Sharp R-4a56 User manual

R-4A56

SHARP CORPORATION

SERVICE MANUAL

In interests of user-safety the oven should be restored to its original

condition and only parts identical to those specified should be used.

MODEL R-4A56

S8406R4A56PJZ

MICROWAVE OVEN

TABLE OF CONTENTS Page

CAUTION, MICROWAVE RADIATION ................................................................................................................ 1

WARNING..............................................................................................................................................................1

PRODUCT SPECIFICATIONS............................................................................................................................. 2

GENERAL INFORMATION ................................................................................................................................... 2

APPEARANCE VIEW........................................................................................................................................... 3

OPERATION SEQUENCE ................................................................................................................................... 4

FUNCTION OF IMPORTANT COMPONENTS .................................................................................................... 5

SERVICING .......................................................................................................................................................... 6

TEST PROCEDURE ............................................................................................................................................ 8

TOUCH CONTROL PANEL ................................................................................................................................ 16

COMPONENT REPLACEMENT AND ADJUSTMENT PROCEDURE............................................................... 20

MICROWAVE MEASUREMENT ........................................................................................................................ 26

WIRING DIAGRAM ............................................................................................................................................. 27

PICTORIAL DIAGRAM....................................................................................................................................... 29

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

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

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

R-4A56

SERVICE MANUAL

PRODUCT SPECIFICATIONS

SHARP CORPORATION

OSAKA, JAPAN

TEST PROCEDURE

SERVICING AND

TROUBLESHOOTING CHART

FUNCTION OF IMPORTANT

COMPONENTS

OPERATING SEQUENCE

APPEARANCE VIEW

MICROWAVE MEASUREMENT

WIRING DIAGRAM

PARTS LIST

TOUCH CONTROL PANEL

ASSEMBLY

COMPONENT REPLACEMENT

AND ADJUSTMENT PROCEDURE

MICROWAVE OVEN

R-4A56

GENERAL IMPORTANT INFORMATION

ThisManualhasbeenpreparedtoprovideSharpCorp.Service

engineers with Operation and Service Information.

It is recommended that service engineers carefully study the

entire text of this manual, so they will be qualified to render

satisfactory customer service.

CAUTION

MICROWAVE RADIATION

DO NOT BECOME EXPOSED TO RADIATION FROM

THE MICROWAVE GENERATOR OR OTHER PARTS

CONDUCTING MICROWAVE ENERGY.

Serviceengineersshouldnotbeexposedtothemicrowave

energy which may radiate from the magnetron or other

microwave generating devices if it is improperly used or

connected. All input and output microwave connections,

waveguides, flanges and gaskets must be secured. Never

operate the device without a microwave energy absorbing

load attached. Never look into an open waveguide or

antenna while the device is energized.

WARNING

Never operate the oven until the following points are ensured.

(A) The door is tightly closed.

(B) The door brackets and hinges are not defective.

(D) The door is not deformed or warped.

(E) There is not any other visible damage with the oven.

Servicing and repair work must be carried out only by trained

service engineers.

All the parts marked "*" on parts list are used at voltages more

than 250V.

Removal of the outer wrap gives access to potentials above

250V.

All the parts marked "∆" on parts list may cause undue

microwave exposure, by themselves, or when they are dam-

aged, loosened or removed.

R-4A56

PRODUCT SPECIFICATIONS

GENERAL INFORMATION

WARNING

THIS APPLIANCE MUST BE EARTHED

IMPOTANT

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

GREEN-AND-YELLOW : EARTH

BLUE : NEUTRAL

BROWN : LIVE

ITEM DESCRIPTION

Power Requirements 240 Volts (for Australia) / 230 - 240 Volts (for New Zealand)

50 Hertz

Single phase, 3 wire earthed

Power Consumption 1.4 kW

Power Output 900 watts nominal of RF microwave energy (IEC 705)

750 watts (2 litre water load)

Operating fequency 2450 MHz

Case Dimensions Width 550 mm

Height 312 mm

Depth 420 mm

Cooking Cavity Dimensions Width 381 mm

Height 210 mm

Depth 411 mm

Turntable diameter 360mm

Control Complement Touch Control System

Clock ( 1:00 - 12:59)

Timer (0 - 99 minutes 99 seconds)

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

INSTANT ACTION pads

AUTO COOK pad

EASY DEFROST pad

NUMBER pads

SERVE QUANTITY pads

POWER LEVEL pad

MORE, LESS pads

STOP/CLEAR pad

AUTO START/CLOCK pad

INSTANT COOK/START pad

Set Weight Approx. 17 kg

R-4A56

APPEARANCE VIEW

1. Ventilation openings

2. Oven lamp

3. Door hinges

4. Safety door latches

5. See through door

6. Coupling

7. Door open button

8. Touch control panel

9. Digital readout

10.Wave guide cover

11.Access cover for oven lamp

replacement

12.Power supply cord

111

12 11 1

12345

6789O

STOP

CLEAR

AUTO

START

CLOCK INSTANT COOK

START

MORE( ),LESS( )PADS

Presstoincrease/decreasethetime

inoneminuteincrementsduring

cookingortoalterthedonenessfor

theAutoCook,InstantActionor

EasyDefrostmode.

AUTOSTART/CLOCKPAD

PresstosetclockorAutoStarttime.

STOP/CLEARPAD

Presstoclearduringprogramming.

Pressoncetostopoperationof

ovenduringcooking;presstwice

tocancelcookingprograme.

