Sharp R-24AT, R-22AT User Manual

1900W/R-2

R-22AT R-24AT

SERVICE MANUAL

SY520R24ATK//

COMMERCIAL

MICROWAVE OVEN

DOUBLE

EXPRESS

QUANTITY

DEFROST

4AT

POWER LEVEL

MANUAL/ REHEAT

STOP / CLEAR

START

SET

CHECK

VOLUME

MODELS

R-22AT R-24AT

R-24AT

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

This revised service manual is applied to

R-22AT from serial No. 050505509 and

R-24AT from serial No. 050508658.

Because many parts have been changed to improve quality of these models from May 2005 production.

And the changed parts are not interchangeable. Please use this service manual for above products.

For old products, please use old service manual (No.SX910R24ATK//) and technical reports.

TABLE OF CONTENTS

Page

SERVICING ................................................................................................................. INSIDE FRONT COVER

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

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

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

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

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

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

FUNCTION OF IMPORTANT COMPONENTS ................................................................................................ 6

TROUBLESHOOTING GUIDE .......................................................................................................................... 7

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

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

COMPONENT REPLACEMENT AND ADJUSTMENT PROCEDURE ........................................................... 24

MICROWAVE MEASUREMENT .................................................................................................................... 31

WIRING DIAGRAM ......................................................................................................................................... 32

PICTORIAL DIAGRAM ................................................................................................................................... 34

CONTROL PANEL CIRCUIT ...........................................................................................................................35

PRINTED WIRING BOARD .............................................................................................................................36

PARTS LIST ................................................................................................................................................... 37

SHARP CORPORATION

R-22AT R-24AT

SERVICING

WARNING TO SERVICE PERSONNEL

Microwave ovens contain circuitry capable of producing very high voltage and current. Contact with following parts will result in electrocution. High voltage capacitors, High voltage transformers, Magnetrons, High voltage rectifier assembly, High voltage fuses, High voltage harness.

REMEMBER TO CHECK 3D

1) Disconnect the supply.

2) Door opened, and wedged open.

3) Discharge high two voltage capacitors.

WARNING: AGAINST THE CHARGE OF THE TWO

HIGH-VOLTAGE CAPACITORS.

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

Sharp recommend that wherever possible fault-finding is carried out with the supply disconnected. It may, in some cases, be necessary to connect the supply after the outer case has been removed, in this event carry out 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 3D checks and reconnect the leads to the primary of the power transformer.

REMEMBER TO CHECK 4R

1) Reconnect all leads removed from components during testing.

2) Replace the outer case (cabinet).

3) Reconnect the supply.

4) Run the oven. Check all functions.

Microwave ovens should not be run empty. To test for the presence of microwave energy within a cavity, place a cup of cold water on the oven turntable, close the door and set the microwave timer for one (1) minut. When the one minute has elapsed (timer at zero) carefully check that the water is now hot. If the water remains cold carry out 3D 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 leakage test should be carried out.

SERVICE MANUAL

COMMERCIAL

MICROWAVE OVEN

R-22AT/ R-24AT

GENERAL IMPORTANT INFORMATION

PRODUCT SPECIFICATIONS

APPEARANCE VIEW

R-22AT R-24AT

This Manual has been prepared to provide Sharp Corp. Service engineers with Operation and Service Information.

It is recommended that service engineers carefully study the entire text of this manual, so they will be qualified to render satisfactory customer service.

CAUTION

MICROWAVE RADIATION

DO NOT BECOME EXPOSED TO RADIATION FROM THE MICROWAVE GENERATOR OR OTHER PARTS CONDUCTING MICROWAVE ENERGY.

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

WARNING

Never operate the oven until the following points are ensured. (A) The door is tightly closed. (B) The door brackets and hinges are not defective. (C) The door packing is not damaged. (D) The door is not deformed or warped. (E) There is not any other visible damage with the oven.

