Sharp R300bw Owner's Manual

SER VICE MANU AL

S5811R300BPW/

MICROWAVE OVEN

R-300BW

MODEL

R-300BW

COOKING CONTROL

DEFROST

MED

MED LOW

MED

HIGH

LOW

HIGH

t

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p

g

i

D

L

i

a

l

2

3

1

4

5

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7

0

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30

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25

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20

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15

14

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

WARNING TO SERVICE PERSONNEL: Microwave ovens con­tain circuitry capable of producing very high voltage and
current, contact with following parts may result in a severe,
possibly fatal, electrical shock. (High Voltage Capacitor, High
Voltage Power Transformer, Magnetron, High Voltage Recti­fier Assembly, High Voltage Harness etc..)

TABLE OF CONTENTS

Page
PRECAUTIONS TO BE OBSERVED BEFORE AND DURING SERVICING TO

AVOID POSSIBLE EXPOSURE TO EXCESSIVE MICROWAVE ENERGY ...................INSIDE FRONT COVER

BEFORE SERVICING ......................................................................................................INSIDE FRONT COVER

WARNING TO SERVICE PERSONNEL................................................................................................................1

MICROWAVE MEASUREMENT PROCEDURE ...................................................................................................2

FOREWORD AND WARNING............................................................................................................................... 3

PRODUCT SPECIFICATIONS ..............................................................................................................................4

GENERAL INFORMATION................................................................................................................................... 4

OPERATION..........................................................................................................................................................6

TROUBLESHOOTING GUIDE ..............................................................................................................................9

TEST PROCEDURE ............................................................................................................................................10

CONTROL PANEL...............................................................................................................................................17

COMPONENT REPLACEMENT AND ADJUSTMENT PROCEDURE ................................................................21

PICTORIAL DIAGRAM ........................................................................................................................................27

CONTROL PANEL CIRCUIT ...............................................................................................................................28

PRINTED WIRING BOARD .................................................................................................................................29

PARTS LIST ........................................................................................................................................................30

PACKING AND ACCESSORIES .........................................................................................................................32

SHARP CORPORATION

This document has been published to be used for after
sales service only.
The contents are subject to change without notice.

R-300BW

PRECAUTIONS TO BE OBSERVED BEFORE AND
DURING SERVICING TO AVOID POSSIBLE
EXPOSURE TO EXCESSIVE MICROWAVE
ENERGY

(a) Do not operate or allow the oven to be operated with the door open.
(b) Make the following safety checks on all ovens to be serviced before activating the magnetron or other

microwave source, and make repairs as necessary: (1) interlock operation, (2) proper door closing, (3)
seal and sealing surfaces (arcing, wear, and other damage), (4) damage to or loosening of hinges and
latches, (5) evidence of dropping or abuse.

(c) Before turning on microwave power for any service test or inspection within the microwave generating

compartments, check the magnetron, wave guide or transmission line, and cavity for proper alignment,
integrity, and connections.

(d) Any defective or misadjusted components in the interlock, monitor, door seal, and microwave

generation and transmission systems shall be repaired, replaced, or adjusted by procedures described
in this manual before the oven is released to the owner.

(e) A microwave leakage check to verify compliance with the Federal Performance Standard should be

performed on each oven prior to releasing oven to the owner.

BEFORE SERVICING

Before servicing an operative unit, perform a microwave emission check as per the Microwave
Measurement Procedure outlined in this service manual.
If microwave emissions level is in excess of the specified limit, contact SHARP ELECTRONICS
CORPORATION immediately @1-800-237-4277.

If the unit operates with the door open, service person should 1) tell the user not to operate the oven
and 2) contact SHARP ELECTRONICS CORPORATION and Food and Drug Administration's
Center for Devices and Radiological Health immediately.

Service personnel should inform SHARP ELECTRONICS CORPORATION of any certified unit found
with emissions in excess of 4mW/cm2. The owner of the unit should be instructed not to use the unit
until the oven has been brought into compliance.

WARNING TO SERVICE PERSONNEL

Microwave ovens contain circuitry capable of pro­ducing very high voltage and current, contact with
following parts
fatal, electrical shock.

(Example)
High Voltage Capacitor, High Voltage Power Trans-

former, Magnetron, High Voltage Rectifier Assem­bly, High Voltage Harness etc..

Read the Service Manual carefully and follow all
instructions.

may result in a severe, possibly

R-300BW

Don't Touch !
Danger High Voltage

Before Servicing

1. Disconnect the power supply cord , and then
remove outer case.

2. Open the door and block it open.

3. Discharge high voltage capacitor.

WARNING:RISK OF ELECTRIC SHOCK.

DISCHARGE THE HIGH-VOLTAGE
CAPACITOR BEFORE SERVICING.

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

Whenever troubleshooting is performed the power supply
must be disconnected. It may in, some cases, be necessary
to connect the power supply after the outer case has been
removed, in this event,

1. Disconnect the power supply cord, and then remove
outer case.

2. Open the door and block it open.

3. Discharge high voltage capacitor.

4. Disconnect the leads to the primary of the power
transformer.

5. Ensure that the leads remain isolated from other
components and oven chassis by using insulation tape.

6. After that procedure, reconnect the power supply cord.

When the testing is completed,

1. Disconnect the power supply cord, and then remove
outer case.

2. Open the door and block it open.

3. Discharge high voltage capacitor.

4. Reconnect the leads to the primary of the power
transformer.

5. Reinstall the outer case (cabinet).

6. Reconnect the power supply cord after the outer case is
installed.

7. Run the oven and check all functions.

After repairing

1. Reconnect all leads removed from components during
testing.

2. Reinstall the outer case (cabinet).

3. Reconnect the power supply cord after the outer case is
installed.

4. Run the oven and 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 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 Before Servicing procedure and re­examine the connections to the component being tested.

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

1

R-300BW

MICROWAVE MEASUREMENT PROCEDURE

A. Requirements:

1) Microwave leakage limit (Power density limit): The power density of microwave radiation emitted by a microwave oven
should not exceed 1mW/cm2 at any point 5cm or more from the external surface of the oven, measured prior to acquisition
by a purchaser, and thereafter (through the useful life of the oven), 5 mW/cm2 at any point 5cm or more from the external
surface of the oven.

2) Safety interlock switches Primary interlock relay and door sensing switch shall prevent microwave radiation emission in
excess of the requirement as above mentioned, secondary interlock switch shall prevent microwave radiation emission
in excess of 5 mW/cm2 at any point 5cm or more from the external surface of the oven.

B. Preparation for testing:
Before beginning the actual measurement of leakage, proceed as follows:

1) Make sure that the actual instrument is operating normally as specified in its instruction booklet.
Important:

Survey instruments that comply with the requirement for instrumentation as prescribed by the performance standard for
microwave ovens, 21 CFR 1030.10(c)(3)(i), must be used for testing.

2) Place the oven tray in the oven cavity.

3) Place the load of 275±15 ml (9.8 oz) of tap water initially at 20±5˚C (68˚F) in the center of the oven cavity.
The water container shall be a low form of 600 ml (20 oz) beaker with an inside diameter of approx. 8.5 cm (3-1/2 in.)
and made of an electrically nonconductive material such as glass or plastic.
The placing of this standard load in the oven is important not only to protect the oven, but also to insure that any leakage
is measured accurately.

4) Set the cooking control on Full Power Cooking Mode

5) Close the door and select a cook cycle of several minutes. If the water begins to boil before the survey is completed,
replace it with 275 ml of cool water.

C. Leakage test:

Closed-door leakage test (microwave measurement)

1) Grasp the probe of the survey instrument and hold it perpendicular to the gap between the door and the body of the oven.

2) Move the probe slowly, not faster than 1 in./sec. (2.5 cm/sec.) along the gap, watching for the maximum indication on
the meter.

3) Check for leakage at the door screen, sheet metal seams and other accessible positions where the continuity of the metal
has been breached (eg., around the switches, indicator, and vents).
While testing for leakage around the door pull the door away from the front of the oven as far as is permitted by the closed
latch assembly.

4) Measure carefully at the point of highest leakage and make sure that the highest leakage is no greater than 4mW/cm2,
and that the secondary interlock switch does turn the oven OFF before any door movement.

NOTE: After servicing, record data on service invoice and microwave leakage report.

2

SERVICE MANUAL

MICROWAVE OVEN

R-300BW

PRODUCT DESCRIPTION

R-300BW

FOREWORD

This Manual has been prepared to provide Sharp Electronics Corp.
Service Personnel with Operation and Service Information for the
SHARP MICROWAVE OVEN, R-300BW.

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

Check the interlock switches and the door seal carefully. Special
attention should be given to avoid electrical shock and microwave
radiation hazard.

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
personnel.

DANGER

Certain initial parts are intentionally not grounded and present
a risk of electrical shock only during servicing. Service
personnel - Do not contact the following parts while the
appliance is energized;
High Voltage Capacitor, Power Transformer, Magnetron, High
Voltage Rectifier Assembly, High Voltage Harness;
If provided, Vent Hood, Fan assembly, Cooling Fan Motor.

GENERAL INFORMATION

OPERATION

TROUBLESHOOTING GUIDE AND
TEST PROCEDURE

CONTROL PANEL

COMPONENT REPLACEMENT
AND ADJUSTMENT PROCEDURE

WIRING DIAGRAM

PARTS LIST

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

Removal of the outer wrap gives access to voltage above 250V.
All the parts marked “∆” on parts list may cause undue microwave

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

SHARP ELECTRONICS CORPORATION

SHARP PLAZA, MAHWAH,

NEW JERSEY 07430-2135

3

R-300BW

SPECIFICATION

ITEM DESCRIPTION

Power Requirements 120 Volts / 12 Amperes

60 Hertz
Single phase, 3 wire grounded

Power Output 900 watts (IEC-705 TEST PROCEDURE)

Operating frequency of 2450MHz

Case Dimensions Width 20-1/2"

Height 11-7/8"
Depth 15-7/8"

Cooking Cavity Dimensions Width 13-3/4"

Height 8-3/8"

1.0 Cubic Feet Depth 14-7/8"
Control Complement Light up dial timer (30 minutes)

Microwave Power for Variable Cooking
Repetition Rate;

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

MEDIUM HIGH ........................................ approx.70% of Full Power

MEDIUM .................................................. approx.50% of Full Power

MEDIUM LOW......................................... approx.30% of Full Power

LOW ........................................................ approx.10% of Full Power

Oven Cavity Light Yes
Safety Standard UL Listed FCC Authorized

DHHS Rules, CFR, Title 21, Chapter 1, Subchapter J

GENERAL INFORMATION

GROUNDING INSTRUCTIONS

This oven is equipped with a three prong grounding plug. It must be plugged into a wall receptacle that is properly installed
and grounded in accordance with the National Electrical Code and local codes and ordinances.
In the event of an electrical short circuit, grounding reduces the risk of electric shock by providing an escape wire for the
electric current.

WARNING: Improper use of the grounding plug can result in a risk of electric shock.