NUMBER PADS

Presstoentercooklingtimes,clock

time,weightorquantityoffood,or

toselecttheAutocookmenus.

EASYDEFROSTPAD

Presstodefrostmeatbyentering

weightonly.

Reheat/Pies/Pastries

1 piece

12345

POWER

LEVEL

EASY

DEFROST



LESS 

2 X 3 X 4 X

AUTOCOOKPAD

PresstoselectAutoCookmode.

AUTOCOOKMENUS

POWERLEVELPAD

Presstoselectmicrowavepower

setting.Ifnotpressed,HIGHis 

automaticallyselected.

2,3,or4SERVEQUANTITYPAD

Tocooktwo,three,orfourserves,

pressrequiredpadpriortopressing

theInstantActionpad.

INSTANTCOOK/STARTPAD

Pressoncetocookfor1minuteatHIGH

orincreaseby1minutemultipleseachtime

thispadispressedduringcooking.

Presstostartovenaftersettingprogrammes.

INSTANTACTIONPADS

Pressoncetocook orreheat8

popular menus.

Rice & Pasta

1/2 uup

1 Fresh Vegetables

2 Frozen Vegetables

3 Jacket Potato

4 Roast Lamb

5 Seasoned Roast

6 Desserts

AUTO

COOK

Frozen 

Dinner

1 serve

Reheat

Beverage/Soup

1 cup

Chicken

Pieces

1 serve

Bacon

1 serve Casseroles

1 serve Fish Fillets

1 serve

TOUCH CONTROL PANEL

R-4A56

OPERATION SEQUENCE

OFF CONDITION

Closing the door activates all door interlock switches

(Upper latch switch, Lower 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, rated

voltage is supplied to the point (A3+A5) in the control unit.

Figure O-1 on page 27

1. The display flashes “88:88”.

2. Tosetanyprogramsorsettheclock,youmustfirsttouch

the STOP/CLEAR pad.

3. “ : “appearsinthe displayandthe timecountsup every

minute.

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

comes on at this time.

MICROWAVE COOKING CONDITION

HIGH COOKING

EnteradesiredcookingtimewiththetouchingNumberpads

and start the oven with touching START pad.

Function sequence

Figure O-2 on page 28

CONNECTED COMPONENTS RELAY

Oven lamp, Fan motor, Turntable motor RY1

Power transformer RY2

1. Rated voltage is supplied to the primary winding of the

powertransformer.Thevoltageisconvertedtoabout3.3

volts A.C. output on the filament winding and high

voltageofapproximately2000voltsA.C.onthesecondary

winding.

2. The filament winding voltage (3.3 volts) heats the

magnetron filament and the high voltage (2000 volts) is

senttothevoltagedoublingcircuit,whereitisdoubledto

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)intotheovencavity,wherethefoodisplacedto

be cooked.

4. When the cooking time is up, a signal 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

CONDITION

DURING DOOR OPEN

SWITCH CONTACT COOKING (NOCOOKING)

Upper latch switches COM-NO Closed Open

Lower latch switch COM-NO Closed Open

Monitor switch COM-NC Open Closed

Stop switch COM-NO Closed Open

The circuits to the power transformer, fan motor and

turntable motor are cut off when the upper latch switch,

lower 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

therelay(RY1) staysclosed.Shownin the displayisthe

remaining time.

6. MONITOR SWITCH CIRCUIT

The monitor switch is mechanically controlled by oven

door, and monitors the operation of the upper and lower

latch switches.

6-1 Whentheoven door isopenedduringor after thecycle

of a cooking program, the upper latch switch, lower

latch switch and stop switch must open their contacts

first.

Afterthatthecontacts(COM-NC)ofthemonitorswitch

can be closed.

6-2. Whentheoven door isclosed,thecontacts (COM-NC)

of the monitor switch must be opened first, and the

contacts(COM-NO) ofthe stop switchmust beclosed.

After that the contacts of the upper latch switch, lower

latch switch and stop switch are closed.

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

upperlatchswitchandlowerlatchswitchremainclosed.

The fuse M8A will blow, because the monitor switch is

closed and a short circuit is caused.

VARIABLE COOKING

When the microwave oven is preset for variable cooking

power.Ratedvoltageissuppliedtothepowertransformer

intermittently within a 32-second time base through the

relay contact which is coupled with the relay (RY2). The

following levels of microwave power are given.

SETTING;

32 sec. ON

24 sec. ON

18 sec. ON

12 sec. ON

6 sec. ON

8 sec. OFF

14 sec. OFF

20 sec. OFF

26 sec. OFF

HIGH

MEDIUM HIGH

MEDIUM

MEDIUM LOW

LOW

Approx. 70%

Approx. 50%

Approx. 30%

Approx. 10%

NOTE: TheON/OFFtimeratiodoesnotexactlycorrespond

to the percentage of microwave power, because

approx. 2 seconds are needed for heating up the

magnetron filament.

R-4A56

FUNCTION OF IMPORTANT COMPONENTS

DOOR OPEN MECHANISM

Thedoorcanbeopenedbypushingthedooropenbuttonon

thecontrolpanel.Whenthedooropenbuttonispushed,the

latch 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.

