Sharp Carousel R-980E User manual

R-980E
43
S5102R980EPJ/
CONVECTION
MICROWAVE OVEN
MODEL R-980E
In interests of user-safety the oven should be restored to its original
condition and only parts identical to those specified should be used.
SERVICE MANUAL
SHARP CORPORATION
TABLE OF CONTENTS
Page
CAUTION, MICROWAVE RADIATION.............................................................................................................. 1
WARNING...........................................................................................................................................................1
PRODUCT SPECIFICATIONS .......................................................................................................................... 2
GENERAL INFORMATION.................................................................................................................................2
APPEARANCE VIEW ........................................................................................................................................ 3
OPERATION SEQUENCE................................................................................................................................. 4
FUNCTION OF IMPORTANT COMPONENTS ................................................................................................. 7
SERVICING ..................................................................................................................................................... 10
TEST PROCEDURE.........................................................................................................................................12
TOUCH CONTROL PANEL ASSEMBLY .........................................................................................................20
COMPONENT REPLACEMENT AND ADJUSTMENT PROCEDURE............................................................ 26
MICROWAVE MEASUREMENT ..................................................................................................................... 31
WIRING DIAGRAM.......................................................................................................................................... 32
PICTORIAL DIAGRAM .................................................................................................................................... 34
CONTROL PANEL CIRCUIT ............................................................................................................................35
PRINTED WIRING BOARD ..............................................................................................................................36
PARTS LIST .................................................................................................................................................... 37
MIX CONV
DEFROST
SENSORCOOK LBS OZ KG HELP
HELP
INFODISPLAY
MULTI
COOK
REHEAT
SENSOR
SENSORINSTANTACTION
POWER
LEVEL
EASY
DEFROST
STOP
CLEAR
CLOCK
LOWMIXHIGHMIX
GRILL CONVEC
LESS MORE
MEMORYPREHEAT
FRESH
VEGETABLES
FFOZEN
VEGETABLES
CASSEROLES
DESSERTS
REHEAT
PIEJACKET
POTATO
1234 5
6 7 8 9 O
INSTANTCOOK
START
40˚C70˚C130˚C150˚C160˚C
180˚C200˚C220˚C230˚C250˚C

R-980E
44

R-980E
1
SERVICE MANUAL
CONVECTION
MICROWAVE OVEN
R-980E
GENERAL IMPORTANT INFORMATION
ThisManualhasbeenpreparedtoprovideSharpCorp.Service
engineers with Operation and Service Information.
It is recommended that service engineers carefully study the
entire text of this manual, so they will be qualified to render
satisfactory customer service.
CAUTION
MICROWAVE RADIATION
DONOTBECOME EXPOSED TORADIATIONFROMTHE
MICROWAVE GENERATOR OR OTHER PARTS
CONDUCTING MICROWAVE ENERGY.
Service engineers should not be exposed to the microwave
energy which may radiate from the magnetron or other
microwave generating devices if it is improperly used or
connected. All input and output microwave connections,
waveguides, flanges and gaskets must be secured. Never
operate the device without a microwave energy absorbing
load attached. Never look into an open waveguide or an-
tenna while the device is energized.
WARNING
Never operate the oven until the following points are ensured.
(A) The door is tightly closed.
(B) The door brackets and hinges are not defective.
(C) The door packing is not damaged.
(D) The door is not deformed or warped.
(E) There is not any other visible damage with the oven.
Servicing and repair work must be carried out only by trained
service engineers.
All the parts marked "*" on parts list are used at voltages more
than 250V.
Removal of the outer wrap gives access to potentials above
250V.
All the parts marked "∆" on parts list may cause undue micro-
wave exposure, by themselves, or when they are damaged,
loosened or removed.