OPERATING SEQUENCE

FUNCTION OF IMPORTANT COMPONENTS

SERVICING AND TROUBLESHOOTING CHART

TEST PROCEDURE

TOUCH CONTROL PANEL ASSEMBLY

COMPONENT REPLACEMENT AND ADJUSTMENT PROCEDURE

MICROWAVE MEASUREMENT

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

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

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

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

SHARP CORPORATION

OSAKA, JAPAN

WIRING DIAGRAM

PARTS LIST

R-22AT R-24AT

PRODUCT DESCRIPTION

SPECIFICATION

ITEM DESCRIPTION

Power Requirements 230 - 240 Volts

50 Hertz

Single phase, 3 wire earthed Power Comsumption Power Output

Case Dimensions Width Height Depth

Cooking Cavity Dimensions Width Height Depth

Control Complement for Touch Control System

2.4 kW Approx. 11 A [R-22AT] / 2.9 kW Approx. 13 A [R-24AT]

1500 W [R-22AT]/ 1900 W [R-24AT] nominal of RF microwave energy

(measured by method of IEC 60705)

Operating frequency 2450 MHz

510mm 335 mm 470mm

330 mm 180 mm 330mm

The combination of cooking time and microwave power

The oven can be programmed a series of up to 3 cookling stages.

The combination of microwave power and cooking time that can be input as

folllows.

Cooking Sequence Micrwave power levelthat can be iused. Cooking time that can be iused.

1 Stage only 0-100% Max. 30 minutes

0-40% all stages Max. 30 minutes any stages

2 or 3 Stage

50-100% Max. 30 minutes for 3 stages

Max. 60 minutes for 2 stages Max. 90 minutes for 3 stages

NOTE:If the oven used with the power level above 40% on any stage, the

maximum cooking time is 30 minutes in total.

Microwave Power level

100% 90% 80% 70% 60% 50% 40% 30% 20% 10% 0%

MANUAL / REPEAT key, NUMBER keys

POWER LEVEL key, STOP / CLEAR key

START Key, DOUBLE QUANTITY key

EXPRESS DEFROST key, SET key

CHECK key, VOLUME key

CSet Weight Approx. 33 kg

GENERAL INFORMATION

WARNING

THIS APPLIANCE MUST BE EARTHED

IMPORTANT

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

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

R-22AT

R-24AT

OVEN

1. Control panel

2. Hole for safety door latches

3. Ceramic floor

4. Splash cover

5. Oven light

6. Air intake filter

7. Air intake openings

8. Oven cavity

9. Door seals and sealing surfaces

10. Door hinges

11. Oven door with see-through window

12. Door safety latches

13. Door handle.

14. Outer cabinet

15. Removable cover over oven light bulb

16. Air vent openings

17. Power supply cord 18 Mounting plate 19 Screw for mounting plate

DISPLAY AND INDICATORS

Check indicators after the oven starts to confirm the oven is operating as desired.

1. Heating indicator This indicator shows cooking in progress.

2. Memory number indicator

3. Express defrost

4. Check mode indicator

5. Power level display

6. Time display

7. Filter indicator

8. Double quantity mode indicator

9. 3rd. stage indicator

10. 2nd. stage indicator

11. 1st. stage indicator

OPERATING KEYS

12. DOUBLE QUANTITY key

13. EXPRESS DEFROST key

14. NUMBER keys

15. MANUAL/ REPEAT key

16. STOP/CLEAR key

17. POWER LEVEL key

18. START key

19. SET key

20. VOLUME key

21. CHECK key

APPEARANCE VIEW

AUTO TOUCH CONTROL PANEL

NUMBER

DOUBLE

QUANTITY

MANUAL/

REPEAT

POWER LEVEL

SET CHECK VOLUME

1 2 3

679

DEF

CHECK

DOUBLE

FILTER

EXPRESS DEFROST

STOP / CLEAR

START

POWER

7 8 9

INSTALLATION INFORMATION

When this commercial microwave oven is installed near other commercial electrical appliances, connect a lead wire to each equivalent potential terminal with equipotential marking between them (insert a lead wire between a washer and an earth angle, and screw them), as shown in Fig. A-1, to make sure that they are at equivalent potential. If any lead wire is not connected between them, when person touch them he/she will get a electric shock.