MONITOR

SWITCH

UPPER

LATCH

SWITCH

STOP

SWITCH

LOWER

LATCH

SWITCH

LATCH

LEVER PLUNGER

SWICTH

LATCH

HEAD

DOOR

OPEN

BUTTON

LATCH

HEAD

LATCH

HOOK

DOOR

Figure D-1. Door Open Mechanism

UPPER LATCH SWITCH, LOWER LATCH SWITCH

AND STOP SWITCH

1. Whenthe oven door is closed, the contacts (COM -NO)

must be closed.

2. Whentheovendoorisopened,thecontacts(COM-NO)

must be opened.

MONITOR SWITCH

1. When the oven door is closed, the contacts (COM- NC)

must be opened.

2. Whentheovendoorisopened,thecontacts(COM-NC)

must be closed.

3. If the oven door is opened and the contacts (COM- NO)

of the upper and lower latch switches fail to open, the

fuse(M8A)blowssimultaneouslywithclosingthecontacts

(COM-NC) of the monitor switch.

CAUTION: BEFOREREPLACINGABLOWNFUSE(M8A)

TEST THE UPPER AND LOWER LATCH

SWITCHES, MONITOR SWITCH AND MONI-

TORRESISTORFORPROPEROPERATION.

(REFERTOCHAPTER“TESTPROCEDURE”.)

MONITOR RESISTOR (0.8Ω20W)

Themonitorresistorpreventsthefuse(M8A)burstingwhen

the fuse blows due to the operation of the monitor switch.

ASYMMETRIC RECTIFIER

Theasymmetricrectifierisasolidstatedevicethatprevents

currentflow inboth directions. Andit preventsthe tempera-

tureriseofthepowertransformerbyblowingthefuse(M8A)

when the high voltage rectifier is shorted.

The rated peak reverse voltage of D1 of the asymmetric

rectifier is 6 KV The rated peak reverse voltage of D2 of the

asymmetricrectifieris1.7KV.D1andD2oftheasymmetric

rectifier or high voltage rectifier are shorted when the each

peak reverse voltage goes beyond the each rated peak

reverse voltage. (The process of blowing the fuse M8A.)

1. Thehighvoltagerectifierisshortedbyanycauseswhen

microwave cooking.

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

beyond the rated peak reverse voltage 1.7 KV in the

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 8A flow through the

primary winding of the power transformer.

6. The fuse (M8A) blows by the large electric currents.

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

THERMAL CUT-OUT 145˚C (OVEN)

The thermal cut-out located on the top of 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. How-

ever, when abnormally high temperatures are reached

within the oven cavity, the oven thermal cut-out will open at

145˚C, causing the oven to shut down. The thermal cut-out

will be close its contacts again when its temperature goes

down lower than -20˚C.

FUSE (M8A)

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.wireharness,H.V.capacitor,magnetronor

secondary winding of power transformer is shorted.

3. Thefusealsoblowswhenupperandlowerlatchswitches

remains closed with the oven door open and when the

monitor switch closes.

TEMPERATURE FUSE 150˚C (MG)

Thisfuseprotectsthemagnetronagainstoverheating.Ifthe

temperature goes up higher than 150˚C because the fan

motor is interrupted, the air inlet duct is blocked or the

ventilationopeningsareobstructed,thefuseblowsandputs

the oven out of operation.

The defective fuse must be replaced with new rated one.

D2 D1

ASYMMETRIC

RECTIFIER

HIGH VOLTAGE RECTIFIER

R-4A56

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 chan-

nelled through the oven cavity to remove steam and va-

pours given off from the heating foods. It is then exhausted

through the exhausting air vents at the oven cavity.

NOISE FILTER (for New Zealand Model)

The noise filter prevents the radio frequency interference

that might flow back in the power circuit.

SERVICING

WARNING TO SERVICE PERSONNEL

Microwave ovens contain circuitry capable of producing very high voltage and current, contact with any part of the

high voltage circuit will result in electrocution. High voltage capacitor, Power transformer, Magnetron, High voltage

rectifier assembly, High voltage harness.

REMEMBER TO CHECK 3D

1) Disconnect the supply.

2) Door opened, and wedged open.

3) Discharge high voltage capacitor.

WARNING: AGAINST THE CHARGE OF THE

HIGH-VOLTAGE CAPACITOR

The high-voltage capacitor remains charged about

60 seconds after the oven has been switched off.

Wait for 60 seconds and then short-circuit the con-

nection of the high-voltage capacitor (that is, of the

connectingleadofthe high-voltage rectifier)against

thechassiswiththe use ofaninsulatedscrewdriver.

Sharp recommend that wherever possible fault-finding

is carried out with the supply disconnected. It may in,

some cases, be necessary to connect the supply after

theoutercasehasbeenremoved,inthiseventcarryout

3D checks and then disconnect the leads to the primary

of the power transformer. Ensure that these leads re-

main isolated from other components and the oven

chassis. (Use insulation tape if necessary.) When the

testing is completed carry out 3D checks and reconnect

the leads to the primary of the power transformer.

REMEMBER TO CHECK 4R

1) Reconnectallleadsremovedfromcomponentsduring

testing.

2) Replace the outer case (cabinet).

3) Reconnect the supply.

4) Run the oven. Check all functions.

Microwave ovens should not be run empty. To test for

thepresenceof microwaveenergywithina cavity, place

acup ofcold water onthe oventurntable, close thedoor

andset themicrowavetimerfortwo(2)minutes.Setthe

powerlevel to HIGHandpush theSTARTbutton. When

the two minutes has elapsed (timer at zero) carefully

checkthatthewaterisnowhot.Ifthewaterremainscold

carry out 3D checks and re-examine the connections to

the component being tested.

