Sharp R-3a56 User manual

R-3A56

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-3A56

S7403R3A56PJZ

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 .......................................................................................................................................................... 7

TEST PROCEDURE ............................................................................................................................................ 9

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

COMPONENT REPLACEMENT AND ADJUSTMENT PROCEDURE............................................................... 21

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

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

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

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

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

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

R-3A56

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

R3A56

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-3A56

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 1.35 kW

Power Output 850 watts nominal of RF microwave energy (IEC 705)

750 watts (2 litre water load)

Operating fequency 2450 MHz

Case Dimensions Width 520 mm

Height 305 mm including foot

Depth 385 mm

Cooking Cavity Dimensions Width 348 mm

Height 197 mm

Depth 368 mm

Turntable diameter 325mm

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 (3 menus)

AUTO COOK pad

CONVENIENCE MEALS

EASY DEFROST pad

NUMBER pads

POWER LEVEL pad

MORE, LESS pads

STOP/CLEAR pad

AUTO START/CLOCK pad

INSTANT COOK/START pad

Set Weight Approx. 15 kg

R-3A56

APPEARANCE VIEW

1. Ventilation opening

2. Oven lamp

3. Door hinges

4. Door safety latches

5. See through door

6. Coupling

7. Door open button

8. Touch control panel

9. Digital readout

10.Wave guide cover

11.Rating label

12.Turntable

13. Roller stay

46

10

1(Rear)



5

11

12345

6789O

STOP

CLEAR

AUTO

START

CLOCK INSTANT COOK

START

Frozen Dinner

1 serve

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

Beverage

1 cup

Reheat 

Pizza

1 piece

Reheat 

Pie

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 3popular

menuS.

Pasta Meal

1 serve

1 Fresh Vegetables

2 Frozen Vegetables

3 Jacket Potato

4 Roast Lamb

5 Comed Meat

6 Chicken Pieces

7 Rice & Pasta 

8 Desserts

CONVENIENCE MEALS

AUTO

COOK

CONVVENIENTMEALSPADS

Pressoncetocook.

TOUCH CONTROL PANEL

HIGH

DEFROST

REHEAT

COOK

AUTO Kg

MED LOW

Indicator

R-3A56

OPERATION SEQUENCE

OFF CONDITION

Closing the door activates all door interlock switches

(1st. latch switch, 2nd. 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. To set any programmes or set the clock, you must first

touch the STOP/CLEAR pad.

3. "88:88" appears in the display and the time counts up

every minute.

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 touching NUMBER

pad 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 channeled through the waveguide (transport

channel)intotheovencavity,wherethefoodisplacedto

be cooked.

4. When the cooking time is up, a signal tone is heard and

therelaysRY1+RY2gobacktotheirhomeposition.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)

1st. latch switches COM-NO Closed Open

2nd. 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 1st. latch switch,

2nd. 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 is mechanically controlled by oven

door, and monitors the operation of the 1st and 2nd.

latch switches.

6-1 Whentheoven door isopenedduringor after thecycle

of a cooking program, the 1st. latch switch, 2nd. 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. After that the

contacts of the 1st. latch switch, 2nd. latch switch and

stop switch are closed.

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

the1st. latch switch, 2nd. latch switch remain closed.

The fuse M8A 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, 230-240 volts A.C. power is supplied to the power

transformer intermittently within a 32-second time base

through the relay contact which is coupled with the current-

limiting relay. 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-3A56

FUNCTION OF IMPORTANT COMPONENTS

DOOR OPEN MECHANISM

The door is opened by pushing the open button on the

control panel, refer to the Figure D-1.

Whentheopenbuttonispushed,theopenbuttonpushesup

theswitchlever,andthentheswitchleverpushesupthethe

latch head. The latch heads are moved upward and re-

leased from latch hook. Now the door will open.

LATCH

HEADS

LATCH HOOK

2ND. LATCH

SWITCH

MONITOR 

SWITCH

SWITCH

LEVER

STOP SWITCH

1ST. LATCH

SWITCH

Figure D-1. Door Open Mechanism

1ST. LATCH SWITCH, 2ND. LATCH SWITCH AND

STOP SWITCH

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

must be closed.

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

ofthe 1st.latch switch and2nd. latchswitch failto open,

the fuse M8A blows simultaneously with closing the

contacts (COM-NC) of the monitor switch.

CAUTION: BEFORE REPLACING A BLOWN FUSE M8A

TESTTHE1ST.LATCHSWITCH, 2ND.LATCH

SWITCH MONITOR SWITCH AND MONITOR

RESISTOR FOR PROPER OPERATION.