COMMERCIAL MICROWAVE OVEN OTHER COMMERCIAL

Equipotential marking

Lead wire

Screw

Washer

Earth angle (Equivalent potential terminal)

Lead wire

Figure A-1

ELECTRICAL APPLIANCE

Equivalent potential terminal

R-22AT R-24AT

OPERATION SEQUENCE

Closing the door activates all door interlock switches (interlock switches 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 (230 - 240 volts, 50Hz), the line voltage is supplied to the control unit through the noise filter.

Figure O-1 on page 32

1. The digital display shows .

IDLE CONDITION

When the door is opened, the contacts of the interlock switches SW1+SW2 and stop switch SW5 open, initiating the following:

Figure O-2 on page 32

1. A signal is input to the control unit energizing the coil of shut-off relay RY-1.

2. The shut-off relay RY-1 contacts close completing circuits to turn on the oven lamp, blower motor and antenna motors.

3. If the door remains open, 60 seconds later the control unit de-energizes shut-off relay RY-1 turning off the oven lamp, blower motor and antenna motors.

When the door is closed, the contacts of the interlock switches SW1+SW2 and stop switch SW5 close. With the closing of the stop switch SW5 contacts, an additional circuit is provided which will permit the operation of the oven when one of the touch pads is depressed. Since the control is enabled through the stop switch SW5, the door must be closed before the touch pads will be effective. When the door is closed, a full 60 second IDLE condition is always provided for selecting and pressing the desired touch pads. A 60 second IDLE condition will also follow the end of each cook cycle.

MICROWAVE COOKING CONDITION

Touch MANUAL/REPEAT key and enter a desired cooking time with the touching NUMBER key. And then touch START key.

NOTE: The programme and the check are canceled

when any keys are not touched for more than 3 minutes during programming.

Function sequence Figure O-3 on page 33

CONNECTED COMPONENTS RELAY Oven lamp/ Blower motor/ Antenna motors RY1 High voltage transformer T1 RY3 High voltage transformer T2 RY4

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

2. The filament winding voltage (3.3 volts) heats the magnetron filament and the high voltage (2000 volts) is sent to the voltage doubling circuit, where it is doubled

to negative voltage of approximately 4000 volts D.C..

3. The 2450 MHz microwave energy produced in the magnetron generates a wave length of 12.24 cm. This energy is channelled through the waveguide (transport channel) into the oven cavity, where the food is placed to be cooked.

4. When the cooking time is up, a signal tone is heard and the relays RY3+RY4 go back to their home position. The circuits to the high voltage transformers T1+T2. The relay RY1 remains and oven lamp, blower motor and antenna motors work for 1 minute.

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

CONDITION DURING DOOR OPEN

SWITCH CONTACT COOKING Interlock switches COM-NO Closed Open Monitor switches COM-NC Open Closed Stop switch COM-NO Closed Open

(NO COOKING)

The circuits to the high voltage transformers T1+T2 are cut off when the interlock and stop switches SW1+SW2+SW5 are made open. The blower motor BM, antenna motors and 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, but the program is cancelled if the oven is not started within 1 minute.

6. MONITOR SWITCH CIRCUIT The monitor switches SW3+SW4 are mechanically controlled by oven door, and monitors the operation of the interlock switches SW1+SW2.

6-1. When the oven door is opened during or after the

cycle of a cooking program, the interlock switches SW1+SW2 and stop switches SW5 must open their contacts first. After that the contacts (COM-NC) of the monitor switches SW3+SW4 can be closed.

6-2. When the oven door is closed, the contacts (COM-

NC) of the monitor switches SW3+SW4 must be opened first. After that the contacts (COM-NO) of the interlock switches SW1+SW2 and stop switch SW5 must be closed.