Whenallserviceworkiscompleted,and the oven is fully assembled,themicrowavepoweroutputshouldbechecked

and microwave leakage test carried out

When troubleshooting the microwave oven, it is helpful to

follow the Sequence of Operation in performing the

checks. Many of the possible causes of trouble will require

that a specific test be performed. These tests are given a

procedure letter which will be found in the “Test Procedure

“section.

TROUBLESHOOTING GUIDE

IMPORTANT: Iftheovenbecomesinoperativebecauseof

a blown fuse M8A in the upper latch switch

- lower latch switch - monitor switch - moni-

tor resistor circuit, check the upper latch

switch, lower latch switch, monitor switch

and monitor resistor before replacing the

fuse M8A.

R-4A56

MAGNETRON

POWER TRANSFORMER

H.V. RECTIFIER ASSEMBLY

HIGH VOLTAGE CAPACITOR

UPPER LATCH SWITCH

LOWER LATCH SWITCH

STOP SWITCH

MONITOR SWITCH

NOISE FILTER (FOR N.Z.)

MONITOR RESISTOR

TEMPERATURE FUSE

THERMAL CUT-OUT

FAN MOTOR

TURNTABLE MOTOR

FUSE M8A

TOUCH CONTROL PANEL

RELAY (RY-1, RY-2)

FOIL PATERN ON P.W.B.

POWER SUPPLY CORD

OVEN LAMP OR SOCKET

HIGH OLTAGE WIRE

SHORTED WIRE HARNESS

OPENED WIRE HARNESS

WALL OUTLET

HOME FUSE OR BREAKER

WRONG OPERATION

MISADJUSTMENT SWITCH

BLOCKED COOLING FAN

BLOCKED VENTILATION OPENING

Home fuse blows when power

supplycordispluggedintowall

outlet.

FUSEM8Ablows when power

supplycordispluggedintowall

outlet.

"88:88"doesnotappearin dis-

play but power supply cord is

plugged into wall outlet.

Display doesnotoperateprop-

erly when STOP/CLEAR pad

is touched.

Oven lamp does not light at

door opened. (Display ap-

pears.)

Oven does not start when the

START pad is touched. (Dis-

play appears)

Oven lamp does not light (Dis-

play appears.)

Fan motor does not operate.

(Display appears.)

Turntablemotorassemblydoes

notoperate.(Displayappears.)

Oven or any electrical parts

does not stop when cooking

time is 0 or STOP/CLEAR pad

is touched.

Oven seems to be operating

butlittle or no heatisproduced

inovenload.(Microwavepower

level is set at HIGH)

Oven does not seems to be

operating properly when ME-

DIUM HIGH, MEDIUM, ME-

DIUM LOW or LOW is set.

(Oven operates properly at

HIGH and then the STOP/

CLEARpadistouchedtheoven

stops.)

Oven goes into cook cycle but

shutsdownbeforeendofcook-

ing cycle.

Oven stops as soon as when

the START pad is touched.

OFF

CONDITION

PROBLEM

CONDITION

POSSIBLE CAUSE

AND

DEFECTIVE PARTS

TEST PROCEDURE

CONDITION

CK = Check / RE = Replace

ABC

EEEEFGHHI I JKMNRE RE CK CKCKCK CKCKCK CKCK

R-4A56

TEST PROCEDURES

PROCEDURE

LETTER

CARRY OUT 3D CHECKS.

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

To test for an open circuit filament use an ohmmeter to make a continuity test between the magnetron

filament terminals, the meter should show a reading of less than 1 ohm.

To test for short filament to anode condition, connect ohmmeter between one of the filament terminals

and the case of the magnetron (ground). This test should be indicated an infinite resistance. If a low or

zero resistance reading is obtained then the magnetron should be replaced.

MICROWAVE OUTPUT POWER (1 Litre water load)

The following test procedure should be carried out with the microwave oven in a fully assembled

condition (outer case fitted). Microwave output power from the magnetron can be measured by way of

IEC 705, i.e. it can be measured by using water load how much it can be absorbed by the water load.

Tomeasurethemicrowaveoutputpower in themicrowave oven,therelationofcalorieandwattis 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.

NEVER TOUCH ANY PART IN THE CIRCUIT WITH YOUR HAND OR AN INSULATED TOOL

WHILE THE OVEN IS IN OPERATION.

AMAGNETRON TEST

The formula is as follows;

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

Our condition for water load is as follows:

Room temperature..............around 20°C PowersupplyVoltage.........Ratedvoltage

Water load.........1000 g Initial temperature...........10±2°C Heating time.........47 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 the test.

3. Temperature of the water

The initial temperature of the water is (10±2)°C.

4. Selectthe initial andfinal watertemperatureso thatthemaximum differencebetweenthe finalwater

temperature and the ambient temperature is 5˚C.

5. Select stirring devices and measuring instruments in order to minimize addition or removal of heat.

6. Thegraduationofthethermometermustbe scaled by 0.1°C at minimumand accuratethermometer.

7. The water load must be (1000±5) g.

8. “t” is measured while the microwave generator is operating at full power. Magnetron filament heat-

up time is not included.

NOTE: The operation time of the microwave oven is “t + 2” sec. 2 sec. is magnetron filament heat-up time.

