SHARP R55TSF Service Manual

SERVICE MANUAL

TOASTER OVEN WITH MICROWAVE

R-55TS-F

SY517R55TSPF/

MODEL

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

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 ............................................................................................................................ 11

TEST PROCEDURE ............................................................................................................................................ 13

TOUCH CONTROL PANEL ................................................................................................................................. 21

COMPONENT REPLACEMENT AND ADJUSTMENT PROCEDURE ................................................................ 27

PICTORIAL DIAGRAM ........................................................................................................................................ 34

CONTROL UNIT CIRCUIT .................................................................................................................................. 35

PRINTED WIRING BOARD ................................................................................................................................. 36

PARTS LIST ........................................................................................................................................................ 37

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

R-55TS-F

Page

SHARP CORPORATION

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

R-55TS-F

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

Don't Touch !
Danger High Voltage

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-55TS-F

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 a microwave leakage test should be carried out.

1

R-55TS-F

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 and the primary interlock relay do turn the oven OFF before any door movement.

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

2

SERVICE MANUAL

R-55TS-F

TOASTER OVEN WITH MICROWAVE

R-55TS-F

FOREWORD

This Manual has been prepared to provide Sharp Electronics Corp.
Service Personnel with Operation and Service Information for the
SHARP TOASTER OVEN WITH MICROWAVE, R-55TS-F.

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.

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.

PRODUCT DESCRIPTION

GENERAL INFORMATION

OPERATION

TROUBLESHOOTING GUIDE AND
TEST PROCEDURE

TOUCH 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-55TS-F

SPECIFICATION

ITEM DESCRIPTION

Power Requirements 120 Volts / 8.5 Amperes (Microwave)/ 10.8 Amperes (Grill and Bake)

60 Hertz / Single phase, 3 wire grounded

Power Output 650 watts (IEC TEST PROCEDURE)

Operating frequency of 2450MHz

Upper Heater Power Output 760 Watts

Lower Heater Power Output 510 Watts

Case Dimensions Width 17-3/4"

Height 11-3/8"
Depth 15-1/8"

Cooking Cavity Dimensions Width 11-1/4"

Height 5-7/8"

0.5 Cubic Feet Depth 11-5/8"

Control Complement Touch Control System

Clock ( 1:00 - 12:59 )
Timer (0 - 95 minutes)

Microwave Power for Variable Cooking
Repetition Rate;

P100 ................................................ Full power throughout the cooking time

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

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

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

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

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

Grill cooking (GRILL) ........... Top and bottom grill mode/ Top grill mode only

Bake cooking (BAKE) ................................. 325 - 400˚F temperature control

AUTOMATIC COOKING pads (TOAST pad, SNACKS pad, BAKE pad)
MICRO pad, GRILL pad, BAKE pad, POPCORN pad, REHEAT pad
BEVERAGE pad, FOZEN ENTREES pad, FRESH VEGETABLES pad
EXPRESS DEFROST pad, TIMER/CLOCK pad, STOP/CLEAR pad
MINUTE PLUS/START pad

Oven Cavity Light Yes

Safety Standard UL Listed FCC Authorized

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

NOTE: Internal capacity is calculated by measuring

maximum width, depth and height.
Actual capacity for holding food is less.

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,
15 or more protected 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

4

grounding adapter properly grounded and polarized. If the extension

3-Pronged
Plug

Grounded
Receptacle Box

Grounding Pin

3-Pronged Receptacle

8

18

7

12

16

14

1

13

9

10

3

5

4

3

2

6

11

11

15

17

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.

OVEN DIAGRAM

R-55TS-F

1 Door opening button

Push to open door.
2 Oven door with see-through window
3 Safety door latches

The oven will not operate unless the door is securely

closed.
4 Door hinges
5 Door seals and sealing surfaces
6 Turntable motor shaft
7 Removable turntable support

Carefully place the turntable support on the turntable

motor shaft(6) in the center of the oven floor.
8 Removable turntable

Place the turntable securely on the turntable support.

The turntable will rotate clockwise or

counterclockwise.

Only remove for cleaning or for the foods specified in

this manual.
9 Top grill heater (top heater)
10 Bottom grill heater (bottom heater)

The bottom heater is under the cavity floor.
11 Ventilation openings (rear)
12 Oven light

It will light when oven is operating or door is open.
13 Waveguide cover: DO NOT REMOVE.
14 Rotary dial
15 Control panel
16 Time display: 95 minutes
17 Food label

The food label in English and in Spanish is packed in

the oven. Attach the selected one to the oven top.
18 Power supply cord

TOUCH CONTROL PANEL

NOTE:
Some one-touch cooking features such as "MINUTE PLUS" are dis­abled after three minutes 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.

