Sharp R-9H56 User manual

R-9H56
SHARP CORPORATION
SERVICE MANUAL
In interests of user-safety the oven should be restored to its original
condition and only parts identical to those specified should be used.
MODEL R-9H56
S8409R9H56PJ/
COVECTION
MICROWAVE OVEN
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 ................................................................................................................................ 21
COMPONENT REPLACEMENT AND ADJUSTMENT PROCEDURE............................................................... 27
MICROWAVE MEASUREMENT ........................................................................................................................ 32
WIRING DIAGRAM ............................................................................................................................................. 33
PICTORIAL DIAGRAM....................................................................................................................................... 35
CONTROL PANEL CIRCUIT .............................................................................................................................. 36
PRINTED WIRING BOARD ................................................................................................................................ 37
PARTS LIST........................................................................................................................................................ 38

R-9H56

R-9H56
1
SERVICE MANUAL
PRODUCT SPECIFICATIONS
SHARP CORPORATION
OSAKA, JAPAN
CAUTION
MICROWAVE RADIATION
DO NOT BECOME EXPOSED TO RADIATION FROM
THE MICROWAVE GENERATOR OR OTHER PARTS
CONDUCTING MICROWAVE ENERGY.
Serviceengineersshouldnotbeexposedtothemicrowave
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
antenna 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
microwave exposure, by themselves, or when they are dam-
aged, loosened or removed.
CONVECTION
MICROWAVE OVEN
R-9H56
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.
TEST PROCEDURE
SERVICING AND
TROUBLESHOOTING CHART
FUNCTION OF IMPORTANT
COMPONENTS
OPERATING SEQUENCE
APPEARANCE VIEW
MICROWAVE MEASUREMENT
WIRING DIAGRAM
PARTS LIST
TOUCH CONTROL PANEL
ASSEMBLY
COMPONENT REPLACEMENT
AND ADJUSTMENT PROCEDURE

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PRODUCT SPECIFICATIONS
ITEM DESCRIPTION
Power Requirements 240 Volts
50 Hertz
Single phase, 3 wire earthed
Power Consumption 1500 W (Microwave)
1600 W (Convection)
Power Output 750 watts nominal of RF microwave energy (AS 2895 1986)
850 watts (IEC-705-1988 )
Operating frequency of 2450MHz
Convection heater 1500 W
Case Dimensions Width 627mm
Height 378mm
Depth 483mm
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(BAKE) ..................................180˚C with 10% of microwave power
HIGH MIX(ROAST)...............................200˚C with 30% of microwave power
GRILL ................................................................................... 250˚C (Preheat)
SENSOR INSTANT ACTION pads
MULTI COOK pad
REHEAT SENSOR pad
CONVECTION COOKING FUNCTION pads
EASY DEFROST pad
NUMBER and TEMPERATURE pads
POWER LEVEL pad
MORE. LESS pads
STOP/CLEAR pad
AUTO START/CLOCK pad
INSTANT COOK/START pad
Set Weight Approx. 29 kg

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APPEARANCE VIEW
111
14 15
111
12
3
45910 213 46
7
8
1. Ventilation opening
2. Oven lamp
3. Door hinges
4. Door safety latches
5. See through door
6. Door open button
7. Touch control panel
8. Digital readout
9. Wave guide cover
10.Coupling
11.Access cover for oven lamp replacement
12.Menu label
13.Rating label
14. low rack
15.High rack
TOUCH CONTROL PANEL
SMART
& EASY
REHEART
SENSOR
LOW MIX HIGH MIX GRILL CONVEC
LESS MORE
12345
67890
STOP
CLEAR
AUTO
START
CLOCK INSTANT COOK
START
40˚C 70˚C 130˚C 150˚C 160˚C
180˚C 200˚C 220˚C 230˚C 250˚ C
MULTI
COOK
Fresh
Vegetables Reheat Pie Jacket Potato
Frozen
Vegetables Casseroles Desserts
POWER
LEVEL EASY DEFROST
CONV GRILL
MIX REHEAT
TEMP COOK
LOW M.LOW MED M.HIGH HIGH
Convection
Fan Symbol
Micro/Defrost
Symbol
Indicator
DEFROST
AUTO
Pcs kg
MULTICOOKPAD
PresstoselectMultiCookmode.
REHEATSENSORPAD
Presstoselect3popularReheat
menus.
SENSORINSTANTACTIONPADS
Pressoncetocookorreheat6
popularmenus.
CONVECTIONCOOKING
FUNCTIONPADS
Presstocookforeachfunction.
MORE( ),LESS( )PADS
Presstoincrease/decreasethetime
inoneminuteincrementsduring
cookingortoalterthedonenessfor
theSensorInstantAction,Reheat
Sensor,MultiCookorEasyDefrost
mode.
INSTANTCOOK/STARTPAD
Pressoncetocookfor1minuteat
HIGHorincreaseby1minute
multipleseachtimethispadis
pressedMicrowave,Convection,
GrillorMixcooking.
AUTOSTART/CLOCKPAD
PresstosetclockorAutoStarttime.
STOP/CLEARPAD
Presstoclearduringprogramming.
Pressoncetostopoperationof
ovenduringcooking;presstwice
tocancelcookingprograme.
NUMBERANDTEMPERATURE
PADS
Presstoentercooklingtimes,clock
time,convectiontemperatureorto
selecttheMultiCookmenus.
EASYDEFROSTPAD
Presstodefrostmeatbyentering
weightonly.
POWERLEVELPAD
Presstoselectmicrowavepower
setting.Ifnotpressed,HIGHis
automaticallyselected.
SENSOR