Measuring method:

1. Measure the initial temperature of the water before the water is added to the vessel.

(Example: The initial temperature T1 = 11°C)

2. Add the 1 litre water to the vessel.

3. Place the load on the centre of the shelf.

4. Operate the microwave oven at HIGH for the temperature of the water rises by a value ∆T of

(10 ±2)˚C.

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

COMPONENT TEST

R-4A56

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 + 2) = 49sec....................................................................... 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

JUDGMENT: The measured output power should be at least ±15 % of the rated output power.

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

INSUFFICIENT.

1000g

T1˚C T2˚C

Heat up for 49 sec.

MICROWAVE OUTPUT POWER (2 Litre water load)

The following test procedure should be carried out with the microwave oven in a fully assembled

condition (with outer case fitted).

Microwave output power from the magnetron can be measured by way of substitution, i.e. it can be

measured by using a water load how much it can be absorbed by the water load. To measure the

microwave output power in the microwave oven, the relation of calorie and watt is used.

Ontheotherhand,ifthetemperature of the waterwith V(ml)rises∆T(˚C)duringthis microwave heating

period, the calorie of the water is V x ∆T.

The formula is as follows;

P = 8330 x ∆T/t

Our condition for water load is as follows:

Room temperature..............23±2˚C Power supply Voltage.........Rated voltage

Water load.........2000 ml Initial temperature...........23±1˚C Heating time .1 min. 51sec.

P = 75 x ∆T

Measuring method:

A) The two water containers must be prepared.

Thewatercontainermustbeone(1)litrebeakermadeofPyrex glassanditsdiameterapproximately

12cm.

B) Putthe one (1)litre water intoeachbeaker (Eachbeakerhas onelitrewater). Theinitialtemperature

of the water should be 23±1˚C.

C) Mark T1 on the one beaker and mark T2 on the other one. And stir the water and measure the

temperature of water the thermometer and note them. The graduation of the thermometer must be

scaled by 0.1˚C at minimum and an accurate mercury thermometer is recommended.

D) Place the two (2) beakers as touching each other in the centre of the oven cavity.

E) Set the timer to 1 minutes and 51 seconds, start the oven at 100% power.

F) The time must be measured with stopwatch or wristwatch.

G) After 1 minutes and 51 seconds, stop the oven by opening the door.

H) Put the two (2) beakers out of the oven cavity and measure the temperature of the water by stirring

the water with thermometer and note them.

R-4A56

TEST PROCEDURES (CONT'D)

BPOWER TRANSFORMER TEST

WARNING: Highvoltagesandlargecurrentsarepresentatthesecondarywindingandfilament

winding of the transformer. It is very dangerous to work near this part when the

oven is on. NEVER make any voltage measurements of the high-voltage circuits,

including the magnetron filament.

CARRY OUT 3D CHECKS.

Disconnect the leads to the primary winding of the power transformer. Disconnect the filament and

secondarywindingconnectionsfromtherestoftheHVcircuitry.Usinganohmmeter,setonalowrange,

it is possible to check the continuity of all three windings. The following readings should be obtained:

a. Primary winding ................... approx. 1.54 Ω

b. Secondary winding............... approx. 84.8 Ω

c. Filament winding .................. less than 1Ω

Ifthereadingobtainedarenotstatedasabove,thenthepowertransformerisprobablyfaultyandshould

be replaced.

CARRY OUT 4R CHECKS.

C HIGH VOLTAGE RECTIFIER ASSEMBLY TEST

HIGH VOLTAGE RECTIFIER TEST

CARRY OUT 3D CHECKS.

Isolate the high voltage rectifier assembly from the HV circuit. The high voltage rectifier can be tested

using an ohmmeter set to its highest range. Connect the ohmmeter across the terminal B+C of the high

voltage rectifier and note the reading obtained. Reverse the meter leads and note this second reading.

The normal resistance is infinite in one direction and more than 100 kΩin the other direction.

Example

Initial temperature .............................................................................T1 = 23˚C T2 = 24˚C

Temperature after 1 min. 51 sec. ..................................................... T1 = 33˚C T2 = 34˚C

Temperature difference Cold-Warm.............................................. ∆T1 = 10˚C ∆T2 = 10˚C

Mean temperature rise ∆T......................... ∆T = (∆T1 ±∆T2) / 2 = (10˚C+10˚C) / 2 = 10˚C

Measured output power

The equation is P= 75 x ∆T ......................................................... P= 75 x 10˚C =750 Watts

NOTE: The measured output power should be at least ±15 % of the rated output power.

CAUTION: 1˚C CORRESPONDS TO 75 WATTS. REPEAT MEASUREMENT IF THE POWER IS

INSUFFICIENT.

COMPONENT TEST

PROCEDURE

LETTER

1 l 1 l

(T1 C) (T2 C)

1 l 1 l

(T1 C) (T2 C)

Heat up for 1min. 51 sec.

1 litre 1 litre 1 litre 1 litre

R-4A56

TEST PROCEDURES (CONT'D)

CARRY OUT 4R CHECKS.

ASYMMETRIC RECTIFIER TEST

CARRY OUT 3D CHECKS.

Isolate the high voltage rectifier assembly from the HV circuit. The asymmetric can be tested using an

ohmmeter set to its highest range across the terminals A+B of the asymmetric rectifier and note the

reading obtained. Reverse the meter leads and note this second reading. If an open circuit is indicated

in both direction then the asymmetric rectifier is good. If an asymmetric rectifier is shorted in either

direction,thentheasymmetricrectifierisprobablyfaultyandmustbereplacedwithhighvoltagerectifier.