5

R-55TS-F

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
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
noise filter and 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.

MICROWAVE COOKING CONDITION

Program desired cooking time by rotating the rotary dial.
Program the power level by touching the MICRO 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)

RELAY CONNECTED COMPONENTS
RY-1 oven lamp/ turntable motor
RY-2 power transformer
RY-5 fan motor

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.

(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.

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:

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
2000 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.

NOTE: If the thermistor temperature is above

250˚F(120˚C), the circuit to RY5 will be maintained
(by thermistor circuit) to continue operation of
the cooling fan motor until the temperature
drops below 250˚F(120˚C).

6. When the door is opened during a cook cycle, the
monitor switch, door sensing switch, secondary interlock
switch, relay (RY1) and primary interlock relay (RY2) are
activated with the following results. The circuits to the
turntable motor, the cooling fan motor, and the high

VARI-MODE ON TIME OFF TIME
P100 (100% power) 32 sec. 0 sec.

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

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

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

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

P-0 (approx. 0% power) 0 sec. 32 sec.

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

the percentage of microwave power, because
approx. 3 seconds are needed for heating of the
magnetron filament.

POWER OUTPUT REDUCTION

If the oven is set more than 20 minutes at MICRO 100%
power level, after the first 20 minutes, the power level will
automatically adjust to 70% to avoid overcooking.

GRILL COOKING CONDITIONS

The oven has two grill cooking conditions. They are the
UPPER HEATER mode and UPPER AND LOWER
HEATERS mode.

6

R-55TS-F

UPPER HEATER MODE (GRILL1)

In this mode, the food is cooked by the upper heater. Press
the GRILL pad once and then enter the cooking time by
rotating the rotary dial. When the START pad is pressed,
the following operations occur (Figure O-3):

1. The relays (RY1, RY3 and RY5) are energized.

2. The numbers of the digital read-out start the count down
to zero.

3. Then the upper heater, turntable motor, oven lamp and
fan motor are energized.

4. Now, the food is grilled by the upper heater.

5. Upon completion of the selected cooking time, audible
signal sounds and the contacts of relays (RY1, RY2 and
RY3) are opened, then the upper heater, turntable
motor and oven lamp are de-energized. But the relay
(RY5) stays closed and the fan motor operates until the
thermistor temperature drops below 250˚F(120˚C).

NOTE: Maximum cooking time is 30 minutes.

UPPER AND LOWER HEATERS MODE (GRILL 2)
In this mode, the food is cooked by both the upper heater

and lower heater. Press the GRILL pad twice and then
enter the cooking time by rotating the rotary dial. When the
START pad is pressed, the following operations occur
(Figure O-4):

1. The relays (RY1, RY3, RY4, and RY5) are energized.

2. The numbers of the digital read-out start the count down
to zero.

3. Then the upper heater, lower heater, turntable motor,
oven lamp and fan motor are energized.

4. Now, the food is grilled by the upper heater and the lower
heater.

5. Upon completion of the selected cooking time, audible
signal sounds and the contacts of relays (RY1, RY3, and
RY4) are opened, then the upper heating elements,
lower heating element, turntable motor and oven lamp
are de-energized. But the relay (RY5) stays closed and
the fan motor operates until the thermistor temperature
drops below 250˚F(120˚C).

NOTE: Maximum cooking time is 30 minutes.

5-2. The oven will continue to function for 30 minutes,

turning the upper heater and the lower heater on
and off, as needed to maintain the selected preheat
temperature. The oven will shutdown completely
after 30 minutes

[BAKE TIME COOKING CONDITION]

6. When the preheat temperature is reached, a beep
signal will sound indicating that the holding temperature
has been reached in the oven cavity. Open the door and
place the food to be cooked in the oven. In this time, to
keep the oven temperature, the fan motor will not
operate when the door is opened. When the START pad
is touched, the following operations occur:

7. The numbers on the digital read-out start to count down
to zero.

8. The relays (RY1, RY3, RY4 and RY5) are energized and
the oven lamp, turntable motor and cooling fan motor
are energized.

9. The relays (RY3 and RY4) are energized (if the cavity
temperature is lower than the selected temperature)
and the main supply voltage is applied to the heating
elements to return to the selected cooking temperature.