SHARP CORPORATION
OSAKA, JAPAN
PRODUCT SPECIFICATIONS
APPEARANCE VIEW
OPERATING SEQUENCE
FUNCTION OF IMPORTANT
COMPONENTS
SERVICING AND
TROUBLESHOOTING CHART
TEST PROCEDURE
TOUCH CONTROL PANEL
ASSEMBLY
COMPONENT REPLACEMENT
AND ADJUSTMENT PROCEDURE
MICROWAVE MEASUREMENT
WIRING DIAGRAM
PARTS LIST

R-980E
2
PRODUCT SPECIFICATIONS
ITEM DESCRIPTION
Power Requirements 230 - 240 Volts
50 Hertz
Single phase, 3 wire earthed
Power Consumption 1600 W (Microwave)
1600 W (Convection)
Power Output 900 watts (IEC Test Procedure)
Operating frequency of 2450MHz
Convection heater 1500 W
Case Dimensions Width 627mm
Height 378mm
Depth 492mm
Cooking Cavity Dimensions Width 410mm
Height 245mm
Depth 410mm
Control Complement Touch Control System
Clock ( 1:00 - 12:59)
Timer (0 - 99 min. 99 sec.)
Microwave Power for Variable Cooking
Repetition Rate;
HIGH ..............................................Full power throughout the cooking time
MED HIGH ........................................................approx. 70% of Full Power
MED ...................................................................approx. 50% of Full Power
MED LOW (DEFROST) .....................................approx. 30% of Full Power
LOW...................................................................approx. 10% of Full Power
Convection Temperature for Variable Cooking
CONVECTION ...................................................40 to 250˚C Temp. control
LOW MIX .......................................... 180˚C with 10% of microwave power
HIGH MIX.......................................... 200˚C with 30% of microwave power
GRILL................................................................................. 250˚C (Preheat)
HELP pad
SENSOR INSTANT ACTION pads
MULTI COOK pad
REHEAT SENSOR pad
CONVECTION COOKING FUNCTION pads
EASY DEFROST pad
NUMBER and TEMPERATURE pads
POWER LEVEL pad
MEMORY pad
MORE. LESS pads
STOP/CLEAR pad
CLOCK pad
INSTANT COOK/START pad
Set Weight Approx. 29 kg
GENERAL INFORMATION
WARNING
THIS APPLIANCE MUST BE EARTHED
IMPORTANT
THE WIRES IN THIS MAINS LEAD ARE COLOURED IN ACCORDANCE WITH THE FOLLOWING CODE:
GREEN-AND-YELLOW : EARTH
BLUE : NEUTRAL
BROWN : LIVE

R-980E
3
APPEARANCEVIEW
1. Ventilation opening
2. Oven lamp
3. Door hinges
4. Door safety latches
5. See through door
6. Door seal and sealing
surfaces
7. Door open button
8. Touch control panel
9. Digital readout
10.Wave guide cover
11.Coupling
12.Menu label
13.Rating label
14. low rack
15.High rack
16.Power supply cord
17.Turntable
18.Roller stay
TOUCH CONTROL PANEL
1
10
2
12
9
8
7
517
18
14 15
13
11 4
6
3
4
16
NOTE:
The directed features are disabled after one minute when the oven is
not in use. These features are automatically enabled when the door
is opened and closed or the STOP/ CLEAR pad is pressed.
HELPINFO DISPLAY
MULTI
COOK
REHEAT
SENSOR
SENSOR INSTANT ACTION
POWER
LEVEL
EASY
DEFROST
STOP
CLEAR CLOCK
LOW MIX HIGH MIX GRILL CONVEC
LESS MORE
MEMORY PREHEAT
FRESH
VEGETABLES
FROZEN
VEGETABLES
CASSEROLES DESSERTS
REHEAT
PIE JACKET POTATO
12345
6 7 8 9 O
INSTANT COOK
START
MULTI COOK PAD
Press to select Multi Cook
mode.
MORE ( ), LESS ( ) PADS
Press to increase/decrease the
time in one minute increments
during cooking or to alter the
doneness for the Sensor In-
stant Action, Reheat Sensor,
Multi Cook or Easy Defrost
modes.
