SHARP R405, R-405KS, R-403KK, R403K Service Manual

SERVICE MANUAL

R-405KS
R-403KK

MICROWAVE OVEN MODELS

R-405KS

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..)

R-403KK

S45M250R405KE

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

TOUCH CONTROL PANEL ................................................................................................................................18

COMPONENT REPLACEMENT AND ADJUSTMENT PROCEDURE ..................................................................23

PICTORIAL DIAGRAM ........................................................................................................................................30

CPU UNIT CIRCUIT ............................................................................................................................................. 31

PRINTED WIRING BOARD ................................................................................................................................. 33

PARTS LIST ........................................................................................................................................................ 34

PACKING AND ACCESSORIES ......................................................................................................................... 41

This document has been published to be used for after

SHARP ELECTRONCS CORPORATION

sales service only.
The contents are subject to change without notice.

Service Headquarters: Sharp Plaza, Mahwah, New Jersey, 07430-2135

R-405KS
R-403KK

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 release 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

Don't Touch !
Danger High Voltage

R-405KS
R-403KK

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 operated 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 re-
examine 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 a microwave leakage test should be carried out.

1

R-405KS
R-403KK

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 switch shall prevent microwave radiation emission in excess of the requirement as above
mentioned. Secondary interlock relay and door sensing 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

O

C (68OF) 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 primary interlock switch/secondary interlock relay does turn the oven OFF before any door movement.

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

2

SERVICE MANUAL

R-405KS
R-403KK

MICROWAVE OVENS

R-405KS & R-403KK

FOREWORD

This Manual has been prepared to provide Sharp Electronics Corp.
Service Personnel with Operation and Service Information for the SHARP
MICROWAVE OVENS R-405KS and R-403KK.

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 no other visible damage with the oven.

PRODUCT DESCRIPTION

GENERAL INFORMATION

OPERATION

TROUBLESHOOTING GUIDE AND
TEST PROCEDURE

TOUCH CONTROL PANEL

COMPONENT REPLACEMENT
AND ADJUSTMENT PROCEDURE

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.

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.

WIRING DIAGRAM

PARTS LIST

SHARP ELECTRONICS CORPORATION

SHARP PLAZA, MAHWAH,

NEW JERSEY 07430-2135

3

R-405KS
R-403KK

SPECIFICATION

ITEM DESCRIPTION

Power Requirements 120 Volts

14.0 Amperes, 1600 watts
60 Hertz
Single phase, 3 wire grounded

Power Output 1100 watts (IEC TEST PROCEDURE)

Operating frequency of 2450MHz

Case Dimensions Width 21-11/16"

Height 12-3/8"
Depth 17-3/8"

Cooking Cavity Dimensions Width 15"

Height 9-7/16"

1.4 Cubic Feet Depth 16-3/4"

Control Complement Touch Control System

Clock ( 1:00 - 12:59 )
Timer (0 - 99 min. 99 seconds)

Microwave Power for Variable Cooking

Repetition Rate;

P-HI .................................................. Full power throughout the cooking time

P-90 .................................................................... approx. 90% of Full Power

P-80 .................................................................... approx. 80% of Full Power

P-70 .................................................................... approx. 70% of Full Power

P-60 .................................................................... approx. 60% of Full Power

P-50 .................................................................... approx. 50% of Full Power

P-40 .................................................................... approx. 40% of Full Power

P-30 .................................................................... approx. 30% of Full Power

P-20 .................................................................... approx. 20% of Full Power

P-10 .................................................................... approx. 10% of Full Power

P-0 ...................................................... No power throughout the cooking time

R-405KS

START, MINUTE PLUS pad, Cook pad, Defrost pad, Number selection pads,
Power Level pad, Timer/Clock pad,Stop/Clear pad, Warm, Melt, Reheat,
Popcorn, Night light and Soften.