MONITOR RESISTOR R 0.8Ω20W

The monitor resistor prevents the fuse M8A bursting when

the fuse M8A blows due to the operation of the monitor

switch.

ASYMMETRIC RECTIFIER

Theasymmetricrectifierisasolidstatedevicethatprevents

currentflow inboth directions. Andit preventsthe tempera-

ture rise of the power transformer by blowing the fuse M8A

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

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. ThelargeelectriccurrentsbeyondM8Aflowthroughthe

primary winding of the power transformer.

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

7. The power supply to the all electrical parts are cut off.

FUSE M8A

1. ThefuseM8Ablowswhenthecontacts(COM-NO)ofthe

1st.latchswitchand2nd.latchswitchremainclosedwith

theovendooropenandwhenthemonitorswitchcloses.

2. The fuse M8A also blows when asymmetric rectifier,

H.V. rectifier, H.V. wire harness, H.V.capacitor,

magnetronorsecondarywindingofpowertransformeris

shorted.

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

circuited, this fuse M8A blows to prevent an electric

shock or fire hazard.

THERMAL CUT-OUT TC 145˚C (MG)

This thermal cut-out protects the magnetron against over-

heating. If the temperature goes up higher than 145˚C

because the fan motor is interrupted, the ventilation open-

ings are blocked, the thermal cut-out will open and the line

voltages to the power transformer will be cut off and the

operation of the magnetron will be stopped.

The defective thermal cut-out must be replaced with new

one.

THERMAL CUT-OUT TC 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

R-3A56

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 defective

thermal cut-out must be replace with new one.

THERMAL CUT-OUT 95˚C (FAN MOTOR)

Thethermalcut-outprotect the fanmotoragainstoverheat-

ing.Ifitstemperaturegoesuphigherthan95˚Cbecausethe

fanmotor islocked or theventilation operatingare blocked,

the contacts of the thermal cut-out will open and switch off

the oven. When the oven cools itself down to 75˚C, the

contacts of the thermal cut-out will close again.

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

themagnetronandcoolsthemagnetron.Thisairischanneled

through the oven cavity to remove steam and vapors given

off from the heating foods. It is then exhausted through the

exhausting air vents at the oven cavity

NOISE FILTER (FOR NEW ZEALAND)

The noise filter prevents the radio frequency interference

that might flow back in the power circuit.

R-3A56

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 1st. latch switch -

2nd. latch switch - monitor switch - monitor

resistor circuit, check the 1st. latch switch,

2nd.latchswitch,monitorswitchand moni-

tor resistor before replacing the fuse M8A.

R-3A56

MAGNETRON

POWER TRANSFORMER

H.V. RECTIFIER ASSEMBLY

HIGH VOLTAGE CAPACITOR

1ST. LATCH SWITCH

2ND. LATCH SWITCH

STOP SWITCH

MONITOR SWITCH

MONITOR RESISTOR

TEMPERATURE FUSE 95˚C

THERMAL CUT-OUT 145˚C

FAN MOTOR

TURNTABLE MOTOR

FUSE M8A

TOUCH CONTROL PANEL

KEY UNIT

RELAY (RY-1, RY-2)

FOIL PATERN ON P.W.B.

POWER SUPPLY CORD

SHORTED WIRE HARNESS

OPENED WIRE HARNESS

OVEN LAMP OR SOCKET

WALL OUTLET

MISADJUSTMENT SWITCH

HOME FUSE OR BREAKER

BLOCKED COOLING FAN

BLOCKED VENTILATION

NOISE FILTER (FOR N.Z.)

Home fuse blows when power

supply cord is plugged into wall

outlet.

FUSE M8A blows when power

supply cord is plugged into wall

outlet.

"88:88"doesnotappearindisplay

but power supply cord is plugged

into wall outlet.

Display does not operate prop-

erly when STOP/CLEAR pad is

touched.

Oven lamp does not light at door

opened. (Display appears.)

Oven does not start when the

START pad is touched. (Display

appears)

Ovenlampdoesnot light(Display

appears.)

Fanmotordoesnotoperate.(Dis-

play appears.)

Turntable motor assembly does

not operate. (Display appears.)

Oven or any electrical parts does

notstopwhen cookingtimeis0or

STOP/CLEAR pad is touched.

Oven seems to be operating but

little or no heat is produced in

ovenload.(Microwavepowerlevel

is set at HIGH)

Oven does not seems to be oper-

ating properly when MEDIUM

HIGH, MEDIUM, MEDIUM LOW

or LOW is set. (Oven operates

properly at HIGH and then the

STOP/CLEARpad is touched the

oven stops.)

Oven goes into cook cycle but

shutsdownbeforeendofcooking

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

EEEEGFFHHIJKLMRECK CKRE CK CKCKCK CKN

R-3A56

TEST PROCEDURES

PROCEDURE

LETTER

CARRY OUT 3D CHECK.

