Sharp R-4A55 Bedienungsanleitung

R4A55

SHARP SERVICE MANUAL

MICROWAVE OVEN

MODEL R-4A55

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

, This is a supplimemental Service Manual For Model R-4A55. This model is Quite similar to Base Model R-4A53

(Refer No. is S7106R4A53PJZ). Use this supplimemental manual together with the Base Model Service Manual.

Refer to Base Model Service Manual for complete operation, service information, etc.

TABLE OF CONTENTS page

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

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

RODUCT SPECIFICATIONS ......................................................................................................................... 2

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

SERVICING ................................................................................................................................................... 4

TEST PROCEDURE ...................................................................................................................................... 5

TOUCH CONTROL PANEL ........................................................................................................................... 9

COMPONENT REPLACEMENT AND ADJUSTMENT PROCEDURE ....................................................... .I4

WIRING DIAGRAM ...................................................................................................................................... 17

PICTORIAL DIAGRAM .................................................. ..1................................................................~ .......... 18

CONTROL PANEL CIRCUIT ...................................................................................................................... .I9

PRINTED WIRING BOA0 ............................................................................................................................ 20

PARTS LIST ................................................................................................................................................. 21

SHARP CORPORATION

SERVICE MANUAL

SHAFZP

MICROWAVE OVEN

R-4A55

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 en-

tire text of this manual, so that they will be qualified to render sat-

isfactory customer service.

CAUTION

MICROWAVE RADIATION

Service engineers should not be exposed to the microwave en-

ergy which may radiate from the magnetron or other microwave

generating devices if it is improperly used or connected. All in-

put and output microwave connections, waveguides, flanges

andgaskets must be secured. Never operate the device without

a microwave energy absorbing load attached. Never look into

an open waveguide.

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.

(0) 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.

SHARP CORPORATION

OSAKA, JAPAN

R4A55R4A55

APPEARANCE VIEW

TEST PROCEDUREST PROCEDURE

PRODUCT SPECIFICATIONS

ITEM

Power Requirements 240 Volts

50 Hertz

DESCRIPTION

Power Consumption

Power Output

Case Dimensions

Single phase, 3 wire earthed

1.4 kW

750 watts nominal of RF microwave energy (AS 2895 1986)

900 watts (IEC-705-1 988 )

Operating frequency of 2450MHz

Width 550mm

Height 312mm

Depth 420mm

Cooking Cavity Dimensions Width 381 mm

Height 21 I mm

Depth 411 mm

Turntable diameter

Control Complement 360mm

Touch Control System

Clock ( 1:00 - 12:59)

Timer (0 - 99 minutes 99 secinds)

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

SERVE QUANTITY

INSTANT ACTION

AUTO COOK

EASY DEFROST

NUMBER pads

POWER LEVEL

MORE, LESS

STOP/CLEAR

Set Weight

AUTO START/CLOCK

INSTANT COOK/START

Approx. 17 kg

R4A55

APPEARANCE VIEW

8.Touch Control Panel

9.Digital readout

1O.Waveguide cover

11.Access cover for oven lamp replacement

12.Power supply cord

1.Ventilation openings

2.Oven lamp

3.Hinges

4.Safety door latches

5.See through door

6.Coupling

7.Door open button

TOUCH CONTROL PANEL

INSTANT ACTION PADS -

Press once to cook or reheat

8 popular menu.

AUTO COOK Chicken Reheat Ffoten

Press to select Auto Cook 1serve

Pieces Bevey;geSoup Dinner

1serve

mode.

AUTO COOK MENUS

NUMBER PADS

Press to enter

clock time, weight or quantity

of food, or to select the Auto

Cook menus.

Bacon Cy&es Fis~~~~ts

1 serve

.- Rice 8 Pasta Reheyt lW&sbie~

5seasonedRoast-

POWER LEVEL PAD-

Press to select microwave

power setting.

If not pressed, HIGH is auto-

matically selected.

