Sharp R-90GCH User manual

51
R-90GCH
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.
HIGH SPEED CONVECTION
MICROWAVE OVEN
TABLE OF CONTENTS Page
CAUTION, MICROWAVE RADIATION........................................................................ INSIDE FRONT COVER
WARNING..........................................................................................................................................................1
SERVICING ...................................................................................................................................................... 2
PRODUCT SPECIFICATIONS ......................................................................................................................... 5
GENERAL INFORMATION................................................................................................................................5
APPEARANCE VIEW ....................................................................................................................................... 6
OPERATION SEQUENCE................................................................................................................................ 7
FUNCTION OF IMPORTANT COMPONENTS ...............................................................................................10
TROUBLESHOOTING GUIDE ....................................................................................................................... 12
TEST PROCEDURE....................................................................................................................................... 14
CONTROL UNIT ASSEMBLYL........................................................................................................................23
PRECAUTIONS FOR USING LEAD-FREE SOLDER .....................................................................................27
COMPONENT REPLACEMENT AND ADJUSTMENT PROCEDURE........................................................... 28
MICROWAVE MEASUREMENT .................................................................................................................... 35
TEST DATA AT A GLANCE ............................................................................................................................36
WIRING DIAGRAM......................................................................................................................................... 37
PICTORIAL DIAGRAM ................................................................................................................................... 40
POWER UNITL CIRCUIT ................................................................................................................................41
CPU UNITL CIRCUIT ......................................................................................................................................42
GRID ASSIGNMENT OF FLUORESENT DISPLAY TUBE .............................................................................43
PRINTED WIRING BOARD .............................................................................................................................44
PARTS LIST ................................................................................................................................................... 45
R-90GCH
SY210R90GCPH/
MODEL
SERVICE MANUAL
SHARP CORPORATION
COMBI

52
R-90GCH
CAUTION
MICROWAVE RADIATION
Personnel 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 antenna while the device is energized.
VARNING
MICKROVAGSSTRALING
Personal får inte utsättas för mikrovågsenergi som kan ustrala från magnetronen eller
andre mikrovågsalstrande anordningar om dessa är felanslutna eller används på fel sätt.
Alla in-och utgångsanslutningar för mikrovågor, vagledare, flänsar och packningar måste
vara fast anslutna.
Mikrovågsgeneratorn får inte arbeta utan att absorberande belastning är ansluten. Titta
aldrig in i ën öppen vågledare eller antenn när mikrovågsgeneratorn är påkopplad eller
laddad.
VAROITUS
MIKROAALTOSÄTELYÄ
Käyttäjä ei saa joutua alttiiksi mikroaaltoenergialle, jota voi säteillä magnetronista tai
muusta mikroaaltoja kehittävästä laitteesta, jos sitä käytetään tai jos se kytketään väärin.
Kaikkien mikroaaltoliitäntöjen sekä syöttö-että ulostulopuolella, aaltoputkien laippojen ja
tiivisteiden tulee olla varmistettuja.
Mikroaaltouunnia ei koskaan saa käyttää ilman kuormaa jossa mikroaaltoenergiaa kuluu.
Avoimeen aaltoputkeen tai antenniin ei koskaan saa katsoa virran ollessa kytkettynä.
ADVARSEL
MIKROBØLGESTRÅLING
Personell må ikke utsettes for mikrobølge-energi som kan utståles fra magnetronen eller
andre mikrobølge-generende deler dersom apparatet feilbetjenes eller blir feiltikoplet.
Alle inn-og ut-tilkoplinger i forbindelse med mikrobølge-strålingen, bølgeledere, flenser og
tetningsringer/pakninger må festes ordentlig.
Aldri bruk apparatet med mindre en mikrobålge-absorberende last er plassert i
ovnsrommet.
Aldri se direkte inn i en åpen bølgeleder eller antenne imens apparatet er strømførende.
ADVARSEL
MIKROBØLGEBESTRÄLING
Man bør ikke udsætte sig for mikrobølgebestråling fra magnetronen eller andre
mikrobølgefrembringende anordninger, hvilket kan ske hvis apparatet er forkert tilsluttet
eller bruges forkert. Alle mikrobølgeindgange og-udgange, bølgeledere, flanger og
tætningsstrimler må være forsvarligt udført.
Anvend aldrig ovnen uden en mikrobølgesabsorberende anordning. Se aldrig ind i en
åben bølgeleder eller antenne, mens ovnen er i brug.

1
R-90GCH
SERVICE MANUAL
SHARP CORPORATION
OSAKA, JAPAN
HIGH SPEED CONVECTION
MICROWAVE OVEN
R-90GCH
GENERAL IMPORTANT INFORMATION
This Manual has been prepared to provide Sharp Corp. 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.
WARNING
Note: The parts marked "*" are used at volt-
age more than 250V. (Parts List)
Anm: Delar märket med "*" har en spänning
överstigande 250V.
Huom: Huolto-ohjeeseen merkitty "tähdella"
osat joissa jännite on yli 250 V.
Bemerk: Deler som er merket "asterisk" er utsatt
for spenninger over 250V til jord.
Bemærk: "Dele mærket med stjerne benyttes
med højere spænding end 250 volt.
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.
Removal of the outer wrap gives access to potential above
250V.
All the parts marked "∆" on the parts list may cause
undue microwave exposure, by themselves, or when
they are damaged, loosened or removed.
SERVICING
PRODUCT SPECIFICATIONS
GENERAL INFORMATION
APPEARANCE VIEW
OPERATING SEQUENCE
FUNCTION OF IMPORTANT
COMPONENTS
TROUBLESHOOTING GUIDE
AND TEST PROCEDURE
TOUCH CONTROL PANEL
COMPONENT REPLACEMENT
AND ADJUSTMENT PROCEDURE
MICROWAVE MEASUREMENT
TEST DATA AT A GLANCE
WIRING DIAGRAM
PARTS LIST