Electrical Requirements
The electrical requirements are a 115 -120 volt 60 Hz, AC only,
15 or 20 amp. fused electrical supply. It is recommended that a separate circuit serving only this appliance be provided. When
installing this appliance, observe all applicable codes and ordinances.
A short power-supply cord is provided to reduce risks of becoming entangled in or tripping over a longer cord.
Where a two-pronged wall-receptacle is encountered, it is the personal responsibility and obligation of the customer to
contact a qualified electrician and have it replaced with a properly
grounded three-pronged wall receptacle or have a grounding adapter
properly grounded and polarized. If the extension cord must be used, it
should be a 3-wire, 15 amp. or higher rated cord. Do not drape over a
countertop or table where it can be pulled on by children or tripped over
accidentally.

3-Pronged Plug

Grounded
Receptacle Box

CAUTION: DO NOT UNDER ANY CIRCUMSTANCES CUT OR RE-

MOVE THE ROUND GROUNDING PRONG FROM THIS
PLUG.

4

Grounding Pin

3-Pronged Receptacle

R-300BW

OVEN DIAGRAM

7

8

9

4

11

1

10

2

56

3

1. One touch door open button.
Push to open door.

2. Door latches.
The oven will not operate unless the
door is securely closed.

3. Removable turntable support.

4. Removable turntable.
The turntable will rotate clockwise or
counterclockwise.

5. Oven lamp.
It will light when oven is operating or door is
opened.

6. Oven door with see-through window.

7. Ventilation openings. (Rear)

8. Control panel.

9. Coupling.

10.Wave guide cover.

11.Power supply cord

CONTROL PANEL

COOKING CONTROL

DEFROST
MED LOW

LOW

MED

MED

HIGH

HIGH

p

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1

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2

3

4

5

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0

7
8

9

13

12

11

10

30

25

20

1415

5

R-300BW

OPERATION

DESCRIPTION OF OPERATING SEQUENCE

The following is a description of component functions during
oven operation.

OFF CONDITION

Closing the door activates door sensing switch and second­ary interlock switch. (In this condition, the monitor switch
contacts are opened.)
When oven is plugged in, 120 volts A.C. is supplied to the
control unit. (Figure O-1).

COOKING CONDITION

Set the variable cooking control to HIGH. When the Light Up
Dial is turned, the following operations occur:

1. The contacts of relays are closed and components
connected to the relays are turned on as follows.
(For details, refer to Figure O-2)

(2) When the door is closed from the open position, the

monitor switch contacts open first. Then the contacts of
the secondary interlock switch and door sensing switch

close. And contacts of the relay (RY1) open.
If the secondary interlock switch and primary interlock relay
(RY2) fail with the contacts closed when the door is opened,
the closing of the monitor switch contacts will form a short
circuit through the monitor fuse, secondary interlock switch,
relay (RY1) and primary interlock relay (RY2), causing the
monitor fuse to blow.

VARIABLE COOKING

When Variable Cooking Power is programmed, the 120
volts A.C. is supplied to the power transformer intermittently
through the contacts of relay (RY-2) which is operated by the
control unit within a 32 second time base. Microwave power
operation is as follows:

RELAY CONNECTED COMPONENTS
RY-1 oven lamp/turntable motor/fan motor
RY-2 power transformer

2. 120 volts A.C. is supplied to the primary winding of the
power transformer and is converted to about 3.2 volts
A.C. output on the filament winding, and approximately
2150 volts A.C. on the high voltage winding.

3. The filament winding voltage heats the magnetron
filament and the H.V. winding voltage is sent to a voltage
doubler circuit.

4. The microwave energy produced by the magnetron is
channelled through the waveguide into the cavity feed­box, and then into the cavity where the food is placed to
be cooked.

5. Upon completion of the cooking time, the power
transformer, oven lamp, etc. are turned off, and the
generation of microwave energy is stopped. The oven
will revert to the OFF condition.

6. When the door is opened during a cook cycle, monitor
switch, door sensing switch, secondary interlock switch,
relay (RY1) and primary interlock relay are activated with
the following results. The circuits to the turntable motor,
the cooling fan motor, and the high voltage components
are de-energized, the oven lamp remains on, and the
digital read-out displays the time still remaining in the
cook cycle when the door was opened.

7. The monitor switch electrically monitors the operation of
the secondary interlock switch and primary interlock
relay and is mechanically associated with the door so
that it will function in the following sequence.

(1) When the door opens from the closed position, the

primary interlock relay (RY2) and secondary interlock
switch open their contacts. And contacts of the relay
(RY1) remains closed. Then the monitor switch contacts
close.

VARI-MODE ON TIME OFF TIME
HIGH 32 sec. 0 sec.

(100% power)
MEDIUM HIGH 24 sec. 8 sec.

(approx. 70% power)
MEDIUM 18 sec. 14 sec.

(approx. 50% power)
MEDIUM LOW 12 sec. 20 sec.

(approx. 30% power)
LOW 6 sec. 26 sec.

(approx. 10% power)

Note: The ON/OFF time ratio does not correspond with

the percentage of microwave power, because
approx. 2 seconds are needed for heating of the
magnetron filament.

6

SCHEMATIC

NOTE: CONDITION OF OVEN

1. LIGHT UP DIAL OFF.

2. DOOR CLOSED.

R-300BW

THERMAL 
CUT-OUT (OVEN)

A5

CONTROL UNIT

OL FM

OVEN
LAMP

SECONDARY
INTERLOCK
SWITCH

THERMAL 
CUT-OUT (MG.)

TTM

(RY-1)

TURN-
TABLE
MOTOR

120V AC
60 Hz

GRN

MONITOR 
FUSE 15A

Figure O-1. Oven Schematic-Off Condition

SCHEMATIC

NOTE: CONDITION OF OVEN

1. DOOR CLOSED.

2. VARIABLE COOKING CONTROL "HIGH".

3. LIGHT UP DIAL ON.

A3 COM.

FAN 
MOTOR

(RY-2)

PRIMARY
INTERLOCK
RELAY

B2A1 B1

DOOR
SENSING
SWITCH

N.O.

MONITOR 
SWITCH

POWER 
TRANSFORMER

CAPACITOR 0.94µF

AC 2000V

RECTIFIER

MAGNETRON

120V AC
60 Hz

GRN

MONITOR 
FUSE 15A

THERMAL 
CUT-OUT (OVEN)

A5

CONTROL UNIT

OL FM

OVEN
LAMP

SECONDARY
INTERLOCK
SWITCH

THERMAL 
CUT-OUT (MG.)

TTM

(RY-1)

TURN-
TABLE
MOTOR

A3 COM.

FAN 
MOTOR

(RY-2)

PRIMARY
INTERLOCK
RELAY

B2A1 B1

DOOR
SENSING
SWITCH

N.O.

Figure O-2. Oven Schematic-Cooking Condition

7

MONITOR 
SWITCH

POWER 
TRANSFORMER

CAPACITOR 0.94µF

AC 2000V

RECTIFIER

MAGNETRON

R-300BW

DESCRIPTION AND FUNCTION OF 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 up
the switch lever, and then the switch lever pushes up the
latch head. The latch heads are moved upward and re­leased from latch hook. Now the door will open.

Door

Latch Hook


Latch
Heads

Switch
Lever

Door
Sensing 
Switch

Monitor
Switch

Secondary
Interlock
Switch

Figure D-1. Door Open Mechanism

DOOR SENSING AND SECONDARY INTERLOCK
SWITCHES

The secondary interlock switch is mounted in the lower
position of the latch hook and the door sensing switch in the
primary interlock system is mounted in the upper position of
the latch hook. They are activated by the latch heads on the
door. When the door is opened, the switches interrupt the
power to all high voltage components. A cook cycle cannot
take place until the door is firmly closed thereby activating
both interlock switches. The primary interlock system con­sists of the door sensing switch and primary interlock relay
located on the control circuit board.

MONITOR SWITCH

The monitor switch is activated (the contacts opened) by the
latch head on the door while the door is closed. The switch
is intended to render the oven inoperative, by means of
blowing the monitor fuse, when the contacts of the primary
interlock relay (RY2) and secondary interlock switch fail to
open when the door is opened.

Functions:

1. When the door is opened, the monitor switch contact
close (to the ON condition) due to their being normally
closed. At this time the primary interlock relay (RY2) and
secondary interlock switch are in the OFF condition
(contacts open) due to their being normally open contact
switches.

2. As the door goes to a closed position, the monitor switch
contacts are first opened and then the door sensing
switch and the secondary interlock switch contacts close.
(On opening the door, each of these switches operate
inversely.)

3. If the door is opened, and the primary interlock relay

(RY2) and secondary interlock switch contacts fail to
open, the monitor fuse blows simultaneously with closing
of the monitor switch contacts.

CAUTION: BEFORE REPLACING A BLOWN MONITOR

FUSE TEST THE DOOR SENSING SWITCH,
PRIMARY INTERLOCK RELAY (RY2), SEC­ONDARY INTERLOCK SWITCH AND MONI­TOR SWITCH FOR PROPER OPERATION.
(REFER TO CHAPTER "TEST PROCEDURE").

NOTE: MONITOR FUSE AND MONITOR SWITCH ARE

REPLACED AS AN ASSEMBLY.

TURNTABLE MOTOR

The turntable motor rotates the turntable located on the
bottom of the oven cavity, so that the foods on the turntable
cook evenly during cooking. The turntable may turn in either
direction.

COOLING FAN MOTOR

The cooling 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 vapors given off from the heating foods. It is then
exhausted through the exhausting air vents at the oven
cavity.

MONITOR FUSE

1. The monitor fuse blows when the contacts (COM-NO) of
the primary interlock relay (RY2) and secondary interlock
switch remain closed with the oven door open and when
the monitor switch closes.

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

OVEN THERMAL CUT-OUT

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 257˚F(125˚C), causing the oven to shut down.

MAGNETRON THERMAL CUT-OUT

The thermal cut-out located near the magnetron 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
203˚F(95˚C) causing the oven to shut down.

8

R-300BW

TROUBLESHOOTING GUIDE

Never touch any part in the circuit with your hand or an uninsulated tool while the power supply is connected.

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.

IMPORTANT: If the oven becomes inoperative because of a blown monitor fuse, check the monitor switch, primary interlock

relay (RY2), door sensing switch and secondary interlock switch before replacing the monitor fuse. If monitor
fuse is replaced, the monitor switch must also be replaced. Use part FFS-BA010WRK0 as an assembly.

IMPORTANT: Whenever troubleshooting is performed with the power supply cord disconnected. It may in, some cases,

be necessary to connect the power supply cord after the outer case has been removed, in this event,

1. Disconnect the power supply cord, and then remove outer case.

2. Open the door and block it open.

3. Discharge high voltage capacitor.

4. Disconnect the leads to the primary of the power transformer.

5. Ensure that the leads remain isolated from other components and oven chassis by using insulation tape.

6. After that procedure, reconnect the power supply cord.

When the testing is completed

1. Disconnect the power supply cord, and then remove outer case.

2. Open the door and block it open.

3. Discharge high voltage capacitor.

4. Reconnect the leads to the primary of the power transformer.

5. Reinstall the outer case (cabinet).

6. Reconnect the power supply cord after the outer case is installed.

7. Run the oven and check all functions.

9

R-300BW

CK = Check / RE = Replace

CONDITION

OFF
CONDITION

COOKING
CONDITION

TEST PROCEDURE

AND

POSSIBLE CAUSE

DEFECTIVE PARTS

PROBLEM

Home fuse or circuit breaker blows when
power cord is plugged into wall receptacle

Monitor fuse blows when power cord is
plugged into wall receptacle.