STOP/CLEAR PAD

Press to clear during program

ming.

Press once to stop operation

of oven during cooking; press

twice to cancel cooking pro-

gramme.

- 2,3 or 4 SERVE QUANTITY

PADS

To cook two, three or four

serves, press required pad

prior to pressing the Instant

Action pad.

)I1u ,,q-q-qg

@q*y~ pj

I I I \

-MORE (A), LESS (r) PADS

Press to increase/decrease

the time in one minute incre-

ments during cooking or to

alter the doneness for the Al

Cook, Instant Action or Easy

Defrost modes.

- EASY DEFROST PAD

Press to defrost meat by en-

tering weight.

r INSTANT COOK/START

AUTO START/CLOCK PAD

Press to set clock or Auto

Start time. by 1 minute multiples each

time this pad is pressed dur-

ing cooking.

Press to start oven after set-

ting programmes.

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.

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 connection of the high-voltage capaci-

tor (that is, of the connecting lead of the high-volt-

age rectifier) against the chassis with the use of

an insulated screwdriver.

Sharp recommend that wherever possible fault-find-

ing is carried out with the supply disconnected. It

may in, some cases, be necessary to connect the

supply after the outer case has been removed, in

this event carry out 3D checks and then disconnect

the leads to the primary of the power 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 3lJ checks and reconnect the leads to the

primary of the power transformer.

REMEMBER TO CHECK%

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 microwave timer for two (2) minutes. Set the

power level to HIGH and push the START button. When

the two minutes has elapsed (timer at zero) carefully

check that the water is now hot. If the water remains cold

carry out a checks and re-examine the connections to

the component being tested.

When all service work is completed, and the oven is fully assembled, the microwave power output should be

checked and microwave reakage test carried out

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 3D CHECKS

Isolate the magnetron from the high voltage circuit by removing all leads connected to the 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 a short circuit 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 microwaveoven in a fully assembled condi-

tion (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. 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/4.187calorie is generated. On the

other hand, if the temperature of the water with V(ml) rises AT (“C) during this microwave heating

period, the calorie of thewater is V x AT

The formula is as follows;

Pxt/4.187=VxAT P(W)=4.187xVxAT/t

Our condition for the water load is as follows:

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

Water load ..... 1000 g Initial temperature ...........10%X Heating time ......................47sec.

P=9OxAT

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)X.

4. Select the initial and final water temperature so that the maximum difference between the final

water temperature and the ambient temperature is 5°C.

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

6. The graduation of the thermometer must be scaled by 0.X at minimum and an accurate ther-

mometer.

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 Tl = 11“C)

2. Add the 1 litre water to the vessel.

3 Place the load on the centre of the shelf.

TEST PROCEDURES

PROCEDURE

LElTER COMPONENT TEST

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

(10 I!I2)“C.

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

6. Measure the final water temperature.

(Example: The final temperature T2 = 21 “C)

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

Initial temperature ............................................................................................Tl = 11“C

Temperature after (47+2)= 49 sec. .................................................................T2 = 21 “C

Temperature difference Cold-Warm ...................................*....................*.... AT1 = 10°C

Measured output power

The equation is “P= 90 x AT” ................................................P= 90 x 10°C = 900 Watts

JUDGEMENT: The measured output power should be at least + 15 % of the rated output

power.

CAUTION: 1°C CORRESPONDS TO 90 WA-ITS. REPEAT MEASUREMENT IF THE POWER IS

INSUFFICIENT.

-- -

T2.C

Heat up for 49 sec.

MICROWAVE OUTPUT POWER (2 Litre water ioad)

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.

On the other hand, if the temperature of the water with V(ml) rises AT (“C) during this microwave

heating period, the calorie of the water is V x AT.

The formulae is as follows;

P =8330xAT/t

Our condition for the 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 ....1min. 51 sec.

P = 75 x AT

Measuring method:

A) The two water containers must be prepared.

The water container must be one (1) litre beaker made of Pyrex glass and its diameter approxi-

mately 12cm.