R-403KK

START, MINUTE PLUS pad, Cook center pad, Defrost center pad, Number
selection pads, Power Level pad, Timer/Clock pad,Stop/Clear pad, Warm, Melt,
Reheat center pad, Popcorn, Night light and Soften.

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 120 volt 60 Hz, AC only,

4

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.

CAUTION: DO NOT UNDER ANY CIRCUMSTANCES CUT OR RE-

MOVE THE ROUND GROUNDING PRONG FROM THIS
PLUG.

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. Auto-Touch control panel.

9. Time display: Digital display, 99
minutes 99 seconds.

10. Wave guide cover.

11. Power supply cord

6

2

Grounded
Receptacle Box

3-Pronged
Plug

Grounding Pin

3-Pronged Receptacle

OVEN DIAGRAM

5

9

10

4

3

8

1

R-405KS
R-403KK

7

11

TOUCH CONTROL PANELS

NOTE:
The directed features are disa­bled after one minute when the
oven is not in use. These features
are automatically enabled when
the door is opened and closed or
the STOP/ CLEAR pad is pressed.

R-405KS R-403KK

5

R-405KS
R-403KK

OPERATION

DESCRIPTION OF OPERATING SEQUENCE

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

OFF CONDITION

Closing the door activates the door sensing switch and
primary 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).

1. The display will show flashing "88:88".
To set any program or set the clock, you must first touch
the STOP/CLEAR pad. The display will clear, and " : "
will appear.

COOKING CONDITION

Program desired cooking time by touching the NUMBER
pads. Program the power level by touching the POWER
LEVEL pad and then a Number pad.
When the START pad is touched, 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)

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

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

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

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

close. And contacts of the relay (RY1) open.
If the primary interlock switch and secondary 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, primary interlock switch,
relay (RY1) and secondary interlock relay (RY2), causing the
monitor fuse to blow.

POWER LEVEL P-0 TO P-90 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 3.3 volts
A.C. output on the filament winding, and approximately
2370 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, the monitor
switch, door sensing switch, primary interlock switch,
relay (RY1) and secondary 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 primary interlock switch and secondary interlock relay

VARI-MODE ON TIME OFF TIME

Power 10(P-HI) 32 sec. 0 sec.
(100% power)

Power 9(P-90) 30 sec. 2 sec.
(approx. 90% power)

Power 8(P-80) 26 sec. 6 sec.
(approx. 80% power)

Power 7(P-70) 24 sec. 8 sec.
(approx. 70% power)

Power 6(P-60) 22 sec. 10 sec.
(approx. 60% power)

Power 5(P-50) 18 sec. 14 sec.
(approx. 50% power)

Power 4(P-40) 16 sec. 16 sec.
(approx. 40% power)

Power 3(P-30) 12 sec. 20 sec.
(approx. 30% power)

Power 2(P-20) 8 sec. 24 sec.
(approx. 20% power)

Power 1(P-10) 6 sec. 26 sec.
(approx. 10% power)

Power 0(P-0) 0 sec. 32 sec.
(0% 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

R-405KS
R-403KK

SCHEMATIC

Note:* Indicates component

NOTE: CONDITION OF OVEN

1. Door Closed

2. CLOCK APPEARS ON DISPLAY

CAVITY
TEMPERATURE
FUSE

MONITOR

"TO SOURCE"

FUSE (20A)

"TO SOURCE"

NOISE
FILTER

RED

"TO LOAD"

C2

C3

"TO LOAD"

BLK

H

GRN

120VAC

GND

60Hz

N

R2

C1

WHT

NOTES:

1.CIRCUITS SUBJECT TO CHANGE WITHOUT NOTICE.

2. TERMINAL WITH PROJECTION OR OPPOSITE BLUE MARK ON LAMP SOCKET
MUST BE CONNECTED TO NEUTRAL WIRE.

3. ONLY CERTAIN MODELS USE THE ABSOLUTE HUMIDITY SENSOR.

4. POWER TRANSFORMER TOP (FINISH LEAD) TERMINAL MUST BE CONNECTED TO THE NEUTRAL (WHT) WIRE.

MAGNETRON
TEMPERATURE
FUSE

RED

(RY1)

N.O.