Oven lamp does not light when door is
opened.

Oven lamp does not go out when door is
closed.

Oven lamp lights but fan motor and turnta­ble motor do not operate.

Oven does not go into cook cycle when
Light Up Dial is turned.

Oven seems to be operating but little or no
heat is produced in oven load. (Food in­completely cooked or not cooked at all at
end of cook cycle.)

Oven goes into a cook cycle but extremely
uneven heating is produced in oven load
(food).

Oven does not cook properly when pro­grammed for variable cooking mode. (Op­erates properly on Cooking Power HIGH
mode.)

RERE A B C D E F F G H RERECK I CKCK J K

SHORT IN POWER CORD

SHORT OR OPENED WIRING

MAGNETRON

POWER TRANSFORMER

H.V. RECTIFIER ASSEMBLY

HIGH VOLTAGE CAPACITOR

THERMAL CUT-OUT

SECONDARY INTERLOCK SWITCH

PRIMARY INTERLOCK SYSTEM

MONITOR SWITCH

MONITOR FUSE

OVEN LAMP OR SOCKET

COOLING FAN MOTOR

TURNTABLE MOTOR

CONTROL PANEL

LOW VOLTAGE

DIRTY OVEN CAVITY

RELAY (RY1)

FOIL PATTERN ON PWB.

10

TEST PROCEDURES

R-300BW

PROCEDURE

LETTER

A MAGNETRON ASSEMBLY TEST

1. Disconnect the power supply cord, and then remove outer case.

2. Open the door and block it open.

3. Discharge high voltage capacitor.

4. To test for an open filament, isolate the magnetron from the high voltage circuit. A continuity check
across the magnetron filament leads should indicate less than 1 ohm.

5. To test for a shorted magnetron, connect the ohmmeter leads between the magnetron filament leads
and chassis ground. This test should indicate an infinite resistance. If there is little or no resistance
the magnetron is grounded and must be replaced.

6. Reconnect all leads removed from components during testing.

7. Reinstall the outer case (cabinet).

8. Reconnect the power supply cord after the outer case is installed.

9. Run the oven and check all functions.

MICROWAVE OUTPUT POWER

The following test procedure should be carried out with the microwave oven in a fully assembled
condition (outer case fitted).

HIGH VOLTAGES ARE PRESENT DURING THE COOK CYCLE, SO EXTREME CAUTION SHOULD
BE OBSERVED.

Power output of the magnetron can be measured by performing a water temperature rise test. This test
should only be used if above tests do not indicate a faulty magnetron and there is no defect in the following
components or wiring: silicon rectifier, high voltage capacitor and power transformer. This test will require
a 16 ounce (453cc) measuring cup and an accurate mercury thermometer or thermocouple type
temperature tester. For accurate results, the following procedure must be followed carefully:

COMPONENT TEST

1. Fill the measuring cup with 16 oz. (453cc) of tap water and measure the temperature of the water with
a thermometer or thermocouple temperature tester. Stir the thermometer or thermocouple through
the water until the temperature stabilizes. Record the temperature of the water.

2. Place the cup of water in the oven. Operate oven at POWER 10(HIGH) selecting more than 60
seconds cook time. Allow the water to heat for 60 seconds, measuring with a stop watch, second hand
of a watch or the digital read-out countdown.

3. Remove the cup from the oven and again measure the temperature, making sure to stir the
thermometer or thermocouple through the water until the maximum temperature is recorded.

4. Subtract the cold water temperature from the hot water temperature. The normal result should be 22
to 43˚F (12.2 to 23.9˚C) rise in temperature. If the water temperatures are accurately measured and
tested for the required time period the test results will indicate if the magnetron tube has low power
output (low rise in water temperature) which would extend cooking time or high power output (high
rise in water temperature) which would reduce cooking time. Because cooking time can be adjusted
to compensate for power output, the magnetron tube assembly should be replaced only if the water
temperature rise test indicates a power output well beyond the normal limits. The test is only accurate
if the power supply line voltage is 120 volts and the oven cavity is clean.

B POWER TRANSFORMER TEST

1. Disconnect the power supply cord, and then remove outer case.

2. Open the door and block it open.

3. Discharge high voltage capacitor.

4. Disconnect the primary input terminals and measure the resistance of the transformer with an
ohmmeter. Check for continuity of the coils with an ohmmeter. On the R x 1 scale, the resistance of
the primary coil should be less than 1 ohm and the resistance of the high voltage coil should be
approximately 106 ohms; the resistance of the filament coil should be less than 1 ohm.

5. Reconnect all leads removed from components during testing.

6. Reinstall the outer case (cabinet).

7. Reconnect the power supply cord after the outer case is installed.

8. Run the oven and check all functions.

11

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TEST PROCEDURES

PROCEDURE

LETTER

(HIGH VOLTAGES ARE PRESENT AT THE HIGH VOLTAGE TERMINAL, SO DO NOT ATTEMPT TO
MEASURE THE FILAMENT AND HIGH VOLTAGE.)

C HIGH VOLTAGE RECTIFIER TEST

1. Disconnect the power supply cord, and then remove outer case.

2. Open the door and block it open.

3. Discharge high voltage capacitor.

4. Isolate the rectifier from the circuit. Using the highest ohm scale of the meter, read the resistance
across the terminals and observe, reverse the leads to the rectifier terminals and observe meter
reading. If a short is indicated in both directions, or if an infinite resistance is read in both directions,
the rectifier is probably defective and should be replaced.

5. Reconnect all leads removed from components during testing.

6. Reinstall the outer case (cabinet).

7. Reconnect the power supply cord after the outer case is installed.

8. Run the oven and check all functions.

NOTE: Be sure to use an ohmmeter that will supply a forward bias voltage of more than 6.3 volts.

D HIGH VOLTAGE CAPACITOR TEST

1. Disconnect the power supply cord, and then remove outer case.

2. Open the door and block it open.

3. Discharge high voltage capacitor.

4. If the capacitor is open, no high voltage will be available to the magnetron. Disconnect input leads
and check for short or open between the terminals using an ohmmeter.
Checking with a high ohm scale, if the high voltage capacitor is normal, the meter will indicate
continuity for a short time and should indicate an open circuit once the capacitor is charged. If the
above is not the case, check the capacitor with an ohmmeter to see if it is shorted between either of
the terminals and case. If it is shorted, replace the capacitor.

5. Reconnect all leads removed from components during testing.

6. Reinstall the outer case (cabinet).

7. Reconnect the power supply cord after the outer case is installed.

8. Run the oven and check all functions.

COMPONENT TEST

E OVEN THERMAL CUT-OUT TEST

1. Disconnect the power supply cord, and then remove outer case.

2. Open the door and block it open.

3. Discharge high voltage capacitor.

4. A continuity check across the thermal cut-out terminals should indicate a closed circuit unless the
temperature of the thermal cut-out reaches approximately 257˚F(125˚C).
An open thermal cut-out indicates overheating of the oven, exchange the oven thermal cut-out and
check inside of oven cavity and for improper setting of cooking time or operation of control unit. Check
for restricted air flow through the vent holes of the oven cavity, especially the cooling fan and air guide.

5. Reconnect all leads removed from components during testing.

6. Reinstall the outer case (cabinet).

7. Reconnect the power supply cord after the outer case is installed.

8. Run the oven and check all functions.

MAGNETRON THERMAL CUT-OUT TEST

1. Disconnect the power supply cord, and then remove outer case.

2. Open the door and block it open.

3. Discharge high voltage capacitor.

4. A continuity check across the thermal cut-out terminals should indicate a closed circuit. If the
temperature of the magnetron reaches approximately 203˚F(95˚C), the thermal cut-out opens. An
open thermal cut-out indicates overheating of the magnetron. Check for restricted air flow to the
magnetron, especially the cooling fan air guide.

12

TEST PROCEDURES

R-300BW

PROCEDURE

LETTER

5. Reconnect all leads removed from components during testing.

6. Reinstall the outer case (cabinet).

7. Reconnect the power supply cord after the outer case is installed.

8. Run the oven and check all functions.
CAUTION: IF THE THERMAL CUT-OUT INDICATES AN OPEN CIRCUIT AT ROOM TEMPERATURE,

REPLACE THERMAL CUT-OUT.

F SECONDARY INTERLOCK SWITCH TEST

1. Disconnect the power supply cord, and then remove outer case.

2. Open the door and block it open.

3. Discharge high voltage capacitor.

4. Isolate the switch and connect the ohmmeter to the common (COM.) and normally open (NO) terminal
of the switch. The meter should indicate an open circuit with the door open and a closed circuit with
the door closed. If improper operation is indicated, replace the secondary interlock switch.

5. Reconnect all leads removed from components during testing.

6. Reinstall the outer case (cabinet).

7. Reconnect the power supply cord after the outer case is installed.

8. Run the oven and check all functions.

PRIMARY INTERLOCK SYSTEM TEST

DOOR SENSING SWITCH

1. Disconnect the power supply cord, and then remove outer case.

2. Open the door and block it open.

3. Discharge high voltage capacitor.

4. Isolate the switch and connect the ohmmeter to the common (COM.) and normally open (NO) terminal
of the switch. The meter should indicate an open circuit with the door open and a closed circuit with
the door closed. If improper operation is indicated, replace the door sensing switch.

5. Reconnect all leads removed from components during testing.

6. Reinstall the outer case (cabinet).

7. Reconnect the power supply cord after the outer case is installed.

8. Run the oven and check all functions.

NOTE: If the door sensing switch contacts fail in the open position and the door is closed, the cooling

fan, turntable and oven light will be activated by RY1.

COMPONENT TEST

PRIMARY INTERLOCK RELAY (RY2)

1. Disconnect the power supply cord, and then remove outer case.

2. Open the door and block it open.

3. Discharge high voltage capacitor.

4. Disconnect two (2) wire leads from the male tab terminals of the Primary Interlock Relay. Check the
state of the relay contacts using a ohmmeter. The relay contacts should be open. If the relay contacts
are closed, replace the circuit board entirely or the relay itself.

5. Reconnect all leads removed from components during testing.

6. Reinstall the outer case (cabinet).

7. Reconnect the power supply cord after the outer case is installed.

8. Run the oven and check all functions.

G MONITOR SWITCH TEST

1. Disconnect the power supply cord, and then remove outer case.

2. Open the door and block it open.

3. Discharge high voltage capacitor.

4. Before performing this test, make sure that the secondary interlock switch and the primary interlock
relay are operating properly, according to the above Switch Test Procedure. Disconnect the wire lead
from the monitor switch (COM) terminal. Check the monitor switch operation by using the ohmmeter
as follows. When the door is open, the meter should indicate a closed circuit. When the monitor switch
actuator is pushed by a screw driver through the lower latch hole on the front plate of the oven cavity

13

R-300BW

TEST PROCEDURES

PROCEDURE

LETTER

with the door opened (in this condition the plunger of the monitor switch is pushed in), the meter should
indicate an open circuit. If improper operation is indicated, the switch may be defective. After testing
the monitor switch, reconnect the wire lead to the monitor switch (COM) terminal and check the
continuity of the monitor circuit.