CONVECTION COOKING
FUNCTION PADS
Press to cook for each func-
tion.
POWER LEVEL PAD
Press to select microwave
power setting.
If not pressed, HIGH is au-
tomatically selected.
NUMBER AND TEMPERATURE
PADS
Press to enter cooking times, clock
time, convection temperature or to
select the Multi Cook menus.
STOP/CLEAR PAD
Press to clear during program-
ming.
Press once to stop operation
of oven during cooking; press
twice to cancel cooking pro-
gram.
HELP PAD
Press to select auto start, in-
formation guide on/off, child
lock, demonstration modes or
info on pad.
Press to get cooking informa-
tion.
REHEAT SENSOR PAD
Press to select 3 popular Reheat
menu.
SENSOR INSTANT ACTION
PADS
Press once to cook or reheat 6
popular menus. (See NOTE)
MEMORY PAD
Press to enter the frequently used
cooking program.
Press to recall the memorized pro-
gram.
EASY DEFROST PAD
Press to defrost meat by en-
tering weight only.
INSTANT COOK/START PAD
Press once to cook for 1 minute
at HIGH or increase by 1 minute
multiples each time this pad is
pressed during Microwave, Con-
vection, Grill or Mix cooking.
(See NOTE)
CLOCK PAD
Press to set Clock
Indicator
MIX CONV
DEFROST
SENSOR
COOK KG HELP
40˚C 70˚C 130˚C 150˚C 160˚C
180˚C 200˚C 220˚C 230˚C 250˚C

R-980E
4
The following is a description of component functions
during oven operation.
Relay and Components Connection
RELAY CONNECTED COMPONENT
RY1 Oven lamp/ Turntable motor
RY2 Power transformer
RY3 Convection heater
RY4 Damper motor
RY5 Convection motor
RY6 Fan motor
OFF CONDITION
Closing the door activates all door interlock switches:
upper latch switch, lower latch switch and stop switch. (In
this condition, the monitor switch contacts are closed.)
When oven is plugged in a wall outlet (230 - 240V, 50Hz),
rated voltage is supplied to the control unit. (Figure O-1):
1. The display flashes “SHARP”, "MICRO-", "WAVE",
'OVEN".
Toset anyprogrammes or setthe clock, youmust first
touch the STOP/CLEAR pad.
“ : “ appears in the display and the time counts up
every minute.
NOTE: When the oven door is opened, the oven lamp
comes on at this time.
2. A signal is input to the control unit, energizing the coil
of shut-off relay (RY4).
RY4contactsclose,completingacircuittothedamper
motor. The damper motor now operates moving the
damper to the open position, thereby closing the
contactsofdamperswitchinputsasignaltothecontrol
unit.
The coil of relay RY4 is de-energized, opening its
contacts, thereby turning off the damper motor.
MICROWAVE COOKING CONDITION
HIGH COOKING
Enter cooking time by pressing the NUMBER pads and
then select microwave cooking and power level by press-
ing the POWER LEVEL pad. When the START pad is
touched, the following operations occur:
1. The contacts of relays are closed and components
connected to relays are turned on (RY1, RY2, RY6).
(Figure O-2)
2. Ratedvoltage is suppliedto the primarywinding of the
power transformer. The voltage is converted to about
3.3 volts A.C. output on the filament winding and high
voltage of approximately 2260 volts A.C. on the high
voltage winding.
3. The filament winding voltage (3.3 volts) heats the
magnetronfilamentandthehighvoltage(2260volts)is
sent to the voltage doubling circuit.
4 The 2450 MHz microwave energy produced in the
magnetron generates a wave length of 12.24 cm. This
energyischannelledthroughthewaveguide(transport
channel)intothe oven cavity,wherethefoodis placed
to be cooked.
5. Upon completion of the cooking time, the power
transformer, oven lamp, etc. are turned off and the
generation of microwave energy is stopped. The oven
will revert to the OFF condition..
