Sharp R363 SM Schematic

SERVICE MANUAL

MICROWAVE OVEN

O K

S06278R363EHW

-3 6 3

R-363(IN)

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 ............................................................................................................................. INSIDE COVER

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

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

CAUTION, MICROWAVE RADIATION, WARNING ................................................................................... 5

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

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

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

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

TEST PROCEDURES .............................................................................................................................. 10

TOUCH CONTROL ASSEMBLY .............................................................................................................. 19

COMPONENT REPLACEMENT AND ADJUSTMENT PROCEDURE ..................................................... 23

TEST DATA AT A GLANCE ..................................................................................................................... 27

MICROWAVE MEASUREMENT .............................................................................................................. 28

WIRING DIAGRAMS ................................................................................................................................ 29

SWITCH UNIT CIRCUIT ............................................................................................................................32

PICTORIAL DIAGRAM .............................................................................................................................. 33

PRINTED WIRING BOARD OF SWITCH UNIT ........................................................................................34

PARTS LIST ............................................................................................................................................. 35

EXPLODED VIEW OF OVEN ....................................................................................................................38

CONTROL PANEL & DOOR PARTS ........................................................................................................39

MISCELLANEOUS/PACKING AND ACCESSORIES ............................................................................... 40

MODELS

SHARP CORPORATION

SERVICE MANUAL

MICROWAVE OVEN

R-363(IN)

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

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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 AGAINST THE CHARGE OF THE HIGHVOLTAGE CAPACITOR

The high-voltage capacitor remains charged about 60 seconds after the oven has been switched off. Wait for 60 seconds and then short-circuit the 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 and then disconnect the leads to the primary of the power transformer. 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.

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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.

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) till chassiet med hjälp av en isolerad 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.

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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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.

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

R-363 -

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.

CAUTION/WARNING

CAUTION

MICROWAVE RADIATION

Service engineers should not be exposed to the microwave energy which may radiate from the magnetron or other microwave generating devices if it is improperly used or connected. All input and output microwave connections, waveguides, flanges and gaskets must be secured. Never operate the device without a microwave energy absorbing load attached. Never look into an open waveguide or antenna while the device is energized.

Servicing and repair work must be carried out only by trained service engineers.

All the parts marked "*" on parts list are used at voltages more than 250V.

Removal of the outer wrap gives access to potentials above 250V.

All the parts marked "∆" on parts list may cause undue microwave exposure, by themselves, or when they are damaged, loosened or removed.

WARNING

THIS APPLIANCE MUST BE EARTHED. 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

Power Requirements 230 Volts 50 Hertz Single phase, 3 wire earthed Power Consumption 1.35 kW Approx. 6.0 A Power Output 900W watts nominal of RF microwave energy

(measured by way of IEC 60705) Operating frequency of 2450 MHz

Case Dimensions Width 520mm

Height 305mm including foot Depth 422mm

Cooking Cavity Dimensions Width 342mm

Height 207mm

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

Clock (1:00-12:59 or 0:00-23:59) Timer (0-99 minutes 90 seconds)

Control Complement 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

EXPRESS COOK key EXPRESS DEFROST key x 3

STOP key POWER LEVEL key MINUTE PLUS/START key

ROTARY KNOB

Set Weight Approx. 18.0 kg

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APPEARANCE VIEW

OVEN

AUTO-TOUCH CONTROL PANEL

1. Door

2. Door hinges

3. Oven lamp

4. Waveguide cover

5. Contol panel

6. Coupling

7. Door latches

8. Oven cavity

9. Door seals and sealing surfaces

10. Safety door latches

11. Door handle

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.

TURNTABLE

ROLLER STAY

COUPLING

COOK

DEFROST

1. Display Window

2. Symbols and Indicators

3. EXPRESS COOK

4. EXPRESS DEFROST

5. +1min/START button

6. STOP button

7. COOKING MODE button

8. TIMER/WEIGHT/POWER knob

5 6

R-363

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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 29

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 29

CONNECTED COMPONENTS RELAY

Oven lamp, Fan motor, Turntable motor RY1 Power transformer RY2

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 ( monitor switch

SW1 + SW3 must open their contacts

COM - NC) of the

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.