5. Reconnect all leads removed from components during testing.

6. Reinstall the outer case (cabinet).

7. Reconnect the power supply cord after the outer case is installed.

8. Run the oven and check all functions.

H BLOWN MONITOR FUSE TEST

1. Disconnect the power supply cord, and then remove outer case.

2. Open the door and block it open.

3. Discharge high voltage capacitor.

4. If the monitor fuse is blown when the door is opened, check the primary interlock relay, secondary
interlock switch and monitor switch according to the "TEST PROCEDURE" for those switches before
replacing the blown monitor fuse.

COMPONENT TEST

SCREW 
DRIVER

RED

WHT

MONITOR 
SWITCH

OHMMETER

CAUTION: BEFORE REPLACING A BLOWN MONITOR FUSE, TEST THE PRIMARY INTERLOCK

RELAY, SECONDARY INTERLOCK SWITCH, DOOR SENSING SWITCH AND MONITOR

SWITCH FOR PROPER OPERATION.
If the monitor fuse is blown by improper switch operation, the monitor fuse and monitor switch must
be replaced with "monitor fuse and monitor switch assembly" part number FFS-BA010WRK0, even
if the monitor switch operates normally. The monitor fuse and monitor switch assembly is comprised
of a 15 ampere fuse and switch.

5. Reconnect all leads removed from components during testing.

6. Reinstall the outer case (cabinet).

7. Reconnect the power supply cord after the outer case is installed.

8. Run the oven and check all functions.

I CONTROL PANEL ASSEMBLY TEST

The control panel consists of circuits including semiconductors such as LSI, ICs, etc. Therefore, unlike
conventional microwave ovens, proper maintenance cannot be performed with only a voltmeter and
ohmmeter.
In this service manual troubleshooting by unit replacement is described according to the symptoms
indicated.

Before testing,

1) Disconnect the power supply cord and then remove outer case.

2) Open the door and block it open.

3) Discharge high voltage capacitor.

4) Disconnect the leads to the primary of the power transformer.

5) Ensure that these leads remain isolated from other components and oven chassis by using
insulation tape.

6) After that procedure, re-connect the power supply cord.

1. Control Panel
The following symptoms indicate a defective control unit.

1-1 In connection with LEDs

a) At a certain LED, all or some LEDs do not light up.
b) At a certain LED, brightness is low.

14

TEST PROCEDURES

R-300BW

PROCEDURE

LETTER

J RELAY TEST

COMPONENT TEST

c) Only one LED does not light up.
d) All or some LEDs continue to light up.
e) A certain group of LEDs do not light up.

f) The LEDs flicker.

1-2 Other possible troubles caused by defective control unit.

a) Buzzer does not sound or continues to sound.
b) Clock is not possible.
c) Cooking time can not be set.
d) Power level can not be set.

When testing is completed,

1) Disconnect the power supply cord and then remove outer case.

2) Open the door and block it open.

3) Discharge high voltage capacitor.

4) Reconnect all leads removed from components during testing.

5) Re-install the outer case (cabinet).

6) Reconnect the power supply cord after the outer case is installed.

7) Run the oven and check all functions.

1. Disconnect the power supply cord and then remove outer case.

2. Open the door and block it open.

3. Discharge high voltage capacitor.

4. Disconnect the leads to the primary of the power transformer.

5. Ensure that these leads remain isolated from other components and oven chassis by using insulation
tape.

6. After that procedure, re-connect the power supply cord.

7. Remove the outer case and check voltage between Pins No. 3 and 5 of the 3 pin connector (A) on
the control unit with an A.C. voltmeter.

The meter should indicate 120 volts, if not check oven circuit.

RY1 Relay Test

These relays are operated by D.C. voltage
Check voltage at the relay coil with a D.C. voltmeter during the microwave cooking operation.

DC. voltage indicated ............. Defective relay.

DC. voltage not indicated ........ Check diode which is connected to the relay coil. If diode is good, control

unit is defective.

RELAY SYMBOL OPERATIONAL VOLTAGE CONNECTED COMPONENTS

RY1 Approx. 12.5V D.C.
RY2 Approx. 12.5V D.C. (*) Power transformer

(*) Oven lamp / Turntable motor / Cooling fan motor

(*) The voltage under the condition when all LEDs light up.

8. Disconnect the power supply cord and then remove outer case.

9. Open the door and block it open.

10.Discharge high voltage capacitor.

11.Reconnect all leads removed from components during testing.

12.Re-install the outer case (cabinet).

13.Reconnect the power supply cord after the outer case is installed.

14.Run the oven and check all functions.

K FOIL PATTERN ON THE PRINTED WIRING BOARD TEST

To protect the electronic circuits, this model is provided with a fine foil pattern added to the primary on
the PWB, this foil pattern acts as a fuse.

1. Foil pattern check and repairs.

1) Disconnect the power supply cord and then remove outer case.

15

R-300BW

TEST PROCEDURES

PROCEDURE

LETTER

COMPONENT TEST

2) Open the door and block it open.

3) Discharge high voltage capacitor.

4) Follow the troubleshooting guide given below for repair.

STEPS OCCURRENCE CAUSE OR CORRECTION

1 Only pattern at "a" is broken. *Insert jumper wire J1 and solder.
2 Pattern at "a" and "b" are broken. *Insert the coil RCILF2003YAZZ between "c" and "d".

5) Make a visual inspection of the varistor.
Check for burned damage and examine

S

P

VRS1

the transformer with a tester for the
presence of layer short-circuit (check
the primary coil resistance which is
approximately 324Ω ± 10%). If any
abnormal condition is detected, replace
the defective parts.

ab

(J1)

d

c

CN - A

15

6) Reconnect all leads removed from components during testing.

7) Re-install the outer case (cabinet).

8) Reconnect the power supply cord after the outer case is installed.

9) Run the oven and check all functions.

2. Follow the troubleshooting guide given below, if indicator does not light up after above check and
repairs are finished.

1) Disconnect the power supply cord and then remove outer case.

2) Open the door and block it open.

3) Discharge high voltage capacitor.

4) Disconnect the leads to the primary of the power transformer.

5) Ensure that these leads remain isolated from other components and oven chassis by using

insulation tape.

6) After that procedure, re-connect the power supply cord.

7) Follow the troubleshooting guide given below for repair.

STEPS OCCURRENCE CAUSE OR CORRECTION

The rated AC voltage is not present between

1

Pins No. 3 and 5 of the 3-pin connector (CN-A).
The rated AC voltage is present primary side Low voltage transformer or secondary circuit defective.

2

of low voltage transformer. Check and repair.

Check supply voltage and oven power cord.

8) Disconnect the power supply cord and then remove outer case.

9) Open the door and block it open.

10) Discharge high voltage capacitor.

11) Reconnect all leads removed from components during testing.

12) Re-install the outer case (cabinet).

13) Reconnect the power supply cord after the outer case is installed.

14) Run the oven and check all functions.

16

CONTROL PANEL ASSEMBLY

OUTLINE OF CONTROL PANEL

R-300BW

Control Unit

Control unit consists of LSI, power source circuit, synchro­nizing signal circuit, ACL circuit, buzzer circuit, encoder
circuit, indicator circuit and potentiometer circuit.

1) LSI

This LSI controls the encoder signal, potentiometer
signal, relay driving signal for oven function, buzzer
signal and LED signal.

2) Power Source Circuit

This circuit generates voltage necessary in the control
unit.

Symbol Voltage Application

VC -5.0V LSI(I-1)

3) Synchronizing Signal Circuit

The power source synchronizing signal is available in
order to compose a basic standard time in the clock
circuit. It accompanies a very small error because it
works on commercial frequency.

5) Buzzer Circuit

The buzzer is responsive to signals from the LSI to emit
audible sounds (key touch sound and completion sound).

6) Door Sensing Switch (Stop Switch)

A switch to "tell" the LSI if the door is open or closed.

7) Relay Circuit

To drive the magnetron, fan motor, turntable motor and
light the oven lamp.

8) Encoder

The encoder generates the pulse signal, and the pulse
signal is sent to the LSI.

9) Indicator Circuit

Indicator elements are the Light-emitting diodes (LD1­LD24).
This circuit consists of 4-digits and 6 segments.

10) Potentiometer Circuit

The circuit makes setting of the power level by variable
resistance.

4) ACL

A circuit to generate a signal which resets the LSI to the
initial state when power is supplied.

17

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DESCRIPTION OF LSI

LSI(IZA882DR)

The I/O signal of the LSI(IZA882DR) are detailed in the following table.

Pin No. Signal I/O Description

1 RST IN Auto clear terminal.

Signal is input to reset the LSI to the initial state when power is applied. Temporarily set
to "L" level the moment power is applied, at this time the LSI is reset. Thereafter set at "H"
level.

2 INT IN

3 AVSS IN

4 VREF IN

5K0IN

6K1IN

7 AVDD IN

8 NC No connection terminal.
9 S0 OUT

10 S1 OUT

11 S2 OUT

12 S3 OUT

13-14 NC No connection terminal.
15 D0 OUT

16 D1 OUT

17 CNVS IN

18 VSS IN

19 D2 OUT

20 D3 OUT

21 D4 OUT

22 D5 OUT

Signal coming from encoder.

When the encoder is turned, the contacts of encoder make pulse signals. And pulse signals
are input into INT.

A/D converter power source voltage.

The power source voltage to drive the A/D converter in the LSI. Connected to VC.

Reference voltage input terminal.

A reference voltage is applied to the A/D converter in the LSI.

Signal coming from potentiometer.

By inputting DC voltage corresponding to the power level set by the potentiometer, this
input is converted into the power level by the A/D converter built into the LSI.

Terminal to change functions according to the model.

Signal in accordance with the model in operation is applied to set up its function.

A/D converter power source voltage.

The power source voltage to drive the A/D converter in the LSI.

Digit selection signal.

Signal is input to the anodes of the light-emitting diodes (LD19 - LD24).

Digit selection signal.

Signal is input to the anodes of the light-emitting diodes (LD13 - LD18).

Digit selection signal.

Signal is input to the anodes of the light-emitting diodes (LD7 - LD12).

Digit selection signal.

Signal is input to the anodes of the light-emitting diodes (LD1 - LD6).

Segment data signal.

Signal is input to the cathodes of the light-emitting diodes (LD1, LD7, LD13 and LD19).

Segment data signal.

Signal is input to the cathodes of the light-emitting diodes (LD2, LD8, LD14 and LD20).

Reference voltage input terminal.

A reference voltage is applied to the A/D converter in the LSI. Connected to VC.