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OPERATION SEQUENCE
Thefollowingisadescriptionofcomponentfunctionsduring
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
Closingthedooractivatesalldoorinterlockswitches:upper
latch switch, lower latch switch and stop switch. (In this
condition, the monitor switch contacts are closed.)
Whenovenispluggedinawalloutlet(240V50Hz),240volts
A.C. is supplied to the control unit. (Figure O-1):
1. The display flashes “88:88”.
To set any programmes or set the clock, you must first
touch the STOP/CLEAR pad.
“ : “appearsinthedisplayandthetimecountsupevery
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).
RY4 contacts close, completing a circuit to the damper
motor. The damper motor mow operates moving the
dampertotheopenposition,therebyclosingthecontacts
of damper switch inputs a signal to the control unit.
ThecoilofrelayRY4isde-energized,openingitscontacts,
thereby turning off the damper motor.
MICROWAVE COOKING CONDITION
HIGH COOKING
Program desired cooking time and Variable Cooking Con-
trol with the touching NUMBER pads and the POWER
LEVELpad.When theSTARTpadistouched,thefollowing
operations occur:
1. The contacts of relays are closed and components
connected to relays are turned on (RY1, RY2, RY6).
(Figure O-2)
2. 240 volts A.C. is supplied to the primary winding of the
power transformer. The voltage is converted to about
3.35 volts A.C. output on the filament winding and high
voltage of approximately 2120 volts A.C. on the high
voltage winding.
3. The filament winding voltage (3.35 volts) heats the
magnetron filament and the high voltage (2120 volts) 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
energy is channelled through the waveguide (transport
channel)intotheovencavity,wherethefoodisplacedto
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
and stop switch are activated with the following results.
Thecircuitstotheturntablemotor,coolingfanmotorand
high voltage components are de-energized, the oven
lamp remains on and the digital read-out displays the
time still remaining in the cook cycle when the door was
opened.
7. Themonitorswitchiselectricallymonitoringtheoperation
of the upper latch switch and lower latch switch and is
mechanically associated with the door so that it will
function in the following sequence.
1) When the door opens from a closed potion, the upper
latchswitchandthelowerlatchswitchopentheircontacts,
and then the monitor switch contacts close.
2) When the door is closed, from the open position, the
monitorswitchcontactsfirstopen,andthenthecontacts
of the upper latch switch and lower latch switch must be
closed.
If the common and normal open contacts of upper latch
switch and the lower latch 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 fuse,
upper latch switch and the lower latch switch, causing the
monitor fuse to blow.
MEDIUM HIGH, MEDIUM, MEDIUM LOW, LOW
COOKING
Whenvariablecookingpowerisprogrammed,the240volts
A.C. is supplied to the power transformer intermittently
throughthecontactsoftherelay(RY2)whichisoperatedby
the control unit within a 32-second time base. Microwave
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
Program desired convection temperature by touching the
CONVECTION pad and the temp. pad. When the START
pad is touched, the following operations occur:
1. Thecoilofshut-offrelaysRY1+RY5+RY6areenergized,
the oven lamp, cooling fan motor, turntable motor and
convection motor are turned on.

R-9H56
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2. Thecoilofrelay(RY4)isenergizedbytheCPUunit.The
damper is moved to the closed position, opening the
damper switch contacts. The opening of the damper
switchcontactssendsasignaltotheLSIontheCPUunit
de-energizing the relay (RY4) and opening the circuit to
the damper motor.
3. The coil of heater relay (RY3) is energized by the CPU
unitandthemainsupplyvoltageisaddedtotheconvection
heater.
4. Whentheoventemperaturereachestheselectedpreheat
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 15 minutes,
turning the convection heater on and off, as needed to
maintain the selected preheat temperature. The oven
will shut-down completely after 15 minutes.
CONVECTION COOKING CONDITION
Whenthepreheattemperatureisreached,abeepsignalwill
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 desired cooking
time and convection temperature by touching the number
pad, CONVECTION pad and Temperature pad. When the
START pad is touched, the following operations occur:
1. Thenumbersofthe digital read-outstartthe count down
to zero.
2. The oven lamp, turntable motor, cooling fan 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
isabove116˚C,thecircuitto(RY6)willbemaintained(by
thethermistorcircuit)tocontinueoperationofthecooling
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
theconvectioncyclehasended,turningofftheconvection
fan motor. This will now cool and allow the damper door
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
Programdesiredcookingtimeandtemperaturebytouching
the number pads and the LOW MI or HIGH MIX pad. When
the START pad is touched, the following operations occur:
1. Thenumbersofthe digital read-outstartthe count down
to zero.
2. The shut-off relay (RY1+RY5+RY6) energized, turning
ontheovenlamp,turntablemotor,coolingfanmotorand
convection motor.
3. The shut-off relay (RY4) is energized.
The damper door is closed from the open position.
4. The heater relay (RY3) is energized, adding the mains
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)contactsandthepowertransformeroperates
through the cook relay (RY2) contacts.
6-3. TheseareoperatedbytheCPUunittosupplyalternately
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.
12 SEC. 20 SEC.
32 SEC.
LOW MIX
BAKE
HIGH MIX
ROAST
MICROWAVE POWER
= APPROX. 30%
CONVECTION
TEMPERATUE
= 300˚F
MICROWAVE POWER
= APPROX. 10%
CONVECTION
TEMPERATUE
= 350˚F (180˚C)
26 SEC.6 SEC.
ON
ON
OFF
OFF
OFF
ON
(MICRO.)
(CONVEC.)
(MICRO.)
(CONVEC.)
Note: During alternate Microwave/Convection operation,
the convection heater is energized only if the cavity
temperature drops below the set temperature.
ABSOLUTE HUMIDITY SENSOR (AH SENSOR)
COOKING CONDITION
IncasewheretheAHsensorisused(REHEATSENSORor
SENSOR INSTANT ACTION), the foods are cooked in
microwavecooking mode withoutfiguring 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 vapour is developed. The
sensor “senses” the vapour and its resistance increases
gradually. When the resistance reaches the value set ac-
cording to the menu, supplementary cooking is started.
Thetimeofsupplementarycookingisdeterminedbyexperi-

