CORPORATION

SER VICE MANU AL

OPEN DOOR

COOKING CONTROL

TIMER

0

5

20

25

10

15

0.5 kg

30

1 kg



DEFROST (Kg)

M

E

D

D

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F

R

O

S

H

I

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H

R-211A

R-211A

1

SER VICE MANUAL

SHARP CORPORATION

OSAKA, JAPAN

MICROWAVE OVEN

R-211A

GENERAL IMPORTANT INFORMATION

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.

CAUTION

MICROWAVE RADIATION

DO NOT BECOME EXPOSED TO RADIATION FROM
THE MICROWAVE GENERATOR OR OTHER PARTS
CONDUCTING MICROWAVE ENERGY.

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.

WARNING

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 potential above
250V.

All the parts marked "∆" on parts list may cause undue
microwave exposure, by themselves, or when they are dam­aged, loosened or removed.

TEST PROCEDURE

SERVICING AND
TROUBLESHOOTING CHART

FUNCTION OF IMPORTANT
COMPONENTS

OPERATING SEQUENCE

APPEARANCE VIEW

WIRING DIAGRAM

PARTS LIST

COMPONENT REPLACEMENT
AND ADJUSTMENT PROCEDURE

MICROWAVE MEASUREMENT

PRODUCT SPECIFICATIONS

2

R-211A

PRODUCT DESCRIPTION

SPECIFICATION

ITEM DESCRIPTION

Power Requirements 220 Volts

50 Hertz

Single phase, 3 wire earthed
Power Consumption 1.06 KW
Power Output 700 watts nominal of RF microwave energy (IEC-705-1988)

Operating fequency 2450 MHz

Case Dimensions Width 450 mm

Height 295 mm including foot

Depth 357 mm
Cooking Cavity Dimensions Width 285 mm

Height 178 mm

Depth 316 mm
Turntable diameter 272mm
Control Complement 30 min. Single Speed Timer.

Microwave Power for Variable Cooking

Repetition Rate;

HIGH .................................. Full power throughout the cooking time

MEDIUM / DEFROST......................... approx. 45% of FULL Power

Set Weight (Approx.) Approx. 14 kg

GENERAL INFORMATION

WARNING

THIS APPLIANCE MUST BE EARTHED

IMPORTANT

THE WIRES IN THIS MAINS LEAD ARE COLOURED IN ACCORDANCE WITH THE FOLLOWING CODE:

GREEN-AND-YELLOW : EARTH
BLUE : NEUTRAL
BROWN : LIVE

R-211A

3

APPEARANCE VIEW

OVEN

6. Coupling

7. Control panel

8. Door lock openings

9. Ventilation openings

1. Power supply cord

2. Oven lamp

3. Door hinges

4. Safety door latches

5. Door

3

2

4

5

6

7

8

1

9

COOKING CONTROL

TIMER

OPEN DOOR

0

5

20

25

10

15

0.5 kg

30

1 kg





DEFROST (Kg)

M

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VARIABLE COOKING CONTROL
There are power levels. The approximate
percentage of microwave power for each 
setting is:

HIGH 100%
MEDIUM/DEFROST 45%

TIMER (0 - 30 min.)
Turn to set cooking time.

DOOR OPEN BUTTON

COOKING CONTROL

TIMER

OPEN DOOR

0

5

20

25

10

15

0.5 kg

30

1 kg





DEFROST (Kg)

M

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MEAT DEFROST GUIDE
(Inner scale)

CONTROL PANEL

4

R-211A

OPERATION SEQUENCE

cycle of a cooking program, the 1st latch switch and
2nd latch switch must open their (COM-NO) contacts
first. After that the contacts (COM-NC) of the monitor
switch can be closed.

7-2. 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 and the
1st latch switch must be closed.

7-3. When the oven door is opened and the (COM-NO)

contacts of the 1st latch switch and the contacts
(COM-NO) of the 2nd latch switch remain closed, the
fuse M6.3A will blow, the monitor switch is closed and
a short circuit is caused.

HIGH, MEDIUM / DEFROST COOKING

When the microwave oven is preset for variable cooking
power, the rated voltage is supplied to the power trans­former intermittently within a 30-second time base through
the vari switch. The following levels of microwave power
are given.

SETTING

HIGH Approx. 100%

Approx. 45%

30 sec. ON

MEDIUM DEFROST

13.5 sec. ON 16.5 sec. OFF

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.

OFF CONDITION

1. When the timer knob is at " 0 ", the oven is OFF
condition.

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

IMPORTANT:
When the oven door is closed, the contacts COM-NC of
the monitor switch must be open.