10.Upon completion of the cooking time, the audible signal
will sound, and oven lamp, turntable motor and cooling
fan motor are de-energized. At the end of the Bake
cooking cycle, if the thermistor temperature is above
250˚F(120˚C), the circuit to RY5 will be maintained (by
the thermistor circuit) to continue operation of the cooling
fan motor until the temperature drops below
250˚F(120˚C), at which time the relay will be de­energized, turning off the fan motor.

NOTE: The actual oven temperature may differ from the

set temperature. Because the oven regulates
the oven temperature by turning the upper and
lower heaters on and off.

BAKE COOKING CONDITION

1. Program desired oven temperature by touching the
BAKE pad. Enter the cooking time by rotating the rotary
dial. When the START pad is touched, the following
operations occur (Figure O-5):

[PREHEATING CONDITION]

2. The coil of shut-off relays (RY1, RY3, RY4 and RY5) are
energized.

3. The numbers of the digital read-out start the count down
to zero.

4. Then the upper heater, lower heater, turntable motor,
oven lamp and fan motor are energized.

5. When the oven temperature reaches the selected
preheat temperature, the following operations occur:
5-1 The relays (RY3 and RY4) are de-energized by the

control unit temperature circuit and thermistor,
opening the circuit to the heating elements.

7

R-55TS-F

NOTE: CONDITION OF OVEN

SCHEMATIC

1. DOOR CLOSED

2. CLOCK APPEARS ON DISPLAY

NOISE FILTER

LN

FUSE
15A

120V AC

60 Hz

NOISE FILTER

RESISTOR 470KΩ 1/2W

NOISE SUPPRESSION COIL

1.0µF / AC 250V

LINE CROSS CAPACITOR

NOTE: " " indicates components with potential above 250V.

TEMPERATURE

THERMAL

FUSE (MAGNETRON)

CUT-OUT

COM. COM.

N.O. N.O.

CONTROL
UNIT

DOOR
SENSING

FAN MOTOR

SWITCH

RY1 RY3

B3 B5

CAPACITOR

LINE BYPASS

0.0033µF / AC 250V

CAPACITOR

LINE BYPASS

0.0033µF / AC 250V

OL

SECONDARY
INTERLOCK
SWITCH

TTM

OVEN LAMP

A3

RY5

TURNTABLE MOTOR

A1 A5

FM

Figure O-1. Oven Schematic-Off Condition

C1

C2

THREMISTOR

COM.

RY2
PRIMARY
INTERLOCK
RELAY

N.O.

UPPER

HEAER

RY4

E3

LOWER

HEAER

OVEN
THERMOSTAT

POWER
TRANSFORMER

MONITOR SWITCH

CAPACITOR

0.82µF
AC 2100V

RECTIFIER

MAGNETRON

NOTE: CONDITION OF OVEN

SCHEMATIC

1. DOOR CLOSED

2. COOKING TIME PROGRAMMED

3. VARIABLE COOKING CONTROL "P100" (100%)

4. "START" PAD TOUCHED

120V AC

60 Hz

LN

FUSE
15A

NOISE FILTER

RESISTOR 470KΩ 1/2W

NOISE FILTER

NOISE SUPPRESSION COIL

1.0µF / AC 250V

LINE CROSS CAPACITOR

CAPACITOR

LINE BYPASS

0.0033µF / AC 250V

CAPACITOR

LINE BYPASS

0.0033µF / AC 250V

THERMAL
CUT-OUT

OL

SECONDARY
INTERLOCK
SWITCH

OVEN LAMP

Figure O-2. Oven Schematic-Microwave Cooking Condition

TEMPERATURE
FUSE (MAGNETRON)

A3

TTM

TURNTABLE MOTOR

RY5

A1 A5

FM

FAN MOTOR

COM. COM.

N.O. N.O.

CONTROL
UNIT

RY1 RY3

B3 B5

DOOR
SENSING
SWITCH

C1

THREMISTOR

C2

COM.

RY2
PRIMARY
INTERLOCK
RELAY

N.O.

UPPER

HEAER

RY4

E3

LOWER

HEAER

OVEN
THERMOSTAT

POWER
TRANSFORMER

MONITOR SWITCH

CAPACITOR

0.82µF
AC 2100V

RECTIFIER

MAGNETRON

8

R-55TS-F

NOTE: CONDITION OF OVEN

SCHEMATIC

1. DOOR CLOSED

2. "GRILL" TOUCHED ONCE

3. COOKING TIME PROGRAMMED

4. "START" PAD TOUCHED

NOISE FILTER

LN

FUSE
15A

120V AC

60 Hz

NOISE FILTER

RESISTOR 470KΩ 1/2W

NOISE SUPPRESSION COIL

1.0µF / AC 250V

LINE CROSS CAPACITOR

SCHEMATIC

NOTE: CONDITION OF OVEN

1. DOOR CLOSED

2. "GRILL" TOUCHED TWICE

3. COOKING TIME PROGRAMMED

4. "START" PAD TOUCHED

NOISE FILTER

LN

FUSE
15A

CAPACITOR

LINE BYPASS

0.0033µF / AC 250V

CAPACITOR

LINE BYPASS

0.0033µF / AC 250V

NOTE: " " indicates components with potential above 250V.