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

interlock switch SW1 (or SW2) remain closed, remains closed, the fuse F1 F10A (or F2 F10A) will blow, because the monitor switch SW3 (or SW4) is closed and a short circuit is caused.

MICROWAVE VARIABLE COOKING

When the microwave oven is preset for variable cooking power, the line voltage is supplied to the high voltage transformers T1+T2 intermittently within a 48 second time base through the contacts of the relays RY3+RY4. The following levels of microwaves power are given.

48 sec. ON

Number key

44sec. ON

Number key 9

40 sec. ON

Number key 8

36 sec. ON

Number key 7

32 sec. ON

Number key 6

26 sec. ON

Number key 5

22 sec. ON

Number key 4

16 sec. ON

Number key 3

12 sec. ON

Number key 2

8 sec. ON

Number key 1

0 sec. ON

Number key 0

NOTE: The ON/OFF time ratio does not exactly corre-

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

R-22AT R-24AT

TWO MAGNETRON OPERATION SYSTEM

Two magnetrons MG1+MG2 are equipped in order to get higher microwave power output. The primary windings of the high voltage transformers T1+T2 are connected so that each magnetron can be oscillated alternatively according to the frequency of the power supply. Refer to the Figure B-1 and B-2.

T2: HIGH VOLTAGE TRANSFORMER

(REAR)

H. V. FUSE H. V. FUSE

H. V. RECTIFIER

MG2: MAGNETRON (LOWER)

C2: H.V. CAPACITOR

H. V. RECTIFIER

Figure B-1. High Voltage Circuit

OPERATION OF MAGNETRON

MG1: MAGNETRON (UPPER)

T1: HIGH VOLTAGE TRANSFORMER

(FRONT)

C1: H.V. CAPACITOR

COMMERCIAL FREQUENCY (50HZ)

POWER OUTPUT BY MAGNETRON T1

POWER OUTPUT BY MAGNETRON T2

Figure B-2. Operation of Magnetron

R-22AT R-24AT

FUNCTION OF IMPORTANT COMPONENTS

DOOR OPEN MECHANISM

1. The door release lever is pulled.

2. The upper latch head is lifted up by the linked door release lever.

3. The head lever is lifted up by the door release lever.

4. The joint lever is lifted up by the head lever.

5. The lower latch head is lifted up by the joint lever.

6. Now both latch heads are lifted up, so they can be released from the latch hook.

7. Now the door can be opened.

Door release lever

Joint lever

Head lever

Latch head

Latch hook

SW4: Monitor switch

(Oven side)

SW3: Monitor switch

SW2: Interlock switch

(Oven side)

SW1: Interlock switch

SW5: Stop switch

Figure D-1. Door Open Mechanism

INTERLOCK SWITCHES SW1, SW2 AND STOP SWITCH SW5

1. When the oven door is closed, the contacts COM-NO must be closed.

2. When the oven door is opened, the contacts COM-NO must be opened.

MONITOR SWITCHES SW3, SW4

The monitor switches SW3, SW4 are activated (the contacts opened) the upper latch head and switch lever A while the door is closed. The switch SW3 (or SW4) is intended to render the oven inoperative by means of blowing the fuse F1 F10A (or F2 F10A) when the contacts of the interlock switch SW1 (or SW2) fail to open when the door is opened.

Function

1. When the door is opened, the monitor switches SW3 +SW4 contacts close (to the ON condition) due to their being normally closed. At this time the interlock switch SW1+SW2 are in the OFF condition (contacts open) due to their being normally open contact switches.

2. As the door goes to a closed position, the monitor switches SW3+SW4 contacts are opened and interlock switch SW1+SW2 contacts are closed (On opening the door, each of these switches operate inversely.)

3. If the door is opened and the interlock switch SW1 (or SW2) contacts fail to open, the fuse F1 F10A (or F2 F10A) blows simultaneously with closing of the monitor switch SW3 (or SW4) contacts.