6 When the door is opened during a cook cycle, the
monitor switch, upper latch switch, lower latch switch
andstopswitchareactivatedwiththefollowingresults.
The circuits to the turntable motor, cooling fan motor
and high voltage components are de-energized, the
ovenlampremainsonandthedigitalread-outdisplays
thetimestillremaininginthecookcycle when the door
was opened.
7. The monitor switch is electrically monitoring the
operation of the upper latch switch and lower latch
switchandismechanicallyassociatedwiththedoorso
that it will function in the following sequence.
1) When the door opens from a closed potion, the upper
latch switch and the lower latch switch open their
contacts, and then the monitor switch contacts close.
2) When the door is closed, from the open position, the
monitorswitchcontactsfirstopen,andthenthecontacts
oftheupperlatchswitchandlowerlatchswitchmustbe
closed.
If the common and normal open contacts of upper latch
switch and the lower latch switch fail with their contacts
closedwhenthedoorisopened,theclosingofthemonitor
switch contacts will form a short circuit through the fuse,
upperlatch switchand the lowerlatch switch, causingthe
monitor fuse to blow.
MEDIUM HIGH, MEDIUM, MEDIUM LOW, LOW
COOKING
When variable cooking power is programmed, the rated
voltageissuppliedto the power transformer intermittently
through the contacts of the relay (RY2) which is operated
by the control unit within a 32-second time base. Micro-
wave power operation is follows:
VARI MODE ON TIME OFF TIME
HIGH (100% power) 32 sec. 0 sec.
MED HIGH (approx. 70% power) 24 sec. 8 sec.
MED (approx. 50% power) 18 sec. 14sec.
MED LOW (approx. 30% power) 12 sec. 20 sec.
LOW (approx. 10% power) 6 sec. 26 sec.
NOTE: TheON/OFFtimeratiodoesnotexactlycorrespond
to the percentage of microwave power, because
approx. 2 seconds are needed for heating up the
magnetron filament.
CONVECTION COOKING CONDITION
PREHEATING CONDITION
Press the PREHEAT pad and then select preheating
temperature by pressing the temperature pad. When the
START pad is touched, the following operations occur:
1. The coil of shut-off relays RY1+RY5+RY6 are
energized,the oven lamp, coolingfanmotor,turntable
motor and convection motor are turned on.
2. The coil of relay (RY4) is energized by the CPU unit.
The damper is moved to the closed position, opening
thedamperswitchcontacts.Theopeningofthedamper
switch contacts sends a signal to the LSI on the CPU
OPERATION SEQUENCE

R-980E
5
unit de-energizing the relay (RY4) and opening the
circuit to the damper motor.
3. Thecoil of heater relay(RY3)is energized bytheCPU
unit and the main supply voltage is added to the
convection heater.
4. When the oven temperature reaches the selected
preheat temperature, the following operations occur:
4-1. The heater relay (RY3) is de-energized by the CPU
unit temperature circuit and thermistor, opening the
circuit to the convection heater.
4-2. The oven will continue to function for 30 minutes,
turning the convection heater on and off, as needed
to maintain the selected preheat temperature. The
oven will shut-down completely after 30 minutes.
CONVECTION COOKING CONDITION
When the preheat temperature is reached, a beep signal
will sound indicating that the holding temperature has
beenreachedinthe ovencavity.Openthedoorandplace
the food to be cooked in the oven. Press the CONVEC-
TION pad and then enter the cooking temperature by
pressingthetemperaturepad.Andthenenterthecooking
time by pressing the NUMBER pads. When the START
pad is touched, the following operations occur:
1. The numbers of the digital read-out start the count
down to zero.
2. Theovenlamp,turntablemotor,coolingfan motor and
convection motor are energized.
3. Heaterrelay(RY3)isenergized(ifthecavitytemperature
is lower than the selected temperature) and the main
supply voltage is applied to the convection heater 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
cavity air temperature is above 116˚C, the circuit to
(RY6) will be maintained (by the thermistor circuit) to
continue operation of the cooling fan motor until the
temperature drops below 116˚C, at which time the
relay will be de-energized, turning off the fan motor.