TEMPERATURE

THERMAL

FUSE (MAGNETRON)

CUT-OUT

COM. COM.

OL

TTM

OVEN LAMP

SECONDARY
INTERLOCK
SWITCH

A3

RY5

TURNTABLE MOTOR

A1 A5

FM

N.O. N.O.

CONTROL
UNIT

DOOR
SENSING

FAN MOTOR

SWITCH

RY1 RY3

B3B1B5

C1

THREMISTOR

C2

RY2

PRIMARY
INTERLOCK
RELAY

COM.

N.O.

UPPER

HEAER

RY4

E3

LOWER

OVEN
THERMOSTAT

Figure O-3. Oven Schematic-GRILL1 Cooking Condition

TEMPERATURE

THERMAL

FUSE (MAGNETRON)

CUT-OUT

COM. COM.

A3

N.O. N.O.

COM.

HEAER

POWER
TRANSFORMER

MONITOR SWITCH

CAPACITOR

0.82µF
AC 2100V

RECTIFIER

MAGNETRON

120V AC

60 Hz

NOISE FILTER

RESISTOR 470KΩ 1/2W

NOISE SUPPRESSION COIL

1.0µF / AC 250V

LINE CROSS CAPACITOR

SCHEMATIC

NOTE: CONDITION OF OVEN

1. DOOR CLOSED

2. "BAKE" TOUCHED ONCE (400˚F)

3. COOKING TIME PROGRAMMED

4. "START" PAD TOUCHED

NOISE FILTER

LN

FUSE
15A

120V AC

60 Hz

NOISE FILTER

RESISTOR 470KΩ 1/2W

1.0µF / AC 250V

LINE CROSS CAPACITOR

CAPACITOR

LINE BYPASS

0.0033µF / AC 250V

CAPACITOR

LINE BYPASS

0.0033µF / AC 250V

CAPACITOR

LINE BYPASS

NOISE SUPPRESSION COIL

0.0033µF / AC 250V

CAPACITOR

LINE BYPASS

0.0033µF / AC 250V

OL

SECONDARY
INTERLOCK
SWITCH

TTM

OVEN LAMP

RY5

TURNTABLE MOTOR

A1 A5

FM

FAN MOTOR

CONTROL
UNIT

DOOR
SENSING
SWITCH

C1

C2

THREMISTOR

RY2
PRIMARY
INTERLOCK
RELAY

RY1 RY3

B3 B5

N.O.

UPPER

HEAER

RY4

E3

LOWER

HEAER

OVEN
THERMOSTAT

Figure O-4. Oven Schematic-GRILL2 Cooking Condition

TEMPERATURE

THERMAL

FUSE (MAGNETRON)

CUT-OUT

COM. COM.

OL

SECONDARY
INTERLOCK
SWITCH

TTM

OVEN LAMP

A3

RY5

TURNTABLE MOTOR

A1 A5

FM

FAN MOTOR

N.O. N.O.

CONTROL
UNIT

RY1 RY3

B3 B5

DOOR
SENSING
SWITCH

C1

THREMISTOR

C2

RY2

PRIMARY
INTERLOCK
RELAY

COM.

N.O.

UPPER

HEAER

RY4

E3

LOWER

HEAER

OVEN
THERMOSTAT

Figure O-5. Oven Schematic-BAKE Cooking Condition

POWER
TRANSFORMER

MONITOR SWITCH

POWER
TRANSFORMER

MONITOR SWITCH

CAPACITOR

0.82µF
AC 2100V

RECTIFIER

CAPACITOR

0.82µF
AC 2100V

RECTIFIER

MAGNETRON

MAGNETRON

9

R-55TS-F

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
Heads

Switch Lever

Latch Hook

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.

3. If the door is opened, and the primary interlock relay
(RY2) and the secondary interlock switch contact 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,
RELAY (RY1), 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 food on the turntable
is cooked evenly. 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 vents surround­ing the magnetron and cools the magnetron. This air is
channelled through the oven cavity to remove steam and
vapours given off from the heating foods. It is then exhausted
through the exhausting air vents at the oven cavity.