CAUTION:BEFORE REPLACING A BLOWN FUSE F1

F10A (OR F2 F10A) TEST THE INTERLOCK SWITCH SW1 (OR SW2) AND MONITOR SWITCHE SW3 (OR SW4) FOR PROPER OPERATION. (REFER TO CHAPTER “TEST PROCEDURE”).

NOISE FILTER

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

FUSES F1, F2 F10A 250V

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

2. The fuse F1 F10A (or F2 F10A) also blows when interlock switch SW1 (or SW2) remains closed with the oven door open and when the monitor switches SW3 (or SW4) closes.

WEAK POINT F3

If the wire harness or electrical components make a shortcircuit, this weak point F3 blows to prevent an electric shock or fire hazard.

HIGH VOLTAGE FUSE(S) F4, F5

The high voltage fuse blows when the high voltage rectifier or the magnetron is shorted.

MAGNETRON TEMPERATURE FUSES TF1, TF2

The temperature fuses TF1, TF2 located on the top of the upper and lower waveguide, are designed to prevent damage to the magnetrons MG1, MG2. If an over heated condition develops in the tube due to blower motor failure, obstructed air ducts, dirty or blocked air intake, etc., the circuit to the magnetrons are interrupted. Under normal operation, the temperature fuses remains closed. However, when abnormally high temperatures are generated within the magnetrons, the temperature fuses will open at 150˚C causing the microwave energy to stop. The defective temperature fuses must be replaced with new rated ones.

EXHAUST TEMPERATURE FUSE TF3

The temperature fuse TF3, located on the side of the exhaust duct assembly, is designed to prevent damage to the oven by fire. If the food load is overcooked, by either error in cook time or defect in the control unit, the temperature fuse will open. Under normal operation, the oven temperature fuse remains closed. However, when abnormally high temperatures are generated within the oven cavity, the oven temperature fuse will open at 120˚C, causing the oven to shut down. The defective temperature fuse must be replaced with new rated one.

R-22AT R-24AT

EXHAUST OVEN THERMISTOR TH3

The thermistor is a negative temperature coefficient type. The temperature in the exhaust duct is detected through the resistance of the thermistor. If the temperature is high, the control panel will display “EE7” and the oven will stop to avoid overheating and catching fire. If the thermistor is open, the control panel will display "EE6" and the oven will stop.

MAGNETRON THERMISTORS TH1, TH2

The thermistor is a negative temperature coefficient type. The air temperature around the magnetron is detected through the resistance of the thermistor. If the temperature is high, the control panel will display "EE17" and the oven will stop to protect the lower magnetron against overheat. If the magnetron thermistor is open, the control panel will display "EE16" and the oven will stop. If the magnetron thermistor is short, the control panel will display "EE19" and the oven will stop.

BLOWER MOTOR BM

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

ANTENNA MOTORS SM

The upper and lower antenna motors SM drive stirrer antennas.

OVEN LAMP OL

The oven cavity light illuminates the interior of the oven so that food being cooked can be examined visually through the door window without having to open the door. The oven lamp is on during the cooking cycle and idle condition.

TROUBLESHOOTING GUIDE

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. IMPORTANT: If the oven becomes inoperative because of a blown fuse F1 F10A (or F2 F10A) in the interlock switch

SW1 (or SW2) - monitor switches SW3 (or SW4) , check the interlock switch SW1 (or SW2) and monitor switches SW3 (or SW4) before replacing the fuse F1 F10A (or F2 F10A).

