SHARP R-1855A Service Manual

SER VICE MANU AL

S99M138R1855E

O VER THE RANGE

MICROWAVE OVEN

MODEL R-1855A

R-1855A

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.

This model for the US and Canada markets, Please refer to the appropriate pages for service information.

TABLE OF CONTENTS

Page
PRECAUTIONS TO BE OBSERVED BEFORE AND DURING SERVICE TO

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

BEFORE SERVICING.......................................................................................................................................... 1

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

FOREWORD........................................................................................................................................................ 4

PRODUCT SPECIFICATIONS......................................................................................................... .................... 5

GENERAL INFORMATION ................................................................................................................................. 5

OPERATION ........................................................................................................................................................ 7

TROUBLESHOOTING GUIDE............................................................................................................................17

TEST PROCEDURE ...........................................................................................................................................20

TOUCH CONTROL PANEL ................................................................................................................................31

COMPONENT REPLACEMENT AND ADJUSTMENT PROCEDURE................................................................37

PICTORIAL DIAGRAM ....................................................................................................................................... 46

CONTROL PANEL CIRCUIT ..............................................................................................................................47

PRINTED WIRING BOARD ................................................................................................................................48

PARTS LIST........................................................................................................................................................49

PACKING AND ACCESSORIES........................................................................................................ .................55

OR:

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

SHARP ELECTRONICS CORPORA TION

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

SHARP CORPORATION

SHARP ELECTRONICS OF CANADA LTD.

Head Office: 335 Britannia Road East, Mississauga, Ontario L4Z 1W9

[phone]

R-1855A

PRECA UTIONS T O BE OBSERVED BEFORE AND
DURING SER VICING TO AVOID POSSIBLE
EXPOSURE TO EXCESSIVE MICRO WAVE
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.

(RD2110U)

BEFORE SER VICING(USA)

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.

(RD2110U)

BEFORE SER VICING(CANAD A)

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 OF
CANADA LTD. immediately.

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 OF CANADA LTD. and NHW, CANADA immediately.

Service personnel should inform SHARP ELECTRONICS OF CANADA LTD. 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.

(RD8100U)

WARNING TO SERVICE PERSONNEL

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

R-1855A

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
high-voltage capacitor (that is the connecting lead of the
high-voltage 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 these 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-1855A

MICRO WA VE MEASUREMENT PR OCEDURE (USA)

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±5OC (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 (3-1/2in.)
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

R-1855A

MICROWAVE MEASUREMENT PROCEDURE (CANADA)

After adjustment of the door switches are completed individually or collectively, switch test and microwave leakage test must
be performed with survey instrument and test result must be confirmed to meet the requirement of the performance standard
for microwave ovens as undermentioned.

A. Requirements:

Every microwave oven shall function in such a manner that when the oven is fully assembled and operating with it's service
controls and user controls adjusted to yield the maximum output, the leakage radiation, at all points at least 5 cm. from the
external surface of the oven, does not exceed:

1) 1.0mW/cm2 with the test load of 275 ± 15 ml of water at an initial temperature 20 ±5oC.

2) 5.0mW/cm

3) 5.0mW/cm

2

when the outer enclosure is removed with a test load of 275 ± 15 ml of water at an initial temperature 20±5oC.

2

without a test load.

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 CSA and NHW performance standard
for microwave ovens must be used for testing recommended instruments are , NARDA 8100 and NARDA 8200.

2) Place the oven tray in the oven cavity.

3) Place the load of 275±15 ml of tap water initially at 20±5oC in the center of the oven cavity.
The water container shall be a low form of 600 ml 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, 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 with enclosure installed :

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 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.

C. Leakage test without enclosure:

1) Remove the enclosure (cabinet).

2) Grasp the probe of the survey instrument and hold it perpendicular to all mechanical and electric parts of the oven that is
accessible to the user of the oven including, but not limited to, the waveguide, cavity seams, magnetron gap between the
door and the body of the oven.

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

4) Measure carefully at the point of highest leakage and make sure that the highest leakage is under 5mW/cm2.

CAUTION: Special attention should be given to avoid electrical shock because HIGH VOLTAGE is generated during this test
No Load test

1) Operate the oven without a load and measure the leakage by the same method as the above test procedure " Leakage
test with enclosure installed"

2) Make sure that the highest leakage should not exceed 5mW/cm2.

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

3

R-1855A

SERVICE MANUAL

OVER THE RANGE

MICROWAVE OVEN

R-1855A

FOREWORD

This Manual has been prepared to provide Sharp Electronics Corp.
Service Personnel with Operation and Service Information for the
SHARP OVER THE RANGE MICROWAVE OVEN, R-1855A.

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.

USA MODEL

SHARP ELECTRONICS CORPORATION

SHARP PLAZA, MAHWAH,

NEW JERSEY 07430-2135

WIRING DIAGRAMS

PARTS LIST

CANADIAN MODEL

OSAKA, JAPAN

4

SPECIFICATION

ITEM DESCRIPTION

Power Requirements 120 Volts / 13.2 Amperes (Microwave), 13.2 Amperes (Convection)

60 Hertz
Single phase, 3 wire grounded

Power Output 850 watts (IEC-705 TEST PROCEDURE)

Operating frequency of 2450MHz
Convection Power Output 1400 watts
Case Dimensions Width 29-15/16"

Height 16-11/32"

Depth 15- 9/32"
Cooking Cavity Dimensions Width 17-1/8"

Height 8-1/16"

1.1 Cubic Feet Depth 13-13/16"
Hood lamp 2 bulbs, 30W x 2, Incandescent light bulbs
Hood fan Horizontal discharge 230 C.F.M. , Vertical discharge 240 C.F.M. ,
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 Powe

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

R-1855A

CUSTOM HELP pad, SENSOR COOK pad, COMPU BROIL pad, COMPU ROAST pad
COMPU BAKE pad, SENSOR REHEAT pad, MINUTE PLUS pad, POPCORN pad
COMPU DEFROST pad, CONVECTION pad, REHEAT pad, LOW MIX/BAKE pad
HIGH MIX/ROAST pad, BROIL pad, SLOW COOK pad, KITCHEN TIMER pad
Number and temperature selection pads, CLOCK pad, KEEP WARM pad
TURNTABLE ON / OFF pad, POWER LEVEL pad, STOP/CLEAR pad,
START / TOUCH ON pad

Oven Cavity Light Yes 30W x 1 Incandescent light bulb
Safety Standard UL Listed FCC Authorized

DHHS Rules, CFR, Title 21, Chapter 1, Subchapter J
Canadian Standards Association.
Department of National Health and Welfare CANADA, Industry CANADA.

