Sharp R733 Schematic

COOK & DEFR

OST

SERVICE MANUAL

COOK & DEFR

OST

GRILL AND

MICROWAVE OVEN

S04273R733EHW

R-733

MODELS

R-733(W/B) R-733(Y/LB/LG/W)F

In interests of user-safety the oven should be restored to its original condition and only parts identical to those specified should be used.

TABLE OF CONTENTS

Page

CAUTION MICROWAVE RADIATION, WARNING ............................................................. INSIDE COVER

GENERAL IMPORTANT INFORMATION .................................................................................................. 1

SERVICING ................................................................................................................................................ 2

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

APPEARANCE VIEW ................................................................................................................................. 6

OPERATION SEQUENCE .......................................................................................................................... 7

FUNCTION OF IMPORTANT COMPONENTS .......................................................................................... 8

TEST PROCEDURE ................................................................................................................................. 10

TOUCH CONTROL ASSEMBLY .............................................................................................................. 18

COMPONENT REPLACEMENT AND ADJUSTMENT PROCEDURE ..................................................... 22

TEST DATA AT A GLANCE ..................................................................................................................... 26

MICROWAVE MEASUREMENT .............................................................................................................. 27

SCHEMATIC DIAGRAMS ......................................................................................................................... 28

PICTORIAL DIAGRAM ............................................................................................................................. 30

CONTROL PANEL CIRCUIT .................................................................................................................... 31

PRINTED WIRING BOARD DIAGRAM ................................................................................................... 32

PARTS LIST ............................................................................................................................................. 33

EXPLODED VIEW OF OVEN ....................................................................................................................36

CONTROL PANEL /DOOR PARTS ...........................................................................................................37

MISCELLANEOUS/PACKING AND ACCESSORIES ................................................................................ 38

SHARP CORPORATION

CAUTION

MICROWAVE RADIATION

Personnel should not be exposed to the mircowave 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 energised.

VARNING

MIKROVAGSSTRALING

Personal får inte utsättas för mikrovågsenergi som kan utstrala 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 en öppen vågledare eller antenn när mikrovågsgeneratorn är påkopplad eller laddad.

VAROITUS

MIKROAALTOSATEILYA

Käyttäjä ei saa joutua alttiiksi mikroaaltoenergialle, jota voi säteillä magnetronista tai muusta mikroaaltoja kehittävästä laitteesta, jos sitä käytetään väärin tai jos se kytketään väärin. Kaikkien mikroaaltoliitäntöjen sekä syöttö-että ulostulopuolella, aaltoputkien laippojen ja tiivisteiden tulee olla varmistettuja. Mikroaaltouunia ei koskaan saa käyttää ilman kuormaa jossa mikroaaltoenergiaa kuluu. Avoimeen aaltoputkeen tai antenniin ei koskaan saa katsoa virran ollessa kytkettynä.

ADVARSEL

MIKRØBOLGESTRÅLING

Personell må ikke utsettes for mikrobølge-energi som kan utstråles fra magnetronen eller andre mikrobølge-generende deler dersom apparatet feilbetjenes eller blir feiltikoplet. Alle inn-og uttilkoplinger 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

MIKRØBOLGEBESTRALING

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 mikrobølgeabsorberende anordning. Se aldrig ind i en åben bølgeleder eller antenne, mens ovnen er i brug.

SERVICE MANUAL

GRILL AND MICROWAVE OVEN

R-733(W/B)/ 733(W/Y/LB/LG/)F

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 in voltage 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.

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 the parts list may cause undue microwave exposure, by themselves, or when they are damaged, loosened or removed.

Never operate the Grill with the oven outer cabinet removed. (Because air flow is eliminated, and the excess heat generated on adjacent components). It can cause permanent damage or a fire.

SHARP CORPORATION OSAKA, JAPAN

R-733 -

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 3D

1) Disconnect the supply.

2) Door opened, and wedged open.

3) Discharge high voltage capacitor.

WARNING :-BEWARE OF THE HIGH-VOLTAGE CAPACITOR CHARGE

The high-voltage capacitor remains charged for about 60 seconds after the oven has been switched off. Wait for 60 seconds and then short-circuit the connection of the high-voltage capacitor (that is, the connecting lead of the high-voltage rectifier) against the chassis,using a screwdriver with an insulated handle.

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 and then disconnect the leads to the primary of the power transformer,before connecting the supply. 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.

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.

3D checks

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 stopcontact is gehaald. Soms is het nodig om de stroomtoevoer weer tot stand te brengen nadat de buitenmantel verwijderd is. Herhaal dan de bovengenoemde 3 stappen en haal de electrische draden uit deprimaire zijde vande 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

REMEMBER TO CHECK 4R

1) Reconnect all leads removed from components during 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 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 the component being tested.