Power source voltage: -5V.

The power source voltage to drive the LSI is input to VSS terminal. Connected to VC.

Segment data signal.

Signal is input to the cathodes of the light-emitting diodes (LD3, LD9, LD15 and LD21).

Segment data signal.

Signal is input to the cathodes of the light-emitting diodes (LD4, LD10, LD16 and LD22).

Segment data signal.

Signal is input to the cathodes of the light-emitting diodes (LD5, LD11, LD17 and LD23).

Segment data signal.

Signal is input to the cathodes of the light-emitting diodes (LD6, LD12, LD18 and LD24).

18

Pin No. Signal I/O Description

23 D6 OUT Magnetron high-voltage circuit driving signal.

To turn on and off the cook relay (RY2). In 100%
POWER operation, the signals hold "L" level
during microwave cooking and "H" level while
not cooking. In other cooking modes (70%, 50%,
30%, 10%) the signal turns to "H" level and "L"
level in repetition according to the power level.

24 D7 IN/OUT Terminal not used.
25 D8 OUT

Oven lamp, turntable motor and fan motor driving signal(Square Waveform : 60Hz).

To turn on and off shut-off relay (RY1).
The square waveform voltage is deliv­ered to the relay (RY1) driving circuit and
relay(RY2) control circuit.

26 NC No connection terminal.
27 F0 IN

Input signal which communicates the door open/close information to LSI.

Door closed; "H" level signal.

Door opened; "L" level signal.
28 F1 Terminal not used.
29 F2 IN

Signal to synchronize LSI with commercial power source frequency.

This is basic timing for all real time processing of

LSI.

ON/OFF time ratio in Micro
cooking
(a. 32second time base)

MICRO ON OFF
COOK
100% 32sec. 0sec.
70% 24sec. 8sec.
50% 18sec. 14sec.
30% 12sec. 20sec.
10% 6sec. 26sec.

16.7 msec

During cooking

R-300BW

H

L

H : GND

30 F3 IN Signal coming from encoder.

Signal similar to INT. Pulse signals are input into F3.
31-32 NC No connection terminal.
33 XOUT OUT

Internal clock oscillation frequency control output.

Output to control oscillation input of XOUT.
34 XIN IN

Internal clock oscillation frequency input setting.

The internal clock frequency is set by inserting the ceramic filter oscillation circuit with

respect to XIN terminal.
35 CNTR OUT

Signal to sound buzzer.

A: Completion sound.

36 VDD IN Power source voltage: 0V.

The power source voltage to drive the LSI is input to VDD terminal.

L (-5V)

16.7 msec

2.0 sec

A

H: GND

L: -5V

19

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SERVICING

1. Precautions for Handling Electronic Components

This unit uses CMOS LSI in the integral part of the
circuits. When handling these parts, the following
precautions should be strictly followed. CMOS LSI have
extremely high impedance at its input and output
terminals. For this reason, it is easily influenced by the
surrounding high voltage power source, static electricity
charge in clothes, etc. and sometimes it is not fully
protected by the built-in protection circuit.
In order to protect CMOS LSI.

1) When storing and transporting, thoroughly wrap them in
aluminium foil. Also wrap all PW boards containing them
in aluminium foil.

2) When soldering, ground the technician as shown in the
figure and use grounded soldering iron and work table.

approx. 1M ohm

2. Shapes of Electronic Components

B

C

Transistor
DTA123ES
DTB123ES
DTA143ES
DTD143ES

Transistor
2SB1238

B

C

E

E

3. Servicing of Touch Control Panel

We describe the procedures to permit servicing of the
touch control panel of the microwave oven and the
precautions you must take when doing so. To perform
the servicing, power to the touch control panel is available
either from the power line of the oven itself or from an
external power source.

(1)Servicing the touch control panel with power supply

of the oven:
CAUTION:
THE HIGH VOLTAGE TRANSFORMER OF THE MI­CROWAVE OVEN IS STILL LIVE DURING SERVIC­ING AND PRESENTS A HAZARD.

Therefore, before checking the performance of the touch
control panel,

1) Disconnect the power supply cord, and then remove

outer case.

2) Open the door and block it open.

3) Discharge high voltage capacitor.

4) Disconnect the leads to the primary of the power

transformer.

5) Ensure that these leads remain isolated from other

components and oven chassis by using insulation
tape.

6) After that procedure, re-connect the power supply

cord.

After checking the performance of the touch control panel,

1) Disconnect the power supply cord.

2) Open the door and block it open.

3) Re-connect the leads to the primary of the power

transformer.

4) Re-install the outer case (cabinet).

5) Re-connect the power supply cord after the outer
case is installed.

6) Run the oven and check all functions.

A.

On some models, the power supply cord between the
touch control panel and the oven itself is so short that the
two can’t be separated. For those models, check and
repair all the controls (sensor-related ones included) of the
touch control panel while keeping it connected to the oven.

B.

On some models, the power supply cord between the
touch control panel and the oven proper is long enough
that they may be separated from each other. For those
models, it is possible to check and repair the controls of the
touch control panel while keeping it apart from the oven
proper; in this case you must short both ends of the door
sensing switch (on PWB) of the touch control panel with a
jumper, which brings about an operational state that is
equivalent to the oven door being closed. As for the
sensor-related controls of the touch control panel, checking
them is possible if dummy resistor(s) with resistance equal
to that of the controls are used.

(2)Servicing the touch control panel with a power

supply from an external power source:

Disconnect the touch control panel completely from the
oven proper, and short both ends of the door sensing
switch (on PWB) of the touch control panel, which brings
about an operational state that is equivalent to the oven
door being closed. Connect an external power source to
the power input terminal of the touch control panel, then
it is possible to check and repair the controls of the touch
control panel it is also possible to check the sensor­related controls of the touch control panel by using the
dummy resistor(s).

4. Servicing Tools

Tools required to service the touch control panel
assembly.

1) Soldering iron: 30W
(It is recommended to use a soldering iron with a
grounding terminal.)

2) Oscilloscope: Single beam, frequency range: DC­10MHz type or more advanced model.

3) Others: Hand tools

5. Other Precautions

1) Before turning on the power source of the control unit,
remove the aluminium foil applied for preventing
static electricity.

2) Connect the connectors of the key unit to the control
unit making sure that the lead wires are not twisted.

3) After aluminium foil is removed, be careful that
abnormal voltage due to static electricity etc. is not
applied to the input or output terminals.

4) Attach connectors, electrolytic capacitors, etc. to
PWB, making sure that all connections are tight.

5) Be sure to use specified components where high
precision is required.

20

R-300BW

COMPONENT REPLACEMENT AND ADJUSTMENT PROCEDURE

WARNING AGAINST HIGH VOLTAGE:

Microwave ovens contain circuitry capable of producing very high voltage and current, contact with following parts may
result in severe, possibly fatal, electric shock.
(Example)
High Voltage Capacitor, Power Transformer, Magnetron, High Voltage Rectifier Assembly, High Voltage Harness etc..

WARNING:

1. Disconnect the power supply cord.

2. Make sure that a definite "click" can be heard when the
microwave oven door is unlatched. (Hold the door in a
closed position with one hand, then push the door open
button with the other, this causes the latch leads to rise,
it is then possible to hear a "click" as the door switches
operate.

3. Visually check the door and cavity face plate for damage
(dents, cracks, signs of arcing etc.).

Carry out any remedial work that is necessary before
operating the oven.
Do not operate the oven if any of the following conditions
exist;

Avoid possible exposure to microwave energy. Please follow the instructions below before
operating the oven.

WARNING FOR WIRING

To prevent an electric shock, take the following pre­cautions.

1. Before wiring,

1) Disconnect the power supply cord.

2) Open the door and block it open.

3) Discharge the high voltage capacitor and wait for 60
seconds.

2. Don’t let the wire leads touch to the followiong parts;

1) High voltage parts:
Magnetron, High voltage transformer, High voltage
capacitor and High voltage rectifier assembly.

2) Hot parts:
Oven lamp, Magnetron, High voltage transformer
and Oven cavity.

1. Door does not close firmly.

2. Door hinge, support or latch hook is damaged.

3. The door gasket or seal is damaged.

4. The door is bent or warped.

5. There are defective parts in the door interlock system.

6. There are defective parts in the microwave generating
and transmission assembly.

7. There is visible damage to the oven.

Do not operate the oven:

1. Without the RF gasket (Magnetron).

2. If the wave guide or oven cavity are not intact.

3. If the door is not closed.

4. If the outer case (cabinet) is not fitted.

3) Sharp edge:

Bottom plate, Oven cavity, Waveguide flange,
Chassis support and other metallic plate.

4) Movable parts (to prevent a fault)

Fan blade, Fan motor, Switch, Switch lever, Open
button.

3. Do not catch the wire leads in the outer case cabinet.

4. Insert the positive lock connector until its pin is locked
and make sure that the wire leads do not come off even
if the wire leads are pulled.

5. To prevent an error function, connect the wire leads
correctly, referring to the Pictorial Diagram.

Please refer to ‘OVEN PARTS, CABINET PARTS, CONTROL PANEL PARTS, DOOR PARTS’, when carrying out any of
the following removal procedures:

OUTER CASE REMOVAL

To remove the outer case, procedure as follows.

1. Disconnect the power supply cord.

2. Open the oven door and block it open.

3. Remove the two (2) screws from the lower portion of the
rear cabinet using a T20H Torx type or GTXH20-100
screw driver.

4. Remove the remaining two (2) screws from rear and one
(1) screw along the right side of outer case.

5. Slide the entire outer case back out about 1 inch (3 cm)
to free it from retaining clips on the cavity face plate.

6. Lift entire outer case from the unit.

21

R-300BW

CAUTION: 1. DISCONNECT OVEN FROM POWER SUP

PLY BEFORE REMOVING OUTER CASE.

2. DISCHARGE THE HIGH VOLTAGE CA­PACITOR BEFORE TOUCHING ANY OVEN
COMPONENTS OR WIRING.

NOTE: When replacing the outer case, the 2 special

Torx screws must be reinstalled in the same
locations.

POWER TRANSFORMER REMOVAL

Special screw

Screw Driver
(Type: TORX T20 H or 
GTXH20-100)

1. Disconnect the power supply cord and remove outer
case.

2. Open the oven door and block it open.

3. Discharge high voltage capacitor.

4. Disconnect wire leads from power transformer,
magnetron and capacitor terminals.

5. Remove four (4) screws holding transformer to bottom
right plate.

6. Remove transformer from bottom right plate.

7. Remove the one (1) terminal insulator and tube from
filament lead (longer one) of power transformer.

TERMINAL INSULATOR REPLACEMENT

1. Disconnect the power supply cord, and then remove
outer case.

2. Open the door and block it open.

3. Discharge high voltage capacitor.

4. Open covers of the terminal insulator by using small flat
type screw driver.

5. Remove the receptacle from the terminal insulator.

6. Now, the terminal insulator is free.

Re-install

1. Install the terminal insulator to receptacle of filament
lead (longer one) of power transformer.

2. Rest transformer on the bottom right plate with its primary
terminals toward the oven face plate.

3.