Weight Approx. 71 lbs.

GENERAL INFORMA TION

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.

5

R-1855A

3-Pronged Plug

Grounded
Receptacle Box

Grounding Pin

3-Pronged Receptacle

Electrical Requirements
The oven is equipped with a 3-prong grounding plug. DO NOT UNDER ANY CIRCUMSTANCES CUT OR REMOVE THE
GROUNDING PIN FROM THE PLUG.
The power supply cord and plug must be connected to a separate 120 Volt AC, 60 Hz, 15 Amp. or more branch circuit, using
a grounded receptacle. The receptacle should be located inside the cabinet directly above the Microwave Oven/Hood
system mounting location.

12

1

3

6

2

16

1. Oven door with see-through window.

2. Door hinges.

3. Stirrer cover.

4. Turntable motor shaft.

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

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

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

8. FAN-HI/LO button.
Push for High/Low/Off.

9. Light button.
Push for On/Off

10.Auto-Touch control panel.

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

12. Ventilation openings.

13.Light Cover.

14.Grease filters.

15.Removable turntable.
The turntable will rotate clockwise or counterclockwise.
Only remove for cleaning.

16.Removable turntable support.

17. Plug

CONTROL PANEL

OVEN DIAGRAM

11

5

4

6

15

10

13

9
8

7

17

14

MIX CONV
DEFROST
SENSOR
TURNTABLE

ON OFF COOK LBS OZ KG HELP

INTERACTIVE COOKING SYSTEM

SENSOR

REHEAT

POPCORN

CONVEC

LOW MIX

BAKE

BROIL

100˚F 150˚F 275˚F 300˚F 325˚F

350˚F 375˚F 400˚F 425˚F 450˚F

KITCHEN

TURNTABLE

ON / OFF

MINUTE

PLUS

COMPU

DEFROST

REHEAT

HIGH MIX

ROAST

SLOW
COOK

12345
67890

TIMER

1 Baked potatoes
2 Frozen vegetables
3 Fresh veg-soft
4 Fresh veg-hard
5 Frozen entrees
6 Hot dogs
7 Bacon
8 Fish, seafood

1 Hamburgers
2 Chicken pieces
3 Steaks
4 Fish steaks

1 Chicken
2 Turkey
3 Turkey breast
4 Pork

1 Cake
2 Brownies
3 Muffins
4 French fries

CLOCK

POWER

LEVEL

KEEP

WARM

STOP

CLEAR

CUSTOM

HELP

SENSOR

COOK

COMPU

BROIL

COMPU

ROAST

COMPU

BAKE

START

TOUCH ON

6

OPERATION

DESCRIPTION OF OPERATING SEQUENCE

R-1855A

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
control unit. (Figure O-1).

1. The display will show , , ,
, , , , and
.

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 touching the NUMBER pads.
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
RY1 Oven lamp
RY2 Power transformer/ Stirrer motor
RY4 Turntable motor
RY5 Fan motor

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.

6. When the door is opened during a cook cycle, monitor

switch, door sensing switch, secondary interlock switch
and third door switch and primary interlock relay are
activated with the following results. The circuits to the
stirrer motor, the cooling fan motor, the turntable motor,
and the high voltage components are de-energized, and
the digital read-out displays the time still remaining in the
cook cycle when the door was opened.

7. The monitor switch is electrically monitoring the operation

of the secondary interlock switch, third door switch and
door sensing switch is mechanically associated with the
door so that it will function in the following sequence.

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

primary interlock relay, door sensing switch,
secondary interlock switch and third door switch
open their contacts, and then the monitor switch
contacts close.

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

monitor switch contacts first open, and then the
contacts of the secondary interlock switch and third

door switch close.
If the secondary interlock switch, third door switch and door
sensing switch fail with their contacts closed when the door
is opened, the closing of the monitor switch contacts will
form a short circuit through the monitor fuse, third door
switch, secondary interlock switch and primary interlock
relay, 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 (RY2) which is operated
by the control unit within an interval second time base.
Microwave power operation is as follows:

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.

CONVECTION COOKING CONDITION

PREHEATING CONDITION

Program desired convection temperature by touching the
PREHEAT pad and the temperature pad.

7

R-1855A

When the START pad is touched, the following operations
occur:

1. The coil of shut-off relays (RY1, RY4, RY5 and RY7) are
energized, the oven lamp, turntable motor, cooling fan
motor and convection motor are turned on.

2. The coil of relay (RY6) is energized by the control unit.
The damper is moved to the closed position, opening the
damper switch contacts. The opening of the damper
switch contacts sends a signal to the LSI on the control
unit de-energizing the relay (RY6) and opening the
circuit to the damper motor.

3. The coil of heater relay (RY3) is energized by the control
unit and the main supply voltage is applied to the heating
element.

4. When the oven temperature reaches the selected preheat
temperature, the following operations occur:
4-1 The heater relay is de-energized by the control unit

temperature circuit and thermistor, opening the
circuit to the heating element.