R-9H56
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AH SENSOR COOKING SEQUENCE
1. In case the AH sensor cooking condition is started, the
coil of shut-off relays (RY1+RY6) are energized, the
oven lamp and cooling fan motor are turned on, but the
power transformer is not turned on.
NOTE: The oven should not be operated on AH SENSOR
COOKING immediately after plugging in the unit.
Wait five minutes before cooking on AH SENSOR
COOKING CONDITION.
2. Afterabout16seconds,thecookrelay(RY2)isenergized.
The power transformer is turned on, microwave energy
is produced and first stage is started. The 16 seconds is
thecoolingtime required toremoveany vapour fromthe
oven cavity and sensor.
Figure O-2
NOTE: Duringthisfirststage,donotopenthedoorortouch
STOP/CLEAR pad.
3. TheovenwillgototheMixCookingConditionatthe2nd.
or 3rd. stage when Reheat pie, Casseroles or Desserts
has been chosen. (Figure O-4)
4. When the sensor detects the vapour emitted from the
food,thedisplayswitchesovertothe 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.
NOTE: Incasewhereasmallquantityoffoodiscooked,the
oven will stop without displaying the remaining
cooking time.
5. Whenthe timer reaches zero, an audible signal sounds.
The shut-off relay (RY1+RY6) and cook relay (RY2) are
de-energized and the power transformer, oven lamp,
etc. are turned off.
6. OpeningthedoorortouchingtheSTOP/CLEARpad,the
timeofdaywill reappear onthedisplay and theovenwill
revert to an OFF condition.
MULTI COOK
MULTI COOK will automatically compute the oven tem-
perature,microwavepowerandcookingtimeforbakingand
roasting. Set the desired program by touching the MULTI
COOK pad, and number pad. Enter the weight by touching
the Number pads. When the START pad is touched, the
following operations occur:
1. TheCOOKindicatorwilllightandtheMicrowaveSymbol
and/or the Convection Fan Symbol will rotate.
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, RY3, RY5 and RY6) are
energized, turning on the oven lamp, turntable motor,
cooling fan motor and convection motor. The power
supply voltage is added to the convection heater.
4. Now, the oven is in the convection cooking mode.
5. Whentheoventemperaturehasreachedtheprogrammed
convection temperature, the oven goes into the
programmed cooking mode.
6. At the end of the MULTI COOK cycle, the damper is
returned to the open position and the oven will go to the
offcondition.Thecoolingfanwillremainonuntiltheoven
has cooled.
EASY DEFROST COOKING
TheEASYDEFROSTkeyisaspecialfunctionkeytodefrost
meats and poultry faster and better.
EASY DEFROST key has 4 defrost stages.
EASY DEFROST automatically defrosts roast beef, etc.
When EASY DEFROST is selected and the food weight is
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
theoven'soperationifthereisafireintheovencavityduring
microwave cooking.
This accomplished by the LSI repeatedly measures the
voltage across the temperature measurement circuit (ther-
mistor) during it's 32-seconds time base comparing the
obtainedvoltagemeasurements.Ifthemostrecent voltage
measuredis300mVgraterthanthepreviousvoltagemeas-
ured, the LSI judges it as a fire in the oven cavity and
switches off the relays to the power transformer, fan motor
and convection motor. The LSI also stops counting down
andclosesthedamperdoorsothatnofreshairwillenterthe
oven cavity. Please refer to the following section for a more
detailed description.
Operation
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 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
voltagemeasuredwhentheprocedureisrepeated(step
2) is greater than 300mV the LSI makes the judgment
thatthereisafireintheovencavityandwillswitchoffthe
relaystothepowertransformer,fanmotorandconvection
motor.TheLSIalsostops counting downandclosesthe
damper door so that no fresh air will enter the oven
cavity.
ment with each food category and inputted into the LSI.
An example of how sensor works:
1. Potatoesatroomtemperature.
Vapour is emitted very slowly.
2. Heat potatoes. Moisture and
humidityisemittedrapidly.You
cansmellthearomaasitcooks.
;
3. Sensor detects moisture and
humidity and calculates
cooking time and variable
power.
MICROWAVE
MICROWAVE
AH SENSOR

R-9H56
7
3. Once the fire sensor feature has shut the unit down, the
programmedcookingcyclemayberesumedby pressing
the"START"padortheunitmayberesetbypressingthe
"CLEAR" pad.
IMPORTANT:
During sensor cooking operation, the fire sensing op-
erationsequencewillnot begin until the AH sensor has
detected vapours and initiated a sensor cooking cycle.
This is because the operation of the convection fan
would interfere with the AH sensor's vapour detection.
CONVECTION
MOTOR
THERMISTOR
Sensing 
Voltage
ON
OFF
ON
OFF
ON
OFF
0 2 24 30 64 (sec.)
3 sec.
Sensing the voltage across the temperature measurement circuit.
6 sec.
332 (sec.)
UPPER AND LOWER LATCH SWITCHES
Those latch switches are mounted in the latch hooks as
showninfigure.Theyareactivatedbythelatchheadsonthe
door.
When the door is opened, the switches interrupt the circuit
to all components except CPU unit and relay unit and oven
lamp. A cook cycle cannot take place until the door is firmly
closed thereby activating both interlock switches.
LATCH HOOK
STOP SWITCH
MONITOR SWITCH
SWITCH LEVER
OPEN LEVER
LATCH
HEADS
DOOR OPEN 
BUTTON
UPPER LATCH SWITCH
LOWER LATCH SWITCH
Figure D-1. Switches
MONITOR SWITCH
The monitor switch is mounted on the latch hook. It is
activated (the contacts opened) by the lower latch head
whenthedoorisclosed.Theswitchisintendedtorenderthe
oven inoperative by means of blowning the fuse when the
contactsofthe commonandnormalopencontactsofupper
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
contactsofupperlatchswitchandlowerlatchswitchare
in the OFF condition (contacts open) due to their being
normally open contacts switch.
2. Asthedoorgoes to aclosedposition,themonitorswitch
contacts are first opened and then the common 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
simultaneouslywithclosingofthemonitorswitchcontacts.
CAUTION: BEFOREREPLACINGABLOWNFUSE TEST
THEUPPERLATCHSWITCH,LOWERLATCH
SWITCH AND MONITOR SWITCH FOR
PROPER OPERATION. (REFER TO CHAP-
TER “TEST PROCEDURE”).
STOP SWITCH
The stop switch is activated by the latch head.
Whenthedoorisopenedwhiletheovenisincookcycle,the
stop switch contacts open to de-energize the relay (RY-
1,RY-2,RY-3,RY-5,RY-6). Then the cook cycle is stopped.
THERMAL CUT-OUT 150˚C (OVEN)
The oven thermal cut-out located on the left side of the
thermal protection plate is designed to prevent damage to
theconvectionheaterunit if anoverheatedcondition devel-
ops in the tube due to cooling fan failure, obstructed air
ducts, dirty or blocked air intake, etc. Under normal opera-
tion, the oven thermal cut-out remains closed. However,
whenabnormally high temperaturesare reached withinthe
heater unit, the oven thermal cut-out will open, causing the
oventoshutdown.Whentheovenhascooledtemperature,
the oven thermal cut-out closes.
THERMAL CUT-OUT 95˚C (FAN MOTOR)
Thethermalcut-outprotect the fanmotoragainst overheat-
ing.Ifitstemperaturegoesuphigherthan95˚Cbecausethe
fanmotor islocked or the ventilation operating 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)
Thisfuseprotectsthemagnetronagainstoverheating.Ifthe
temperature goes up higher than 150˚C because the fan
motor is interrupted, the air inlet duct is blocked or the
ventilationopeningsareobstructed,thefuseblowsandcuts
off the power supplying to the power transformer. The
defective fuse must be replaced with new rated one.
FUNCTION OF IMPORTANT COMPONENTS