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R-90GCH
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 sec-
onds after the oven has been switched off. Wait for 60
seconds and then short-circuit the connection of the high-
voltage capacitor (that is, of the connecting lead of the high-
voltage rectifier) against the chassis with the use of an
insulated 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 the outer
case has been removed, in this event carry out 3D checks and
then disconnect the leads to the primary of the power trans-
former. Ensure that these leads remain 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.
SERVICING
WARNING TO SERVICE PERSONNEL
GB Microwave ovens contain circuitry capable of producing very high voltage and current, contact with following parts will
result in electrocution.
High voltage capacitor, Power transformer, Magnetron, High voltage rectifier assembly, High voltage harness.
REMEMBER TO CHECK 4R
1) Reconnect all leads removed from components during
testing.
2) Replace the outer case (cabinet) and back plate.
3) Reconnect the supply.
4) Run the oven. 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 3D checks and re-examine the connections to the compo-
nent being tested.
When all service work is completed, and the oven is fully
assembled, the microwave power output should be checked and
a microwave leakage test should be carried out.
NL Magnetronovens bevatten circuits die een zeer hoge spanning en stroom kunnen voortbrengen. Contact met de volgende
onderdelen kan elektrocutie tot gevolg hebben.
Hoogspanningscondensator, hoogspanningstransformator, magnetron, hoogspanningsgelijkrichter, hoogspannings
kabelboom.
VERGEET DE VOLGENDE 3 STAPPEN NIET
1) Haal de stekker uit het stopcontact.
2) Open de deur en zorg ervoor dat hij niet dicht kan vallen.
3) Ontlaad de hoogspanningscondensator.
PAS OP VOOR DE ELECTRISCHE LADING VAN DE
HOOGSPANNINGSCONDENSATOR
De hoogspanningscondensator blijft nog ongeveer 60
seconden lang opgeladen, nadat de oven is uitgeschakeld.
Wacht 60 seconden voordat u de verbinding van de
hoogspannings-condensator (m.a.w. de verbindingsdraad
van de hoogspanningsgelijkrichter) met een geïsoleerde
schroevedraaier kortsluit tegen het chassis.
Sharp beveelt ten sterkste aan dat, voor zover mogelijk,
defecten worden opgespoord wanneer de stekker uit het
stopcontactisgehaald.Somsishetnodigomdestroomtoevoer
weer tot stand te brengen nadat de buitenmantel verwijderd
is. Herhaal dan de bovengenoemde 3 stappen en haal de
electrische draden uit de primaire zijde van de
vermogenstransformator. Zorg ervoor dat deze draden
geïsoleerd blijven van andere elementen en van het chassis
van de oven. (Gebruik zo nodig isolatieband.) Wanneer de
test is uitgevoerd, herhaalt u de bovenstaande 3 stappen en
verbindt u de electrische draden weer aan de primaire zijde
van de vermogenstransformator.
VERGEET DE VOLGENDE 4 STAPPEN NIET
1) Sluit de draden weer aan diezijn losgehaald voor de test.
2) Plaats de buitenmantel weer om het toestel heen (kabinet)
en achterplaat.
3) Stop de stekker weer in het stopcontact.
4) Zet de oven aan. Controleer alle functies.
Magnetronovens mogen niet leeg aangezet worden. Om te
controleren of er microgolf-energie binnen de oven wordt
geproduceerd, plaatst u een mok met koud water op de
draaitafel van de oven, sluit de deur, zet de oven op HIGH en
steltde klok vande magnetron inop twee (2)minuten. Wanneer
de twee minuten voorbij zijn (klok staat op nul), controleert u
voorzichtig of het water heet is. Indien het water nog steeds
koud is, herhaalt u de allereerste drie stappen en controleer
nogmaals de aansluitingen naar de geteste onderdelen.
Wanneer alle reparaties zijn uitgevoerd en de oven weer in
elkaar is gezet, moet de het magnetronvermogen worden
gecontroleerd en moet worden gecontroleerd of er geen
microgolflekkage is.

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ELos hornos de microondas contienen circuitos eléctricos capaces de producir voltajes de alta tensión y descargas
eléctricas. Para evitar el riesgo de electrocución, absténgase de tocar los siguientes componentes: condensador de alta
tensión, transformador de alta tensión, magnetrón, dispositivo del rectificador de alta tensión y arnés de alta tensión.
RECUERDE LA COMPROBACION 3D
1) Desconecte la alimentación.
2) Deje la puerta abierta y calzada.
3) Descargue el condensador de alto voltaje.
ADVERTENCIA SOBRE LA CARGA DEL
CONDENSADOR DE ALTOVOLTAJE
El condensador de alto voltaje permanece cargado unos
60 segundos después de haber apagado el horno.Espere
60 segundos y luego ponga en cortocircuito la conexión del
condensador de alto voltaje (esto es, del conductor de
conexión del rectificador de alto voltaje) al chasis con un
destornillador de mango aislado.
Se recomienda encarecidamente que siempre que sea
posible la localización de fallos se realice con la alimentación
desconectada. Puede ser que en algunos casos sea
necesario conectar la alimentación después de haber retirado
la carcasa exterior.En este caso, realice las comprobaciones
3D y luego desconecte los conductores del primario del
transformador de alimentación. Asegúrese de que estos
conductores permanezcan aislados de otros componentes y
del chasis del horno. (Use cinta aislante si es necesario).
Cuando termine la prueba efectúe las comprobaciones 3D y
reconecte los conductores al primario del transformador de
alimentación.
RECUERDE LA COMPROBACION 4C
1) Conecte todos los componentes desconectados de los
componentes durante la prueba.
2) Coloque la carcasa exterior (cabina) y la placa posterior
3) Conecte la alimentación.
4) Compruebe todas sus funciones despues de poner en
marcha el horno.
Los hornos de microondas no deben funcionar vacíos. Para
comprobar la presencia de energía de microondas dentro de
una cavidad, coloque una taza de agua fría en el plato giratorio
del horno, cierre la puerta y ponga la potencia en HIGH (alta)
y coloque el temporizador en dos (2) minutos. Cuando
transcurran los dos minutos (temporizador a cero) compruebe
cuidadosamente que el agua se ha calentado. Si el agua
permaneciese fría, efectúe las comprobaciones 3D y vuelva a
examinar las conexiones de los componentes que han sido
probados.
Cuando haya terminado la intervención en el equipo y el horno
haya sido ensamblado de nuevo completamente, deberá
comprobar la potencia de salida de microondas y realizar una
prueba de fugas de microondas.
SV Mikrovågsugnar innehåller kretsar som producerar mycket höga spänningar och strömmar.
Kontakt med följande komponenter kan leda till dödsfall:
Högspänningskondensator, transformator, magnetron, högspännings likriktare, högspännings kablage.
KOM IHÅG ATT KONTROLLERA 3 STEG
1) Koppla från strömkällan.
2) Öppna dörren på glänt.
3) Ladda ur högspänningskondensatorn.
VARNING FÖR LADDNINGEN I
HÖGSPÄNNINGSKONDENSATORN
Högspänningskondensatorn är laddad i 60 sekunder efter
det att ugnen stängts av. Vänta 60 sekunder och korislut
sedan kondensatoms anslutning (dvs anslutningen till
högspänningslikriktaren)tillchassietmedhjälpavenisolerad
skruvmejsel.
Sharp rekommenderar att felsökning sker med strömmen
fränkopplad. Ibland kan det var nödvändigt att koppla på
strömmen efter det att höljet avlägsnats, utför da 3 Steg
kontrollen och koppla sedan från ledarna till transformatorns
primärsida. Se till att ledarna är isolerade från andra
komponenter och chassiet. (Använd isoleringsband om det
behövs). När Du testat färdigt utför Du 3 Steg kontrollen och
ansluter ledningarna till transformatorns primärsida igen.
KOM IHÅG ATT KONTROLLERA 4 STEG
1) Anslut alla ledningar som använts vid testning
2) Sätt tillbaka ytterhöljet och bakre plåten.
3) Anslut strömkällan på nytt.
4) Sätt på ugnen. Kontrollera alla funktioner.
Mikrovågsugnar får inte användas tomma. Kontrollera
mikrovågsstrålningen i olika delar av ugnen genom att placera
en kopp med kallt vatten på ugnens tallrik, stäng dörren, ställ
in HIGH och ställ in 2 minuter på timern. När två minuter har gått
(timem visar 0) kontrollerar du om vattnet är varmt. Om vattnet
fortfarande är kallt utför Du 3 steg kontroller och kontrollerar
anslutningarna till varje enskild komponent på nytt.
När all service är klar och ugnen ihopskruvad skall ugnens
uteffekt och eventuellt mikrovågsläckage kontrolleras.