4-2. The oven will continue to function for 30 minutes,

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

CONVECTION COOKING CONDITION

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.
Program convection temperature and desired cooking time
by touching the CONVECTION pad, Temperature pad and
NUMBER pad.
When the START pad is touched, the following operations
occur:

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

2. The oven lamp, turntable motor, cooling fan motor and
convection motor are energized.

3. Heater relay (RY3) is energized (if the cavity temperature
is lower than the selected temperature) and the main
supply voltage is applied to the heating element to return
to the selected cooking temperature.

4. Upon completion of the cooking time, the audible signal
will sound, and oven lamp, turntable motor, cooling fan
motor and convection motor are de-energized. At the
end of the convection cycle, if the oven temperature is
above 275OF, the circuit to RY5 will be maintained (by
the thermistor circuit) to continue operation of the
cooling fan motor until the temperature drops below
245OF, at which time the relay will be de-energized,
turning off the fan motor. Relay RY7 will however, open
as soon as the convection cycle has ended, turning off
the convection motor.

5. At the end of the convection cook cycle, shut-off relay
(RY6) is energized turning on the damper motor. The
damper is returned to the open position, closing the
damper switch contacts which send a signal to the
control unit, de-energizing shut-off relay (RY6).

AUTOMATIC MIX COOKING CONDITION

Touch the LOW MIX/BAKE or HIGH MIX/ROAST pad. The
LOW MIX/BAKE pad is preprogrammed for 325OF with 10%
microwave power, while the HIGH MIX/ROAST pad is
preprogrammed for 325OF with 30% microwave power.
Program desired cooking time. When the START pad is

touched, the following operations occur:

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

2. The shut-off relays (RY1, RY4, RY5 and RY7) are
energized, turning on the oven lamp, turntable motor,
cooling fan motor and convection motor.

3. The shut-off relay (RY6) is energized.
The damper plate is closed from the open position.

4. The heater relay (RY3) is energized, applying the main
supply voltage to the heating element.

5. Now, the oven is in the convection cooking condition.

6. When the oven temperature reaches the selected
temperature, the following operations occur:
6-1. The power supply voltage is alternated to the

heating element and power transformer.

6-2. The heating element operates through the heater

relay (RY3) contacts and the power transformer
operates through the primary interlock relay (RY2)
contacts.

6-3. These are operated by the control unit to supply

alternately within a 32 second time base, convection
heat and microwave energy.

The relationship between the convection and microwave
power operations are as follows.

Note: The ON and OFF time ratio does not correspond

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

26 SEC.6 SEC.

(MICRO.)

(CONVEC.)

(MICRO.)

(CONVEC.)

ON

OFF

LOW MIX

BAKE

12 SEC. 20 SEC.

ON

OFF

ON

OFF

32 SEC.

HIGH MIX

ROAST

MICROWAVE POWER

= APPROX. 10%

CONVECTION

TEMPERATURE

= 325˚F (165˚C)

MICROWAVE POWER

= APPROX. 30%

CONVECTION

TEMPERATURE

325˚F (165˚C)

Note: During alternate Microwave/Convection operation,

the convection heater is energized only if the cavity
temperature drops below the set temperature.

SENSOR COOKING CONDITION

Using the SENSOR COOK, SENSOR REHEAT or POP­CORN function, the foods are cooked or defrosted without
figuring time, power level or quantity. When the oven senses
enough steam from the food, it relays the information to its
microprocessor which will calculate the remaining cooking
time and power level needed for best results.
When the food is cooked, water vapor is developed. The
sensor “senses” the vapor and its resistance increases
gradually. When the resistance reaches the value set
according to the menu, supplementary cooking is started.

8

R-1855A

The time of supplementary cooking is determined by
experiment with each food category and inputted into the
LSI.
An example of how sensor works:

1. Potatoes at room temperature. Vapor is emitted very
slowly.

MICROWAVE

2. Heat potatoes. Moisture and humidity is emitted rapidly.
You can smell the aroma as it cooks.

AH SENSOR

MICROWAVE

3. Sensor detects moisture and humidity and calculates
cooking time and variable power.

Cooking Sequence.

1. Touch SENSOR COOK, SENSOR REHEAT or
POPCORN pad. When Sensor Cook is touched, to
choose menu the number pad should be touched.

NOTE: The oven should not be operated on SENSOR

COOK, SENSOR REHEAT or POPCORN
immediately after plugging in the unit. Wait five
minutes before cooking on SENSOR COOK,
SENSOR REHEAT or POPCORN.

2. The coil of shut-off relays (RY1, RY4 and RY5) are
energized, the oven lamp, turntable motor and cooling
fan motor are turned on, but the power transformer is not
turned on.

3. After about 32 seconds, the cook relay (RY2) is energized.
The power transformer is turned on, microwave energy
is produced and first stage is started.
The 32 seconds is the cooling time required to remove
any vapor from the oven cavity and sensor.

NOTE: During this first stage, do not open the door or touch

STOP/CLEAR pad.

4. When the sensor detects the vapor emitted from the
food, the display switches over to the remaining cooking
time and the timer counts down to zero.
At this time, the door may be opened to stir food, turn it
or season, etc.

5. When the timer reaches zero, an audible signal sounds.
The shut-off relay and cook relay are de-energized and
the power transformer, oven lamp, etc. are turned off.

6. Opening the door or touching the STOP/CLEAR pad, the
time of day will reappear on the display and the oven will
revert to an OFF condition.

COMPU BROIL, COMPU ROAST, COMPU BAKE

COMPU BROIL, COMPU ROAST and COMPU BAKE will

automatically compute the oven temperature, microwave
power and cooking time for broiling, roasting and baking. Set
the desired program by touching one of the COMPU BROIL,
COMPU ROAST or COMPU BAKE pad, and number pad.
Enter the weight by touching the Number pads. When the
START pad is touched, the following operations occur:

1. The COOK indicator will light and the CONV or MIX
indicator will light.

2. The cooking time will appear on the display and start
counting down to zero. The cooking time is adjusted
automatically according to the weight of the food.