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

RY1 + RY2 go back to their home 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.

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

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.

RY2. The following levels of

32 sec. ON

Approx100% = 900Watts

24 sec. ON

18 sec. ON

12 sec. ON

6 sec. ON

8 sec. OFF

Approx. 70% = 630Watts

14 sec. OFF

Approx. 50% = 450Watts

20 sec. OFF

Approx. 30% = 270Watts

26 sec. OFF

Approx. 10% = 90Watts

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FUNCTION OF IMPORTANT COMPONENTS

FUSE F1 F8A 250V

DOOR OPEN MECHANISM

The door can be opened by puiiing the door handle. When the door handle is pulled, the latch head is moved upward, and released from the latch hook now the door can be opened.

Latch Hooks

1. If the wire harness or electrical components are short-

2. The fuse also blows when monitored latch switch

3. The fuse blows when the asymmetric rectifier, H.V.

circuited, this fuse blows to prevent an electric shock or fire hazard.

SW1 remains closed with the oven door open and when the monitor switch

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

SW2 closes.

Stop Switch SW3

Monitor Switch SW2

Monitored Latch Switch SW1

Figure D-1. Door Open Mechanism

MONITORED LATCH SWITCH SW1 STOP 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 ( must be opened.

MONITOR SWITCH SW2

1. When the oven door is closed, the contacts ( must be opened and the contacts ( closed.

2. When the oven door is opened, the contacts ( must be closed and the contacts (COM - NO) must be closed.

3. If the oven door is opened and the contacts ( of the monitored latch switch F8A blows simultaneously with closing the contacts (

- NC) of the monitor switch SW2.

SW1 fail to open, the fuse F1

COM - NO) must be

COM - NO)

COM - NC)

COM - NO)

COM

THERMAL CUT-OUT 125

The thermal cut-out protects the magnetron against overheat. 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 MG will be stopped. The defective thermal cut-out one.

THERMAL CUT-OUT 125

The thermal cut-out located on the top of the oven cavity is designed to prevent damage to the oven if the food in the oven catches fire due to over heating caused 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 125°C, causing the oven to shut down. The defective thermal cut-out

TURNTABLE MOTOR

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

FAN MOTOR

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

NOISE FILTER

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

TC2 must be replaced with new one.

°C TC1 (MG)

TC1 will open

T will be cut off

TC1 must be replaced with new

°C TC2 (OVEN)

CAUTION: BEFORE REPLACING A BLOWN FUSE F1 F8A,

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

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FUNCTION OF IMPORTANT COMPONENTS

ASYMMETRIC RECTIFIER

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

when the high voltage rectifier is shorted.

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 the each peak reverse voltage goes beyond the each rated peak reverse voltage. (The process of blowing the fuse

F1)

1. The high voltage rectifier is shorted by any causes when microwave cooking.

2. The peak reverse voltage of D2 of the rectifier goes beyond the rated peak reverse voltage 1.7 KV in the voltage doubler circuit.

3. D2 of the rectifier is shorted.

4. The large electric currents flow through the high voltage winding of the power transformer.

5. The large electric currents beyond 10A flow through the primary winding of the power transformer.

6. The fuse

F1 blows by the large electric currents.

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

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TEST PROCEDURES

CONDITION

OFF CONDITION

TEST PROCEDURE

POSSIBLE CAUSE

AND

DEFECTIVE PARTS

PROBLEM

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

Fuse F8A blows when the door is opened. Special fuse blows when power supply 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 lamp does not light when door is opened.

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

(Display appears.)

ABCDEEEF GHI

R T R

C A

E R

A S S E M B L Y

M O N

T O R

E D

L A

T C H

I T

I T C

| O U

1 2 5 C

O T

L T E R

COOKING CONDITION

Oven lamp does not light. (Display appears.)