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R-90GCH
IIforni a microonde contengono un circuito elettrico in grado di generare tensioni e correnti estremamente elevate.
L’eventuale contatto con i seguenti componenti può causare la folgorazione:
condensatore ad alta tensione; trasformatore ad alta tensione; magnetron; rettificatore alta tensione; cablaggio ad alta
tensione.
TRE OPERAZIONI IMPORTANTI PER
INCOMINCIARE
1) Scollegare l'alimentazione elettrica.
2) Verificare che la porta sia bloccata in posizione
aperta.
3) Scaricare il condensatore ad alta tensione.
ATTENZIONE AL CONDENSATORE AD ALTA
TENSIONE: PUO ESSERE CARICO
Il condensatore ad alta tensione rimane carico per circa
60 secondi dopo lo spegnimento del forno.Occorre quindi
spettare 60 secondi prima di cortocircuitare, utilizzando
un cacciavite con impugnatura isolata, il collegamento
del condensatore ad alta tensione (cioè del conduttore
di collegamento del raddrizzatore ad alta tensione) sul
telaio del forno.
Sharp raccomanda, nei limiti del possibile, che la ricerca
dei guasti avvenga in assenza di alimentazione elettrica.
In alcuni casi tuttavia, può essere necessario alimentare
l'apparecchio dopo aver rimosso la scatola esterna. In
questo caso eseguire i tre controlli sopra citati e quindi
scollegare i connettori dal primario del trasformatore.
Assicurarsi che tali connettori non vengano a contatto con
altri componenti, ne con il telaio del forno (fare uso, se
necessario, di nastro isolante). Al termine dell'intervento,
eseguire nuovamente i tre controlli e ricollegare i conduttori
al primario del trasformatore.
QUATTRO VERIFICHE IMPORTANTI DA NON
DIMENTICARE
1) Ricollegare tutti i conduttori staccati dai vari componenti
durante l'intervento.
2) Rimontarelascatola esterna(cabinet)e lapiastraposteriore
3) Ripristinare l'alimentazione elettrica.
4) Rimettere in funzione il forno.Controllare tutte le funzioni.
I forni a microonde non devono mai funzionare a vuoto.Per
verificare la presenza di energia da microonde all'interno
di una cavitá, mettere una tazza di acqua fredda sul piatto
rotante del forno, chiudere la porta, regolare la potenza su
HIGH ed impostate il temporizzatore su due (2) minuti.
Trascorsi i due minuti (temporizzatore a zero), controllare
accuratamente che ora l'acqua sia calda. Se l'acqua è
rimasta fredda, eseguire i tre controlli iniziali e verificare
nuovamente i collegamenti del componente in questione.
Dopo aver portato a termine le operazioni di manutenzione
e rimontato il forno, è necessario controllare la potenza delle
microonde emesse ed eseguire un test per verificare che
non vi sia alcuna dispersione.

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R-90GCH
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
PRODUCT DESCRIPTION
SPECIFICATION
ITEM DESCRIPTION
Power Requirements 230 Volts / 50 Hertz / Single phase, 3 wire earthed
Power Consumption Microwave cooking 1.8 kW Approx. 8.2 A
Grill cooking 2.9 kW Approx. 12.6 A
Convection cooking 2.9 kW Approx. 12.6 A
DUAL 1 cooking 3.2 kW Approx. 14.0 A
DUAL 2 cooking 3.2 kW Approx. 14.0 A
Power Output 1000 W nominal of RF microwave energy (measured by method of IEC 60705)
Operating fequency 2450 MHz
Top heating element Power Output 1500 W
Side heating element Power Output 1200 W
Case Dimensions Width 550 mm Height 405 mm (including foot) Depth 625 mm
Cooking Cavity Dimensions Width 408 mm Height 230 mm Depth 345 mm
Turntable diameter 330 mm
Control Complement Touch Control System
Clock (1:00 - 12:59 or 0:00 - 23:59) / Timer (0 - 99 minutes 90 sec.)
Microwave Power for Variable Cooking
Repetition Rate;
100 % (HIGH) .......................... Full power throughout the cooking time
70 % (MEDIUM HIGH) ........................... approx. 70% of FULL Power
50 % (MEDIUM) ..................................... approx. 50% of FULL Power
30 % (MEDIUM LOW) ............................ approx. 30% of FULL Power
10 % (LOW)............................................ approx. 10% of FULL Power
Convection temperature control range:
250˚C, 230˚C, 220˚C, 200˚C, 180˚C, 160˚C, 130˚C, 100˚C, 70˚C and 40˚C
MICRO COOK key, LESS/MORE keys, WEIGHT keys
MICRO DEFROST key, BASIC COOK key, RECIPES key
COMBI MENU keys, TIME keys, LANGUAGE key, STOP key
DUAL MODE keys, GRILL key, CONVECTION key
MICROWAVE POWER LEVEL key, INFO key
TIMER/CLOCK SETTING key, (START)+1min key
Set Weight Approx. 39 kg

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APPEARANCE VIEW
OVEN
Operatiing keys:
1MICRO COOK key
By pressing this key you can select the
MICRO COOK menu.
2LESS/MORE keys
3WEIGHT keys
4MICRO DEFROST key
By pressing this key you can select
theMICRO DEFROST menu.
5BASIC COOK key
6RECIPES key
7COMBI MENU keys
For selecting the menu of BASIC
COOK andRECIPES.
1. Control panel
2. Waveguide cover (DO NOT REMOVE)
3. Oven lamp
4. Oven cavity
5. Coupling
6. Door latches
7. Door opening handle
(To open the door, pull the handle down and forward.
Never hold the door handle when moving the oven.)
8. Door seals and sealing surfaces
9. Ventilation cover (DO NOT REMOVE)
10.Outer cabinet
8 TIME keys
9 LANGUAGE key
10 STOP key
11 DUAL MODE keys
There are two Dual modes:
Dual 1: Microwave and Grill with high
speed air circulation.
Dual 2: Microwave and Convection with
high speed air circulation.
12 GRILL key
13 CONVECTION key
By pressing this key you can adjust
the convection temperature.
14 MICROWAVE POWER LEVEL key
By pressing this key you can adjust
the Microwave power level.
15 INFO key
16 TIMER/CLOCK SETTING key
17 (START)+1min key
Digital display and indicators:
18 HIGH SPEED indicator
19 GRILL indicator
20 CONVECTION indicator
21 MICROWAVE indicator
22 COOKINGINPROGRESSindicator
23 MORE/LESS indicator
CONTROL PANEL
11.Power cord
12.Air-vent openings
13.Turntable
14. Turntable support
15.Low rack
16.High rack
17.Splash guard
NOTE:
Some one-touch cooking features such as " (START)+1min" are disabled after three minutes when the
oven is not in use. These features are automatically enabled when the door is opened and closed or the
STOP key is pressed.
COMBI
23
22
2120
1918
2 31
6 75
4
1098
16 1712 13 14 15
11
16
15 17
1
2
3
4
57
8
6
13
5
14
12
9
10
11