3. The shut-off relays (RY1, RY4, RY5 and RY7) are
energized, turning on the oven lamp, turntable motor,
cooling fan motor and convection motor. The power
supply voltage is applied to the heating element.

4. Now, the oven is in the convection cooking mode or
Automatic Mix Cooking condition.

5. When the oven temperature has reached the
programmed convection temperature, the oven goes
into the programmed cooking mode.

6. At the end of the cooking cycle, the damper is returned
to the open position and the oven will go to the off
condition. The cooling fan will remain on until the oven
has cooled.

COMPU DEFROST COOKING

The COMPU DEFROST key is a special function key to
defrost meats and poultry faster and better. COMPU
DEFROST automatically defrosts roast beef, etc.. When
the COMPU DEFROST is selected and the food weight is
entered by using the COMPU DEFROST pad, the oven will
cook according to the special cooking sequence.

FIRE SENSING FEATURE (MICROWAVE MODE)

This model incorporates a sensing feature which will stop
the oven's operation if there is a fire in the oven cavity during
microwave cooking.
This is accomplished by the LSI repeatedly measuring the
voltage across the temperature measurement circuit (ther­mistor) during it's 32-seconds time base comparing the
obtained voltage measurements. If the most recent voltage
measured is 100mV greater than the previous voltage
measured, the LSI judges it as a fire in the oven cavity and
switches off the relays to the power transformer and fan
motor. The LSI also stops counting down and closes the
damper plate so that no fresh air will enter the oven cavity.
Please refer to the following section for a more detailed
description.

Operation

The following operation will start 4 minutes after the start
pad is touched. Please refer to the timing diagrams below.

1. The thermistor operates within a 32-seconds time base
and it is energized for three (3) seconds and off for 29
seconds. Two (2) seconds after the thermistor is
energized, the voltage across the temperature
measurement circuit is sampled by the LSI and twenty
one (21) seconds after the thermistor is cut off the LSI
turns on the convection motor for six (6) seconds.

2. The above procedure is repeated. If the difference
between the first voltage measured (in step 1) and the
voltage measured when the procedure is repeated (step

2) is greater than 100mV the LSI makes the judgment
that there is a fire in the oven cavity and will switch off

9

R-1855A

the relays to the power transformer and fan motor. The
LSI also stops counting down and closes the damper
door so that no fresh air will enter the oven cavity.

3. Once the fire sensor feature has shut the unit down, the
programmed cooking cycle may be resumed by pressing
the "START" pad or the unit may be reset by pressing the
"CLEAR" pad.

IMPORTANT:
During sensor cooking operation, the fire sensing
operation sequence will not begin until the AH sensor
has detected vapors and initiated a sensor cooking
cycle. This is because the operation of the convection
fan would interfere with the AH sensor's vapor detec­tion.

CONVECTION

MOTOR

THERMISTOR

Sensing

Voltage

0 2 24 30 64 (sec.)

3

ON

OFF

3 sec.

ON

OFF

ON

OFF

Sensing the voltage across the temperature measurement circuit.

6 sec.

32 (sec.)

3. RE-CIRCULATION (INSIDE VENTING)
The air handing is same as VERTICAL VENTING except
that the final air discharge is directed horizontally
through the upper front of the oven into the kitchen. IN
this case, the accessory charcoal filter lit RK-220 must
be provided to filter the air before it leaves the oven.

: AIR FLOW

HOOD FAN MOTOR

HOOD EXHAUST
LOUVER

HOOD
INTAKE
DUCT R

CHARCOAL
FILTER

VENTILATION METHODS HOT AIR EXHAUST

1. VERTICAL VENTING
For this venting method, hot air rising from the
conventional range below is drawn in by the hood fan
motor through the grease filters at the right and left sides
of the base cover, up through the right and left side intake
ducts, then discharged vertically at rear center top of the
oven, into the customer's vent system.

: AIR FLOW

HOOD FAN MOTOR

HOOD
INTAKE
DUCT R

GREASE
FILTER

2. HORIZONTAL VENTING
The air handing is same as VERTICAL VENTING except
that the final air discharge is directed horizontally out
from the top rear of the oven into the customer's vent
system.