Whentheasymmetricrectifierisdefective,checkwhethermagnetron,highvoltagerectifier,highvoltage

wire or filament winding of the power transformer is shorted.

CARRY OUT 4R CHECKS.

NOTE: FOR MEASUREMENT OF THE RESISTANCE OF THE RECTIFIER, THE BATTERIES OF THE

MEASURING INSTRUMENT MUST HAVE A VOLTAGE AT LEAST 6 VOLTS, BECAUSE

OTHERWISE AN INFINITE RESISTANCE MIGHT BE SHOWN IN BOTH DIRECTIONS.

PROCEDURE

LETTER COMPONENT TEST

D2 D1

ASYMMETRIC

RECTIFIER

HIGH VOLTAGE RECTIFIER

D HIGH VOLTAGE CAPACITOR TEST

CARRY OUT 3D CHECKS.

A. Isolate the high voltage capacitor from the circuit.

B. Continuity check must be carried out with measuring instrument which is set to the highest resistance

range.

C. Anormalcapacitorshowscontinuityforashorttime(kick)andthenaresistanceofabout10MΩafterithas

been charged.

D. A short-circuited capacitor shows continuity all the time.

E. An open capacitor constantly shows a resistance about 10 MΩbecause of its internal 10MΩresistance.

F. When the internal wire is opened in the high voltage capacitor shows an infinite resistance.

G. The resistance across all the terminals and the chassis must be infinite when the capacitor is normal.

If incorrect reading are obtained, the high voltage capacitor must be replaced.

CARRY OUT 4R CHECKS.

ESWITCH TEST

CARRY OUT 3D CHECKS.

Isolate the switch to be tested and using an ohmmeter check between the terminals as described in the

following table. Table: Terminal Connection of Switch

Plunger Operation COM to NO COM to NC

Released O.C. S.C.

Depressed S.C. O.C.

COM; Common terminal,

NO; Normally open terminal

NC; Normally close terminal

S.C.; Short circuit

O.C.; Open circuit

If incorrect readings are obtained, make the necessary switch adjustment or replace the switch.

CARRY OUT 4R CHECKS.

FNOISE FILTER TEST

CARRY OUT 3D CHECKS.

Disconnect the leads from the terminals of the noise

filter.Usinganohmmeter,check between theterminals

as described in the following table. L (min) Cx ±20% Cy ±20%

1.0 mH 0.068µF 2200pF

If incorrect readings are ob-

tained,replacethenoisefilter

unit.

CARRY OUT 4R CHECKS.

MEASURING POINT INDICATION OF OHMMETER

Between N and L Open circuit

Between terminal N and WHITE Short circuit

Between terminal L and RED Short circuit

M8A

Cy RED

WHT

R-4A56

PROCEDURE

LETTER COMPONENT TEST

TEST PROCEDURES (CONT'D)

GMONITOR RESISTOR TEST

CARRY OUT 3D CHECKS.

Disconnecttheleadsfromthemonitorresist.Usinganohmmeterandsetonalowrange.Checkbetween

the terminals of the monitor resistor.

The resistance of monitor resistor is approx. 0.8 ohms.

If incorrect readings are obtained, replace the monitor resistor.

CARRY OUT 4R CHECKS.

H TEMPERATURE FUSE OR THERMAL CUT-OUT TEST

CARRY OUT 3D CHECKS.

Disconnect the leads from the terminals of the temperature fuse or thermal cut-out. Then using an

ohmmeter, make a continuity test across the two terminals as described in the table below.

CARRY OUT 4R CHECKS .Table: Thermal cut-out Test

Temperature of "ON" condition Temperature of "OFF" condition Indication ofohmmeter

Parts Name (closed circuit) (˚C) (open circuit) (˚C) (When room temperature

is approx. 20˚C)

Thermal cut-out 145˚C -20˚C Above 145˚C Closed circuit.

Temperature fuse 150˚C This is not resetable type Above 150˚C Closed circuit.

If incorrect readings are obtained, replace the temperature fuse or thermal cut-out.

Anopencircuittemperature fuse 150˚C(MG)indicatesthatthe magnetron hasoverheated,thismaybe

due to restricted ventilation, cooling fan failure or a fault condition within the magnetron or HV circuit.

An open circuit thermal cut-out 145˚C (OVEN) indicates that the foods in the oven may catch fire, this

may be due to over heating produced by improper setting of the cooking time or failure of the control

panel.

CARRY OUT 3D CHECKS.

Disconnect the leads from the motor.

Using an ohmmeter, check the resistance between the two terminals as described in the table below.

IMOTOR WINDING TEST

Table: Resistance of Motor

Motors Resistance

Fan motor Approximately 295 Ω

Turntable motor Approximately 12.5 kΩ

If incorrect readings are obtained, replace the motor.

CARRY OUT 4R CHECKS.

LIVE TEST FOR MOTOR WINDINGS

CAUTION: THE FOLLOWING PROCEDURE REQUIRES THE OVEN TO BE CONNECTED TO THE

SUPPLYAND SHOULDONLY BE USEDIF THERELEVANT “COLD” CHECKSFOR THE

MOTOR UNDER TEST ARE INCONCLUSIVE.

1. CARRY OUT 3D CHECKS.

2. Disconnect the leads from the primary of the power transformer. Make sure that the leads remain

isolated from other oven components and chassis. (Use insulation tape if necessary.)