7
R-90GCH
OPERATION
DESCRIPTION OF OPERATING SEQUENCE
The following is a description of component functions
during oven operation.
OFF CONDITION
Closing the door activates the door sensing switch SW4
and secondary interlock switch SW1 and 3rd. latch switch
SW3. (In this condition, the monitor switch SW2 contacts
are opened.)
IMPORTANT:
When the oven door is closed, the contacts COM-NC
of the monitor switch SW2 must be open. When the
microwave oven is plugged in a wall outlet (230V /
50Hz), the line voltage is supplied to the noise filter.
Figure O-1 on page 37
1. The display will show "SELECT LANGUAGE" in 3
languages.
Toset any program orset the clock,you mustfirst touch
the STOP key. The display will clear, and
" . 0 " will appear.
NOTE: When the door is opened, the oven lamp comes on.
OnceyouselectthelanguageusingtheLANGUAGE
key, the display will show "PRESS STOP" when
you plug the oven in.
2. A signal is input to the control unit, energizing the coil
ofshut-offrelay(RY-4).RY4contactsclose,completing
a circuit to the damper motor. The damper motor now
operates moving the damper to the open position,
therebyclosing the contactsofthe damper switch SW5
inputs a signal to the control unit. The coil of relay RY-
4 is de-energized, opening its contacts, thereby turning
off the damper motor.
MICROWAVE COOKING CONDITION
HIGH COOKING
Program desired cooking time by touching the TIME keys.
When the (START)+1min key is touched, the following
operations occur:
1. The contacts of relays are closed and components
connected to the relays are turned on as follows.
(For details, refer to Figure O-2)
RELAY CONNECTED COMPONENTS
RY-1 Oven lamp/Turntable motor
RY-2 High voltage transformer
RY-3 Convection motor
RY-4 Damper motor
RY-5 Fan motor
RY-6 Convection motor
SSR1 Top heating element
SSR2 Side heating element
2. The line voltage is supplied to the primary winding of
the high voltage transformer. The voltage is converted
to about 3.3 volts A.C. output on the filament winding
and high voltage of approximately 2000 volts A.C. on
the secondary winding.
3. The filament winding voltage (3.3 volts) heats the
magnetron filament and the high voltage (2000 volts) is
sent to the voltage doubling circuit, where it is doubled
to negative voltage of approximately 4000 volts D.C..
4. The 2450 MHz microwave energy produced in the
magnetron generates a wavelength of 12.24 cm. This
energy is channelled through the waveguide (transport
channel) into the oven cavity, where the food is placed
to be cooked.
5. When the cooking time is up, a signal tone is heard and
the relays RY1 + RY2 + RY5 go back to their home
position. The circuits to the oven lamp, high voltage
transformer, fan motor and turntable motor are cut off.
6. When the oven door is opened during a cooking cycle,
the switches come to the following condition.
Switch Contact Condition
During Oven Door
Cooking Open(No cooking)
Secondary interlock
switch COM-NO Closed Opened
Door sensing switch SW4 COM-NO Closed Opened
3rd. latch switch SW3 COM-NO Closed Opened
Monitor switch SW2 COM-NC Opened Closed
The circuit to the high voltage transformer is cut off
when the contacts of relay RY2, and the contacts
(COM-NO) of the secondary interlock switch SW1 are
made open. The circuit to the fan motor is cut off when
the relay RY5 is made open. The circuit to the turntable
motor is cut off when the contacts (COM-NO) of the
secondary interlock switch SW1 are made open. The
oven lamp remains on even if the oven door is opened
after the cooking cycle has been interrupted, because
the relay RY1 stays closed. Shown in the display is
remaining time.
7. MONITOR SWITCH CIRCUIT
The monitor switch SW2 is mechanically controlled by
the oven door, and monitors the operation of the
secondary interlock switch SW1 and the relay RY2.
7-1.When the oven door is opened during or after the
cycle of a cooking program, the secondary interlock
switch SW1 and the door sensing switch SW4 must
open their contacts (COM-NO) first. After that the
contacts (COM-NC) of the monitor switch SW2 can
be closed and the contacts (COM-NO) of 3rd. latch
switch SW3 are made open.
7-2.When the oven door is closed, the contacts (COM-
NC) of the monitor switch SW2 must be opened and
the contacts (COM-NO) of 3rd. latch switch SW3
must be closed. After that the contacts (COM-NO) of
the secondary interlock switch SW1 and the door
sensing switch SW4 are made closed.
7-3.When the oven door is opened and the contacts
(COM-NO) of the secondary interlock switch SW1
remain closed, the fuse F2 F10A will blow. Because
the relay RY2 and monitor switch SW2 are closed
and a short circuit is caused.
MEDIUM HIGH, MEDIUM, MEDIUM LOW, LOW
COOKING
When the microwave oven is preset for variable cooking
power, the line voltage is supplied to the high voltage
transformer intermittently within a 32-second time base
through the relay contact which is coupled with the cur-

8
R-90GCH
rent-limiting relay RY2. The following levels of microwave
power are given.
NOTE: The ON/OFF time ratio does not correspond
with the percentage of microwave power,
because approx. 3 seconds are needed for
heating of the magnetron filament.
CONVECTION COOKING CONDITION
PREHEATING CONDITION
Program desired convection temperature by touching the
CONVECTION key. When the (START)+1min key is
touched, the following operations occur: (Figure O-3)
1. The coil of shut-off relays (RY1, RY3 and RY5) are
energized, the oven lamp, cooling fan motor, turntable
motorandconvectionmotorareturnedon.Thecontacts
(COM-NO) of relay RY6 are opened.
2. The coil of relay (RY4) is energized by the control unit.
The damper is moved to the closed position, closing
the damper switch SW5 contacts. The closing of the
damper switch SW5 contacts sends a signal to the LSI
on the control unit de-energizing the relay (RY4) and
opening the circuit to the damper motor.
3. The solid-state relays (SSR1+SSR2) are energized
by the control unit and the main supply voltage is
applied to the top and side heating elements.
4. When the oven temperature reaches the selected
preheat temperature, the following operations occur:
4-1. The solid-state relays (SSR1+SSR2) are de-
energized by the control unit temperature circuit
and thermistor, opening the circuit to the heating
elements.
4-2. The oven will continue to function for 30 minutes,
turningthe heating elements onand off,as needed
to maintain the selected preheat temperature. The
oven will shutdown completely after 30 minutes
CONVECTION COOKING CONDITION
Enter the cooking time by touching TIME keys and select
the temperature by touching CONVECTION key. When
the (START)+1min key is touched, the following opera-
tions occur: Figure O-3 on page 38
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. The contacts (COM-
NO) of relay RY6 are opened.
3. The damper is moved to the closed position.
4. The solid-state relays (SSR1+SSR2) are energized (if
the cavity temperature is lower than the selected
temperature) and the main supply voltage is applied to
the heating elements to return to the selected cooking
temperature.
5. 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 111˚C, the circuit to RY5 will be maintained (by
thethermistor circuit) tocontinue operation ofthe cooling
fan motor until the temperature drops below 90˚C, at
which time the relay will be de-energized, turning off the
fan motor. Relay RY3 will however, open as soon as the
convection cycle has ended, turning off the convection
fan motor.
6. At the end of the convection cook cycle, if the cavity air
temperature is below 120˚C, shut-off relay (RY4) is
energized turning on the damper motor. The damper is
returned to the open position, closing the damper
switch SW5 contacts which send a signal to the control
unit, de-energizing shut-off relay (RY4).
GRILL COOKING
Enter cooking tim nd then touch the GRILL key. When the
(START)+1min key is touched, following operations
occur; Figure O-4 on page 38
1. The contacts of the relays RY1, RY3 and RY5 are
closed, and the oven lamp, turntable motor, convection
motor and fan motors are energized. The contacts
(COM-NO) of relay RY6 are closed.
NOTE :The rotate direction of the convection motor is
reverse to one of the convection cooking by
the relay RY6.
2. The damper is moved to the closed position.
3. The solid-state relays (SSR1+SSR2) are energized
and the main supply voltage is applied to the top and
side heating elements.
NOTE :After cooking, the operation of the fan motors,
damper motor is the same as one of the
convection cooking.
DUAL1 COOKING
Enter cooking time and then touch DUAL1 key. When the
(START)+1min key is touched, following operations
occur; Figure O-5 on page 39
1. The contacts of the relays RY1, RY3 and RY5 are
closed,and the ovenlamp, turntable motor,convection
motor and fan motors are energized. The contacts
(COM-NO) of relay RY6 are closed.
NOTE :The rotate direction of the convection motor is
revers to one of the convection cooking.
2. The damper is moved to the closed position.
3. The solid-state relays (SSR1+SSR2) are energized
and the main supply voltage is applied to the top and
side heating elements.
4. The relay RY2 is energized and the microwave energy
is generated by magnetron.
NOTE: After cooking, the operation of the fan motors,
damper motor is the same as one of the
convection cooking.
DUAL2 COOKING
Enter cooking time and then touch DUAL2 key. When the
(START)+1min key is touched, following operations
occur; Figure O-6 on page 39
1. The contacts of the relays RY1, RY3 and RY5 are
closed,andtheovenlamp, turntablemotor,convection
motor and fan motors are energized. The contacts
100% (HIGH) 32 sec. ON
70% (MEDIUM
HIGH) Approx. 70%
100%
24 sec. ON 8 sec. OFF
14 sec. OFF
20 sec. OFF
26 sec. OFF
50% (MEDIUM) Approx. 50%
18 sec. ON
30% (MEDIUM
LOW) Approx. 30%
12 sec. ON
10% (LOW) Approx. 10%
6 sec. ON