R-9H56
8
FUSE M8A 250V
1. If the wire harness or electrical components are short-
circuited, this fuse blows to prevent an electric shock or
fire hazard.
2. The fuse also blows when upper latch switch and lower
latch switch remain closed with the oven door open and
when the monitor switch closes.
3. The fuse M8A also blows when asymmetric rectifier,
H.V. rectifier, H.V. wire harness, H.V. capacitor,
magnetronorsecondarywindingofpowertransformeris
shorted.
ASYMMETRIC RECTIFIER
Theasymmetricrectifierisasolidstatedevicethatprevents
currentflowinsbothdirections.Anditpreventsthetempera-
ture rise of the power transformer by blowing the fuse M8A
when the high voltage rectifier is shorted.
FAN MOTOR
The 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 chan-
nelled through the oven cavity to remove steam and va-
pours given off from the heating foods. It is then exhausted
through the exhausting air vents at the oven cavity.
CONVECTION HEATER
The convection heater is located at the rear of the oven
cavity.Itisintended to heatairdrivenbytheconvectionfan.
The heated air is kept in the oven and force-circulated and
reheated by the convection heater.
CONVECTION COOKING SYSTEM
This oven is designed with a hot air heating system where
food is not directly heated by the convection heater, but is
heated by forced circulation of the hot air produced by the
convectionheater. The air heated by the convection heater
is circulated through the convection passage provided on
theouter casing of the oven cavity by means of the convec-
tion fan which is driven by the convection motor. It then
enterstheinsideoftheoventhroughtheventholesprovided
on the left side of the oven. Next, the hot air heats the food
ontheturntableandleavestheovencavitythroughthevent
in the oven cavity left side wall. Without leaving the oven,
this hot air is reheated by the convection heater, passes
throughtheconvectionpassageandenterstheinsideofthe
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
beingcooked.Whenthetemperatureinsidetheovencavity
reachesthe selected temperature,the convection heateris
de-energized.Whenthetemperatureinsidetheovencavity
dropsbelowtheselectedtemperature,theconvectionheater
isenergized again. In this way, the inside of the ovencavity
is maintained at approximately the selected temperature.
Whentheconvectiontimereaches0,theconvectionheater
isde-energizedandtheconvectionfanstops operating and
theovenshutsoff.Uponcompletionofthecookingtime,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 tempera-
tureisabove116˚C,thecircuittoRY6willbemaintained(by
the thermistor circuit) to continue operation of the cooling
fanmotoruntilthetemperaturedropsbelow116˚C,atwhich
timetherelaywillbede-energized,turningoffthefanmotor.
Relay RY5 will however, open as soon as the convection
cycle has ended, turning off the convection fan motor. This
will now cool and 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.
These components are operated by a signal that judges if
microwave cooking or convection cooking operation is
selected by the CPU unit.
The rated peak reverse voltage of D1 of the asymmetric
rectifier is 6 KV The rated peak reverse voltage of D2 of the
asymmetricrectifieris1.7KV.D1andD2oftheasymmetric
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. Thehighvoltagerectifierisshortedbyanycauseswhen
microwave cooking.
2. The peak reverse voltage of D2 of the rectifier goes
beyond the rated peak reverse voltage 1.7 KV in the
voltagedoubler circuit.
3. D2 of the rectifier is shorted.
4. The large electric currents flow through the high voltage
winding of the power transformer.
5. The large electric currents beyond 8A flow through the
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.
The temperature in the oven cavity is detected through the
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
The monitor resistor prevents the fuse M8A 250V bursting
when the fuse M8A 250V blows due to the operation of the
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 pro-
vides the heated air.
D2 D1
ASYMMETRIC
RECTIFIER
HIGH VOLTAGE RECTIFIER
AB
C

R-9H56
9
Microwave Cooking:
Damperisintheopenposition,becauseaportionofcooling
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
sensed in the control unit, and operates shut-off relay
(RY4).
1-2. Contacts of shut-off relay (RY4) close, the damper
motor is energized, opening the damper door.
1-3. Whenthe damper is moved to the open positionbythe
damper cam, damper switch is closed (ON position).
1-4. Thesignal of damper switch is re-sensed in thecontrol
unit and shut-off relay (RY4) is turned off.
1-5. The240 volts A.C. to the damper motor is stopped 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 Dampermotorisenergizedbytouchingtheconvection,
temperature 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 (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
(RY4) is energized, and the damper is returned to the
open position.
NOTE: If the damper door is not in the proper position,
closedduringconvectionoropenduringmicrowave,
the control unit will stop oven operation after 1
minute.
Cooking Mode Operation of Damper
Microwave cooking OPEN
Convection cooking CLOSE
Sensor cooking OPEN
Automatic mix cooking CLOSE
Grill cooking CLOSE
Slow cooking CLOSE
DAMPER DUCT
DAMPER
DAMPER CAM
DAMPER MOTOR
DAMPER SWITCH
DAMPER SHAFT
Figure D-2. Damper Mechanism