3. Connect a voltmeter, set to 250V AC, across the motor terminals. (Refer to the relevant motor test

procedure or pictorial diagram for the correct terminal numbers.)

4. Arrange the meter in a position where it can be read during the test.

(Do not touch the meter, meter leads or oven circuitry while the oven is active.)

R-4A56

TEST PROCEDURES (CONT'D)

PROCEDURE

LETTER COMPONENT TEST

5. Close the oven door.

6. Set the power level to HIGH and set the relevant timer for about three (3) minutes.

7. Note the reading on the meter and carefully observe the motor under test to see if it is turning.

8. CARRY OUT 3D CHECKS.

9. Remove test meter leads.

10.Reconnect the leads to the primary of the power transformer.

If a reading of the line voltage was obtained (step 7) but the motor was not turning then it is faulty and

shouldbereplaced.If the meterindicatedthatnosupplywaspresentthenthewiringtothemotorshould

be checked for continuity.

JBLOWN FUSE F M8A

CARRY OUT 3D CHECKS.

1. If the fuse M8A is blown, there could be shorts or ground in electrical parts or wire harness.

Check them and replace the defective parts or repair the wire harness.

2. If the fuse M8A is blown when the door is opened, check the upper latch switch, lower latch switch,

monitor switch and monitor resistor.

IfthefuseM8Aisblownbyincorrectdoorswitchingreplacethedefectiveswitch(s)andthefuseM8A.

3. Ifthe fuseM8A isblown, therecould bea shortin the asymmetric rectifier or there couldbe aground

in wire harness. A short in the asymmetric rectifier may have occurred due to short or ground in H.V.

rectifier, magnetron, power transformer or H.V. wire. Check them and replace the defective parts or

repair the wire harness.

CARRY OUT 4R CHECKS.

CAUTION: ONLY REPLACE FUSE M8A WITH THE CORRECT VALUE REPLACEMENT

The touch control panel consists of circuits including semiconductors such as LSI, ICs, etc. Therefore,

unlike conventional microwave ovens, proper maintenance cannot be performed with only a voltmeter

and ohmmeter.

In this service manual, the touch control panel assembly is divided into two units, Control Unit and Key

Unit, and troubleshooting by replacement is described according to the symptoms indicated.

1. Key Unit.

The following symptoms indicate a defective key unit. Replace the key unit.

a) When touching the pads, a certain pad produces no signal at all.

b) When touching a number pad, two figures or more are displayed.

c) When touching the pads, sometimes a pad produces no signal.

2. Control Panel

The following symptoms indicate a defective control unit. Replacing the control unit.

2-1 In connection with pads.

a) When touching the pads, a certain group of pads do not produce a signal.

b) When touching the pads, no pads produce a signal.

2-2 In connection with indicators

a) At a certain digit, all or some segments do not light up.

b) At a certain digit, brightness is low.

c) Only one indicator does not light.

d) The corresponding segments of all digits do not light up; or they continue to light up.

e) Wrong figure appears.

f) A certain group of indicators do not light up.

g) The figure of all digits flicker.

2-3 Other possible troubles caused by defective control unit.

a) Buzzer does not sound or continues to sound.

b) Clock does not operate properly.

c) Cooking is not possible.

d) Proper temperature measurement is not obtained.

K TOUCH CONTROL PANEL ASSEMBLY TEST

R-4A56

TEST PROCEDURES (CONT'D)

PROCEDURE

LETTER COMPONENT TEST

IfthedisplayfailstoclearwhentheSTOP/CLEARpadisdepressed,firstverifytheribbonismakinggood

contact,verifythatthedoorsensingswitch(stopswitch)operatesproperly;thatisthecontactsareclosed

whenthedoorisclosedandopenwhenthedoorisopen.Ifthedoor sensingswitch(stopswitch)isgood,

disconnect the flat ribbon that connects the key unit to the control unit and make sure the door sensing

switch is closed (either close the door or short the stop switch connecter). Use the Key unit matrix

indicated on the control panel schematic and place a jumper wire between the pins that correspond to

the STOP/CLEAR pad making momentary contact. If the control unit responds by clearing with a beep

the key unit is faulty and must be replaced. If the control unit does not respond, it is a faulty and must

bereplaced. Ifaspecificpaddoesnotrespond,theabovemethodmaybeused(afterclearingthecontrol

unit) to determine if the control unit or key pad is at fault.

L KEY UNIT TEST

KEY UNIT

STOP

CLEAR

POWER

LEVEL

G-12

G-11

G-10

G-9

G-8 G-7 G-6 G-5 G-4 G-3 G-2 G-1

LESS

234

890

AUTO

COOK

AUTO

START

CLOCK

EASY

DEFROST

Reheat

Beverage

/Soup

INSTANT

COOK

START

Rice

Pasta

Frozen

Dinner

4 X 3 X 2 X

Bacon

Casseroles Chicken

Pieces

Reheat

Pie/

Pastries

Fish

Fillets

MRELAY TEST

1. CARRY OUT 3D CHECKS.

2. Disconnect the leads from the primary of the power transformer, Make sure that the leads remain

isolated from other oven components and chassis. (Use insulation tape if necessary)

3. Close the door.

4. Reconnect the supply.

5. Check the voltage between Pin Numbers 3 and 5 of 3-pin connector (A) on the control unit with an

A.C. voltmeter. The meter should indicated 240 volts, if no cheak oven circuit.