9
R-90GCH
(COM-NO) of relay RY6 are opened.
2. The damper is moved to the closed position.
3. The solid-state relays (SSR1+SSR2) and relay RY2
are energized, and the main supply voltage is applied
to the top and side heating elements and the high
voltage transformer alternately.
NOTE: Aftercooking, theoperation ofthe fanmotors,
damper motor is the same as one of the
convection cooking.
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 fire sensing feature will
operate when the microwave power level is set to 80% or
more. This is accomplished by the LSI repeatedly meas-
uring the voltage across the temperature measurement
circuit (thermistor) during it's 32-seconds time base com-
paring the obtained voltage measurements. If the most
recent voltage measured is 300 mV greater than the
previousvoltage measured, theLSI judgesitas a fire inthe
oven cavity and switches 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. Please refer to the
following section for a more detailed description.
AUTOMATIC COOKING
Automatic cooking will automatically compute the oven
temperature, microwave power and cooking time. And the
oven will cook according to the special cooking sequence.
POWER CONTROL FOR MANUAL COOKING
Following table shows the power control for manual cook-
ing.
Operation
Please refer to the timing diagrams below.
1. The fire sensing will start after 30 minutes when the
oven is started.
2. 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
five (25) seconds after the thermistor is cut off the LSI
turns on the convection fan for three (3) seconds.
3. 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 300 mV 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.
Micro ON
Side heaer
%
-
-
70
50
30
10
70
50
30
10
70
50
30
10
70
50
30
10
0
0
0
0
-
-
-
-
-
-
-
-
-
-
-
220
˚ C
220
˚ C
190˚C - 200˚C
220 - 250 ˚ C
180˚C
40 - 160
˚ C
190˚C - 200˚C
220 - 250˚C
180˚C
40 - 160˚C
Cool oven
(Oven Temperature
less than 59˚C)
After preheating
(Oven Temperature
more than 100˚C)
Warm oven
(Oven Temperature
60˚C - 99˚C)
Side heaer
%
-
100
30
50
70
90
30
50
70
90
0
50
70
90
0
50
70
90
20
20
20
20
100
60
60
70
40
50
60
30
40
50
Top heaer
%
-
100
30
50
70
90
30
50
70
70
0
0
70
70
0
0
70
70
20
20
20
20
100
50
50
60
40
40
50
30
30
40
70%
-
50%
50%
30%
10%
50%
50%
30%
10%
50%
50%
30%
10%
50%
50%
30%
10%
-
-
-
-
-
-
-
-
-
-
Micro
%
10, 30, 50
70, 100
-
70
50
30
10
70
50
30
10
70
50
30
10
70
50
30
10
70
50
30
10
-
-
-
-
-
-
-
-
-
-
Micro. OFF Oven
temperature Powr down time
Power after powr down time
Manual
MENU
MICROWAVE
GRILL
REHAET
CONV.
DUAL1
DUAL2
Air
Balancel
Jet
Jet
Conv.
Conv.
Conv.
Conv.
Conv.
Conv.
Conv.
Conv.or Jet
-
0%
-
-
-
50%
0%
0%
0%
--
40 - 250
˚ C
40 - 200
˚ C
220 - 230
˚ C
250
˚ C
40 - 200
˚ C
220 - 230
˚ C
250
˚ C
40 - 200
˚ C
220 - 230
˚ C
250
˚ C
40 min.
30 min.
All
20 min.
All
20 min.
35 min.
20 min.
45 min.
30 min.
No
20 min.
30 min.
30 min.
20 min.
30 min.
30 min.
No
30 min.
30 min.
-
-
-
-
-
-
-
-
-
-
50%
30%
30%
30%
-
-
20%
30%
30%
30%
30%
30%
-
30%
30%
-
0%
0%
20%
20%
20%
-
-
20%
30%
30%
30%
30%
30%
-
30%
30%
Top heaer Side heaer
Side heaer
Micro. Micro.ON Micro.OFF

10
R-90GCH
FUNCTION OF IMPORTANT COMPONENTS
DOOR OPEN MECHANISM
The door is opened by pulling the door handle down and
forward, referring to the figure D-1. When the door handle
is pulled down, the latch heads are moved upward. And
then when the door handle is pulled forward, the latch
heads are released from the latch hooks right and left.
Now, the door will open.
Figure D-1. Door Open Mechanism
DOOR SENSING SWITCH SW4, SECONDARY
INTERLOCK SWITCH SW1 AND 3RD. LATCH
SWITCH SW3
1. When the oven door is closed, the contacts (COM-NO)
must be closed.
2. When the oven door is opened, the contacts (COM-
NO) must be opened.
MONITOR SWITCH SW2
1. When the oven door is closed, the contacts (COM-NC)
must be opened.
2. When the oven door is opened, the contacts (COM-
NC) must be closed.
3. If the oven door is opened and the contacts (COM-NO)
of the secondary interlock switch SW1 and the relay
RY2 fail to open, the fuse F10A blows simultaneously
with closing the contacts (COM-NC) of the monitor
switch SW2.
CAUTION: BEFORE REPLACING A FUSE TEST THE
SECONDARY INTERLOCK SWITCH SW1,
RELAY RY2 AND MONITOR SWITCH SW2
FOR PROPER OPERATION. (REFER TO
CHAPTER "TEST PROCEDURE".)
FUSE F2 (F10A)
1. The fuse F2 (F10A) blows when the contacts (COM-
NO) of the secondary interlock switch SW1 and relay
RY2 remain closed with the oven door open and when
the monitor switch closes.
2. If the wire harness or electrical components are short-
circuited, the fuse F2 (F10A) blows to prevent an
electric shock of fire hazard.
HIGH VOLTAGE FUSE F3
The high voltage fuse F3 blows when the high voltage
rectifier or the magnetron is shorted.
NOISE FILTER
The noise filter prevents the radio frequency interference
that might flow back in the power circuit.
THERMISTOR
The thermistor is a negative temperature coefficient type.
The temperature in the oven cavity is detected through the
resistanceof the thermistor, andthen thecontrol unitcauses
the heater relay to operate, thus the current to the heating
elements is turned ON/OFF. If the convection cooking or
some cooking modes which use the top / side heating
elements is started and the oven temperature does not rise
above 37.8˚C, the control unit will stop the oven after 10
minutes. In this case, the thermistor may be opened.
The LSI also stops counting down and closes the
damper door so that no fresh air will enter the oven
cavity.
4. 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.
CONVECTION
MOTOR
THERMISTOR
Sensing
Voltage
ON
OFF
ON
OFF
ON
OFF
023283132 (sec.) 64 (sec.)
3 sec.
Sensing the voltage across temperature measurement circuit.
3 sec.
Monitor switch
Latch hook left
Latch
head
3rd. latch
switch
Latch hook right
Latch
head
Door handle
Secondary
interlock switch
(Monitored latch switch)
Door
sensing switch
(Primary interlock
relay control switch)
SW2:
SW1:
SW3:
SW4:

11
R-90GCH
MAGNETRON TEMPERATURE FUSE TF
The temperature fuse located on the waveguide flange is
designed to prevent damage to the magnetron if an over
heated condition develops in the magnetron due to cooling
fan failure, obstructed air guide, dirty or blocked air intake,
etc. Under normal operation, the temperature fuse remains
closed. However, when abnormally high temperatures are
reached within the magnetron, the temperature fuse will
open at 150˚C causing the oven to shut down.
TOP HEATER THERMAL CUT-OUT TC1
The thermal cut-out located on the thermal cover upper is
designed to prevent damage to the top heating element
unit if an over heated condition develops in the top heating
element unit due to convection fan failure, thermistor
failure, obstructed air ducts, dirty or blocked air intake, etc.
Under normal operation, the thermal cut-out remains
closed. However, when abnormally high temperature are
reached within the top heating element unit, the thermal
cut-out will open at 170˚C causing the oven to shut down.
When the thermal cut-out has cooled, the thermal cut-out
closes at 155˚C.
SIDE HEATER THERMAL CUT-OUT TC2
The thermal cut-out located on the thermal cover left is
designed to prevent damage to the side heating element
unit if an over heated condition develops in the top heating
element unit due to convection fan failure, thermistor
failure, obstructed air ducts, dirty or blocked air intake, etc.
Under normal operation, the thermal cut-out remains
closed. However, when abnormally high temperature are
reached within the side heating element unit, the thermal
cut-out will open at 150˚C causing the oven to shut down.
When the thermal cut-out has cooled, the thermal cut-out
closes at 130˚C.
TOP HEATING ELEMENT H1
The top heating element is located at the top 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 top heating element.
SIDE HEATING ELEMENT H2
The side heating element is located at the left side of the
oven cavity. It is intended to heat air driven by the convec-
tion fan. The heated air is kept in the oven and force-
circulated and reheated by the top heating element.
TURNTABLE MOTOR TTM
The turntable motor rotates the turntable located in the
bottom of the oven cavity, so that the food on the turntable
is cooked evenly during cooking. The turntable may turn in
either direction.
FAN MOTOR (MAGNETRON SIDE) FM
Thefan motordrives abladewhich drawsexternal coolair.
This cool air is directed through the air vents surrounding
the magnetron and cools the magnetron. This air is chan-
nelled through the oven cavity to remove steam and
vapors given off from the heating foods. It is then ex-
hausted through the exhausting air vents at the oven
cavity.
FAN MOTOR (HIGH VOLTAGE TRANSFORMER
SIDE) FM
Thefan motordrives ablade which drawsexternal coolair.
This cool air is directed through the air vents surrounding
the power transformer and cools the power transformer.
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.
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 elements. The air heated by the heating elements 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 CM. It then
entersthe inside of theoven throughthe ventholes provided
on the top and left sides 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 back side wall.
Without leaving the oven, this hot air is reheated by the
heating elements, passes through the convection passage
andenterstheinsideofthe oven cavity again, in a continuing
cycle.In this way,the hot aircirculates insidetheoven cavity
to raise its temperature and, at the same time, comes into
contact with the food being cooked. When the temperature
insidethe oven cavity reachesthe selectedtemperature, the
heating elements are de-energized. When the temperature
inside the oven cavity drops below the selected tempera-
ture, the heating elements are energized again. In this way,
the inside of the oven cavity is maintained at approximately
theselectedtemperature.Whentheconvectiontimereaches
0, the heating elements are de-energized and the convec-
tion fan stops operating and the oven shuts off.
Flow of hot air:
The rotation direction of the convection motor CM is
controlled by relay RY6. When the convection fan rotates
clockwise, the hot air from the oven cavity left side wall
blows stronger than one from the oven cavity top wall. (
This mode is called “Convection mode”.) When the con-
vection fan rotates counterclockwise, the hot air from the
oven cavity top wall blows stronger than one from the oven
cavity left side wall. (This mode is called “JET mode”.)
Figure D-2. Rotation direction of convection fan
Side heating
element unit
Top heating
element unit
Convection
fan Convection mode
JET
mode
FRONT VIEW

12
R-90GCH
Figure D-3. Flow of hot air
DAMPER OPEN-CLOSE MECHANISM
Usually, the damper is in the open position except during
convection cooking, preheat, grill, dual1, dual2 or all
cooking modes which use the top / side heating elements.
Damper position is set automatically by damper motor
DM, damper switch SW5, motor cam and damper shaft.
These components are operated by a signal that judges
if microwave cooking, convection cooking operation or
other cooking operation is selected by the control unit.
Microwave Cooking:
Damper is in the open position, because a portion of cooling
air is channelled 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 compart-
ment.
Convection, Preheat, Grill, Dual1, Dual2, or all cook-
ing modes which use the top / side heating elements:
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 DM is energized, opening the damper door.
1-3. Whenthe damper ismovedto the openpositionby
thedampercamthedamper switch SW5 isopened
(OFF position).
1-4. The signal from damper switch SW5 is re-sensed
inthe control unitandshut-off relay (RY4)isturned
off.
1-5. The rated voltage to the damper motor DM 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 and (START)+1min keys.
3-2. When damper is in the closed position (damper
switch SW5 is ON), 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, if the cavity
air temperature is below 121˚C, shut-off relay
(RY4) is energized, and the damper is returned to
the open position.
NOTE: Ifthe damper door is not in the proper position,
closed during convection or open during
microwave, the control unit will stop oven
operation after 1 minute.
TROUBLESHOOTING GUIDE
When troubleshooting the microwave oven, it is helpful to
followtheSequence ofOperationinperformingthechecks.
Many of the possible causes of trouble will require that a
specific test be performed. These tests are given a proce-
dure letter which will be found in the "Test Procedure
"section.
IMPORTANT: If the oven becomes inoperative because
of a blown fuse F2 (F10A) in the second-
ary interlock swith SW1 - monitor switch
SW2- primary interlock relay RY2 circuit,
checkthemonitorswitchSW2,relay(RY1),
primary interlock relay (RY2) and second-
ary interlock switch SW1 before replacing
the fuse F2 (F10A).
Hot air
Hot air
Hot air
Convection
fan
Hot air
Oven cavity left side
Oven cavity
top wall
Side heating
element unit
Side heating
element unit
Top heating element unit Top heating element unit
Turntable
Convection Mode JET Mode

13
R-90GCH
Home fuse blows when power cord is plugged into wall receptacle.
Fuse F1 20A blows when power cord is plugged into wall receptacle
"SELECT LANGUAGE" does not appear in display when power cord is
first plugged into wall receptacle.
Display does not operate properly when STOP key is touched. (The time
of day should appear on the display with beep sound.)
Oven lamp does not light with door opened.
Oven lamp does not light in cook cycle. (It light when door is opened).
Cooking cycle runs 1 minute then shuts down.
Oven lamp light, but turntable motor does not operate.
Turntable motor operates normally but cooling fan motor does not
operate.
Oven does not go into a cook cycle, when (START)+1min key is touched.
Low or no power is produced during microwave cooking (The food is
heated incompletely or not heated at all)
Extremely uneven heating is produced in oven load (food).
Function of variable cooking does not operate properly except HIGH
(100%) power.
Oven does not go into cook cycle when (START)+1min is touched.
Heating elements do not heat.
Temperature in the oven cavity is lower or higher than preset.
Convection cycle runs for 10 minutes then shuts down.
Convection motor does not operate of all or properly.
AMAGNETRON
BHIGH VOLTAGE TRANSFORMER
CH.V. RECTIFIER ASSEMBLY
DHIGH VOLTAGE CAPACITOR C1
E SECONDARY INTERLOCK SWITCH SW1
E3RD. LATCH SWITCH SW3
E DOOR SENSING SWITCH SW4
EMONITOR SWITCH SW2
FHIGH VOLTAGE FUSE F3
GNOISE FILTER
H FUSE F1 20A
JMAGNETRON TEMPERATURE FUSE
K THERMAL CUT-OUT (TOP) TC1
MTOP HEATING ELEMENT H1
OTHERMISTOR
P/U DAMPER MOTOR
QDAMPER SWITCH SW5
VTOUCH CONTROL PANEL
WTACT SWITCH
XRELAY RY-1
XRELAY RY-2
XRELAY RY-3
XRELAY RY-4
XRELAY RY-5
XRELAY RY-6
ZFUSE1 ON PWB.
YSOLID-STATE RELAY (TOP) SSR1
YSOLID-STATE RELAY (SIDE) SSR2
Replace OVEN LAMP
UFAN MOTOR (MAGNETRON)
UTURNTABLE MOTOR
SCONVECTION MOTOR
Check LOOSE WIRING
Check SHORTED IN POWER CORD
Check NO POWER AT OUTLET
Check LOW VOLTAGE
LTHERMAL CUT OUT (SIDE) TC2
NSIDE HEATING ELEMENT H2
U FAN MOTOR (HIGH VOLTAGE TRANSFORMER)
ZT/C TRANSFORMER
IFUSE F2 F10A
RCONVECTION MOTOR CAPACITOR C2
Check MISADJUSTMENT SWITCH
POSSIBLE CAUSE
AND
DEFECTIVE PARTS
TEST PROCEDURE
CONDITION COOKING CONDITION (MICROWAVE)
(CONVECTION/
GRILL/ DUAL)
OFF CONDITION
PROBLEM