When all service work is completed, and the oven is fully assembled, the microwave power output should be checked and a microwave leakage test carried out.

bovenstaande 3 stappen en verbindt u de electrische draden weer aan de primaire zijde van de vermogenstransformator.

3D checks and re-examine the connections to

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).

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 stelt de klok van de magnetron in op 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.

R-733 -

SERVICING

Los 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 ALTO VOLTAJE

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).

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.

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) till chassiet med hjälp av en isolerad skruvmejsel.

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 4 STEG

1) Anslut alla ledningar som använts vid testning

2) Sätt tillbaka ytterhöljet.

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.

R-733 -

SERVICING

I forni 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) Rimontare la scatola esterna.

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.

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.

R-733 -

IMPORTANT: If the oven becomes inoperative because of

a blown fuse F8A in the monitored latch switch - monitor switch circuit, check the monitored latch switch and monitor switch before replacing the fuse F8A.

PRODUCT SPECIFICATIONS

SPECIFICATION

ITEM DESCRIPTION

Power Requirements 230 Volts

50 Hertz Single phase, 3 wire grounded

Power Consumption Microwave cooking 1.52 kW Approx. 7.1 A

Grill cooking 1.25 kW Approx. 5.3 A Dual cooking 2.7 kW Approx. 12.4 A

Power Output 900W watts nominal of RF microwave energy

(measured by way of IEC 705) Operating frequency of 2450 MHz Grill Heating Element Power Output 1200W (600W x 2) Case Dimensions Width 520mm

Height 305mm including foot

Depth 413mm Cooking Cavity Dimensions Width 342mm

Height 207mm

Depth 368mm Turntable diameter 325mm Control Complement Jog Touch Control

Clock(1:00-12:59 or 0:00-23:59)

Timer (90 minutes)

Microwave Power for Variable Cooking

Repetition Rate;

HIGH .................. Full power throughout the cooking time

MEDIUM HIGH ...................... approx. 70% of Full Power

MEDIUM ................................ approx. 50% of Full Power

MEDIUM LOW ....................... approx. 30% of Full Power

LOW ...................................... approx. 10% of Full Power

FUNCTION KEYS:

AUTO COOK key

MODE key

STOP key,

ROTARY knob

MINUTE PLUS/START key Set Weight Approx. 18.7 kg

GENERAL INFORMATION

WARNING THIS APPLIANCE MUST BE EARTHED

IMPORTANT

THE WIRES IN THIS MAINS LEAD ARE COLOURED IN ACCORDANCE WITH THE FOLLOWING CODE:

GREEN-AND-YELLOW : EARTH BLUE : NEUTRAL BROWN : LIVE

As part of our policy of continuous improvement, we reserve the right to alter design and specifications without notice

R-733 -

APPEARANCE VIEW

OVEN

1. Door

2. Door hinges

3. Grill Guide

4. Lamp filter

5. Waveguide cover

6. Contol panel

7. Coupling

8. Door open button

9. Door latches

10. Oven cavity

11. Safety door latches

12. Ventilation openings

13. Outer case

14. Rear back plate

15. Power supply cord

1. Place the roller stay on the coupling.

2. Then place the turntable on it.

AUTO-TOUCH CONTROL PANEL

COOK & DEFROST

Low rack

High rack

1. Display Window

2. Key Button

3. Start Button

4. Rotary Knob

5. Door Open Button

R-733F

R-733 -

R-733

OPERATING SEQUENCE

OFF CONDITION

Closing the door activates all door interlock switches (monitored latch switch and stop switch).

IMPORTANT When the oven door is closed, the monitor switch contacts COM - NC must be open. When the microwave oven is plugged in a wall outlet (230V 50Hz), the line voltage is supplied to the point A1+A3 in the control unit.

Figure O-1 on page 28

1. The display flashes "88:88”.

2. To set any programmes or set the clock, you must first touch the STOP pad.

3. “:” appears in the display.

NOTE: When the oven door is opened, the oven lamp

comes on at this time.

MICROWAVE COOKING CONDITION

HIGH COOKING

Enter a desired cooking time with the ROTARY knob and start the oven by touching START button.

Function sequence Figure O-2 on page 28

CONNECTED COMPONENTS RELAY Oven lamp, Fan motor, Turntable motor RY1 Grill heater RY2 Power transformer RY3

1. The line voltage is supplied to the primary winding of the power transformer. The voltage is converted to about 3.3 volts A.C. output on the filament winding and high voltage of approximately 2000 volts A.C. on the secondary winding.

2. 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.

3. 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) into the oven cavity, where the food is placed to be cooked.

4. When the cooking time is up, a single tone is heard and the relays position. The circuits to the oven lamp, power transformer, fan motor and turntable motor are cut off.