R-9H56
10
WARNING TO SERVICE PERSONNEL
Microwave ovens contain circuitry capable of producing very high voltage and current, contact with any part of the
high voltage circuit will result in electrocution. High voltage capacitor, Power transformer, Magnetron, High voltage
rectifier assembly, High voltage harness.
REMEMBER TO CHECK 3D
1) Disconnect the supply.
2) Door opened, and wedged open.
3) Discharge high voltage capacitor.
WARNING: AGAINST THE CHARGE OF THE
HIGH-VOLTAGE CAPACITOR
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 con-
nection of the high-voltage capacitor (that is, of the
connectingleadofthe high-voltage rectifier)against
thechassiswiththe use ofaninsulated screwdriver.
Sharp recommend that wherever possible fault-finding
is carried out with the supply disconnected. It may in,
some cases, be necessary to connect the supply after
theoutercasehasbeenremoved,inthiseventcarryout
3D checks and then disconnect the leads to the primary
of the power transformer. Ensure that these leads re-
main isolated from other components and the oven
chassis. (Use insulation tape if necessary.) When the
testing is completed carry out 3D checks and reconnect
the leads to the primary of the power transformer.
REMEMBER TO CHECK 4R
1) Reconnectallleadsremovedfromcomponentsduring
testing.
2) Replace the outer case (cabinet).
3) Reconnect the supply.
4) Run the oven. Check all functions.
Microwave ovens should not be run empty. To test for
thepresenceof microwaveenergywithin acavity,place
acup ofcold water on the oven turntable, closethe door
andset themicrowavetimerfortwo(2)minutes.Setthe
powerlevel to HIGHand pushthe START button.When
the two minutes has elapsed (timer at zero) carefully
checkthatthewaterisnowhot.Ifthewaterremainscold
carry out 3D checks and re-examine the connections to
the component being tested.
Whenallserviceworkiscompleted,and the oven is fully assembled,themicrowavepoweroutputshouldbechecked
and microwave leakage test carried out
SERVICING
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.
TROUBLESHOOTING GUIDE
IMPORTANT: Iftheovenbecomesinoperativebecauseof
a blown fuse M8A in the upper latch switch
- lower latch switch - monitor switch - moni-
tor resistor circuit, check the upper latch
switch, lower latch switch, monitor switch
and monitor resistor before replacing the
fuse M8A.

R-9H56
11
MAGNETRON POWER TRANSFORMER H.V. RECTIFIER ASSEMBLY HIGH VOLTAGE CAPACITOR
LATCH AND STOP SWITCHES MONITOR SWITCH DAMPER SWITCH MAIN FUSE TEMPERATURE FUSE 150˚C THERMAL CUT-OUT
CONVECTION HEATER THERMISTOR FAN MOTOR TURNTABLE MOTOR CONVECTION MOTOR DAMPER MOTOR
MONITOR RESISTOR TOUCH CONTROL PANEL KEY UNIT RELAY (RY-1) RELAY (RY-2) RELAY (RY-3)
RELAY (RY-4) RELAY (RY-5) RELAY (RY-6) FOIL PATERN ON P.W.B. AH. SENSOR OVEN LAMP OR SOCKET OPENED OR SHORTED WIRE HARNESS
WALL OUTLET LOW POWER SUPPLY VOLTAGE SHORTED POWER CORD
Home fuse blows when power
supply cord is plugged into wall
outlet.
Fuse M8A blows when power
cord is plugged into wall outlet.
88:88 does not appear in display
when power cord is first plugged
into wall outlet.
Display does not operate prop-
erly when STOP/CLEAR pad is
touched.(The time ofday should
appear on the display with beep
sound during normal condition.)
Oven lamp does not light with
door opened.
Oven lamp does not light at all
Oven lamp light, but turntable
motor does not operate.
Coolingfanmotor doesnotoper-
ate.
The oven stops after1 minute
Oven does not go into a cook
cycle, when START pad is
touched.
Low or no power is produced
during microwave cooking (The
food is heated incompletely or
not heated at all)
Extremelyunevenheatingispro-
duced in oven load (food).
Functionofvariablecookingdoes
notoperateproperlyexceptHIGH
power.
CONV indicator lights, but heat-
ing element does not heat.
Temperatureintheovencavityis
lower or higher than preset.
Convection cycle runs 1 minute
then the oven shuts down.
Convection cycle runs 3 minutes
then the oven shuts down.
Ovenisin the sensor cooking con-
dition but AH sensor does not end
1st.stageordoesnotstopcooking
cycle or the oven stops soon.
CK = Check / RE = Replace
OFF
CONDITION
PROBLEM
TEST PROCEDURE
POSSIBLE CAUSE
AND
DEFECTIVE PARTS
ABC D EEEFGGHI JJJJKLMNNNNNNOPRE CKCK CK RE
CONDITION
COOKING
CONDITION
(MICROWAVE)
(CONVECTION)
(AH. SENSOR)

R-9H56
12
TEST PROCEDURES
PROCEDURE
LETTER
CARRY OUT 3D CHECK.
Isolate the magnetron from high voltage circuit by removing all leads connected to filament terminal.
To test for an open circuit filament use an ohmmeter to make a continuity test between the magnetron
filament terminals, the meter should show a reading of less than 1 ohm.
To test for short filament to anode condition, connect ohmmeter between one of the filament terminals
and the case of the magnetron (ground). This test should be indicated an infinite resistance. If a low or
zero resistance reading is obtained then the magnetron should be replaced.
MICROWAVE OUTPUT POWER (1 Litre water load)
The following test procedure should be carried out with the microwave oven in a fully assembled
condition (outer case fitted). Microwave output power from the magnetron can be measured by way of
IEC 705, i.e. it can be measured by using water load how much it can be absorbed by the water load.
Tomeasurethemicrowaveoutputpower in themicrowaveoven,therelation of calorie andwattisused.
When P(W) heating works for t(second), approximately P x t/4.187 calorie is generated. On the other
hand, if the temperature of the water with V(ml) rises ∆T (°C) during this microwave heating period, the
calorie of the water is V x ∆T.
NEVER TOUCH ANY PART IN THE CIRCUIT WITH YOUR HAND OR AN INSULATED TOOL
WHILE THE OVEN IS IN OPERATION.
AMAGNETRON TEST
The formula is as follows;
P x t / 4.187 = V x ∆T P (W) = 4.187 x V x ∆T / t
Our condition for water load is as follows:
Room temperature..............around 20°C PowersupplyVoltage.........Ratedvoltage
Water load.........1000 g Initial temperature...........10±2°C Heating time.........49 sec.
P = 85 x ∆T
COMPONENT TEST
Measuring condition:
1. Container
The water container must be a cylindrical borosilicate glass vessel having a maximum material
thickness of 3 mm and an outside diameter of approximately 190 mm.
2. Temperature of the oven and vessel
The oven and the empty vessel are at ambient temperature prior to the start the test.
3. Temperature of the water
The initial temperature of the water is (10±2)°C.
4. Selectthe initial and final water temperature so that the maximum difference between thefinal water
temperature and the ambient temperature is 5°C.
5. Select stirring devices and measuring instruments in order to minimize addition or removal of heat.
6. Thegraduationofthethermometermustbe scaled by 0.1°Catminimumandaccuratethermometer.
7. The water load must be (1000±5) g.
8. “t” is measured while the microwave generator is operating at full power. Magnetron filament heat-
up time is not included.
NOTE: The operation time of the microwave oven is “t + 2” sec. 2 sec. is magnetron filament heat-up time.
Measuring method:
1. Measure the initial temperature of the water before the water is added to the vessel.
(Example: The initial temperature T1 = 11°C)
2. Add the 1 litre water to the vessel.
3. Place the load on the centre of the shelf.
4. Operate the microwave oven at HIGH for the temperature of the water rises by a value ∆T of
(10 ±2)°C.
5. Stir the water to equalize temperature throughout the vessel.