14
R-90GCH
TEST PROCEDURES
PROCEDURE
LETTER COMPONENT TEST
NEVER TOUCH ANY PART IN THE CIRCUIT WITH YOUR HAND OR AN INSULATED TOOL
WHILE THE OVEN IS IN OPERATION.
1. CARRY OUT 3D CHECKS.
2. Remove the back plate from the oven, referring to “BACK PLATE REMOVAL”.
3. To test for an open filament, isolate the magnetron from the high voltage circuit. A continuity check
across the magnetron filament leads should indicate less than 1 ohm.
4. To test for a shorted magnetron, connect the ohmmeter leads between the magnetron filament
leads and chassis ground. This test should indicate an infinite resistance. If there is little or no
resistance the magnetron is grounded and must be replaced.
5. Reconnect all leads removed from components during testing.
6. Reinstall the outer case (cabinet) and the back plate.
7. Reconnect the power supply cord after the outer case and back plate are installed.
8. Run the oven and check all functions.
MICROWAVE OUTPUT POWER (IEC60705)
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 IEC
60705, i.e. it can be measured by using 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. 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.
The formula is as follows;
P x t / 4.187 = V x ∆T+ 0.55 x mc (T2-T0)/4.187 P (W) = 4.187 x V x ∆T / t + 0.55 x mc (T2-T0)/t
Our condition for water load is as follows:
Room temperature (T0) ... around 20°CPower supply Voltage.............. Rated voltage
Water load..................................1000 g Initial temperature (T1) ...................... 10±1°C
Heating time.............................. 42 sec. Mass of container (mc)......................... 330 g
T2............................ Final Temperature P = 100 x ∆T + 0.55 x mc (T2-T0)/42
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 of the test.
3. Temperature of the water
The initial temperature of the water is (10±1)˚C.
4. Select the initial and final water temperature so that the maximum difference between the final
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. The graduation of the thermometer must be scaled by 0.1˚C at minimum and an accurate
thermometer.
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 + 3” sec. 3 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 ˚C.
5. Stir the water to equalize temperature throughout the vessel.
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.
AMAGNETRON ASSEMBLY TEST

15
R-90GCH
TEST PROCEDURES
PROCEDURE
LETTER COMPONENT TEST
Room temperature ....................... To = 21˚C Initial temperature .................... T1 = 11°C
Temperature after (42 + 3) = 45 sec. ..................................................................... T2 = 21°C
Temperature difference Cold-Warm.................................................................... ∆T1 = 10°C
Measured output power
The equation is “P = 100 x ∆T” ................................................ P = 100 x 10°C = 1000 Watts
WARNING: High voltage and large currents are present at the secondary winding and
filament winding of the high voltage 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.
1. CARRY OUT 3D CHECKS.
2. Remove the back plate from the oven, referring to “BACK PLATE REMOVAL”.
3. Disconnect the leads to the primary winding of the high voltage transformer. Disconnect the
filament and secondary winding connections from the rest of the HV circuitry. Using an ohmmeter,
set on a low range, it is possible to check the continuity of all three winding. The following readings
should be obtained:-
a. Primary winding .......................... 1.2 ohms approximately
b. Secondary winding ...................... 95 ohms approximately
c. Filament winding..................................... less than 1 ohm
If the readings obtained are not stated as above, then the high voltage transformer is probably
faulty and should be replaced.
4. Also, the high voltage transformer has the thermostat in the primary coil. Measure the resistance
of the primary coil. The resistance of the primary coil should be above resistance unless the
temperature of the thermostat in the primary coil reaches approximately 160˚C. The thermostat
resets automatically at 105˚C. If an ohmmeter indicates an open circuit under normal condition,
replace the high voltage transformer because the primary coil (thermostat) has opened. An open
primary coil (thermostat) indicates overheating of the high voltage transformer. Check for
restricted air flow to the high voltage transformer, especially the fan motor (high voltage
transformer side).
5. CARRY OUT 4R CHECKS.
BHIGH VOLTAGE TRANSFORMER TEST
1. CARRY OUT 3D CHECKS.
2. Remove the back plate from the oven, referring to “BACK PLATE REMOVAL”.
3. 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 of
the high voltage rectifier and note the reading obtained. Reverse the meter leads and note this
secondreading. The normalresistance isinfinitein one directionand morethan 100kΩintheother
direction.
4. CARRY OUT 4R CHECKS.
CHIGH VOLTAGE RECTIFIER TEST
JUDGEMENT: The measured output power should be at least ±15 % of the rated output power.
CAUTION: 1°C CORRESPONDS TO 100 WATTS. REPEAT MEASUREMENT IF THE POWER IS
INSUFFICIENT.
Heat up for 45 sec.
1000g
1000g
1000g
T1˚C T2˚C

16
R-90GCH
TEST PROCEDURES
PROCEDURE
LETTER COMPONENT TEST
NOTE: FOR MEASUREMENT OF THE RESISTANCE OF THE RECTIFIER, THE BATTERIES OF
THEMEASURINGINSTRUMENTMUSTHAVEAVOLTAGEATLEAST6VOLTS,BECAUSE
OTHERWISE AN INFINITE RESISTANCE MIGHT BE SHOWN IN BOTH DIRECTIONS.
If incorrect readings are obtained, make the necessary switch adjustment or replace the switch.
3. CARRY OUT 4R CHECKS.
1. CARRY OUT 3D CHECKS.
2. Remove the back plate from the oven, referring to “BACK PLATE REMOVAL”.
3. If the high voltage fuse F3 is blown, there could be a short in the high voltage rectifier or the
magnetron.
Check them and replace the defective parts and the high voltage fuse F3.
4. CARRY OUT 4R CHECKS.
CAUTION: ONLY REPLACE HIGH VOLTAGE FUSE F3 WITH THE CORRECT VALUE REPLACE-
MENT.
Table: Terminal Connection of Switch
Plunger Operation COM to NO COM to NC
Released Open circuit Short circuit
Depressed Short circuit Open circuit
COM; Common terminal,
NO; Normally open terminal
NC; Normally close terminal
FHIGH VOLTAGE FUSE F3 TEST
1. CARRY OUT 3D CHECKS.
2. Disconnect the leads from the terminals of noise filter.
Using an ohmmeter, check between the terminals as described
in the following table.
MEASURING POINTS INDICATION OF OHMMETER
Between N and L Approx. 680 kΩ
Between terminal N and WHITE Short circuit
Between terminal L and RED Short circuit
If incorrect readings are obtained, replace the noise filter unit.
CARRY OUT 4R CHECKS.
GNOISE FILTER TEST
1. CARRY OUT 3D CHECKS.
2. Remove the back plate from the oven, referring to “BACK PLATE REMOVAL”.
3. Isolate the high voltage capacitor from the circuit.
4. Continuity check must be carried out with measuring instrument which is set to the highest
resistance range.
5. A normal capacitor shows continuity for a short time (kick) and then a resistance of about 10MΩ
after it has been charged.
6. A short-circuited capacitor shows continuity all the time.
7. An open capacitor constantly shows a resistance about 10 MΩbecause of its internal 10MΩ
resistance.
8. When the internal wire is opened in the high voltage capacitor, the capacitor shows an infinite
resistance.
9. 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.
10.CARRY OUT 4R CHECKS.
DHIGH VOLTAGE CAPACITOR C1 TEST
ESWITCH TEST
1. CARRY OUT 3D CHECKS.
2. Isolate the switch to be tested and using an ohmmeter check between the terminals as described
in the following table.
F1: FUSE 20A
NL
LINE CROSS CAPACITOR 1.0µ/AC275V
NOISE SUPPRESSION COIL
LINE BYPASS
CAPACITOR
0.0047µ/AC250V
LINE BYPASS
CAPACITOR
0.0047µ/AC250V
RESISTOR
10M 1/2W
RESISTOR 680K 1/2W
WHT RED
NOISE FILTER