R-22AT R-24AT

EEP ROM I-2

N KEY UNIT

TOUCH CONTROL TRANSFORMER T3 Due to programme lock Over the max. cooking time No power at wall outlet HOME FUSE or BREAKER

Mis adjustment of switches P FUSE 2.5A O RELAY RY-4 O RELAY RY-3 O RELAY RY-1 M TOUCH CONTROL PANEL

Opened wire harness

Shorted wire harness

POWER SUPPLY CORD K NOISE FILTER

OVEN LAMP OR SOCKET J BLOWER MOTOR BM J ANTENNA MOTORS SM

I EXHAUST THERMISTOR TH3 I MAGNETRON THERMISTOR (Lower) TH2

I MAGNETRON THERMISTOR (Upper) TH1 L HIGH VOLTAGE FUSE F5 L HIGH VOLTAGE FUSE F4 H EXHAUST TEMPERATURE FUSE TF3 H MAGNETRON TEMPERATURE FUSE TF2 H MAGNETRON TEMPERATURE FUSE TF1 F WEAK POINT F3 G FUSE F10A F2 G FUSE F10A F1 E STOP SWITCH SW5 E MONITOR SWITCH SW4 E MONITOR SWITCH SW3 E NTERLOCK SWITCH SW2 D INTERLOCK SWITCH SW1 D H.V. CAPACITOR C2 D H.V. CAPACITOR C1

H.V. WIRE HARNESS C H.V. RECTIFIER ASSEMBLY FOR MG2 C H.V. RECTIFIER ASSEMBLY FOR MG1 B HIGH VOLTAGE TRANSFORMER T2 (Rear) B HIGH VOLTAGE TRANSFORMER T1 (Front) A MAGNETRON MG2 (Lower) A MAGNETRON MG1 (Upper)

TESTPROCEDURE

AND

POSSIBLE CAUSE

DEFECTIVE PARTS

PROBLEM

“ . “ does not appear on display when power cord is plugged into

wall outlet.

Control panel can not accept key in.

Fuse F1 or F2 blows when the door is opened.

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

Weak point F3 blows when power cord is plugged into wall outlet.

Oven lamp, fan motor and antenna motors do not work for 1

minute when the door is opened or after cooking.

Fuse F1 or F2 blows when power cord is plugged into wall outlet.

Oven lamp does not light when door is opened. (Blower and antenna

motors work)

Blower motor does not work when door is opened. (Oven lamp

lights and antenna motors work)

“EE 1” (Magnetron MG1 failure)

“EE 2” (Magnetron MG2 failure)

“EE 3” (Magnetron MG1 and MG2 failure)

“EE 6” (Exhaust thermistoropen)

“EE 7” (Exhaust air temperature is high)

“EE 9” (Exceeded max. heating time)

Oven lamp, blower motor and antenna motors do not work.

OFF

CONDITION

Oven lamp does not work.

Blower motor does not work.

Oven does not stop after end of cooking cycle.

Home fuse blows when starting the oven.

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

It passed more than 1 minute after cooking but oven lamp, blower

motor and stirrer motors do not stop.

“EE 16” (Thermistor of magnetron are open.)

“EE 17” (Magnetron temperature is high.)

“EE 19” (Magnetron thermistor short)

“EE 10” (Fault of memory)

Antenna motors do not work.

CONDITION

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.

R-22AT R-24AT

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 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 microwave oven in a fully assembled condition (outer case fitted). Microwave output power from the magnetron can be measured by way of IEC 60705, i.e. it is measured by how much power the water load can absorb. To measure the microwave output power in the microwave oven, the relation of calorie and watt is used. When P(W) heating works for t(second), approximately P x t/4.187 calorie is generated. On the other hand, if the temperature of the water with V(ml) rises ∆T (°C) during this microwave heating period, the calorie of the water is V x ∆T.

The formula is as follows;

P x t / 4.187 = V x ∆ T+ 0.55 x mc (T2-T0) P (W) = 4.187 x V x ∆T / t + 0.55 x mc (T2-T0)/t

Our condition for water load is as follows:

Room temperature (T0) ...... around 20°C Power supply Voltage .............. Rated voltage

Water load ..................................... 1000 g Initial temperature (T1) ...................... 10±1°C

Heating time ................

28 sec. [R-22AT] / 22sec. [R-24AT]

Mass of container (mc) .....

330 g

T2 ......... Final Temperature P = 150 x ∆T [R-22AT] / P = 190 x ∆T [R-24AT]

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±1)°C.