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

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

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

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

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

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

MICROWAVE OUTPUT POWER (1 Litre water load)

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

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

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

Tomeasurethemicrowaveoutputpower in 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.........49 sec.

P = 85 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 5K.

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

6. Thegraduationofthethermometermustbe scaled by 0.1°C at minimum andaccurate 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 + 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-3A56

TEST PROCEDURES

PROCEDURE

LETTER COMPONENT TEST

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

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

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

Temperature after (49 + 2) = 51 sec...................................................................... T2 = 21°C

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

Measured output power

The equation is “P = 85 x ∆T”....................................................... P = 85 x 10°C = 850 Watts

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

CAUTION: 1°C CORRESPONDS TO 85 WATTS REPEAT MEASUREMENT IF THE POWER IS

INSUFFICIENT.

1000g

T1˚C T2˚C

Heat up for51 sec.

MICROWAVE OUTPUT POWER (2 Litre water load)

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

condition (with outer case fitted).

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

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

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

Ontheotherhand,ifthetemperature of the 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

Our condition for water load is as follows:

Room temperature..............around 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-3A56

TEST PROCEDURES (CONT'D)

BPOWER TRANSFORMER TEST

WARNING: Highvoltagesandlargecurrentsarepresentatthesecondarywindingandfilament

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

on.NEVERmake anyvoltagemeasurementsofthehigh-voltagecircuits,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. 1.73 Ω

b. Secondary winding............... approx. 104.7 Ω

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

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

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.

R-3A56

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,

O.C.; Open circuit

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

CARRY OUT 4R CHECKS.

ETHERMAL CUT-OUT TEST

CARRY OUT 3D CHECKS.

Disconnect the leads from the terminals of the 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 Below- 20˚C Above 145˚C Closed circuit.

Thermal cut-out 95˚C Below 75˚C Above 95˚C Closed circuit.

R-3A56

PROCEDURE

LETTER COMPONENT TEST

TEST PROCEDURES (CONT'D)

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

An open circuit thermal cut-out 145˚C (MG) indicates that the magnetron has overheated, this may be

due to resistricted 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.

An open circuit thermal cut-out 95˚C (FAN) indicates that the fan motor winding has overheated, this

may be due to blocked ventilation or locked cooling fan.

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.

G MONITOR RESISTOR TEST

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.

HMOTOR WINDING TEST

Table: Resistance of Motor

Motors Resistance

Fan motor Approximately 370 Ω

Turntable motor Approximately 16.08 kΩ

If incorrect readings are obtained, replace the motor. CARRY OUT 4R CHECKS

J TOUCH CONTROL PANEL ASSEMBLY TEST

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

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

andohmmeter.Inthisservicemanual,thetouchcontrolpanelassemblyisdividedintotwounits,Control

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

indicated.

IBLOWN 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 2nd. 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 occured 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

R-3A56

TEST PROCEDURES (CONT'D)

PROCEDURE

LETTER COMPONENT TEST

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 problems 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.

K KEY UNIT TEST

IfthedisplayfailstoclearwhentheSTOP/CLEARpadisdepressed.firstverifytheribbonismakinggood

contact,verifythatthedoorsensingswitch(stopswitch)operatesproperly;thatisthecontactsareclosed

whenthedoorisclosedandopenwhenthedoorisopen.Ifthedoorsensingswitch(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 iumper 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

faulty and must be replaced. If a spe-

cific pad does not respond, the above

method may be used (after clearing

the control unit) to determine if the

control unit or key pad is at fault.

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

INSTANT

COOK

START

Frozen

Dinner

Reheat

Pie

4 X 3 X 2 X

Reheat

Pizza

Pasta

Meal

L RELAY TEST

CARRY OUT 3D CHECKS.

Remove the outer case and check voltage between Pin Nos. 3 and 5 of the 3 pin connector (A) on the

control unit with an A.C. voltmeter.

The meter should indicat 240 volts, if not check oven circuit.

RY1 and RY2 Relay Test

Check voltage at the relay coil with a D.C. voltmeter during the microwave cooking operation.

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

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

control unit is defective.

RELAY SYMBOL OPERATIONAL VOLTAGE CONNECTED COMPONENTS

RY1 Approx. 26.0 V.D.C. Oven lamp/ Turntable motor/ Cooling fan motor

RY2 Approx. 25.5 V.D.C. Power transformer

CARRY OUT 4R CHECKS.

R-3A56

TEST PROCEDURES (CONT'D)

PROCEDURE

LETTER COMPONENT TEST

M 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.

CARRY OUT 3D CHECKS.