Secure transformer with four screws to bottom right plate.

4. Re-connect wire leads (primary and high voltage) to
power transformer and filament leads of transformer to
magnetron and high voltage capacitor. Refer to
"PICTORIAL DIAGRAM" on page 27.

5. Re-install outer case and check that oven is operating
properly.

Installation

1. Insert the receptacle into terminal insulator.

2. Close covers of the terminal insulator, as shown below.

3. Reconnect all leads removed from components during
testing.

4. Reinstall the outer case (cabinet).

5. Reconnect the power supply cord after the outer case is
installed.

6. Run the oven and check all functions.

Terminal 
insulator

Flat type
screw driver

HIGH VOLTAGE RECTIFIER AND HIGH VOLTAGE CAPACITOR REMOVAL

1. Disconnect the power supply cord and remove outer
case.

2. Open the door and block it open.

3. Discharge high voltage capacitor.

4. Disconnect the high voltage wire B from the high voltage
capacitor.

5. Disconnect the high voltage wire of high voltage rectifier
assembly from the magnetron.

6. Remove one (1) screw holding capacitor holder to oven
cavity rear plate.

COVERS

RECEPTACLE

7. Disconnect rectifier terminal from capacitor.
High voltage rectifier assembly is now free.

8. Remove one (1) screw holding high voltage rectifier
assembly to capacitor holder.

9. Remove capacitor holder. Capacitor is now free.

CAUTION: WHEN REPLACING HIGH VOLTAGE RECTI-

FIER AND HIGH VOLTAGE CAPACITOR,
GROUND SIDE TERMINAL OF THE HIGH
VOLTAGE RECTIFIER MUST BE SECURED
FIRMLY WITH A GROUNDING SCREW.

22

Oven lamp
socket

Terminal

Wire lead

Terminal hole

Flate type small
screw driver

MAGNETRON REMOVAL

Terminal

Push

Pull down

4

5

Lever

Positive lock®
connector

R-300BW

Removal

1. Disconnect the power supply cord and remove outer case.

2. Open the door and block it open.

3. Discharge high voltage capacitor.

4. Disconnect wire leads from magnetron.

5. Remove the one (1) screw holding chassis support to
magnetron.

6. Remove the chassis support from oven.

7. Carefully remove the four (4) screws holding magnetron
to waveguide flange.

8. Lift up magnetron with care so that magnetron antenna
is not hit by any metal object around antenna.

9. Now, the magnetron is free.

Re-install

1. Re-install the magnetron to waveguide flange with the
four (4) screws as shown in Figure C-1.

2. Insert the two (2) tabs of the chassis support to the oven
cavity front plate and the back plate.

3. Re-install the chassis support to magnetron with the one
(1) screw.

OVEN LAMP AND LAMP SOCKET REMOVAL

1.

Disconnect the power supply cord and remove outer case.

2. Open the door and block it open.

3. Discharge high voltage capacitor.

4. Bend the tab of the partition angle holding the lamp
socket.

5. Lift up the oven lamp socket.

6. Pull the wire leads from the oven lamp socket by pushing
the terminal hole of the oven lamp socket with the small
flat type screw driver.

7. Now, the oven lamp socket is free.

4. Reconnect the wire leads to the magnetron. Refer to
"PICTORIAL DIAGRAM" on page 27.

5. Re-install outer case and check that the oven is operating
properly.

CAUTION: WHEN REPLACING MAGNETRON, BE SURE

THE R.F. GASKET IS IN PLACE AND MOUNT­ING SCREWS ARE TIGHTENED SECURELY

Screws

Magnetorn

Waveguide flange

Figure C-1. Magnetron replacement

Figure C-2. Oven lamp socket

POSITIVE LOCK® CONNECTOR (NO-CASE TYPE) REMOVAL

1. Disconnect the power supply cord, and remove outer
case.

2. Open the door and block it open.

3. Discharge high voltage capacitor.

4. Push the lever of positive lock® connector.

5. Pull down on the positive lock® connector.

CAUTION: WHEN CONNECTING THE POSITIVE LOCK

CONNECTORS TO THE TERMINALS, IN­STALL THE POSITIVE LOCK® SO THAT THE
LEVER FACES YOU

CONTROL PANEL ASSEMBLY REMOVAL

1.

Disconnect the power supply cord and remove outer case.

2. Open the door and block it open.

3. Discharge high voltage capacitor.

4. Disconnect the wire leads and connector CN-B from
panel components.

®

Figure C-3. Positive lock® connector

5. Make one (1) tab of the oven cavity front plate straight
holding the control panel assembly to the oven flange.

6. Slide the control panel assembly upward and remove it.

7. Now, individual components can be removed.

23

R-300BW

TURNTABLE MOTOR REMOVAL

1. Disconnect the power supply cord.

2. Remove turntable and turntable support from oven cavity.

3. Lay the oven on it's backside. Remove the turntable
motor cover by snipping off the material in four corners.

4. Where the corners have been snipped off bend corner
areas flat. No sharp edges must be evident after removal
of the turntable motor cover.

COOLING FAN MOTOR REMOVAL

REMOVAL

1.

Disconnect the power supply cord and remove outer case.

2. Open the door and block it open.

3. Discharge high voltage capacitor.

4. Disconnect the wire leads from the fan motor.

5. Remove the magnetron from the waveguide flange,
referring to "MAGNETRON REMOVAL".

6.

Release the snap of the main wire harness from the fan duct.

7. Remove one (1) screw holding the fan duct assembly to
oven cavity.

8.

Release the main wire harness from the hole of the fan duct.

9. Release the fan duct from the waveguide flange.

10.Release the fan duct assembly from the oven cavity.

11.Remove the fan blade from the fan motor shaft according
to the following procedure.

12.Hold the edge of the rotor of the fan motor by using a pair
of groove joint pliers.

CAUTION:
* Make sure that no metal pieces enter the gap between

the rotor and the stator of the fan motor because the
rotor is easily shaven by pliers and metal pieces may
be produced.

* Do not touch the pliers to the coil of the fan motor

because the coil may be cut or injured.

* Do not disfigure the bracket by touching with the

pliers.

13.Remove the fan blade from the shaft of the fan motor by
pulling and rotating the fan blade with your hand.

14. Now, the fan blade will be free.

CAUTION:
* Do not reuse the removed fan blade because the

hole (for shaft) may be larger than normal.

Coil

Groove joint pliers

5. Disconnect wire leads from turntable motor.
(See "Positive lock connector removal")

6. Remove two (2) screws holding turntable motor to oven
cavity.

7. Now the turntable motor is free.

8. After replacement use the one (1) screw to fit the
turntable motor cover.

15.Remove the two (2) screws holding the fan motor to the
fan duct.

16.Now, the fan motor is free.

INSTALLATION

1. Install the fan motor to the fan duct with the two (2)
screws.

2. Install the fan blade to the fan motor shaft according to
the following procedure.

3. Hold the center of the bracket which supports the shaft
of the fan motor on the flat table.

4. Apply the screw lock tight into the hole (for shaft) of the
fan blade.

5. Install the fan blade to the shaft of fan motor by pushing
the fan blade with a small, light weight, ball peen hammer
or rubber mallet.

CAUTION:
* Do not hit the fan blade hard when installing

because the bracket may be disfigured.

* Make sure that the fan blade rotates smooth after

installation.

* Make sure that the axis of the shaft is not slanted.

6. Catch three holes of fan duct on three tabs of the
waveguide flange.

7. Install the fan duct assembly to the oven cavity with the
one (1) screw.

8. Insert the snap of the main wire harness to the hole of the
fan duct and insert the main wire harness into the hole of
the fan duct.

9. Install the magnetron and the chassis support to the
oven cavity, referring to "Re-install of MAGNETRON
REMOVAL".

10.Connect the wire leads to the fan motor, referring to the
pictorial diagram.

Shaft

Stator

Gap
Bracket

Rotor

Shaft

Axis

Stator

Rotor

These are the positions
that should be pinched
with pliers

Table

Center of
bracket

Side ViewRear View

24

R-300BW

DOOR SENSING SWITCH/SECONDARY INTERLOCK SWITCH AND MONITOR SWITCH REMOVAL

1.

Disconnect the power supply cord and remove outer case.

2. Open the door and block it open.

3. Discharge high voltage capacitor.

4. Disconnect wire leads from the switches.

5.

Remove two (2) screws holding latch hook to oven flange.

6. Remove latch hook assembly from oven flange.

7. Push outward on the two (2) retaining tabs holding switch
in place.

8. Switch is now free.
At this time switch lever will be free, do not lose it.

Re-install

1. Re-install each switch in its place. The secondary
interlock/monitor switches are in the lower position and
the door sensing switch is in the upper position.

2. Re-connect wire leads to each switch.
Refer to pictorial diagram.

3. Secure latch hook (with two (2) mounting screws) to
oven flange.

4. Make sure that the monitor switch is operating properly
and check continuity of the monitor circuit. Refer to
chapter "Test Procedure" and Adjustment procedure.

DOOR SENSING SWITCH/SECONDARY INTERLOCK SWITCH AND MONITOR SWITCH ADJUSTMENT

1. Disconnect the power supply cord, and then remove
outer case.

2. Open the door and block it open.

3. Discharge high voltage capacitor.

If the door sensing switch, secondary interlock switch and
monitor switch do not operate properly due to a
misadjustment, the following adjustment should be made.

4. Loosen the two (2) screws holding latch hook to the oven
cavity front flange.

5. With door closed, adjust latch hook by moving it back and
forth, and up and down. In and out play of the door
allowed by the upper and lower position of the latch hook
should be less than 0.5mm. The vertical position of the
latch hook should be adjusted so that the door sensing
switch and secondary interlock switch are activated with
the door closed. The horizontal position of the latch hook
should be adjusted so that the plunger of the monitor
switch is pressed with the door closed.

6. Secure the screws with washers firmly.

7. Check the operation of all switches. If each switch has
not activated with the door closed, loosen screw and
adjust the latch hook position.

After adjustment, check the following.

1. In and out play of door remains less than 0.5mm when in
the latched position. First check upper position of latch

hook, pushing and pulling upper portion of door toward
the oven face. Then check lower portion of the latch
hook, pushing and pulling lower portion of the door
toward the oven face. Both results (play in the door)
should be less than 0.5mm.

2. The door sensing switch and secondary interlock switch
interrupt the circuit before the door can be opened.

3. Monitor switch contacts close when door is opened.

4. Re-install outer case and check for microwave leakage
around door with an approved microwave survey meter.
(Refer to Microwave Measurement Procedure.)

Door

Latch Hook


Latch
Heads

Switch
Lever

Door
Sensing 
Switch

Monitor
Switch

Secondary
Interlock
Switch

Figure C-4. Latch Switch Adjustments

DOOR REPLACEMENT

REMOVAL

1. Disconnect the power supply cord.

2. Push the open button and open the door slightly.

3. Insert a putty knife (thickness of about 0.5mm) into the
gap between the choke cover and door frame as shown
in Figure C-5 to free engaging parts.