B) Put the one (1) litre water into each beaker (Each beaker has one litre water). The initial tempera-

ture of the water should be 239°C.

C) Mark Tl 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 minute and 51 seconds start the oven at HIGH.

R-4A55

TEST PROCEDURES

PROCEDURE

LETTER COMPONENT TEST

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

G) After 1 minute 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.

Example

Initial temperature .......................................................*........................... Tl = 23°C T2 = 24°C

Temperature after 1 min. 51 set I

. *.......................................................... Tl = 33°C T2 = 34°C

Temperature difference Cold-Warm ...................................................ATI = 10°C ?,T2 = 10°C /

Mean temperature rise AT ..............................AT /

Measured output power = (AT1 31AT2) /2 = (1O”C+1O”C) / 2 = 10°C I

The equation is P= 75 x AT I

..............................................................

P= 75 x 10°C = 750 Watts /

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

CAUTION: 1°C CORRESPONDS TO 75 WATTS.

REPEAT MEASUREMENT IF THE POWER IS INSUFFICIENT. I

- -

(Tl “C) (Tl “C)

Heat up for mtn. 5 set

Eli

(T2 “C)

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

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 symp-

toms 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 problems caused by defective control unit.

a) Buzzer does not sound or continues to sound.

TEST PROCEDURES

PROCEDURE

LETTER COMPONENT TEST

b) Clock does not operate properly.

c) Cooking is not possible.

d) Proper temperature measurement is not obtained.

M RELAY 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 4-pin connector (A) on the control unit with an

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

6. RYl AND RY2 Test

These are operated by D.C. voltage. Check voltage at 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 1

RYl Approx. 26.5V.D.C. Oven lampnurntable motor/Cooling fan motor

RY2 Approx. 25.8V.D.C. Power transformer

N PROCEDURES TO BE TAKEN WHEN THE FOIL PAlTERN 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

the PWB, this foil pattern acts as a fuse. If the foil pattern is open, follow the troubleshooting guide

given below for repair.

Problem: POWER ON, indicator does not light up.

STEPS OCCURANCE CAUSE OR CORRECTION

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

POWER terminal of CPU connector (CN-A) term “Low voltage transformer” when refering to

transformer Tl .

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

side of low voltage transformer. Check and repair.

Only pattern at ‘a” is broken. *insert jumper wire Jl and solder. (CARRY OUT 3D

CHECKS BEFORE REPAIR)

Pattern at “a” and “b” are broken. ‘Insert the coil RCILF2003YAZZ between “c” and “d”.

(CARRY OUT 3D CHECKS BEFORE REPAIR)

is- i hi -- I I- . I i

NOTE:*At the time of these repairs, make a v

ual inspection of the varistor for burning

damage and test the T/C transformer

with an ohmmeter for the presence of

layer short-circuit (check primary coil re-

sistance). If any abnormal condition is

detected, replace the defective parts.

CARRY OUT @ CHECKS RYI c#-

TOUCH CONTROL PANEL ASSEMBLY

OUTLINE OF TOUCH CONTROL PANEL

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

communicated 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 ROo - RO3, Rio

- R13. When a key pad is touched, a signal is completed

through the key unit and passed back to the LSI through

R23, R30 - R32 to perform the function that was

requested.

Control Unit

Control unit consists of LSI, power source circuit,

synchronizing signal circuit, ACL circuit, buzzer circuit

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 for generates voltage necessary in the control

unit.

Symbol

VFl

VF2

Voltage

-5V

-29v

3Vac

Application

LSI(IC1)

Fluorescent display tube : Grid

and anode voltage

Filament of fluorescent display

tube

(VFl to VF2 voltage)

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

A circuit to generat a signal which resets the LSI to the

initial state when power is supplied.

5) Buzzer Circuit

The buzzer responsive to signals from the LSI to emit

noticing sounds (key touch sound and completion

sound).

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 a 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, 13segments are

used for displaying figures.

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