5. When the door is opened during a cook cycle, the switches come to the following condition.

RY1 + RY3 go back to their home

CONDITION

SWITCH CONTACT COOKING (NO COOKING) Monitored latch switch COM-NO Closed Open Monitor switch COM-NC Open Closed

COM-NO Closed Open

Stop switch COM-NO Closed Open

DURING DOOR OPEN

The circuits to the power transformer, fan motor and turntable motor are cut off when the primary latch switch and stop switch 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 the remaining time.

6. MONITOR SWITCH CIRCUIT The monitor switch

SW2 is mechanically controlled by oven door, and monitors the operation of the monitored latch switch

SW1

6-1 When the oven door is open during or after the

cycle of cooking program, the monitored latch and stop switches first. After that the contacts (

SW1 + SW3 must open their contacts

COM - NC) of the

monitor switch SW2 can be closed.

6-2 When the oven door is closed, the contacts

(

COM - NC) of the monitor switch SW2 must be opened. After that contacts of the monitored latch and stop switches

SW1 + SW3 are closed.

6-3 When the oven door is opened and the contacts of

the monitored latch switch

SW1 remain closed, the fuse F8A will blow, because the monitor switch is 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 power transformer intermittently within a 48-second time base through the relay contact which is coupled with the current-limiting relay microwave power are given.

SETTING

HIGH

MEDIUM HIGH

MEDIUM

MEDIUM LOW

LOW

RY3. The following levels of

48 sec. ON

36 sec. ON

26 sec. ON

16 sec. ON

8 sec. ON

12 sec. OFF

22 sec. OFF

32 sec. OFF

40 sec. OFF

Approx100% = 900Watts

Approx. 70% = 630Watts

Approx. 50% = 450Watts

Approx. 30% = 270Watts

Approx. 10% = 90Watts

R-733 -

NOTE: The ON/OFF time ratio does not exactly

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

OPERATING SEQUENCE

GRILL COOKING CONDITION

In this condition the food is cooked by grill heater energy. Program desired cooking time and grill mode using MODE button and ROTARY knob. When the START button is touched, the following operations occur:

Figure O-3 on page 29

1. The relay

RY1 and RY2 are energized.

2. The numbers of the digital readout start the count down to zero.

3. Then the grill heating elements, turntable motor, oven lamp and fan motor are energized.

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

5. Upon completion of the selected cooking time, audible signal sounds, and contacts of relays are opened, then the activated components as item 4 are de-energized.

DUAL COOKING CONDITION

In this condition the food is cooked by both microwave energy and grill heating elements energy simultaneously.

Figure O-4 on page 29

1. The contact of monitored latch switch

2. The relay

RY1, RY2 and RY3 are energized.

SW1 are closed.

3. The numbers of the digital readout start the count down to zero.

4. Then following components are energized.

Power transformer Grill heating elements Magnetron Turntable motor H.V. capacitor Fan motor H.V. rectifier Oven lamp

5. Now, the food is cooked by microwave and grill heating elements energy simultaneously.

6. Upon completion of selected cooking time, audible signal sounds, and contacts of relays are opened, then the activated components as item 4 are de- energized.

7. When cooking in dual mode the microwave power is limited to 70% (via the I.C.).

AUTO COOK PROGRAMME

Keep on touching the AUTO COOK pad until the desired cooking programme appears in the display. Then using the ROTARY knob, enter the weight and touch the START button. The cooking modes and cooking time are automatically computed and selected based on the programmes.

FUNCTION OF IMPORTANT COMPONENTS

DOOR OPEN MECHANISM

The door can be opened by pushing the door open button on the control panel. When the door open button is pushed, the open lever is moved upward, operating the latch head. The latch head is moved upward, and released from the latch hook. Now, the door can be opened.

DOOR

LATCH HOOK

LATCH HEADS

DOOR OPEN BUTTON

MONITOR SWITCH (SW2)

MONITORED LATCH SWITCH (SW1)

STOP SWITCH (SW3)

OPEN LEVER

MONITORED LATCH SWITCH SW1 STOP SWITCH SW3

1. When the oven door is closed, the contacts (

2. When the oven door is opened, the contacts (

MONITOR SWITCH SW2

1. When the oven door is closed, the contacts (

2. When the oven door is opened, the contacts (

3. If the oven door is opened and the contacts (

CAUTION: BEFORE REPLACING A BLOWN FUSE F1 F8

COM - NO)

must be closed.

COM - NO)

must be opened.

COM - NC) must be opened and the contacts (COM - NO) must be closed.

COM - NC)

must be closed and the contacts (

COM - NO) must be

closed.

COM - NO) of the monitored latch switch SW1 fail to open, the fuse F1 F8A blows simultaneously with closing the contacts (

COM

- NC) of the monitor switch SW2.