4. Pry the principles of the lever and lift up the choke cover
by inserting a putty knife as shown Figure C-5.

5. Release choke cover from door panel.

6. Now choke cover is free.

7. Release two (2) pins of door panel from two (2) holes of
upper and lower oven hinges by lifting up.

8. Now, door assembly is free from oven cavity.

25

1

Choke Cover

11

12

10

9

8

13

7

2

3

5

6

Putty Knife

Figure C-5. Door Disassembly

4

Door Frame

R-300BW

9. Release door panel from seven (7) tabs of door frame by
sliding door panel downward.

10.Now, door panel with sealer film is free.

11.Tear sealer film from door panel.

12.Now, door panel is free.

13.Slide latch head upward and remove it from door frame
with releasing latch spring from door frame and latch
head.

14.Now, latch head and latch spring are free.

15.Remove door screen from door frame by releasing two
(2) tabs.

16.Now, door screen is free.

RE-INSTALL

1. Re-install door screen to door frame by fitting two (2) tabs
of door frame to two (2) holes of door screen.

2. Re-install the latch spring to the latch head. Re-install the
latch spring to the door frame. Re-install latch head to
door frame.

3. Re-install door panel to door frame by fitting seven (7)
tabs of door frame to seven (7) holes of door panel.

4. Hold the door panel to the door frame by sliding the door
panel upward.

5. Put sealer film on door panel. Refer to "Sealer Film"
about how to handle new one.

6. Catch two (2) pins of door panel on two (2) hole of upper
and lower oven hinges.

7. Re-install choke cover to door panel by pushing.

Note: After any service to the door;
(A) Make sure that door sensing switch and secondary

interlock switch are operating properly. (Refer to
chapter "Test Procedures".).

(B) An approved microwave survey meter should be

used to assure compliance with proper microwave
radiation emission limitation standards.

After any service, make sure of the following :

1. Door latch heads smoothly catch latch hook through
latch holes and that latch head goes through center of
latch hole.

2. Deviation of door alignment from horizontal line of cavity
face plate is to be less than 1.0mm.

3. Door is positioned with its face pressed toward cavity
face plate.

4. Check for microwave leakage around door with an
approved microwave survey meter. (Refer to Microwave
Measurement Procedure.)

Note: The door on a microwave oven is designed to act as

an electronic seal preventing the leakage of
microwave energy from oven cavity during cook
cycle. This function does not require that door be air­tight, moisture (condensation)-tight or light-tight.
Therefore, occasional appearance of moisture, light
or sensing of gentle warm air movement around
oven door is not abnormal and do not of themselves,
indicate a leakage of microwave energy from oven
cavity.

Pin

Upper oven hinge

Door panel

Lower oven
hinge

Lower 
oven

Pin

hinge

Choke cover

Figure C-6. Door Replacement

SEALER FILM

Installation

1. Put the adhesive tape on the backing film of the sealer
film as shown in Fig. C-7.

2. Tear the backing film by pulling the adhesive tape.

3. Put the pasted side of the sealer film on the door panel

Sealer film

Backing film

Adhesive tape

Figure C-7. Sealer film

26

R-300BW

1

A

B

C

BLKBLK

OVEN

THERMAL CUT-OUT

2

GRN

N

H

BLK

WHT

NOTE:

The grounding conductor of

the power supply cord has

been grounded by power

supply cord fixing screw.

The screw must allways be

kept tight.

3

NOTE:

The neutral (WHT) wire must be

connected to the terminal with "N"

mark on the power supply cord.



POWER SUPPLY 

CORD 120V 60Hz

WHT

45

RECTIFIER
H.V.

HIGH VOLTAGE

CAPACITOR

MAGNETRON

POWER 

TRANSFORMER

HIGH VOLTAGE COMPONENTS

RED

GRY

GRY

6

A

B

C

D

E

F

G

OVEN LAMP 

AND SOCKET

BLK

WHT

BLUE MARK

NOTE:

Hot (YLW) wire must be

connected to the terminal

with blue mark on the

oven light socket.

GRY

GRN

N.O.

COM.

DOOR

SENSING

SWITCH

GRN

BLK

BLK

THERMAL CUT-OUT (MG.)

GRN

CN-A



WHT



5

D

BLK

BLK

GRY

WHT

BLK

BLK

WHT

FAN MOTOR

TURNTABLE

MOTOR

E

Figure S-1. Pictorial Diagram

FUSE

BLK

&

HOLDER

ORG

CN-B



RED

GRY

BLK

GRN



12

WHT

N.C.

COM.

MONITOR

SWITCH

WHT

GRY

NO

SECONDARY

INTERLOCK

SWITCH

WHT

COM.

WHT

F

G

BLK

BLK

ORG







1

32

4

RED

RED

H

1

CONTROL UNIT

2

T1



RY2

CN-A

3



27

SP1

CN-B

45

H

6

R-300BW

1

A

SWITCH

B 1

B

D30

C

B 2

Q40

SP1

R40 3.3k

DTA143ES

2

D20

C30

R30 4.7k

HIGH

VOLTAGE

TRANSFORMER

NO

COM

D22

Q22

DTA143ES

R31 47k

3

AC

OVEN LAMP

FAN MOTOR

TURNTABLE

MOTOR

A 1

A 3

Q20

DTA143ES

D21

R21

300

+

–

R20 4.7k

RY1

C20 0.1µ/50v

Q21

DTD143ES

RY2

1/2w
100
R22

45

6

A

(A)

B

C21 10µ/35v

–

+

C

: IF NOT SPECIFIED 1/4w ± 5%

: IF NOT SPECIFIED 1SS270A

(JE)

: IF NOT SPECIFIED 0.01µF / 16v

D

0 V

Q2

DTA123ES

E

F

C6

G

H

R6 4.7k

D3

T1

(A)

+

ZD1 HZ6A3

+

D1

VRS1

CN-A

AC120V

60Hz

C5 0.1µ/50v
C4 47µ/16v

–

C2 0.1µ/50v
C1 470µ/35v

–

R7 10k

D4

D2

10G471K

c

A 5

R4 2k 1/2w

D1-D4

11ES1

d

a

D5

C3

b

(J1)

ZD2 HZ4A2

R5 4.7k

4MHz
CF1

VC

Q1 2SB1238

R1 100 2w

(JB)

(JA)

150

LD6LD12LD24

R55

150

36

35

34

33

31

27

26

F 330F 229F 128F 0

XIN

N C32N C

K 06K 1
5

VR1

AVDD
7

N C

S 0

S 111S 212S 3

N C
8

9

10

VDD

CNTR

XOUT



INT

RST

VREF

AVSS

1

2

3

4

D 825D 724D 623D 522D 421D 320D 2

I-1 IZA882DR

D 016D 1

N C14N C

CNVS

13

15

17

WH-A

19

VSS
18

LD5LD11LD17

R54

LD4LD10LD16LD22

150

R53

LD3LD9LD15LD21

150
R52

150

LD2LD8LD14LD20

R51

150LD1LD7LD13LD19
R50

DTB123ES

Q53

DTB123ES

Q52

DTB123ES

Q51

DTB123ES

Q50

C60

R63 100k

R62 100k

C61

R60 4.7k

CBA

R61 4.7k

LD18

LD23

SW1

D

E

Figure S-2. Control Panel Circuit

F

G

H

1

2

3

28

45

6

R-300BW

1

A

B

C

2

LD4

LD3

LD2

LD1

LD24

LD23

11

E

Q50

B

Q51

12

3

LD7

9

LD5

LD22

8

E

B

LD6

LD21

E

Q52

B

ABC

Q53

LD8

1
2
3
4
5

SW1

R60
R61

LD19

LD20

10

R50

R51

E

B

R52

C61

18

45

LD9

LD10

LD11

6

LD12

LD13

LD14

LD15

LD16

LD18

LD17

7

R63

R53

R54

R55

R62

C60

1314151617

6

A

B

C

D

E

F

G

SP1

C2

26

B

ZD2

E

Q2

C1

R6

D4

D3

25242322212019

(JA)

(JB)

32

R5

C3

33

38

R4

R40

B

Q1

R1

ZD1

C6

S

D

28

27

C5

R30

1

R20

VRS1

29

CF1

2

CN - A

D5

R31

C30

36

B

Q23

C20

B

D30

D20

D23

D22

15

Q22

E

RY3

RY2

41

VR1

E

GRILL MICRO

DIP

F

WH - A

G

WH - A

,F

31

30

Q40

E

34

35

CN - B

37

B

C4

C21

B

Q20

EEQ21

E

E

Q10

(JE)

(JC)

R22

B

40

39

ZD3

R10

D21

(JD)
R21

R7

P

RY1

H

1

D2

D1

T1

Figure S-3. Printed Wiring Board

2

(J1)

3

29

45

H

6

R-300BW

PARTS LIST

Note: The parts marked “∆” may cause undue microwave exposure.

The parts marked “*” are used in voltage more than 250V.

REF. NO. PART NO. DESCRIPTION Q'TY CODE

ELECTRIC PARTS

1- 1 QSW-MA110WRE0 2nd interlock switch / door sensing switch 2 AK
1- 2 QFSHDA009WRE0 Fuse holder 1 AH
1- 3 FFS-BA010WRK0 Monitor fuse and monitor switch assembly 1 AK
1- 4 RTHM-A078WRE0 Thermal cut-out 125 deg. 1 AL
1- 5 FACCDA048WRE0 Power supply cord 1 AW
1- 5 FACCDA075WRE0 Power supply cord (Interchangeable) 1 AN
1- 6 FH-DZA075WRK0 High voltage rectifier assembly 1 AS

*

1- 7 RC-QZA168WRE0 High voltage capacitor 1 AV

*

1- 7 RC-QZA126WRE0 High voltage capacitor (Interchangeable) 1 AX

*

1- 8 RV-MZA267WRE0 Magnetron 1 BL

∆

*

1- 8 RV-MZA197WRE0 Magnetron (Interchangeable) 1 BN

∆

*

1- 9 RMOTEA355WRE0 Fan motor 1 AU
1- 9 RMOTEA338WRE0 Fan motor (Interchangeable) 1 AV
1-10 QSOCLA021WRE0 Oven lamp socket 1 AH
1-11 RLMPTA030WRE0 Oven lamp 1 AF
1-12 RMOTDA161WRE0 Turntable motor 1 AU
1-13 RTHM-A107WRE0 Thermal cut-out 95 deg. 1 AM
1-14 RTRN-A536WRE0 Power transformer 1 BP

*

CABINET PARTS

2- 1 GCABUA649WRP0 Outer case cabinet 1 AZ
2- 2 GDAI-A261WRW0 Bottom left plate 1 AP
2- 3 GDAI-A286WRW0 Bottom right plate 1 AN
2- 4 GLEGPA019WRE0 Foot 2 AD
2- 5 GLEGPA067WRF0 Leg 1 AE