OVEN
LAMP
RELAY

WHT

GRY

COM.

ORG
ORG

RED

(RY2)

RED

COM.

BRN

TURN

TTM

TABLE
MOTOR

WHT

N.O.

WHT
WHT

B2

B1

F3

F2

ORG

GRN
GRN

GRN

GRN

DOOR
SENSING
SWITCH

PNK

HUMIDITY

SENSOR

F1

ORG

FAN

FM

MOTOR

WHT

MONITOR
SWITCH

WHT

RED

N.C.

COM.

WHT

RED

WHT

WHT

POWER
TRANSFORMER

HIGH
VOLTAGE
CAPACITOR
xx µF

HIGH
VOLTAGE
RECTIFIER

MAGNETRON

BRN

ORG

N.O.

SECONDARY
INTERLOCK
RELAY

CONTROL UNIT

ORG

OVEN

OL

LAMP

GRY

COM.

GRY

WHT

PRIMARY
INTERLOCK
SWITCH

Figure O-1 Oven Schematic - Off Condition

SCHEMATIC

NOTE: CONDITION OF OVEN

1. DOOR CLOSED

2. COOKING TIME PROGRAMMED

3. VARIABLE COOKING CONTROL "HIGH"

4. "START" PAD TOUCHED

CAVITY
TEMPERATURE
FUSE

MONITOR

"TO SOURCE"

FUSE (20A)

"TO SOURCE"

NOISE
FILTER

RED

"TO LOAD"

C2

C3

"TO LOAD"

BLK

H

GRN

120VAC

GND

60Hz

N

R2

C1

WHT

NOTES:

1.CIRCUITS SUBJECT TO CHANGE WITHOUT NOTICE.

2. TERMINAL WITH PROJECTION OR OPPOSITE BLUE MARK ON LAMP SOCKET
MUST BE CONNECTED TO NEUTRAL WIRE.

3. ONLY CERTAIN MODELS USE THE ABSOLUTE HUMIDITY SENSOR.

4. POWER TRANSFORMER TOP (FINISH LEAD) TERMINAL MUST BE CONNECTED TO THE NEUTRAL (WHT) WIRE.

MAGNETRON
TEMPERATURE
FUSE

RED

N.O.

GRY

(RY1)

OVEN
LAMP
RELAY

WHT

COM.

ORG
ORG

BRN

ORG

N.O.

ORG

OVEN

OL

LAMP

GRY

COM.

GRY

WHT

PRIMARY
INTERLOCK
SWITCH

(RY2)

SECONDARY
INTERLOCK
RELAY

CONTROL UNIT

N.O.

WHT
WHT

TTM

BRN

WHT

RED
RED

COM.

TURN
TABLE
MOTOR

B2

B1

F3

F2

ORG

GRN
GRN

GRN

GRN

DOOR
SENSING
SWITCH

PNK

HUMIDITY

SENSOR

F1

ORG

FAN

FM

MOTOR

WHT

MONITOR
SWITCH

WHT

RED

N.C.

COM.

WHT

RED

WHT

WHT

POWER
TRANSFORMER

HIGH
VOLTAGE
CAPACITOR
xx µF

HIGH
VOLTAGE
RECTIFIER

MAGNETRON

Figure O-2 Oven Schematic - Cooking Condition

7

R-405KS
R-403KK

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.

Latch Heads

Door

Switch Lever

Door Sensing
Switch

Monitor S witch

Primary Interlock
Switch

Figure D-1. Door Open Mechanism

DOOR SENSING AND PRIMARY INTERLOCK
SWITCHES

The primary interlock switch is mounted in the lower position
of the latch hook and the door sensing switch in the second­ary 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 secondary interlock system consists of the
door sensing switch and secondary 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 secondary
interlock relay (RY2) and primary 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 secondary interlock relay (RY2) and primary
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 primary interlock switch contacts close. (On opening
the door, each of these switches operate inversely.)