Relay (RY5) will however, open as soon as the
convectioncyclehasended,turningofftheconvection
fanmotor.Thiswillnowcoolandallowthedamperdoor
to open.
5. At the end of the convection cook cycle, shut-off relay
(RY4) 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 (RY4).
AUTOMATIC MIX COOKING CONDITION
Choose the LOW MIX or HIGH MIX by pressing the LOW
MIXpadorHIGHMIXpad.Andthenentercookingtimeby
pressing the NUMBER pads. When the START pad is
touched, the following operations occur:
1. The numbers of the digital read-out start the count
down to zero.
2. Theshut-offrelay(RY1+RY5+RY6)energized,turning
on the oven lamp, turntable motor, cooling fan motor
and convection motor.
3. The shut-off relay (RY4) is energized.
The damper door is closed from the open position.
4. Theheaterrelay(RY3) is energized, addingthemains
supply voltage to the convection heater.
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 added to the convection
heater and power transformer alternately.
6-2. The convection heater operates through the heater
relay (RY3) contacts and the power transformer
operates through the cook relay (RY2) contacts.
6-3. These are operated by the CPU unit to supply
alternately within a 48 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
withthepercentageofmicrowavepower,because
approx. 2 seconds are needed for heating of the
magnetron filament.
16 SEC. 32 SEC.
48 SEC.
LOW MIX
HIGH MIX
MICROWAVE POWER
= APPROX. 30%
CONVECTION
TEMPERATURE
= 200˚C
MICROWAVE POWER
= APPROX. 10%
CONVECTION
TEMPERATURE
= 180˚C
40 SEC.8 SEC.
ON
ON
OFF
OFF
OFF
ON
(MICRO.)
(CONVEC.)
(MICRO.)
(CONVEC.)
Note: DuringalternateMicrowave/Convectionoperation,
the convection heater is energized only if the
cavity temperature drops below the set
temperature.
ABSOLUTE HUMIDITY SENSOR (AH SENSOR)
COOKING CONDITION
Incase where theAHsensor is used(REHEATSENSOR
or SENSOR INSTANT ACTION), the foods are cooked in
microwave cooking mode without figuring time, power
level or quantity. When the oven senses enough steam
from the food, it relays the information to its microproces-
sor which will calculate the remaining cooking time and
power level needed for best results. When the food is
cooked, water vapour is developed. The sensor “senses”
the vapour and its resistance increases gradually. When
the resistance reaches the value set according to the
menu, supplementary cooking is started. 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. Vapour is emitted very
slowly.

R-980E
6
2. Heatpotatoes.Moistureandhumidityisemittedrapidly.
You can smell the aroma as it cooks. ;
3. Sensor detects moisture and humidity and calculates
cooking time and variable power.
AH SENSOR COOKING SEQUENCE
1. IncasetheAHsensorcookingconditionisstarted,the
coil of shut-off relays (RY1+RY6) are energized, the
ovenlampandcoolingfanmotorareturnedon,butthe
power transformer is not turned on.
NOTE: TheovenshouldnotbeoperatedonAHSENSOR
COOKING immediately after plugging in the unit.
Waitfiveminutesbeforecooking onAHSENSOR
COOKING CONDITION.
2. After about 16 seconds, the cook relay (RY2) is
energized. The power transformer is turned on,
microwaveenergyisproducedandfirststageisstarted.
The16seconds is thecoolingtimerequiredto remove
any vapour from the oven cavity and sensor.
(Figure O-2)
NOTE: During this first stage, do not open the door or
touch STOP/CLEAR pad.
3. The oven will go to the Mix Cooking Condition at the
2nd. or 3rd. stage when Reheat pie, Casseroles or
Desserts has been chosen. (Figure O-3)
4. When the sensor detects the vapour emitted from the
food,thedisplayswitchesovertotheremainingcooking
timeandthetimercountsdowntozero.Atthistime,the
door may be opened to stir food, turn it or season, etc.