TEST THE MONITORED LATCH SWITCH SW1 AND MONITOR SWITCH SW2 FOR PROPER OPERATION. (REFER TO CHAPTER ”TEST PROCEDURE”.)

Figure D-1. Door Open Mechanism

R-733 -

FUNCTION OF IMPORTANT COMPONENTS

FUSE F1 F8A 250V

This fuse blows when monitored latch switch

SW1 remains closed with the oven door open and when the contacts (

COM + NC) of monitor switch SW2 closes.

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 blows when the asymmetric rectifier, H.V.

rectifier, H.V. wire harness, H.V. capacitor, magnetron or secondary winding of power transformer is shorted.

SPECIAL FUSE

F2 15A

If the wire harness or electrical components are shortcircuited, this fuse blows to prevent an electric shock or fire hazard.

THERMAL CUT-OUT 125

°C TC1 (MG)

The thermal cut-out protects the magnetron against overheating. If this temperature goes up higher than 125°C because the fan motor is interrupted, or the ventilation openings are blocked, the thermal cut-out and line voltages to the power transformer and the operation of the magnetron defective thermal cut-out

TC1 must be replaced with a new

MG will be stopped. The

TC1 will open

T1 will be cut off

one.

NOISE FILTER

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

GRILL HEATING ELEMENT (GH)

The grill heating element

GH is located on the top of the oven cavity assembly. The grill heating element emits heat to grill foods.

ASYMMETRIC RECTIFIER

The asymmetric rectifier is a solid state device that prevents current flow in both directions. And it prevents the temperature rise of the power transformer by blowing the fuse

when the high voltage rectifier is shorted.

D2 D1

ASYMMETRIC RECTIFIER

HIGH VOLTAGE RECTIFIER

The rated peak reverse voltage of D1 of the asymmetric rectifier is 6 KV. The rated peak reverse voltage of D2 of the asymmetric rectifier is 1.7 KV. D1 and D2 of the asymmetric rectifier or high voltage rectifier are shorted when each peak reverse voltage goes beyond the rated peak reverse voltage.

THERMAL CUT-OUT 160

°C TC2 (OVEN)

The thermal cut-out located on the top the oven cavity is designed to prevent damage to the oven if the foods in the oven catch fire due to over heating produced by improper setting of cook time or failure of control unit. Under normal operation, the oven thermal cut-out remains closed. However, when abnormally high temperatures are reached within the oven cavity, the oven thermal cut-out will open at 160°C, causing the oven to shut down. The defective thermal cut-out

TC2 must be replaced with new one.

TURNTABLE MOTOR

The turntable motor drives the turntable roller assembly to rotate the turntable.

FAN MOTOR

The fan motor drives a blade which draws in external cool air. This cool air is directed through the air vanes surrounding the magnetron and cools the magnetron. This air is then channeled through the oven cavity to remove steam and vapours given off from heating the food. It is then exhausted through the exhaust air vents at the rear of the oven cavity.

The process of blowing the fuse

F1 will blow during a

fault condition.

1. The high voltage rectifier is shorted circuited during

microwave cooking.

2. The peak reverse voltage of D2 of the rectifier goes

beyond the rated peak reverse voltage of 1.7 KV in the voltage doubler circuit.

3. D2 of the rectifier then breaks down and short-circuits.

4. A large electric current then flows through the high

voltage winding of the power transformer.

5. A large electric current >10A flows through the primary

winding of the power transformer.

6. The fuse

F1 blows due to its 8A current rating.

7. The power supply to the power transformer is cut off.

R-733 -

TEST PROCEDURES

CONDITION

OFF CONDITION

COOKING CONDITION (COMMON)

MICROWAVE COOKING CONDITION

GRILL COOKING CONDITION

DUAL COOKING CONDITION

TEST PROCEDURE

POSSIBLE CAUSE

AND

DEFECTIVE PARTS

PROBLEM

Fuse F2 15A blows when power cord is plugged into wall outlet.

Fuse F8A blows when the door is opened.

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

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

“88:88” does not appear in display when power cord is plugged into wall outlet.

Display does not operate properly when STOP pad is touched.

Oven does not start when START pad is touched. (Display appears.)

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

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

Turntable motor assembly does not operate. (Oven lamp light.)

Oven or electrical parts do not stop when cooking time is 0 or STOP pad is touched.

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

Oven stops as soon as the START pad is touched. (Except for Grill Cooking)

Oven seems to be operating but little or no heat is produced in oven load. (Microwave power level is set at ”HIGH”)

Oven does not operate properly during the variable cooking condition except ”HIGH” cooking condition. (Oven operates properly at HIGH)

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

Grill Heating element does not operate.

Oven seems to be operating but little or no heat is produced in oven load. (Microwave power does not seem to be generated properly)

Grill Heating element does not operate.

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