: AIR FLOW

HOOD FAN MOTOR

HOOD
INTAKE
DUCT R

TO DUCTTO DUCT

TO DUCT

GREASE
FILTER

10

SCHEMATIC

HIGH
VOLTAGE
RECTIFIER

HIGH
VOLTAGE
CAPACITOR

0.9 F

POWER
TRANSFORMER

MAGNETRON

RY8

HL

HL

HOOD
LAMP

HOOD
MOTOR

HOOD
CAPACITOR

GRY BRN

BRN

C1A3A1

GRYBLU

RED

YEL

HOOD FAN
THERMAL
CUT OUTS

BLK
RED

FUSE
20A

RED RED

MAGNETRON
TEMPERATURE
FUSE

C3

BRN

C9

BLK

C5

C7

BLU

PPL

WHT

BLK

RED

YEL

PNK

RY10

RY9

WHT

WHT

RED

BLK

BLK

WHT-WHT

MONITOR
SWITCH

STIR­RER
MOTOR

WHT

BRN

BLK

F1 F2 F3

E3 E4E6E5E2E1

RY1RY7RY4RY5RY6

DAMPER

THERMISTOR SWITCH

HEATING
ELEMENT

DOOR
SENSING
SWITCH

BLK

GRN

PNK

RED

N.O.
RY3

PPL

COM
RY3

COM
RY2

N.O.
RY1

DAMPER
MOTOR

FAN
MOTOR

OVEN
LAMP

ORG

OLCMFM

TTM

DM

CONVE­CTION
MOTOR

SECONDARY
INTERLOCK
SWITCH

TURN
TABLE
MOTOR

ORG

WHT

ORG

BLK

BLK

ORG

ORG

ORG

BLK

BRN WHT

BRN PPL

GRY

B7B1B3B5

A5

ORG

BLU

WHT

PPL

COM
RY1

N.O.
RY2

AH SENSOR

WHT WHT

RY3 RY2

CONTROL UNIT

STM

GRY

THIRD DOOR
SWITCH

120VAC
60Hz

BLK

WHT

GRN

GND

NOISE
FILTER

NOISE

RESISTOR

PNK

PRIMARY INTERLOCK

RELAY

HIGH
VOLTAGE
RECTIFIER

HIGH
VOLTAGE
CAPACITOR

0.9 F

POWER
TRANSFORMER

MAGNETRON

RY8

HL

HL

HOOD
LAMP

HOOD
MOTOR

HOOD
CAPACITOR

GRY BRN

BRN

C1A3A1

GRYBLU

RED

YEL

HOOD FAN
THERMAL
CUT OUTS

BLK
RED

FUSE
20A

RED RED

MAGNETRON
TEMPERATURE
FUSE

C3

BRN

C9

BLK

C5
C7

BLU
PPL

WHT

BLK

RED

YEL

PNK

RY10

RY9

WHT

WHT

RED

BLK

BLK

WHT-WHT

MONITOR
SWITCH

STIR­RER
MOTOR

WHT

BRN

BLK

F1 F2 F3

E3 E4E6E5E2E1

RY1RY7RY4RY5RY6

DAMPER

THERMISTOR SWITCH

HEATING
ELEMENT

DOOR
SENSING
SWITCH

BLK

GRN

PNK

RED

N.O.
RY3

PPL

COM
RY3

COM
RY2

N.O.
RY1

DAMPER
MOTOR

FAN
MOTOR

OVEN
LAMP

ORG

OLCMFM

TTM

DM

CONVE­CTION
MOTOR

SECONDARY
INTERLOCK
SWITCH

TURN
TABLE
MOTOR

ORG

WHT

ORG

BLK

BLK

ORG

ORG

ORG

BLK

BRN WHT

BRN PPL

GRY

B7B1B3B5

A5

ORG

BLU

WHT

PPL

COM
RY1

N.O.
RY2

AH SENSOR

WHT WHT

RY3 RY2

CONTROL UNIT

STM

GRY

THIRD DOOR
SWITCH

120VAC
60Hz

BLK

WHT

GRN

GND

NOISE
FILTER

NOISE

RESISTOR

PNK

PRIMARY INTERLOCK

RELAY

NOTE: CONDITION OF OVEN

1. DOOR CLOSED.

2. CLOCK APPEARS ON DISPLAY.

R-1855A

Note:

When servicing units between serial number 111112 and 112161, use the
schematics in Figure O-1 through O-4.

Ref 2-6(TMAPCB058MRR0)

SCHEMATIC

NOTE: CONDITION OF OVEN

1. DOOR CLOSED.

2. COOKING TIME PROGRAMMED.

3. START PAD TOUCHED.

Figure O-2. Oven Schematic - Microwave Cooking Condition

Ref 2-6(TMAPCB058MRR0)

Figure O-1. Oven Schematic - Off Condition

11

R-1855A

SCHEMATIC

NOTE: CONDITION OF OVEN

1. DOOR CLOSED.

2. CONVECTION PAD TOUCHED.

3. DESIRED TEMP. TOUCHED.

4. START PAD TOUCHED.

120VAC
60Hz

BLK

WHT

GRN

GND

NOISE
FILTER

FUSE
20A

RED RED

BLK
RED

HOOD FAN
THERMAL
CUT OUTS

NOISE

RESISTOR

WHT

BLK

RED

YEL

GRYBLU

BRN
PNK

BLU
PPL

HOOD
MOTOR

C3

C9

C5
C7

HOOD
CAPACITOR

RED

HL

GRY BRN

MAGNETRON
TEMPERATURE
FUSE

BLK

RY9

RY10

YEL

HOOD

BRN

LAMP

HL

PNK

RY8

C1A3A1

A5

ORG

DAMPER
MOTOR

CONTROL UNIT

ORG

DM

BLU

FAN
MOTOR

ORG

TURN
TABLE
MOTOR

PPL

SECONDARY
INTERLOCK
SWITCH

ORG

BLK

CONVE­CTION
MOTOR

BLK

TTM

WHT

STM

WHT

BLK

WHT-WHT

THIRD DOOR
SWITCH

POWER
TRANSFORMER

RED

HIGH

WHT

VOLTAGE
CAPACITOR

0.9 F

HIGH
VOLTAGE
RECTIFIER

HEATING
ELEMENT

OVEN
LAMP

COM

BRN PPL

RY3

ORG

DOOR
SENSING
SWITCH

RED

N.O.

PPL

RY3

RY3 RY2

THERMISTOR SWITCH

PNK

GRN

PRIMARY INTERLOCK

N.O.
RY2

WHT WHT

BLK

RELAY

DAMPER

BLK

BRN

E3 E4E6E5E2E1

F1 F2 F3

AH SENSOR

BLK

MONITOR
SWITCH

STIR­RER
MOTOR

WHT

ORG

BLK

ORG

OLCMFM

WHT

COM

N.O.