3. If the door is opened, and the secondary interlock relay
(RY2) and primary 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,
SECONDARY INTERLOCK RELAY (RY2), RE­LAY (RY1), PRIMARY 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 channeled
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.

CAVITY TEMPERATURE FUSE

The cavity temperature fuse located on the top of the oven
cavity, is designed to prevent damage to the oven by fire. If the
food load is overcooked, by either error in cook time or defect
in the control unit, the cavity temperature fuse will open.
Under normal operation, the cavity temperature fuse remains
closed. However, when abnormally high temperatures are
reached within the oven cavity, the cavity temperature fuse will
open at 302OF(150OC) causing the oven to shut down.
NOTE: This is a fuse. It does not reset.

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.

Magnetron TEMPERATURE FUSE

The magnetron temperature fuse 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 magnetron temperature fuse
remains closed. However, when abnormally high temperatures
are reached within the magnetron, the magnetron temperature
fuse will open at 302OF(150OC) causing the oven to shut down.
NOTE: This is a fuse. It does not reset.

8

R-405KS
R-403KK

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, relay (RY1)

secondary interlock relay (RY2), door sensing switch and primary interlock switch before replacing the monitor
fuse. If the monitor fuse is replaced, the monitor switch must also be replaced. Use part FFS-BA016/KIT 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.

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R-403KK

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

C/T fuse blows when power cord is
plugged into wall receptacle.

All letters and indicators do not ap­pear in display when power cord is
first plugged into wall outlet.

Display does not operate properly
when STOP/CLEAR key is touched.
(Buzzer should sound and ":" or time
of day should appear in display.)

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 START pad is touched

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 Cooking Power P­50 mode. (Operates properly on
Cooking P-HI (HIGH) mode.)

Oven goes into COMPU DEFROST
but food is not defrosted well.

RE RE

ABCD EEF FG H

SHORT IN POWER CORD

SHORT OR OPENED WIRING

MAGNETRON

POWER TRANSFORMER

H.V. RECTIFIER ASSEMBLY

RE RE CKICK CK CK

HIGH VOLTAGE CAPACITOR

CAVITY TEMPERATURE FUSE

MAGNETRON TEMP FUSE

SECONDARY INTERLOCK SYSTEM

PRIMARY INTERLOCK SWITCH

MONITOR SWITCH

MONITOR FUSE

OVEN LAMP OR SOCKET

COOLING FAN MOTOR

TURNTABLE MOTOR

TOUCH CONTROL PANEL

WRONG OPERATION

LOW VOLTAGE

JKLM

DIRTY OVEN CAVITY

KEY UNIT

RELAY (RY1)

COMPU DEFROST

FOIL PATTERN ON PWB.

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.

TEST PROCEDURES

COMPONENT TEST

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TEST PROCEDURES

R-405KS
R-403KK

PROCEDURE

LETTER

COMPONENT TEST

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:

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 33
to 62OF(18.6 to 34.5OC) 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 90 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.

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

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TEST PROCEDURES

PROCEDURE

LETTER

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 CAVITY TEMPERATURE 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. A continuity check across the cavity temperature fuse terminals should indicate a closed circuit unless
the temperature of the cavity temperature fuse reaches approximately 302OF(150OC). An open cavity
temperature fuse indicates overheating of the oven, exchange the cavity temperature fuse 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 TEMPERATURE 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. A continuity check across the magnetron temperature fuse terminals should indicate a closed circuit
unless the temperature of the magnetron temperature fuse reaches approximately 302OF(150OC). An
open magnetron temperature fuse indicates overheating of the magnetron. Check for restricted air flow
to the magnetron, especially the cooling fan 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.

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