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 0.1°C at minimum and be an accurate thermometer.

7. The water load must be (1000±5) g.

8. “t” is measured while the microwave generator is operating at full power. Magnetron filament heatup time is not included.

NOTE: The operation time of the microwave oven is “t + 3” sec. (3 sec. is magnetron filament heat-up time.)

Measuring method:

1. Measure the initial temperature of the water before the water is added to the vessel. (Example: The initial temperature T1 = 11°C)

2. Add the 1 litre water to the vessel.

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

4. Operate the microwave oven at HIGH until the temperature of the water rises by a value ∆ T of (10 ± 2) K.

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.

R-22AT R-24AT

TEST PROCEDURES

PROCEDURE

LETTER COMPONENT TEST

Room temperature ................................................................................................. T0 = 21°C

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

Temperature after (28 + 3) = 31 sec [for R-22AT].................................................. T2 = 21°C

Temperature after (22 + 3) = 25 sec [for R-24AT].................................................. T2 = 21°C

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

Measured output power

The equation is “P = 150 x ∆T” [for R-22AT] ........................... P = 150 x 10°C = 1500 Watts

The equation is “P = 190 x ∆T” [for R-24AT] ........................... P = 190 x 10°C = 1900 Watts

JUDGMENT: The measured output power should be within the range of ± 15 % of the rated output

power.

CAUTION: 1° C CORRESPONDS TO 150 WATTS [R-22AT]/ 190 WATTS [R-24AT]. REPEAT

MEASUREMENT IF THE POWER IS INSUFFICIENT.

1000g

T1˚C

1000g

T2˚C

Heat up for 31 sec. for R-22AT Heat up for 25 sec. for R-24AT

MICROWAVE OUTPUT POWER (2000 cc alternative method)

The power output of this oven is rated using the method specified by IEC 60705. Full details of how to curry out this procedure can be found in the Sharp Technical Training notes which is available from Sharp Parts Centre (part number SERV-LITMW01).

The IEC-60705 procedure must be carried out using laboratory-type procedures and equipment.

These requirements make the procedure unsuitable for routine performance checks.

NOTE: The following test method gives an indication of the output power only, it cannot be used to

establish the actual/rated output power. If the true output power is required, then the IEC60705 test method must be used.

Alternative simplified method:

1. Place 2 litres of cold water (between 12°C and 20°C) in a suitable container.

2. Stir the water and measure the temperature in °C. Note temperature as T1.

3. Place the container in the microwave and heat the water for 56 sec. [R-22AT]/ 44 sec. [R-24AT] on fill power.

4. When the 56 sec. [R-22AT]/ 44 sec. [R-24AT] is completed, remove the container and stir the water. Note temperature as T2.

5. Calculate the output power using the following formula: R.F. Power Output = (T2 - T1) x 150 for R-22AT. R.F. Power Output = (T2 - T1) x 190 for R-24AT.

NOTE: The result from this test should be within the allowance of 2000cc alternative method.

(±10%).

MICROWAVE LEAKAGE TEST This oven should be tested for microwave leakage on completion of any repair or adjustment, following the procedure described in the Sharp Technical Training notes (part number SERV-LITMW01). The maximum leakage permitted in BS EN 60335-2-25 is 50W/m2 (equivalent to 5W/m2), however it is not normal to detect any significant leakage, therefore, any leakage which is detected should be investigated.

It is essential that only leakage detectors with current calibration traceable to National Physical Laboratories are used.

Suitable leakage detectors: CELTEC A100

APOLLO X1

TEST PROCEDURES

PROCEDURE

LETTER COMPONENT TEST

B HIGH VOLTAGE TRANSFORMER TEST

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

filament winding of the high voltage 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 high voltage transformer. Disconnect the filament and secondary winding connections from the rest of the HV circuitry. Using an ohmmeter, set on a low range, it is possible to check the continuity of all three windings. The following readings should be obtained:

R-22AT R-24AT a. Primary winding approximately 1.8 Ω approximately 1.2 Ω b. Secondary winding approximately 75 Ω approximately 75 Ω c. Filament winding less than 1 Ω

If the readings obtained are not stated as above, then the high voltage transformer is probably faulty and should be replaced. CARRY OUT 4R CHECKS.