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

inspectionofthevaristorforburningdamage

and examine the transformer with tester for

the presence of layer short-circuit (check

primary coil resistance). If any abnormal

condition is detected, replace the defective

parts.

CARRY OUT 4R CHECKS.

(VRS2)

VRS1

(J1) CN - A POWER

RY1

RY2

(RY3)

(J2+)

NNOISE FILTER TEST

If incorrect readings are obtained, replace the noise filter unit.

CARRY OUT 4R CHECKS.

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 0.0022µF

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

WHT

RED

STEPS OCCURANCE CAUSE OR CORRECTION

1 The rated AC voltage is not present at Check supply voltage and oven power cord.

POWER terminal of CPU connector (CN-A)

2 The rated AC voltage is present at primary Low voltage transformer or secondary circuit defective.

side 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-3A56

TOUCH CONTROL PANEL ASSEMBLY

OUTLINE OF TOUCH CONTROL PANEL

The touch control section consists of the following units

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 R10-R13, R20-R22.

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

thekey unit andpassed backtothe LSIthroughR00-R03to

perform the function that was requested.

Control Unit

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

nizingsignalcircuit,ACLcircuit,buzzercircuit and indicator

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 voltage necessary in the control

unit.

Symbol Voltage Application

VC -5V LSI(IC1)

VP -30V Fluorescent display tube : Grid

and anode voltage

VF1 2.2Vac Filament of fluorescent display

tube

VF2 (VF1 to VF2 voltage)

3) Synchronizing Signal Circuit

The 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 (Stop 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 5-digits, 13-segments are

used for displaying figures.

R-3A56

DESCRIPTION OF LSI

LSI(IZA593DR)

The I/O signal of the LSI(IZA593DR) is detailed in the following table.

Pin No. Signal I/O Description

1 Vdisp IN Anode (segment) of Fluorescent Display illumination voltage: -30V

Vp voltage of power source circuit input.

2R00IN Signal coming from touch key.

WheneitheroneofG12linekeysonkeymatrixistouched,acorrespondingsignal will

be input into R00.

3R01IN Signal coming from touch key.

WheneitheroneofG11linekeysonkeymatrixistouched,acorrespondingsignal will

be input into R01.

4R02IN Signal coming from touch key.

WheneitheroneofG10linekeysonkeymatrixistouched,acorrespondingsignal will

be input into R02.

5R03IN Signal coming from touch key.

When either one of G9 line keys on key matrix is touched, a corresponding signal out

ofR20-R22,R10-R13willbe inputintoR03.When no keyistouched,the signalisheld

at "L" level.

6 TEST IN Connected to VC.

7 RESET IN Auto clear terminal.

Signal is input to reset the LSI to the initial state when power is supplied. Temporarily

setto"L"level the momentpowerissupplied,atthistimetheLSIisset.Thereafterset

at "H" level.

8 OSC1 IN Internal clock oscillation frequency input setting.

Theinternalclockfrequencyissetby inserting the ceramic filter oscillationcircuitwith

respect to OSC1 terminal.

9 OSC2 OUT Internal clock oscillation frequency control output.

Output to control oscillation input of OSC2.

10/11 GND/AVSS IN/IN Connected to VC.

12 AN0 OUT Oven lamp,turntable motor and cooling fan motor driving signal. (Square

Waveform : 50Hz)

Toturn on andoff the controlrelay.The pulsesignal(50Hz) isdeliveredto thecontrol

relay driving circuit and cook relay control circuit.

13 AN1 OUT Terminal not used.

14 AN2 OUT Magnetron high-voltage circuit driving signal.

To turn on and off the cook relay. In low operation, the signals holds "L" level during

microwave cooking and "H" level while not cooking. In other cooking modes (MED

HIGH, MED,MED LOW,LOW) the signal turns to "H" level and "L" level in repetition

according to the power level.

15 AN3 OUT Terminal not used.

16 AN4 IN Input signal which communicates the door open/close information to LSI.

Door closed; "H" level signal.

Door opened; "L" level signal.

17 AN5 IN Terminal to change cooking constant.

18-19 AN6-AN7 IN Connected to VC.

20/21 AVCC/VCC IN/IN Connected to GND.

22 INT0 IN Signal synchronized with commercial source freqency(50Hz).

This is basic timing for time processing of LSI.

23 D1 OUT Terminal not used.

24 D2 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.

R-3A56

Pin No. Signal I/O Description

25 BUZZ OUT Signal to sound buzzer.

A: key touch sound(0.12sec.).

B: Completion sound(2.4sec.).

26 D4 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.

27 D5 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.

28 D6 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.

29 D7 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.

30 D8 OUT Segment data signal.