R-9H56
13
TEST PROCEDURES
PROCEDURE
LETTER COMPONENT TEST
6. Measure the final water temperature. (Example: The final temperature T2 = 21°C)
7. Calculate the microwave power output P in watts from above formula.
Initial temperature.................................................................................................. T1 = 11°C
Temperature after (49 + 2) = 51 sec...................................................................... T2 = 21°C
Temperature difference Cold-Warm .................................................................... ∆T1 = 10°C
Measured output power
The equation is “P = 85 x ∆T”....................................................... P = 85 x 10°C = 850 Watts
JUDGMENT: The measured output power should be at least ±15 % of the rated output power.
CAUTION: 1°C CORRESPONDS TO 85 WATTS REPEAT MEASUREMENT IF THE POWER IS
INSUFFICIENT.
1000g
1000g
1000g
T1˚C T2˚C
Heat up for51 sec.
MICROWAVE OUTPUT POWER (2 Litre water load)
The following test procedure should be carried out with the microwave oven in a fully assembled
condition (with outer case fitted).
Microwave output power from the magnetron can be measured by way of substitution, i.e. it can be
measured by using a water load how much it can be absorbed by the water load. To measure the
microwave output power in the microwave oven, the relation of calorie and watt is used.
Ontheotherhand,ifthetemperature of the waterwithV(ml)rises∆T (˚C)duringthismicrowaveheating
period, the calorie of the water is V x ∆T.
The formula is as follows;
P = 8330 x ∆T / t
Our condition for water load is as follows:
Room temperature..............23±2˚C Power supply Voltage.........240 volts.
Water load.........2000 ml Initial temperature...........23±1˚C Heating time .1 min. 51sec.
P = 75 x ∆T
Measuring method:
A) The two water containers must be prepared.
Thewatercontainermustbeone(1)litrebeakermadeofPyrex glassanditsdiameterapproximately
12cm.
B) Putthe one (1) litre waterinto eachbeaker (Eachbeaker has one litre water).The initialtemperature
of the water should be 23±1˚C.
C) Mark T1 on the one beaker and mark T2 on the other one. And stir the water and measure the
temperature of water the thermometer and note them. The graduation of the thermometer must be
scaled by 0.1˚C at minimum and an accurate mercury thermometer is recommended.
D) Place the two (2) beakers as touching each other in the centre of the oven cavity.
E) Set the timer to 2 minutes and 20 seconds, start the oven at 100% power.
F) The time must be measured with stopwatch or wristwatch.
G) After 1 minutes and 51 seconds, stop the oven by opening the door.
H) Put the two (2) beakers out of the oven cavity and measure the temperature of the water by stirring
the water with thermometer and note them.

R-9H56
14
TEST PROCEDURES (CONT'D)
Example
Initial temperature .............................................................................T1 = 23˚C T2 = 24˚C
Temperature after 1 min. 51 sec. ..................................................... T1 = 33˚C T2 = 34˚C
Temperature difference Cold-Warm.............................................. ∆T1 = 10˚C ∆T2 = 10˚C
Mean temperature rise ∆T......................... ∆T = (∆T1 ±∆T2) / 2 = (10˚C+10˚C) / 2 = 10˚C
Measured output power
The equation is P= 75 x ∆T ........................................................ P= 75 x 10˚C = 750 Watts
NOTE: The measured output power should be at least ±15 % of the rated output power.
CAUTION: 1˚C CORRESPONDS TO 75 WATTS. REPEAT MEASUREMENT IF THE POWER IS
INSUFFICIENT.
COMPONENT TEST
PROCEDURE
LETTER
1 l 1 l
(T1 C) (T2 C)
1 l 1 l
(T1 C) (T2 C)
Heat up for 1min. 51 sec.
B POWER TRANSFORMER TEST
WARNING: High voltages and large currents are present at the secondary winding and filament
winding of the power transformer. It is very dangerous to work near this part when
the oven is on. NEVER make any voltage measurements of the high-voltage circuits,
including the magnetron filament.
CARRY OUT 3D CHECKS.
Disconnect the leads to the primary winding of the power transformer. Disconnect the filament and
secondarywindingconnectionsfromtherestoftheHVcircuitry.Usinganohmmeter,setonalowrange,
it is possible to check the continuity of all three windings. The following readings should be obtained:
a. Primary winding ................... approx. 1.3 Ω
b. Secondary winding............... approx. 72 Ω
c. Filament winding .................. less than 1Ω
Ifthereadingobtainedarenotstatedasabove,thenthepowertransformerisprobablyfaultyandshould
be replaced.
CARRY OUT 4R CHECKS.
C HIGH VOLTAGE RECTIFIER ASSEMBLY TEST
HIGH VOLTAGE RECTIFIER TEST
CARRY OUT 3D CHECKS.
Isolate the high voltage rectifier assembly from the HV circuit. The high voltage rectifier can be tested
using an ohmmeter set to its highest range. Connect the ohmmeter across the terminal B+C of the high
voltage rectifier and note the reading obtained. Reverse the meter leads and note this second reading.
The normal resistance is infinite in one direction and more
than 100 kΩin the other direction.
CARRY OUT 4R CHECKS.
AB
C
D2 D1
ASYMMETRIC
RECTIFIER
HIGH VOLTAGE RECTIFIER