THERMAL CUT-OUT 125˚C

This thermal cut-out protects the upper heater against
overheating. If the temperature goes up higher than 257˚F
(125˚C) because the fan motor is interrupted or the ventilation
openings are blocked, the thermal cut-out will open and
line voltages to all electrical parts will be cut off and the
operation of the oven will be stopped. The thermal cut-out
will not resume.

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), relay (RY1) and secondary interlock
switch fail to open when the door is opened.

Functions:

1. When the door is opened, the monitor switch contacts
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 its being normally open contact
switches. But the contacts of relay (RY1) are closed to
turn on the oven lamp.

2. As the door goes to a closed position, the monitor switch
contacts are first opened and then the door sensing switch
and secondary interlock switch contacts close. At this time,
the contacts of the relay (RY1) and the primary interlock
relay (RY2) are in the OFF condition (contacts open)

OVEN THERMOSTAT

The oven thermostat is located on the top of the oven cavity.
The oven thermostat will open at higher than 302˚F (150˚C).
And the oven thermostat will close at lower than 266˚F
(130˚C).

TEMPERATURE FUSE (MAGNETRON)

The temperature fuse, located near the magnetron, is
designed to prevent damage to the magnetron. If an over
heated condition develops in the magnetron due to cooling
fan failure, obstructed air guide, dirty or blocked air intake,
etc., the temperature fuse will open.
Under normal operation, the temperature fuse remains
closed. However, when abnormally high temperatures are
reached within the oven cavity, the temperature fuse will
open at 302˚F (150˚C), causing the oven to shut down.

UPPER HEATER

The upper heater is located on the top of the oven cavity
assembly. The upper heater sends out heat to cook foods.

10

R-55TS-F

LOWER HEATER

The lower heater is located under the bottom of the oven
cavity assembly. The lower heater sends out heat to cook
foods.

NOISE FILTER

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

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-BA038WRKZ
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.

11

R-55TS-F

CK = Check / RE = Replace

TEST PROCEDURE

POSSIBLE CASE

AND

DEFECTIVE PARTS

CONDITION PROBLEM

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

Monitor fuse blows when the door
is opened.

Oven lamp does not light when
door is opened. (Display operates.)

OFF
CONDITION

COOKING
CONDITION
(COMMON MODE)

MICROWAVE
COOKING
CONDITION

GRILL
COOKING
CONDITION

BAKE
COOKING
CONDITION

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

"88:88"

does not appear in display
when power cord is plugged into wall
outlet.

Display does not operate properly
when STOP/CLEAR pad is pressed.

Oven does not start when the
START pad is pressed. (Display
operates.)

Oven lamp does not light. (Turntable
motor operates.)

Fan motor does not operate. (Oven
lamp lights.)

Turntable motor does not operate.
(Oven lamp lights.)

Oven or electrical parts does not
stop when cooking time is 0 or
STOP/CLEAR pad is pressed.

Oven goes into cook cycle but shuts
down before end of cooking cycle.

Oven seems to be operating but little
or no heat is produced in oven load.

Oven does not operate properly
during variable cooking condition
except 100% cooking condition.

Function of EXPRESS DEFROST
does

not operate properly.

Upper heater does not operate.

Lower heater does not operate.

Upper and lower heaters do not
operate.

Upper heater does not operate.

Lower heater does not operate.

Upper and lower heater do not
operate.

Temperature is lower or higher than
preset.

Oven stops after 4 minutes 15 sec..

ABCDEEE F FGH I IJ MNOOOOOP Q

MAGNETRON

POWER TRANSFORMER

H.V. RECTIFIER ASSEMBLY

HIGH VOLTAGE CAPACITOR

OVEN THERMOSTAT

THERMAL CUT-OUT 125˚C

TEMPERATURE FUSE (MAGNETRON)

SECONDARY INTERLOCK SWITCH

PRIMARY INTERLOCK SYSTEM

MONITOR SWITCH

MONITOR FUSE

L

UPPER HEATER

LOWER HEATER

THERMISTOR

TOUCH CONTROL PANEL

NOISE FILTER

SWITCH UNIT

RELAY RY1

RELAY RY2

RELAY RY3

RERERE RE

RELAY RY4

RELAY RY5

EXPRESS DEFROST

FOIL PATTURN ON P.W.B.

FAN MOTOR

CK CK CK

TURNTABLE MOTOR

POWER SUPPLY CORD

OVEN LAMP

SHORTED WIRE HARNESS

OPENED WIRE HARNESS

MIS-ADJUSTMENT OF SWITCHES

12