R-22AT R-24AT

C HIGH VOLTAGE RECTIFIER ASSEMBLY TEST

CARRY OUT 3D CHECKS.

Isolate the high voltage rectifier assembly from the HV circuit. The high voltage rectifier can be tested using an ohmmeter set to its highest range. Connect the ohmmeter across the terminal B+C of the high voltage rectifier and note the reading obtained. Reverse the meter leads and note this second reading. The normal resistance is infinite in one direction and more than 100 kΩ in the other direction. CARRY OUT 4R CHECKS.

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.

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. A normal capacitor shows continuity for a short time (kick) and then a resistance of about 10MΩ

after it has been charged. D. A short-circuited capacitor shows continuity all the time. E. An open capacitor constantly shows a resistance about 10 MΩ because of its internal 10MΩ

resistance. 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.

HIGH VOLTAGE RECTIFIER

CARRY OUT 4R CHECKS.

E SWITCH 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.

R-22AT R-24AT

TEST PROCEDURES

PROCEDURE

LETTER COMPONENT TEST

Table: Terminal Connection of Switch

Plunger Operation COM to NO COM to NC

Released Open circuit Short circuit Depressed Short circuit Open circuit

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

CARRY OUT 4R CHECKS.

F WEAK POINT F3 TEST

CARRY OUT 3D CHECKS.

If the weak point F3 is blown, there could be a shorts or grounds in electrical parts or wire harness. Check them and replace the defective parts or repair the wire harness.

CARRY OUT 4R CHECKS.

CAUTION: Only replace weak point F3 with the correct value replacement.

G FUSE F1, F2 F10A TEST

COM; Common terminal, NO; Normally open terminal NC; Normally close terminal

CARRY OUT 3D CHECKS.

If the fuse F1 F10A (or F2 F10A) is blown when the door is opened, check the interlock switch SW1 (or SW2) and monitor switch SW3 (or SW4). If thefuse F1 F10A (or F2 F10A) is blown by incorrect door switching replace the defective switch(s) and the fuse F1 F10A (or F2 F10A).

CARRY OUT 4R CHECKS.

CAUTION: Only replace fuse F1 F10A (or F2 F10A) with the correct value replacement.

H TEMPERATURE FUSE TF1, TF2, TF3 TEST

1. CARRY OUT 3D CHECKS.

2. A continuity check across the temperature fuse terminals should indicate a closed circuit unless the temperature of the temperature fuse reaches specfied temperature as shown below.

Open Close Display or temperature temperature Condition Check point

Magnetron temperature fuse (Upper)

TF1

Magnetron temperature fuse (Lower)

Exhaust temperature fuse

TF2

TF3

150˚C

120˚C

Non resetable type

EE1

EE3

EE2

Oven shut off

Magnetron Test magnetron

Magnetron MG1, MG2 Failure: Test magnetron MG1, MG2. Check blower motor and ventilation opening.

Magnetron MG2 Failure: Test magnetron

Food has been burned in oven. Temperature of oven inside is very high.

MG1 Failure:

MG1 and Blower motor.

MG2 and Blower motor.

3. CARRY OUT 4R CHECKS.

CAUTION: IF THE temperature fuse INDICATES AN OPEN CIRCUIT AT ROOM TEMPERATURE,

REPLACE temperature fuse.

I THERMISTOR TH1, TH2, TH3 TEST

1. CARRY OUT 3D CHECKS.

2. Follow the procedures below for each thermistor.

2-1. THERMISTOR TEST Disconnect the connector of the thermistor from the switch harness. Measure the resistance of the magnetron thermistor with an ohmmeter. Connect the ohmmeter leads to the leads of the thermistor.

Resistance: Approx. 500 kΩ -- 1 MΩ

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