R-9H56
15
TEST PROCEDURES (CONT'D)
PROCEDURE
LETTER COMPONENT TEST
ASYMMETRIC RECTIFIER TEST
CARRY OUT 3D CHECKS.
Isolate the high voltage rectifier assembly from the HV circuit. The asymmetric can be tested using an
ohmmeter set to its highest range across the terminals A+B of the asymmetric rectifier and note the
reading obtained. Reverse the meter leads and note this second reading. If an open circuit is indicated
in both direction then the asymmetric rectifier is good. If an asymmetric rectifier is shorted in either
direction,thentheasymmetricrectifierisprobablyfaultyandmustbereplacedwithhighvoltagerectifier.
Whentheasymmetricrectifierisdefective,checkwhethermagnetron,highvoltagerectifier,highvoltage
wire or filament winding of the power transformer is shorted.
CARRY OUT 4R CHECKS.
NOTE: FOR MEASUREMENT OF THE RESISTANCE OF THE RECTIFIER, THE BATTERIES OF THE
MEASURING INSTRUMENT MUST HAVE A VOLTAGE AT LEAST 6 VOLTS, BECAUSE
OTHERWISE AN INFINITE RESISTANCE MIGHT BE SHOWN IN BOTH DIRECTIONS.
D HIGH VOLTAGE CAPACITOR TEST
CARRY OUT 3D CHECKS.
A. Isolate the high voltage capacitor from the circuit.
B. Continuity check must be carried out with measuring instrument which is set to the highest resistance
range.
C. Anormalcapacitorshowscontinuityforashorttime(kick)andthenaresistanceofabout10MΩafterithas
been charged.
D. A short-circuited capacitor shows continuity all the time.
E. An open capacitor constantly shows a resistance about 10 MΩbecause of its internal 10MΩresistance.
F. When the internal wire is opened in the high voltage capacitor shows an infinite resistance.
G. The resistance across all the terminals and the chassis must be infinite when the capacitor is normal.
If incorrect reading are obtained, the high voltage capacitor must be replaced.
CARRY OUT 4R CHECKS.
ESWITCH TEST
CARRY OUT 3D CHECKS.
Isolate the switch to be tested and using an ohmmeter check between the terminals as described in the
following table. Table: Terminal Connection of Switch
Plunger Operation COM to NO COM to NC
Released O.C. S.C.
Depressed S.C. O.C.
COM; Common terminal
NO; Normally open terminal
NC; Normally close terminal
S.C.; Short circuit
O.C.; Open circuit
If incorrect readings are obtained, make the necessary switch adjustment or replace the switch.
CARRY OUT 4R CHECKS.
F BLOWN FUSE F M8A
CARRY OUT 3D CHECKS.
1. If the fuse M8A is blown, there could be shorts or grounds in electrical parts or wire harness. Check
them and replace the defective parts or repair the wire harness.
2. If the fuse M8A is blown when the door is opened, check the upper latch switch, lower latch switch,
monitor switch and monitor resistor.
IfthefuseM8Aisblownbyincorrectdoorswitching,replacethedefectiveswitch(s)andthefuseM8A.
3. If the fuse M8A is blown, there could be short in the asymmetric rectifier or there is a ground in wire
harness.Ashortintheasymmetricrectifier may have occured due toshortorgroundinH.V.rectifier,
magnetron,powertransformeror H.V. wire.Checkthemandreplacethedefectivepartsorrepairthe
wire harness.
CARRY OUT 4R CHECKS.
CAUTION: Only replace fuse with the correct value replacement.

R-9H56
16
PROCEDURE
LETTER COMPONENT TEST
TEST PROCEDURES (CONT'D)
GTEMPERATURE FUSE AND THERMAL CUT-OUT TEST
CARRY OUT 3D CHECKS.
Disconnect the leads from the terminals of the temp. fuse or thermal cut-out. Then using an ohmmeter,
make a continuity test across the two terminals as described in the table below.
CARRY OUT 4R CHECKS.
Table: Temperature Fuse and Thermal cut-out Test
Temperature of “ON” condition Temperature of “OFF” condition Indication ofohmmeter
Parts Name (closed circuit) (˚C) (open circuit) (˚C) (When room temperature
is approx. 20˚C)
Temp. fuse 150˚C This is not resetable type. Above 150 ˚C Closed circuit
Thermal cut-out 150˚C Below 130˚C Above 150˚C Closed circuit.
Thermal cut-out 95˚C Below 75˚C Above 95˚C Closed circuit.
If incorrect readings are obtained, replace the temp. fuse or thermal cut-out.;
Anopencircuittemperature fuse 150˚C(MG)indicates that themagnetronhasoverheated, this maybe
due to resistricted ventilation, cooling fan failure or a fault condition within the magnetron or HV circuit.
Anopencircuitthermalcut-out150˚C(OVEN)indicatesthattheconvectionmotorhasoverheated,this
may be due to convection motor locked.
Anopencircuitthermalcut-out95˚C(FM)indicatesthatthefanmotorwindinghasoverheated,thismay
be due to blocked ventilation or locked cooling fan.
CARRY OUT 3D CHECKS.
Before carring out the following tests make sure the heater is fully cool.
1. Resistance of heater
Disconnect the wire leads to the heater to be tested. Using ohmmeter with low resistance range.
Check the resistance across the terminals of the heater.
The resistance of heater is approximately 37.5 ohms.
2. Insulation resistance
Disconnect the wire leads to the heater to be tested. Check the insulation resistance between the
element and cavity using a 500V - 100Mohms insulation tester. The insulation resistance should be
more than 10Mohms in the cold start.
If the results of above test 1 and/or 2 are out of above specifications, the heater is probably faulty and
should be replaced.
CARRY OUT 4R CHECKS.
H CONVECTION HEATER TEST
CARRY OUT 3D CHECKS.
Disconnectconnector-EfromtheCPUunit.Measuretheresistanceofthethermistorwithanohmmeter.
Connect the ohmmeter leads to Pin No’s E-3 and E-4 of the thermistor harness.
Room Temp. .................. 20˚C - 30˚C
Resistance ..................... Approx. 350kΩ- 155kΩ
If the meter does not indicate above resistance, replace the thermistor.
CARRY OUT 4R CHECKS.
ITHERMISTOR TEST
JMOTOR WINDING TEST
CARRY OUT 3D CHECKS.