CONTROL PANEL PARTS

3- 1 CPWBFA795WRK0 Control unit 1 BM
3- 1A QCNCMA430DRE0 3-pin connector (CN-A) 1 AG
3- 1B QCNCMA414DRE0 2-pin connector (CN-B) 1 AB
3- 1C FW-VZA234DRE0 Lead wire (WH-A) 1 AD
C1 VCEAB31VW477M Capacitor 470uF 35V 1 AC
C2 RC-KZA087DRE0 Capacitor 0.1uF 50V 1 AA
C3 VCKYD11CY103N Capacitor 0.01uF 16V 1 AA
C4 VCEAB31CW476M Capacitor 47uF 16V 1 AA
C5 RC-KZA087DRE0 Capacitor 0.1uF 50V 1 AA
C6 VCKYD11CY103N Capacitor 0.01uF 16V 1 AA
C20 VCEAB31HW104M Capacitor 0.1uF 50V 1 AM
C21 VCEAB31VW106M Capacitor 10uF 35V 1 AA
C30 VCKYD11CY103N Capacitor 0.01uF 16V 1 AA
C60-61 VCKYD11CY103N Capacitor 0.01uF 16V 2 AA
CF1 RCRS-A012DRE0 Ceramic resonator (CST4.00MGW) 1 AD
D1-4 VHD11ES1///-1 Diode (11ES1) 4 AB
D5 VHD1SS270A/-1 Diode (1SS270ATA) 1 AA
D20-22 VHD1SS270A/-1 Diode (1SS270ATA) 3 AA
D30 VHD1SS270A/-1 Diode (1SS270ATA) 1 AA
I-1 RH-IZA882DRE0 LSI 1 AK
LD1-24 VHPLTL1CHE/-3 Light emitting diode (LED) 24 AD
Q1 VS2SB1238//-3 Transistor (2SB1238) 1 AA
Q2 VSDTA123ES/-3 Transistor (DTA123ES) 1 AA
Q20 VSDTA143ES/-3 Transistor (DTA143ES) 1 AB
Q21 VSDTD143ES/-3 Transistor (DTD143ES) 1 AC
Q22 VSDTA143ES/1B Transistor (DTA143ES) 1 AA
Q40 VSDTA143ES/-3 Transistor (DTA143ES) 1 AB
Q50-53 VSDTB123ES/-3 Transistor (DTB123ES) 4 AC
R1 VRS-L63DA101J Resistor 100 ohm 2W 1 AD
R4 VRD-B12HF202J Resistor 2.0k ohm 1/2W 1 AB
R5-6 VRD-B12EF472J Resistor 4.7k ohm 1/4W 2 AA
R7 VRD-B12EF103J Resistor 10k ohm 1/4W 1 AA
R20 VRD-B12EF472J Resistor 4.7k ohm 1/4W 1 AA
R21 VRD-B12EF301J Resistor 300 ohm 1/4W 1 AA
R22 VRD-B12HF101J Resistor 100 ohm 1/2W 1 AB
R30 VRD-B12EF472J Resistor 4.7k ohm 1/4W 1 AA
R31 VRD-B12EF473J Resistor 47k ohm 1/4W 1 AA
R40 VRD-B12EF332J Resistor 3.3k ohm 1/4W 1 AA
R50-55 VRD-B12EF151J Resistor 150 ohm 1/4W 6 AA
R60-61 VRD-B12EF472J Resistor 4.7k ohm 1/4W 2 AA

30

REF. NO. PART NO. DESCRIPTION Q'TY CODE

R62-63 VRD-B12EF104J Resistor 100k ohm 1/4W 2 AA
RY1 RRLY-A111DRE0 Relay (JV12S-KT) 1 AL
RY2 RRLY-A097DRE0 Relay (DU12D1-1P(M)) 1 AL
SP1 RALM-A014DRE0 Buzzer (PKM22EPT-THAI) 1 AG
SW1 RVR-BA018WRE0 Rotary encoder 1 AL
T1 RTRNPA126DRE0 Transformer 1 AP
VR1 RVR-BA014DRE0 Potentiometer 1 AF
VRS1 RH-VZA032DRE0 Varistor (10G471K) 1 AE
ZD1 VHEHZ6A3///-1 Zener diode (HZ6A3) 1 AC
ZD2 VHEHZ4A2///-1 Zener diode (HZ4A2) 1 AA
3- 2 HPNLTA134WRE0 Timer sheet 1 AG
3- 3 JKNBKA598WRF0 Timer knob 1 AF
3- 4 LHLD-A186WRF0 LED holder 1 AL
3- 5 HPNLCB467WRR0 Control panel 1 AU
3- 6 JKNBKA605WRF0 Vari. knob 1 AF
3- 7 MSPRTA189WRE0 Vari. spring 1 AE
3- 8 JBTN-B029WRF0 Open button 1 AG
3- 9 MSPRCA050WRE0 Open button spring 1 AB
3- 10 XEPSD30P08XS0 Screw : 3mm x 8mm 5 AA

OVEN PARTS

4- 1 PCUSUA376WRP0 Cushion 1 AG
4- 2 PPACGA084WRF0 TTM packing 1 AF
4- 3 PHOK-A106WRF0 Latch hook 1 AL

∆

4- 4 LBNDKA099WRW0 Capacitor holder 1 AD
4- 5 NFANJA029WRE0 Fan blade 1 AL
4- 6 PDUC-A652WRP0 Fan duct 1 AU
4- 7 ************* Oven cavity (Not a replaceable part) 1--

∆

4- 8 LANGFA175WRP0 Chassis support 1 AX
4- 9 LANGQA452WRP0 Partition angle 1 AK
4-10 LANGQA454WRP0 MG thermo angle 1 AH
4-11 MLEVPA226WRF0 Switch lever 1 AF
4-12 NCPL-A045WRF0 Coupling 1 AH
4-13 PCUSGA353WRP0 Cushion 1 AH
4-14 PCOVPA275WRE0 Waveguide cover 1 AR
4-15 PCUSGA339WRP0 Cushion 1 AG
4-16 PCUSUA212WRP0 Cushion 1 AB
4-17 PCUSUA235WRP0 Cushion 1 AF
4-18 GCOVHA385WRF0 Choke cover 1 AG

DOOR PARTS

5- 1 FDORFA318WRT0 Door panel 1 BE

∆

5- 2 PSHEPA382WRE0 Sealer film 1 AH
5- 3 GWAKPA549WRR0 Door frame 1 AZ

∆

5- 4 HPNL-A690WRR0 Door screen 1 AT
5- 5 LSTPPA139WRF0 Latch head 1 AF

∆

5- 6 MSPRTA187WRE0 Latch spring 1 AC
5- 7 XCPSD40P08000 Screw : 4mm x 8mm 1 AA
5- 8 XCPSD40P08WN2 Screw : 4mm x 8mm 1 AC

MISCELLANEOUS

6- 1 FROLPA079WRK0 Turntable support 1 AQ
6- 2 NTNT-A084WRE0 Turntable tray 1 AR
6- 3 FW-VZB681WRE0 Main wire harness 1 AW
6- 4 QW-QZA150WRE0 High voltage wire B 1 AF

*

6- 5 PZET-A012WRE0 Terminal insulator 1 AB
6- 6 TCAUAA166WRR0 DHHS caution label 1 AC
6- 7 TCAUAA189WRR0 Monitor caution label 1 AG
6- 8 TINSEA756WRR0 Instruction book 1 AG
6- 9 FW-VZB682WRE0 Switch harness 1 AG
6-10 TCAUAA240WRR0 Screw caution 1 AC
6-11 TCAUAA243WRR0 Earth caution 2 AC

SCREWS,NUTS AND WASHERS

7- 1 XFPSD40P08K00 Screw : 4mm x 8mm 10 AA
7- 2 XHPSD30P06000 Screw : 3mm x 6mm 1 AA
7- 3 XHTSD40P08RV0 Screw : 4mm x 8mm 3 AA
7- 4 XHTSD40P12RV0 Screw : 4mm x 12mm 1 AA
7- 5 XOTSD40P12RV0 Screw : 4mm x 12mm 6 AA
7- 6 XOTSD40P12000 Screw : 4mm x 12mm 13 AA
7- 7 XOTSE40P08000 Screw : 4mm x 8mm 1 AA
7- 8 LX-CZA070WRE0 Special screw (Torx tamper proof screw) 2 AC

R-300BW

31

R-300BW

1

A

HOW TO ORDER REPLACEMENT PARTS

To have your order filled promptly and correctly, please furnish the following information.

1. MODEL NUMBER 2. REF. NO. 3. PART NO. 4. DESCRIPTION

Order Parts from the authorized SHARP parts Distributor for your area.
Defective parts requiring return should be returned as indicated in the Service Policy.

2

3

CONTROL PANEL PARTS

3-1

45

3-10

3-10

6

A

B

C

3-8

D

E

3-6

3-9

3-5

5-3

3-7

5-1

3-3

3-2

3-4

5-8

5-2

3-10

B

3-10

C

DOOR PARTS

4-18

D

5-7

E

5-4

F

G

H

Actual wire harness may be different from illustration.

1

6-3

2

5-6

6-4

6-5

3

32

5-5

MISCELLANEOUS

(CAPACITOR)

6-9



45

F

G

H

6

R-300BW

1

OVEN AND CABINET PARTS

A

B

C

4-17

2

4-1

1-11

4-9

1-10

1-4

7-2

6-7

6-11

3

2-1

7-5

7-3

4-10

1-13

1-8

4-16

45

7-5

7-8

7-1

6-11

6-6

6

A

7-5

7-8

B

7-7

C

D

4-7

E

4-12

4-14

F

2-2

G

7-6

2-4

1-12

4-2

7-1

6-9

4-11

7-5

7-5
7-1

4-15

4-3

1-1

1-1

1-14

1-2

1-3

4-13

7-6

7-5

1-9

1-5

7-3

7-1

4-4

7-4

4-6

6-10

4-5

1-6

1-7

7-1

7-6

4-8

6-2

7-3

D

E

F

G

7-6

H

1

2-5

7-6

7-6

7-6

2

7-6

7-6

7-6

2-4

3

33

2-3

6-1

45

H

6

R-300BW

A

B

C

D

E

F

PACKING AND ACCESSORIES

1

INTO THE
OVEN CAVITY

2

DOOR PROTECTION SHEET
SPADPA204WRE0

6- 8 INSTRUCTION BOOK
& PRINTING MATTER

6- 2 TURNTABLE TRAY

6- 1 TURNTABLE SUPPORT

TRAY PACK
SPADFA397WRE0

3

45

TOP PAD ASSEMBLY
FPADBA341WRK0

PLASTIC BAG
SSAKHA034WRE0

BOTTOM PAD ASSEMBLY
FPADBA342WRK0

6

A

B

C

D

E

F

G

H

1

Not replaceable items.

2

3

45

COPYRIGHT © 1998 BY SHARP CORPORATION

ALL RIGHTS RESERVED.

No part of this publication may be repro­duced, stored in retrieval systems, or trans­mitted in any form or by any means, elec­tronic, mechanical, photocopying, record­ing, or otherwise, without prior written per­mission of the publisher.

PACKING CASE
SPAKCD105WRE0

G

H

6

34

'98 SHARP CORP. (5S2.530E) Printed in U.S.A