NOTE: In case where a small quantity of food is cooked,
theovenwillstopwithoutdisplayingtheremaining
cooking time.
5. Whenthetimerreacheszero,anaudiblesignalsounds.
The shut-off relay (RY1+RY6) and cook relay (RY2)
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.
MULTI COOK
MULTICOOKwillautomaticallycomputeandsettheoven
temperature, microwave power and cooking time for bak-
ingand roasting. Setthedesiredprogram by touchingthe
MULTI COOK pad, and number pad. Enter the weight by
touching the Number pads. When the START pad is
touched, the oven works on Mix cooking mode, Convec-
tion cooking mode or Preheating mode according to the
special cooking sequence.
EASY DEFROST COOKING
The EASY DEFROST key is a special function key to
defrost meats and poultry faster and better.
EASY DEFROST key has 4 defrost stages.
EASY DEFROST automatically defrosts roast beef, etc.
WhenEASYDEFROSTisselectedandthefoodweightis
entered by using the number pads, the oven will cook
according to the special cooking sequence. (Figure O-2)
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 accomplished by the LSI repeatedly measures the
voltageacrossthetemperaturemeasurementcircuit(ther-
mistor) during it's 32-seconds time base comparing the
obtained voltage measurements. If the most recent volt-
age measured is 300mV grater than the previous voltage
measured,theLSIjudgesitasafireintheovencavityand
switchesofftherelaystothepowertransformer,fanmotor
and convection motor. The LSI also stops counting down
and closes the damper door so that no fresh air will enter
the oven cavity. Please refer to the following section for a
more detailed description.
Operation
Please refer to the timing diagrams below.
1. Thethermistoroperateswithina32-secondstimebase
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
measurementcircuit is sampledbytheLSI and twenty
one (21) seconds after the thermistor is cut off the LSI
turns on the cooling fan 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 300mV the LSI makes the
judgment that there is a fire in the oven cavity and will
switch off the relays to the power transformer, fan
motor and convection motor. The LSI also stops
counting down and closes the damper door so that no
fresh air will enter the oven cavity.
3. Oncethefiresensorfeaturehasshuttheunitdown,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
operationsequencewill notbeginuntil theAHsensor
has detected vapours and initiated a sensor cooking
cycle.Thisisbecausetheoperationoftheconvection
fanwouldinterferewiththeAHsensor'svapourdetec-
tion.
MICROWAVE
MICROWAVE
AH SENSOR
CONVECTION
MOTOR
THERMISTOR
Sensing
Voltage
ON
OFF
ON
OFF
ON
OFF
0 2 3 24 30 32 (sec.) 64 (sec.)
3 sec.
Sensing the voltage across temperature measurement circuit.
6 sec.

R-980E
7
DOOR OPEN MECHANISM
The door is opened by pushing the open button on the
control panel, refer to the Figure D-1.
Whentheopenbuttonispushed,theopenleverpushesup
the switch lever, and then the switch lever pushes up the
the latch head. The latch heads are moved upward and
released from latch hook. Now the door will open.
Figure D-1. Door Open Mechanism
UPPERLATCHSWITCH,LOWERLATCHSWITCH
AND STOP SWITCH
1. Whentheovendoorisclosed,thecontacts(COM-NO)
must be closed.
2. When the oven door is opened, the contacts (COM-
NO) must be opened.
MONITOR SWITCH
The monitor switch is mounted on the latch hook. It is
activated (the contacts opened) by the lower latch head
when the door is closed. The switch is intended to render
theoven inoperative by meansofblowning the fusewhen
the contacts of the common and normal open contacts of
upper latch switch and lower latch 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 common and normal open
contacts of upper latch switch and lower latch switch
are in the OFF condition (contacts open) due to their
being normally open contacts switch.
2. As the door goes to a closed position, the monitor
switchcontacts are firstopenedand then thecommon
and normal open contacts of upper latch switch close.