Fan motor does not operate. (Display appears.) Turntable motor assembly does not operate.

(Display appears.) Oven or any electrical parts do not stop when

cooking time is 0 or STOP pad is touched. 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 stops when 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.

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TEST PROCEDURES

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TEST PROCEDURES

PROCEDURE

LETTER COMPONENT TEST

A MAGNETRON TEST

NEVER TOUCH ANY PART IN THE CIRCUIT WITH YOUR HAND OR AN INSULATED TOOL WHILE THE OVEN IS IN OPERATION.

CARRY OUT

Isolate the magnetron from high voltage circuit by removing all leads connected to filament terminal.

To test for an open circuit filament use an ohmmeter to make a continuity test between the magnetron filament terminals, the meter should show a reading of less than 1 ohm.

To test for short filament to anode condition, connect ohmmeter between one of the filament terminals and the case of the magnetron (ground). This test should be indicated an infinite resistance. If a low or zero resistance reading is obtained then the magnetron should be replaced.

MICROWAVE OUTPUT POWER (IEC-60705-1988)

The following test procedure should be carried out with the microwave oven in a fully assembled condition (outer case fitted). Microwave output power from the magnetron can be measured by way of IEC 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(g) rises ∆T (°C) during this microwave heating period, the calorie of the water is V x ∆T.

The formula is as follows;

Our condition for water load is as follows:

3D CHECK

P x t / 4.187 = V x ∆ T P (W) = 4.187 x V x ∆T / t

Room temperature..............around 20°C Power supply Voltage.........Rated voltage

Water load.........1000 g Initial temperature...........10 ± 2°C Heating time ...47+3=50 sec.

P = 90 x ∆T

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 ± 2)°C.

4. Select the initial and final water temperature so that the maximum difference between the final water temperature and the ambient temperature is 5K.

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 ± 2) K.

5. Stir the water to equalize temperature throughout the vessel.

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TEST PROCEDURES

PROCEDURE

LETTER COMPONENT TEST

6. Measure the final water temperature. (Example: The final temperature T2 = 21°C)

7. Calculate the microwave power output P in watts from above formula.

Initial temperature ......................................................................................................... T1 = 11°C

Temperature after (47 + 3) = 50 sec. ............................................................................ T2 = 21°C

Temperature difference Cold-Warm............................................................................ ∆T1 = 10°C

Measured output power

The equation is “P = 90 x ∆T” ................................................. P = 90 x 10°C = 900 Watts Approx.

JUDGMENT: The measured output power should be at least

CAUTION: 1°C CORRESPONDS TO 90 WATTS. REPEAT MEASUREMENT IF THE POWER IS

INSUFFICIENT.

1000g

T1˚C

B POWER TRANSFORMER TEST

WARNING: High voltages and large currents are present at the secondary winding and

filament winding of the power transformer. It is very dangerous to work near this part when the oven is on. NEVER make any voltage measurements of the high-voltage circuits, including the magnetron filament.

CARRY OUT 3D CHECKS

± 15 % of the rated output power.

1000g

T2˚C

Heat up for 50 sec.

Disconnect the leads to the primary winding of the power 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 windings. The following readings should be obtained:-

a. Primary winding ............2 ohms approximately

b. Secondary winding ....... 130 ohms approximately

c. Filament winding ...........less than 1 ohm

If the reading obtained are not stated above, then the power transformer is probably faulty and should be replaced.

CARRY OUT

4R CHECKS

C HIGH VOLTAGE RECTIFIER ASSEMBLY TEST

CARRY OUT

3D CHECKS.

Isolate the high voltage rectifier assembly from the HV circuit. The high voltage rectifier can be tested using an ohmmeter set to its highest range. Connect the ohmmeter across the terminal B + C of the high voltage rectifier and note the reading obtained. Reverse the meter leads and note this second reading. The normal resistance is infinite in one direction and more than 100 kΩ in the other direction.

CARRY OUT 4R CHECKS

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