BRN WHT

GRY

RY2

RY1

B7B1B3B5

RY1RY7RY4RY5RY6

COM
RY1

GRY

Ref 2-6(TMAPCB058MRR0)

Figure O-3. Oven Schematic - Convection Cooking Condition (CONVEC, PREHEAT, BROIL, SLOW COOK)

SCHEMATIC

NOTE: CONDITION OF OVEN

1. DOOR CLOSED.

2. MIX COOKING PAD TOUCHED.

3. DESIRED TEMP. TOUCHED.

4. COOKING TIME PROGRAMMED.

5. START PAD TOUCHED.

NOTE: RY2 and RY3 will alternately close during cook cycle

MAGNETRON

FUSE
20A

RED RED

BRN

BLK

PNK

RED

HOOD FAN

NOISE
FILTER

THERMAL
CUT OUTS

NOISE

RESISTOR

WHT

BLK

RED

YEL

GRYBLU

HOOD
MOTOR

120VAC
60Hz

BLK

GRN

GND

WHT

Ref 2-6(TMAPCB058MRR0)

Figure O-4. Oven Schematic - Automatic Mix cooking Condition

BLU
PPL

C3

C9

C5
C7

MAGNETRON
TEMPERATURE
FUSE

BLK

HOOD
CAPACITOR

RED

YEL

HOOD
LAMP

HL

GRY BRN

RY9

RY10

HL

BRN

PNK

C1A3A1

RY8

A5

ORG

DAMPER
MOTOR

CONTROL UNIT

DM

ORG

BLU

FAN
MOTOR

ORG

PPL

TURN
TABLE
MOTOR

SECONDARY
INTERLOCK
SWITCH

ORG

BLK

CONVE­CTION
MOTOR

BLK

TTM

WHT

GRY

B7B1B3B5

12

STM

BLK

WHT

WHT-WHT

THIRD DOOR
SWITCH

POWER
TRANSFORMER

RED

HIGH

WHT

VOLTAGE
CAPACITOR

0.9 F

HIGH
VOLTAGE
RECTIFIER

MAGNETRON

HEATING
ELEMENT

OVEN
LAMP

COM

BRN PPL

RY3

ORG

DOOR
SENSING
SWITCH

RED

N.O.

PPL

RY3

RY3 RY2

THERMISTOR SWITCH

PNK

GRN

PRIMARY INTERLOCK

N.O.
RY2

WHT WHT

BLK

RELAY

DAMPER

BLK

BRN

E3 E4E6E5E2E1

F1 F2 F3

AH SENSOR

BLK

MONITOR
SWITCH

STIR­RER
MOTOR

WHT

ORG

BLK

ORG

OLCMFM

WHT

COM

N.O.

BRN WHT

RY2

RY1

RY1RY7RY4RY5RY6

COM
RY1

GRY

SCHEMATIC

HIGH
VOLTAGE
RECTIFIER

HIGH
VOLTAGE
CAPACITOR

0.9 F

POWER
TRANSFORMER

MAGNETRON

RY8

HL

HL

HOOD
LAMP

HOOD
MOTOR

HOOD
CAPACITOR

GRY BRN

BRN

C1A3A1

GRYBLU

RED

YEL

HOOD FAN
THERMAL
CUT OUTS

BLK
RED

FUSE
20A

RED RED

MAGNETRON
TEMPERATURE
FUSE

C3

BRN

C9

BLK

C5
C7

BLU
PPL

WHT

BLK

RED

YEL

PNK

RY10

RY9

WHT

WHT

RED

BLK

BLK

WHT-WHT

MONITOR
SWITCH

STIR­RER
MOTOR

WHT

BRN

BLK

F1 F2 F3

E3 E4E6E5E2E1

RY1RY7RY4RY5RY6

DAMPER

THERMISTOR SWITCH

HEATING
ELEMENT

DOOR
SENSING
SWITCH

BLK

GRN

PNK

RED

N.O.
RY3

PPL

COM
RY3

COM
RY2

N.O.
RY1

DAMPER
MOTOR

FAN
MOTOR

OVEN
LAMP

ORG

OLCMFM

TTM

DM

CONVE­CTION
MOTOR

SECONDARY
INTERLOCK
SWITCH

TURN
TABLE
MOTOR

ORG

WHT

ORG

BLK

BLK

ORG

ORG

ORG

BLK

BRN WHT

BRN PPL

GRY

B7B1B3B5

A5

ORG

BLU

WHT

PPL

COM
RY1

N.O.
RY2

AH SENSOR

WHT

WHT

RY3 RY2

CONTROL UNIT

STM

GRY

THIRD DOOR
SWITCH

120VAC
60Hz

BLK

WHT

GRN

GND

NOISE
FILTER

NOISE

RESISTOR

PNK

PRIMARY INTERLOCK

RELAY

NOTE: CONDITION OF OVEN

1. DOOR CLOSED.

2. CLOCK APPEARS ON DISPLAY.

R-1855A

Note:
When servicing units with serial number 112162 and above, use the schematics

in Figure 1-1 through 1-4.

BRN
PNK

HOOD
MOTOR

BLU

PPL

C3

C9

C5
C7

MAGNETRON
TEMPERATURE
FUSE

BLK

HOOD
CAPACITOR

RED

YEL

HOOD
LAMP

HL

GRY BRN

RY9

RY10

120VAC
60Hz

BLK

WHT

GRN

GND

NOISE
FILTER

RED RED

BLK
RED

HOOD FAN
THERMAL
CUT OUTS

NOISE

RESISTOR

WHT

YEL

GRYBLU

FUSE
20A

BLK

RED

Ref 2-6(TMAPCB063MRR0)

SCHEMATIC

NOTE: CONDITION OF OVEN

1. DOOR CLOSED.

2. COOKING TIME PROGRAMMED.

3. START PAD TOUCHED.

SECONDARY
INTERLOCK
SWITCH

ORG

A5

ORG

FAN

ORG

MOTOR

DM

DAMPER
MOTOR

BLU

RY8

C1A3A1

PNK

BRN

HL

CONTROL UNIT

ORG

PPL

TURN
TABLE
MOTOR

TTM

CONVE­CTION
MOTOR

BLK

WHT

BLK

ORG

BLK

ORG

OVEN

OLCMFM

LAMP

WHT

COM

N.O.

BRN WHT

GRY

RY2

RY1

B7B1B3B5

RY1RY7RY4RY5RY6

COM
RY1

GRY

COM

BRN PPL

RY3

HEATING
ELEMENT

ORG

DOOR
SENSING
SWITCH

RED

N.O.