(On opening the door, each of these switches operate
inversely.)
3 If the door is opened during cooking, and the common
and normal open contacts of upper latch switch and
lower latch switch fail to open, the fuse blows
simultaneously with closing of the monitor switch
contacts.
CAUTION: BEFORE REPLACING A BLOWN FUSE
TESTTHEUPPERLATCHSWITCH,LOWER
LATCH SWITCH AND MONITOR SWITCH
FOR PROPER OPERATION. (REFER TO
CHAPTER “TEST PROCEDURE”).
FUNCTION OF IMPORTANT COMPONENTS
THERMAL CUT-OUT 150˚C (CONV.)
The oven thermal cut-out located on the left side of the
thermalprotectionplateis designedtopreventdamageto
the convection heater unit if an overheated condition
develops in the tube due to cooling fan failure, obstructed
air ducts, dirty or blocked air intake, etc. Under normal
operation,theoventhermalcut-outremainsclosed. How-
ever, when abnormally high temperatures are reached
within the heater unit, the oven thermal cut-out will open,
causingtheoventoshutdown.Whentheovenhascooled
temperature, the oven thermal cut-out closes.
THERMAL CUT-OUT 95˚C (FAN MOTOR)
The thermal cut-out protect the fan motor against over-
heating. If its temperature goes up higher than 95˚C
because the fan motor is locked or the ventilation operat-
ing are blocked, the contacts of the thermal cut-out will
open and switch off the oven. When the thermal cut-out
cools itself down to 75˚C, the contacts of the thermal cut-
out will close again.
TEMPERATURE FUSE 150˚C (MG)
This fuse protects the magnetron against overheating. If
the temperature goes up higher than 150˚C because the
fan motor is interrupted, the air inlet duct is blocked or the
ventilation openings are obstructed, the fuse blows and
cutsoffthepowersupplyingtothepowertransformer.The
defective fuse must be replaced with new rated one.
FUSE M8A 250V
1. If the wire harness or electrical components are short-
circuited,thisfuseblowstopreventanelectricshockor
fire hazard.
2. Thefusealsoblowswhenupperlatchswitchandlower
latchswitchremainclosedwiththeovendooropenand
when the monitor switch closes.
3. The fuse M8A also blows when asymmetric rectifier,
H.V. rectifier, H.V. wire harness, H.V. capacitor,
magnetronorsecondarywindingofpowertransformer
is shorted.
ASYMMETRIC RECTIFIER
The asymmetric rectifier is a solid state device that pre-
vents current flow ins both directions. And it prevents the
temperature rise of the power transformer by blowing the
fuse M8A when the high voltage rectifier is shorted.
The rated peak reverse voltage of D1 of the asymmetric
rectifieris6KVTheratedpeakreversevoltageofD2ofthe
asymmetricrectifieris1.7KV.D1andD2oftheasymmet-
ric rectifier or high voltage rectifier are shorted when the
each peak reverse voltage goes beyond the each rated
peak reverse voltage. (The process of blowing the fuse
M8A.) .
1. The high voltage rectifier is shorted by any causes
when microwave cooking.
2. The peak reverse voltage of D2 of the rectifier goes
LATCH HOOK
LATCH
HEADS
STOP SWITCH
MONITOR SWITCH
LOWER LATCH SWITCH
SWITCH LEVER
OPEN LEVER
DOOR OPEN
BUTTON
UPPER LATCH SWITCH
D2 D1
ASYMMETRIC
RECTIFIER HIGH VOLTAGE
RECTIFIER

R-980E
8
temperature inside the oven cavity reaches the selected
temperature,theconvectionheaterisde-energized.When
the temperature inside the oven cavity drops below the
selected temperature, the convection heater is energized
again. In this way, the inside of the oven cavity is main-
tained at approximately the selected temperature.