R-9H56
17
TEST PROCEDURES (CONT'D)
PROCEDURE
LETTER COMPONENT TEST
Disconnect the leads from the motor.
Using an ohmmeter, check the resistance between the two terminals as described in the table below.
Table: Resistance of Motor
Motors Resistance
Fan motor Approximately 295 Ω
Turntable motor Approximately 10.5 kΩ
Convection fan motor Approximately 210 Ω
Damper motor Approximately 11 kΩ
If incorrect readings are obtained, replace the motor.
CARRY OUT 4R CHECKS.
The touch control panel consists of circuits including semiconductors such as LSI, ICs, etc. Therefore,
unlike conventional microwave ovens, proper maintenance cannot be performed with only a voltmeter
andohmmeter.Inthisservicemanual,thetouchcontrolpanelassemblyisdivided intotwounits,Control
Unit and Key Unit and troubleshooting by unit replacement is described according to the symptoms
indicated.
1. Key Unit. Note: Check key unit ribbon connection before replacement.
The following symptoms indicate a defective key unit. Replace the key unit.
a) When touching the pads, a certain pad produces no signal at all.
b) When touching a number pad, two figures or more are displayed.
c) When touching the pads, sometimes a pad produces no signal.
2. Control Unit.
The following symptoms indicate a defective control unit. Replacethe control unit.
2-1 In connection with pads.
a) When touching the pads, a certain group of pads do not produce a signal.
b) When touching the pads, no pads produce a signal.
2-2 In connection with indicators.
a) At a certain digit, all or some segments do not light up.
b) At a certain digit, brightness is low.
c) Only one indicator does not light.
d) The corresponding segments of all digits do not light up; or they continue to light up.
e) Wrong figure appears.
f) A certain group of indicators do not light up.
g) The figure of all digits flicker.
2-3 Other possible troubles caused by defective control unit.
a) Buzzer does not sound or continues to sound.
b) Clock does not operate properly.
c) Cooking is not possible.
d) Proper temperature measurement is not obtained.
L TOUCH CONTROL PANEL ASSEMBLY TEST
KMONITOR RESISTOR TEST
CARRY OUT 3D CHECKS.
Disconnecttheleadsfromthemonitorresist.Usinganohmmeterandsetonalowrange.Checkbetween
the terminals of the monitor resistor.
The resistance of monitor resistor is approx. 0.8 ohms.
If incorrect readings are obtained, replace the monitor resistor.
CARRY OUT 4R CHECKS.

R-9H56
18
TEST PROCEDURES (CONT'D)
PROCEDURE
LETTER COMPONENT TEST
M KEY UNIT TEST
If the display fails to clear when the STOP/CLEAR pad is depressed, first verify the flat ribbon is making
goodcontact,verifythatthedoorsensingswitch(stopswitch)operates properly; that is thecontactsare
closed when the door is closed and open when the door is open.
If the door sensing switch (stop switch) is good, disconnect the flat ribbon that connects the key unit to
the control unit and make sure the door sensing switch is closed (either close the door or short the door
sensing switch connector). Use the key unit matrix indicated on the control panel schematic and place
a jumper wire between the pins that correspond to the STOP/CLEAR pad making momentary contact.
If the control unit responds by
clearing with a beep the key unit
is faulty and must be replaced. If
thecontrolunitdoesnotrespond,
it is faulty and must be replaced.
If a specific pad does not re-
spond, the above method may
be used (after clearing the con-
trol unit) to determine if the con-
trol unit or key pad is at fault.
G-11 G-12
G-3
G-4
G-5 G-6 G-7 G-8 G-9 G-10
G-2
G-1
KEY UNIT
12345
67890
STOP
CLEAR
AUTO START
Reheat
Pie
EASY
DEFROST
LESS
POWER
LEVEL
40˚C 70˚C 130˚C 150˚C 160˚C
180˚C 200˚C 220˚C 230˚C 250˚C
CLOCK
HIGH MIXLOW MIXCONVEC
GRILL
REHEAT
SENSOR
MULTI
COOK
Frozen
Vegetables
Desserts
Fresh
Vegetables
Jacket
Potato
INSTANT COOK
START
MORE
Casseroles
N RELAY TEST
emove the outer case and check voltage between Pin Nos. 7 and 9 of the 9-pin connector (A) on the
control unit with an A.C. voltmeter. The meter should indicate 240 volts, if not check oven circuit.
Shut-off, Cook and Heater Relay Test
These relays are operated by D.C. voltage.
Check voltage at the relay coil with a D.C. voltmeter during the microwave cooking operation or
convection cooking operation.
DC. voltage indicated ............... Defective relay.
DC. voltage not indicated ......... Check diode which is connected to the relay coil. If diode is good,
control unit is defective.
RELAY SYMBOL OPERATIONAL
VOLTAGE CONNECTED COMPONENTS
RY1 Approx. 19.0 V.D.C. Oven lamp/Turntable motor
RY2(COOK) Approx. 18.0 V.D.C. Power transformer
RY3(HEATER) Approx. 18.0 V.D.C. Heating element
RY4 Approx. 19.0 V.D.C. Damper motor
RY5 Approx. 19.0V.D.C. Convection motor
RY6 Approx. 19.0 V.D.C. Cooling fan motor
O PROCEDURES TO BE TAKEN WHEN THE FOIL PATTERN ON THE PRINTED WIRING BOARD
(PWB) IS OPEN.
To protect the electronic circuits, this model is provided with a fine foil pattern added to the primary on
thePWB, this foil pattern actsas afuse. Ifthe foil pattern is open,follow thetroubleshooting guidegiven
below for repair.
STEPS OCCURANCE CAUSE OR CORRECTION
1 The rated voltage is not applied to POWER
terminal of CPU connector (CN-A) Check supply voltage and oven power cord.
2 The rated voltage is applied to primary side of
power transformer. Power transformer or secondary circuit defective. Check and repair.
3 Only pattern at "a" is broken. *Insert jumper wire J1 and solder.
4 Pattern at "a" and "b" are broken. *Insert the coil RCILF2003YAZZ between "c" and "d".