Figure O-1 on page 20

MICROWAVE COOKING CONDITION

HIGH COOKING

Set the variable cooking control to HIGH and then set the
timer.

Function sequence

Figure O-2 on page 20

1. Following components are energized.

Power transformer H.V. capacitor Timer motor
Magnetron H.V. rectifier Fan motor

Turntable motor Oven lamp

2. 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.

3. The filament winding voltage (3.3 volts) heats the
magnetron filament and the high voltage (2000 volts) is
sent to the voltagedoubling circuit, where it is doubled
to negative voltage of approximately 4000 volts D.C..

4. 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.

5. When the cooking time is up, the timer returns to "0",
the bell rings and the contacts of the timer are opened.
Then following components are turned off.

Power transformer Magnetron Timer motor
Turntable motor H.V. capacitor Fan motor

H.V. rectifier Oven lamp

6. When the oven door is opened during a cooking cycle,
the switches come to the following positions and they
are common to the other cooking conditions too.

Switch Contact Condition

During Oven Door

Cooking Open(No cooking)
1st latch Switch COM-NO Closed Opened
Monitor Switch COM-NC Opened Closed
2nd latch switch COM-NO Closed Opened

The circuit to the power transformer, turntable motor,
timer motor, fan motor and oven lamp are cut off when
the COM-NO contacts of the 2nd latch switch and 1st
latch switch are made open. The timer stops to indicate
how much cooking time remains.

7. MONITOR SWITCH CIRCUIT
The monitor switch is mechanically controlled by the
oven door, and monitors the operation of the 1st latch
switch and 2nd latch switch.

7-1. When the oven door is opened during or after the

R-211A

5

FUNCTION OF IMPORTANT COMPONENTS

DOOR OPEN MECHANISM

The door is opened by pushing the open button on the
control panel, refer to the Figure D-1.
When the open button is pushed, the open button pushes
the switch lever up and in turn the latch heads are released
from latch hook. When the latch heads are released, the
switch lever returns to its original position by its own
weight.

LATCH HOOK

LATCH
HEADS

DOOR

MONITOR SWITCH

1 ST. LATCH
SWITCH

SWITCH LEVER

2ND. LATCH
SWITCH

Figure D-1. Door Open Mechanism

1ST. LATCH SWITCH AND 2ND. LATCH SWITCH

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

2. When the oven door is opened, the contacts (COM­NO) must be opened.

MONITOR SWITCH

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

2. When the oven door is opened, the contacts (COM­NC) must be closed.

3. If the oven door is opened and the contacts (COM-NO)
of the 1st latch switch and 2nd latch switch fail to open,
the fuse blows simultaneously with closing the con­tacts (COM-NC) of the monitor switch.

CAUTION: BEFORE REPLACING A FUSE F TEST

THE 1ST LATCH SWITCH SW1, 2ND LATCH
SWITCH, MONITOR SWITCH AND MONI­TOR RESISTOR R FOR PROPER OPERA­TION. (REFER TO CHAPTER "TEST PRO­CEDURE".)

MONITOR RESISTOR 0.8Ω 20W
The monitor resistor prevents the fuse F bursting when

the fuse blows due to the operation of the monitor
switch.

FUSE

1. The fuse blows when the contacts (COM-NO) of the 1st
latch switch and 2nd latch switch remain closed with
the oven door open and when the monitor switch
closes.

2. If the wire harness or electrical components are short­circuited, the fuse blows to prevent an electric shock of
fire hazard.

TEMPEATURE FUSE 120˚C (OVEN)

The temp. fuse located on the top of the oven cavity is
designed to prevent damage to the oven if the foods in the
oven catch fire due to over heating produced by improper
setting of cook time or failure of control unit. Under normal
operation, the temp. fuse remains closed. However, when
abnormally high temperatures are reached within the
oven cavity, the temp. fuse will open at 120˚C, causing the
oven to shut down. The defective fuse must be replaced
with a new one.

THERMAL CUT-OUT 95˚C (MAGNETRON )

The thermal cut-out located on the top of the oven cavity
is designed 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 95˚C, causing the oven to shut down. When the
magnetron has cooled to 75˚, the thermal cut-out closes
and cook cycle will resume.

TURNTABLE MOTOR

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

FAN MOTOR

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

TIMER MOTOR (WITH VARI-SWITCH)

Timer switch

1. When the timer is at "0" position, the switch of the timer
are opened.

2. When the timer is turned clockwise from "0" position,
the switch of the timer are closed.

Vari-switch

If the variable cooking control is set at HIGH or ME­DIUM DEFROST, cooking position, Rated voltage is
supplied to the power transformer intermittently within
a 30 seconds time base. The following chart shows the
vari-switch operation in the various modes.
are given.