17
R-90GCH
TEST PROCEDURES
PROCEDURE
LETTER COMPONENT TEST
HBLOWN FUSE F1 20A
1. CARRY OUT 3D CHECKS.
2. If the fuse F1 20A is blown, there is a shorts or grounds in electrical parts or wire harness Check
then and replace the defective parts or repaire the wire harness.
3. CARRY OUT 4R CHECKS.
CAUTION: ONLY REPLACE FUSE F1 20A WITH CORRECT VALUE REPLACEMENT.
1. CARRY OUT 3D CHECKS.
2. If the fuse F2 F10A is blown when the door is opened, check the secondary interlock switch, relay
RY2 and monitor switch.
3. If the fuse F2 F10A is blown by incorrect door switching, replace the defective switch(s) and the
fuse F2 F10A.
4. If the fuse F2 F10A is blown, there is a shorts or grounds in electrical parts or wire harness.
Check them and replace the defective parts or repair the wire harness.
5. CARRY OUT 4R CHECKS.
CAUTION: ONLY REPLACE FUSE F2 F10A WITH CORRECT VALUE REPLACEMENT.
IBLOWN FUSE F2 F10A
1. CARRY OUT 3D CHECKS.
2. A continuity check across the temperature fuse terminals should indicate a closed circuit unless
the temperature of the magnetron reaches approximately 150˚C. An open temperature fuse TF
indicates overheating of the magnetron. Check for restricted air flow to the magnetron, especially
the cooling duct and cooling fan.
3. CARRY OUT 4R CHECKS.
CAUTION: IF THE TEMPERATURE FUSE TF INDICATES AN OPEN CIRCUIT AT ROOM TEM-
PERATURE, REPLACE TEMPERATURE FUSE.
J MAGNETRON TEMPERATURE FUSE TF TEST
1. CARRY OUT 3D CHECKS.
2. A continuity check across the thermal cut-out TC1 terminals should indicate a closed circuit unless
the temperature of the thermal cut-out TC1 reaches approximately 170˚C. The thermal cut-out
TC1 resets automatically at approximately 155˚C. If thermal cut-out TC1 has opened under
normal condition, replace the same item as in the parts list.
An open thermal cut-out TC1 indicates overheating of the top heating element unit. Check for
restricted air flow to the top heat element unit through the vent holes of the oven cavity, especially
the heater duct upper and convection fan.
3. CARRY OUT 4R CHECKS.
CAUTION: IF THE THERMAL CUT-OUT TC1 INDICATES AN OPEN CIRCUIT AT ROOM TEM-
PERATURE, REPLACE THERMAL CUT-OUT TC1.
K THERMAL CUT-OUT (TOP HEATER) TC1 TEST
1. CARRY OUT 3D CHECKS.
2. A continuity check across the thermal cut-out TC2 terminals should indicate a closed circuit unless
the temperature of the thermal cut-out TC2 reaches approximately 150˚C. The thermal cut-out
TC2 resets automatically at approximately 130˚C. If thermal cut-out TC2 has opened under
normal condition, replace the same item as in the parts list.
An open thermal cut-out TC2 indicates overheating of the side heating element unit. Check for
restricted air flow to the side heat element unit through the vent holes of the oven cavity, especially
the heater duct left and convection fan.
3. CARRY OUT 4R CHECKS.
CAUTION: IF THE THERMAL CUT-OUT TC2 INDICATES AN OPEN CIRCUIT AT ROOM TEM-
PERATURE, REPLACE THERMAL CUT-OUT TC2.
LTHERMAL CUT-OUT (SIDE HEATER) TC2 TEST

18
R-90GCH
TEST PROCEDURES
PROCEDURE
LETTER COMPONENT TEST
1. CARRY OUT 3D CHECKS.
2. Make sure the heating element is fully cooled and test as follows;
a. Disconnect wire leads from the heating element and measure the resistance with an ohmmeter.
Onthe R x1scale, the resistancebetweenthe heating elementterminalsshould be approximately
34Ω.
b. Disconnect wire leads from the heating element and measure the insulation resistance with
500V - 100MΩinsulation resistance meter. The insulation resistance between heating element
terminal and cavity should be more than 0.5MΩ.
3. If the meter does not indicate above resistance, replace the top heating element.
4. CARRY OUT 4R CHECKS.
MTOP HEATING ELEMENT H1 TEST
1. CARRY OUT 3D CHECKS.
2. Make sure the heating element is fully cooled and test as follows;
a. Disconnectwireleads from the heatingelement and measurethe resistance withan ohmmeter. Onthe
R x 1 scale, the resistance between the heating element terminals should be approximately 43 Ω.
b. Disconnect wire leads from the heating element and measure the insulation resistance with
500V - 100MΩinsulation resistance meter. The insulation resistance between heating element
terminal and cavity should be more than 0.5MΩ.
3. If the meter does not indicate above resistance, replace the side heating element.
4. CARRY OUT 4R CHECKS.
N SIDE HEATING ELEMENT H2 TEST
1. CARRY OUT 3D CHECKS.
2. Remove the back plate from the oven, referring to “BACK PLATE REMOVAL”.
3. Disconnect connector-E from the control unit. Measure the resistance of the thermistor with an
ohmmeter. Connect the ohmmeter leads to Pin No’s E-5 and E-6.
Room Temperature Resistance
68˚F(20˚C) - 86˚F(30˚C) Approx. 360 kΩ- 152 KΩ
4. If the meter does not indicate above resistance, replace the thermistor.
5. CARRY OUT 4R CHECKS.
OTHERMISTOR TEST
When the power cord is plugged into the wall receptacle and the rated voltage is supplied to the
damper motor, the motor operates until the damper is opened and the damper switch closes. Then
the damper motor stops operation.
If the damper motor does not operate, check for A.C. voltage with a voltmeter at the motor.
1. CARRY OUT 3D CHECKS.
2. Remove the back plate from the oven, referring to “BACK PLATE REMOVAL”.
3. Disconnect the leads to the primary of the high voltage transformer.
4. Ensure that the leads remain isolated from other components and oven chassis by using insulation
tape.
5. Disconnect the wire leads of motor and connect the meter leads to the wire leads of main wire
harness.
6. Reconnect the power cord into the wall receptacle.
7. If the rated voltage is indicated at the wire leads, replace the motor and if the rated voltage is not
indicated, check the wire harness and control unit.
8. Disconnect the oven from power supply.
9. Open the door and wedge it open.
10.Discharge high voltage capacitor.
11.CARRY OUT 4R CHECKS.
PDAMPER MOTOR DM TEST
QDAMPER SWITCH SW5 TEST
1. CARRY OUT 3D CHECKS.