PPL

RY3

RY3 RY2

Figure 1-1. Oven Schematic - Off Condition

THERMISTOR SWITCH

PNK

GRN

N.O.
RY2

WHT

WHT

BLK

F1 F2 F3

PRIMARY INTERLOCK

RELAY

DAMPER

BLK

BRN

E3 E4E6E5E2E1

AH SENSOR

BLK

MONITOR
SWITCH

STIR­RER
MOTOR

WHT

STM

BLK

WHT

WHT-WHT

THIRD DOOR
SWITCH

POWER
TRANSFORMER

RED

HIGH

WHT

VOLTAGE
CAPACITOR

0.9 F

HIGH
VOLTAGE
RECTIFIER

MAGNETRON

Ref 2-6(TMAPCB063MRR0)

Figure 1-2. Oven Schematic - Microwave Cooking Condition

13

R-1855A

SCHEMATIC

NOTE: CONDITION OF OVEN

1. DOOR CLOSED.

2. CONVECTION PAD TOUCHED.

3. DESIRED TEMP. TOUCHED.

4. START PAD TOUCHED.

120VAC
60Hz

BLK

WHT

GRN

GND

NOISE
FILTER

RED RED

BLK
RED

HOOD FAN
THERMAL
CUT OUTS

RESISTOR

WHT

YEL

GRYBLU

FUSE
20A

NOISE

BLK

RED

BRN
PNK

HOOD
MOTOR

BLU

PPL

C9

C5

C7

C3

HL

GRY BRN

MAGNETRON
TEMPERATURE
FUSE

BLK

RY9

RY10

HOOD
CAPACITOR

RED

YEL

HOOD
LAMP

A5

ORG

ORG

DM

DAMPER
MOTOR

BLU

RY8

C1A3A1

PNK

BRN

HL

CONTROL UNIT

FAN
MOTOR

ORG

TURN
TABLE
MOTOR

PPL

SECONDARY
INTERLOCK
SWITCH

ORG

BLK

CONVE­CTION
MOTOR

BLK

TTM

WHT

STM

BLK

WHT

THIRD DOOR
SWITCH

POWER
TRANSFORMER

WHT-WHT

RED

WHT

HIGH
VOLTAGE
CAPACITOR

0.9 F

HIGH
VOLTAGE
RECTIFIER

HEATING
ELEMENT

COM

BRN PPL

RY3

ORG

DOOR
SENSING
SWITCH

RED

N.O.

PPL

RY3

RY3 RY2

PNK

GRN

WHT

WHT

THERMISTOR SWITCH

BLK

PRIMARY INTERLOCK

RELAY

N.O.
RY2

DAMPER

BLK

BRN

E3 E4E6E5E2E1

F1 F2 F3

AH SENSOR

BLK

MONITOR
SWITCH

STIR­RER
MOTOR

WHT

ORG

BLK

ORG

OVEN

OLCMFM

LAMP

WHT

COM

N.O.

BRN WHT

GRY

RY2

RY1

B7B1B3B5

RY1RY7RY4RY5RY6

COM
RY1

GRY

Ref 2-6(TMAPCB063MRR0)

Figure 1-3. Oven Schematic - Convection Cooking Condition (CONVEC, PREHEAT, BROIL, SLOW COOK)

SCHEMATIC

NOTE: CONDITION OF OVEN

1. DOOR CLOSED.

2. MIX COOKING PAD TOUCHED.

3. DESIRED TEMP. TOUCHED.

4. COOKING TIME PROGRAMMED.

5. START PAD TOUCHED.

NOTE: RY2 and RY3 will alternately close during cook cycle

MAGNETRON

FUSE
20A

RED RED

BRN

BLK

PNK

RED

HOOD FAN

NOISE
FILTER

THERMAL
CUT OUTS

NOISE

RESISTOR

WHT

BLK

RED

YEL

GRYBLU

HOOD
MOTOR

120VAC
60Hz

BLK

GRN

GND

WHT

Ref 2-6(TMAPCB063MRR0)

BLU
PPL

C3

C9

C5

C7

MAGNETRON
TEMPERATURE
FUSE

BLK

HOOD
CAPACITOR

RED

HOOD
LAMP

HL

GRY BRN

YEL

RY9

RY10

A5

ORG

ORG

DM

DAMPER
MOTOR

BLU

RY8

C1A3A1

PNK

BRN

HL

CONTROL UNIT

FAN
MOTOR

ORG

TURN
TABLE
MOTOR

PPL

SECONDARY
INTERLOCK
SWITCH

ORG

CONVE­CTION
MOTOR

BLK

TTM

WHT

BLK

ORG

BLK

ORG

OVEN

OLCMFM

LAMP

WHT

COM

N.O.

BRN WHT

GRY

B7B1B3B5

RY2

RY1

RY1RY7RY4RY5RY6

COM
RY1

GRY

COM

BRN PPL

RY3

HEATING
ELEMENT

ORG

RED

N.O.

PPL

RY3

RY3 RY2

DOOR
SENSING
SWITCH

PNK

WHT

THERMISTOR SWITCH

BLK

BLK

F1 F2 F3

PRIMARY INTERLOCK

RELAY

BRN

E3 E4E6E5E2E1

AH SENSOR

GRN

WHT

N.O.
RY2

DAMPER

BLK

MONITOR
SWITCH

STIR­RER
MOTOR

WHT

Figure 1-4. Oven Schematic - Automatic Mix cooking Condition

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STM

BLK

WHT

THIRD DOOR
SWITCH

POWER
TRANSFORMER

WHT-WHT

RED

WHT

HIGH
VOLTAGE
CAPACITOR

0.9 F

HIGH
VOLTAGE
RECTIFIER

MAGNETRON

DESCRIPTION AND FUNCTION OF COMPONENTS

R-1855A

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

LATCH HOOK

DOOR

LATCH
HEADS

OPEN LEVER

DOOR SENSING
SWITCH

MONITOR FUSE

MONITOR
SWITCH

SECONDARY
INTERLOCK
SWITCH

THIRD
DOOR
SWITCH

Figure D-1. Door Open Mechanism

SECONDARY INTERLOCK SWITCH, THIRD DOOR
SWITCH & DOOR SENSING SWITCH

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

operate inversely.)