6. RY1 AND RY2 Test

These are operated by D.C. voltage. Check voltage at the relay coil with a D.C. voltmeter during the

microwave cooking.

DC. voltage indicated ................... Defective relay.

DC. voltage not indicated ................Check diode which is connected to the relay coil. If diode is

good, control unit is defective.

RELAY SYMBOL OPERATIONAL VOLTAGE CONNECTED COMPONENTS

RY1 APPROX. 26.5V D.C. Oven lamp / Turntable motor / Cooling fan motor

RY2 APPROX. 25.8V D.C. Power transformer

R-4A56

TEST PROCEDURES (CONT'D)

PROCEDURE

LETTER COMPONENT TEST

N PROCEDURES TO BE TAKEN WHEN THE FOIL PATTERN ON THE PRINTED WIRING BOARD

(PWB) IS OPEN

To protect the electronic circuits, this model is provided with a fine foil pattern added to the primary on

thePWB, this foilpattern actsasa fuse.Ifthe foilpatternis open,followthe troubleshootingguidegiven

below for repair.

Problem: POWER ON, indicator does not light up.

NOTE: At the time of these repairs, make a visual

inspectionofthevaristorforburningdamage

andexaminethetransformerwithtesterfor

the presence of layer short-circuit (check

primary coil resistance). If any abnormal

conditionisdetected,replacethedefective

parts.

CARRY OUT 4R CHECKS.

RY2

US:RED,CD:GRY

GE:BLK,AS:BRN

D32

(TAB1)

(COM.)

(TAB2)

(H.V.)

(J1)

VRS1

D31

(H.V.)

POWER

O.L.,F.M.,T.T.M.,

CN–A

RY1

5731

d c

STEPS OCCURANCE CAUSE OR CORRECTION

1 The rated voltage is not applied to POWER Check supply voltage and oven main unit.

terminal of CPU connector (CN-A).

2 The rated voltage is applied to primary side Low voltage transformer or secondary circuit defective.

of low voltage transformer. Check and repair.

3 Only pattern at "a" is broken. *Insert jumper wire J1 and solder.

(CARRY OUT 3D CHECKS BEFORE REPAIR)

4 Pattern at "a" and "b" are broken. *Insert the coil RCILF2003YAZZ between "c" and "d".

(CARRY OUT 3D CHECKS BEFORE REPAIR)

R-4A56

TOUCH CONTROL PANEL ASSEMBLY

OUTLINE OF TOIUCH CONTROL PANEL

3) Synchronizing Signal Circuit

This power source synchronizing signal is available in

order to compose a basic standard time in the clock

circuit. It accompanies a very small error because it

works on commercial frequency.

4) ACL Circuit

AcircuittogenerateasignalswhichresetstheLSItothe

initial state when power is supplied.

5) Buzzer Circuit

The buzzer is responsive to signals from the LSI to emit

noticingsounds(keytouchsoundandcompletionsound).

6) Door Sensing Switch

A switch to “tell” the LSI if the door is open or closed.

7) Relay Circuit

To drive the magnetron, fan motor, turntable motor and

light the oven lamp.

8) Indicator Circuit

Indicator element is a Fluorescent Display.

Basically, a Fluorescent Display is triode having a

cathode, a grid and an anode. Usually, the cathode of a

Fluorescent Display is directly heated and the filament

serves as cathode.

The Fluorescent Display has 6-digits, 13-segments are

used for displaying figures.

The touch control section consists of the following unit as

shown in the touch control panel circuit.

(1) Key Unit

(2) Control Unit

The principal functions of these units and the signals com-

municated among them are explained below.

Key Unit

The key unit is composed of a matrix, signals generated in

the LSI are sent to the key unit through R00-R03,R10-R13.

When a key pad is touched, a signal is completed through

the key unit and passed back to the LSI through R23,R30-

R32to perform the function that was requested.

Control Unit

Control unit consists of LSI, power source circuit, synchro-

nizingsignalcircuit,ACLcircuit,buzzercircuitandindicator

circuit.

1) LSI

This LSI controls the key strobe signal, relay driving

signal for oven function and indicator signal.

2) Power Source Circuit

This circuit generates voltages necessary in the control

unit.

Symbol Voltage Application

VC -5V LSI(IC1)

VP -29V Fluorescentdisplaytube:Grid

and anode voltage

VF1 3Vac Filamentoffluorescentdisplay

tube

VF2 (VF1 to VF2 voltage)

R-4A56

DESCRIPTION OF LSI

LSI(IZA430DR)

The I/O signal of the LSI(IZA430DR) is detailed in the following table.

Pin No. Signal I/O Description

1 D10 OUT Digit selection signal.

Refer to the touch control panel circuit about the relation between signals and digits.

Normally,onepulseisoutputineverysynchronizedsignalperiod,andinputtothegrid

of the fluorescent display.

2 D11 OUT Segment data signals.

Refer to the touch control panel circuit for the relationship between signals and

indicators. Normally, one pulse is output in every synchronized signal period, and

input to the anode of the fluorescent display.

3 TG1 OUT Signal to sound buzzer.

A: key touch sound (0.12sec.).

B: Completion sound (2.4sec.).

4 Vdisp IN Anode (segment) of Fluorescent Display illumination voltage:-29V.

Vp voltage of power source circuit input.

5R00OUT Segment data signal.

Signal similar to D11.

Key strobe signal.