When the convection time reaches 0, the convection
heater is de-energized and the convection fan stops
operating and the oven shuts off. Upon completion of the
cookingtime,theaudiblesignalwillsound,andovenlamp,
turntable motor, cooling fan motor and convection motor
arede-energized.Attheendoftheconvectioncycle,ifthe
cavity air temperature is above 116˚C, the circuit to RY6
will be maintained (by the thermistor circuit) to continue
operation of the cooling fan motor until the temperature
drops below 116˚C, at which time the relay will be de-
energized, turning off the fan motor. Relay RY5 will how-
ever, open as soon as the convection cycle has ended,
turningofftheconvectionfanmotor.Thiswillnowcooland
allow the damper door to open.
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, motor cam and damper shaft.
Thesecomponents are operatedbyasignal that judgesif
microwave cooking or convection cooking operation is
selected by the CPU unit.
Microwave Cooking:
Damper is in the open position, because a portion of
cooling air is channelled through the cavity to remove
steam and vapours 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
sensedinthecontrolunit,andoperatesshut-offrelay
(RY4).
1-2. Contacts of shut-off relay (RY4) close, the damper
motor is energized, opening the damper door.
1-3. When the damper is moved to the open position by
the damper cam, damper switch is closed (ON
position).
1-4. The signal of damper switch is re-sensed in the
control unit and shut-off relay (RY4) is turned off.
1-5. Theratedvoltagetothedampermotorisstoppedand
the motor turns off.
2. When oven is microwave cooking:
Damper is in the open position
3. When oven is convection cooking:
3-1 Dampermotorisenergizedbytouchingtheconvection,
temperature and START pads.
3-2. When damper is in the closed position (damper
switchisOFF),itssignalissensedbythecontrolunit,
and shut-off relay (RY4) 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
beyond the rated peak reverse voltage 1.7 KV in the
voltagedoubler circuit.
3. D2 of the rectifier is shorted.
4. Thelargeelectriccurrentsflowthroughthehighvoltage
winding of the power transformer.
5. Thelargeelectriccurrents beyond 8A flow throughthe
primary winding of the power transformer.
6. The fuse M8A blows by the large electric currents.
7. The power supply to the power transformer is cut off.
THERMISTOR
The thermistor is a negative temperature coefficient type.
Thetemperatureintheovencavityisdetectedthroughthe
resistance of the thermistor, and then the control unit
causes the heating element relay to operate, thus the
current to the heating element is turned ON/OFF.
MONITOR RESISTOR
ThemonitorresistorpreventsthefuseM8A250Vbursting
whenthefuseM8A250Vblowsduetotheoperationofthe
monitor switch.
TURNTABLE MOTOR
The turntable motor drives the turntable supporting plate
to rotate the turntable.
CONVECTION MOTOR
The convection motor drives the convection fan and
provides the heated air.
FAN MOTOR
Thefanmotordrivesabladewhichdrawsexternalcoolair.
Thiscool air isdirectedthroughthe air vanessurrounding
the magnetron and cools the magnetron. This air is chan-
nelled through the oven cavity to remove steam and
vapours given off from the heating foods. It is then ex-
hausted through the exhausting air vents at the oven
cavity.
CONVECTION HEATER
The convection heater is located at the rear of the oven
cavity. It is intended to heat air driven by the convection
fan.Theheatedairiskeptintheovenandforce-circulated
and reheated by the convection heater.
CONVECTION COOKING SYSTEM
Thisovenisdesignedwithahotairheatingsystemwhere
foodis not directlyheatedby the convectionheater, but is
heatedby forced circulationofthe hot airproduced by the
convection heater. The air heated by the convection
heater is circulated through the convection passage pro-
vided on the outer casing of the oven cavity by means of
the convection fan which is driven by the convection
motor.Itthenenterstheinsideoftheoventhroughthevent
holesprovidedontheleftsideoftheoven.Next,thehotair
heatsthefoodontheturntableandleavestheovencavity
through the vent in the oven cavity left side wall. Without
leavingtheoven,thishotairisreheatedbytheconvection
heater, passes through the convection passage and en-
ters 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