3. If the door is opened, and the primary interlock relay,
secondary interlock switch and third door 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 PRIMARY INTERLOCK RE­LAY, THIRD DOOR SWITCH, DOOR SENS­ING SWITCH, MONITOR SWITCH AND SEC­ONDARY INTERLOCK SWITCH FOR PROPER
OPERATION. (REFER TO CHAPTER "TEST
PROCEDURE").

NOTE: MONITOR FUSE, SECONDARY INTERLOCK

SWITCH AND MONITOR SWITCH ARE
REPLACED AS AN ASSEMBLY.

TEMPERATURE FUSE (MG)

The temperature fuse located near the waveguide 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 temperature fuse remains closed.
However, the temperature fuse will open at 302OF (150OC)
causing the oven to shut down.

THERMAL CUT-OUT (HOOD )

This thermal cut-out located on the base plate right and the
hood intake duct (left), It is designed to automatically turn
on the hood fan motor whenever the hot air rising from the
conventional range below causes the temperature at the
thermal cut-out to rise to 140OF (60OC) or higher, thus
removing this hot air from around microwave oven. When
the temperature around the thermal cut-out drops to 113OF
(45OC) or lower, the thermal cut-out shuts off the food fan
motor.

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. Turntable will turn in either
direction. The turntable motor can be turned off by touching
TURNTABLE ON/OFF pad.

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 switch and third door 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, secondary interlock
switch and third 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,
secondary interlock switch and third door switch contacts
close. (On opening the door, each of these switches

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.

HOOD FAN MOTOR

The hood fan motor is a two-speed, single-phase, double
pole induction type, requiring a hood fan capacitor. It is
located outside the upper rear part of the oven cavity, is to
remove, from around the oven, hot air rising from the
conventional electric or gas range over which it is installed.
This air is then expelled either vertically or horizontally
through the customer supplied duct system, or discharged
back into the kitchen.

15

R-1855A

STIRRER MOTOR

The stirrer motor drives the stirrer fan to stir the microwave
radiation from the waveguide.

HOOD LAMP

The hood lamps are mounted at the hood lamp angle on the
base cover. When the hood lamp button is pushed, the hood
lamp relay (RY8) contacts close turning both hood lamps on.

HEATING ELEMENT

The heating element is located at the left side of the oven
cavity. It is intended to heat air driven by the convection fan.
The heated air is kept in the oven and force-circulated and
reheated by the heating element.

CONVECTION COOKING SYSTEM

This oven is designed with a hot air heating system where
food is not directly heated by the heating element, but is
heated by forced circulation of the hot air produced by the
heating element.
The air heated by the heating element is circulated through
the convection passage provided on the outer casing of the
oven cavity by means of the convection fan which is driven
by the convection motor. It then enters the inside of the oven
through the vent holes provided on the left side of the oven.
Next, the hot air heats the food on the turntable and leaves
the oven cavity through the vent in the center of the oven
cavity left side wall.
Without leaving the oven, this hot air is reheated by the
heating element, passes through the convection passage
and enters the inside of the oven cavity again, in a continuing
cycle.
In this way, the hot air circulates inside the oven cavity to
raise its temperature and, at the same time, comes into
contact with the food being cooked.
When the temperature inside the oven cavity reaches the
selected temperature, the heating element is de-energized.
When the temperature inside the oven cavity drops below
the selected temperature, the heating element is energized
again. In this way, the inside of the oven cavity is maintained
at approximately the selected temperature.
When the convection time reaches 0, the heating element
is de-energized and the convection fan stops operating and
the oven shuts off.

DAMPER OPEN-CLOSE MECHANISM

Usually, the damper is in the open position except during
convection cooking. Damper position is set automatically
by damper motor, damper switch and motor cam. These
components are operated by a signal that judges if micro­wave cooking or convection cooking operation is selected
by the control unit.

Microwave Cooking:

Damper is in the open position, because a portion of cooling
air is channeled through the cavity to remove steam and
vapors given off from the heating foods.
It is then exhausted at the top of the oven cavity into a
condensation compartment.

Convection Cooking:

Damper is in the closed position, so that no hot air will be
allowed to leak out the oven cavity.

Damper Operation

1. When power supply cord is plugged in:
1-1. When power supply cord is plugged in, a signal is

sensed in the control unit, and operates shut-off
relay (RY6).

1-2. Contacts of shut-off relay (RY6) close, the damper

motor is energized, opening the damper plate.

1-3. When the damper is moved to the open position by

the damper cam the damper switch is closed (ON
position).

1-4. The signal from damper switch is re-sensed in the

control unit and shut-off relay (RY6) is turned off.

1-5. The 120 volts A.C. to the damper motor is removed

and the motor turns off.

2. When oven is microwave cooking:
Damper is in the open position.

3. When oven is convection cooking:
3-1. Damper motor is energized by touching the

convection, temperature, number and START pads.

3-2. When damper is in the closed position (damper

switch is OFF), its signal is sensed by the control
unit, and shut-off relay (RY6) is de-energized.

3-3. The damper is held in the closed position during the

convection cooking operation.

3-4. At the end of the convection cooking, shut-off relay

(RY6) is energized, and the damper is returned to
the open position.

NOTE: If the damper plate is not in the proper position,

closed during convection or open during microwave,
the control unit will stop oven operation after 1
minute.

DAMPER PLATE

DAMPER CAM

DAMPER SWITCH

DAMPER MOTOR

Figure D-2. Damper Mechanism

16