SETTING

HIGH Approx. 100%

Approx. 45%

30 sec. ON

MEDIUM DEFROST

13.5 sec. ON 16.5 sec. OFF

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.

6

R-211A

SERVICING

REMEMBER TO CHECK 4R

1) Reconnect all leads removed from components
during testing.

2) Replace the outer case (cabinet).

3) Reconnect the supply.

4) Run the oven. Check all functions.

Microwave ovens should not be run empty. To test for
the presence of microwave energy within a cavity, place
a cup of cold water on the oven turntable, close the door
and set the power level to HIGH. And set the microwave
timer for two (2) minutes. When the two minutes has
elapsed (timer at zero) carefully check that the water is
now hot. If the water remains cold carry out 3D checks
and re-examine the connections to the component
being tested.

REMEMBER TO CHECK 3D

1) Disconnect the supply.

2) Door opened, and wedged open.

3) Discharge high voltage capacitor.
WARNING AGAINST THE CHARGE OF THE

HIGH-VOLTAGE CAPACITOR

The high-voltage capacitor remains charged
about 60 seconds after the oven has been
switched off. Wait for 60 seconds and then short­circuit the connection of the high-voltage capaci­tor (that is, of the connecting lead of the high­voltage rectifier) against the chassis with the use
of an insulated screwdriver.

Sharp recommend that wherever possible fault-finding
is carried out with the supply disconnected. It may in,
some cases, be necessary to connect the supply after
the outer case has been removed, in this event carry out
3D checks and then disconnect the leads to the primary
of the power transformer. Ensure that these leads
remain isolated from other components and the oven
chassis. (Use insulation tape if necessary.) When the
testing is completed carry out 3D checks and reconnect
the leads to the primary of the power transformer.

When all service work is completed, and the oven is fully assembled, the microwave power output should be checked
and microwave leakage test carried out.

When troubleshooting the microwave oven, it is helpful to
follow the Sequence of Operation in performing the
checks. Many of the possible causes of trouble will require
that a specific test be performed. These tests are given a
procedure letter which will be found in the "Test Procedure
"section.

TROUBLESHOOTING GUIDE

IMPORTANT: If the oven becomes inoperative because

of a blown fuse M6.3A in the 1st. latch
switch - 2nd. latch switch - monitor switch

- monitor resistor circuit, check the 1st.
latch switch, 2nd. latch switch, monitor
switch and monitor resistor before replac­ing the fuse M6.3A.

WARNING TO SERVICE PERSONNEL

Microwave ovens contain circuitry capable of producing very high voltage and current. Contact with following parts
will result in electrocution.
High voltage capacitor, Power transformer, Magnetron, High voltage rectifier assembly, High voltage harness.

R-211A

7

TROUBLESHOOTING CHART

PROBLEM

Fuse M6.3A blows when power
cord is plugged into wall outlet.

Fuse M6.3A blows when
the door is opened.

Home fuse blows when
power cord is plugged into
wall outlet.

Oven does not operate at all.
Oven goes into cook cycle

but shuts down before end of
cooking cycle.

Oven lamp does not light.
(Fan motor rotates)

Fan motor does not operate,
but oven lamp lights.

Timer motor does not oper­ate, but oven lamp lights.

Turntable motor does not op­erate, but oven lamp lights.

Oven seems to be operating
but little or no heat is pro­duced in oven load. (Micro­wave power control is set at
"HIGH" position, and turnta­ble motor operates.)

Oven does not operate prop­erly in another position ex­cept "HIGH" position.

POSSIBLE CAUSE

AND

DEFECTIVE PARTS

TEST PROCEDURE

OFF
CONDITION

CONDITION

MAGNETRON

POWER TRANSFORMER

H.V. RECTIFIER ASSEMBLY

HIGH VOLTAGE CAPACITOR

1ST. LATCH SWITCH

2ND. LATCH SWITCH

MONITOR SWITCH

TEMPERATURE FUSE 120˚C (OVEN)

THERMAL CUT-OUT 95˚C (MG)

TIMER MOTOR

TIMER CONTACT

TIMER DEFROST SWITCH

FAN MOTOR

TURNTABLE MOTOR

FUSE M6.3A

POWER SUPPLY CORD

SHORTED WIRE HARNESS

OPENED WIRE HARNESS

OVEN LAMP OR SOCKET

BLOCKED VENTILATION OPENING

MISADJUSTMENT SWITCH

HOME FUSE OR BREAKER

WALL OUTLET

BLOCKED COOLING FAN

POWER SELECT SWITCH

ABCDEEEGGJ J JHHI E

COOKING
CONDITION