Sharp R-480E, R-480E(K) Service Manual

R-480E R-480E(K)

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 ................................................................................................ 6

SERVICING ...................................................................................................................................................... 7

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

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

COMPONENT REPLACEMENT AND ADJUSTMENT PROCEDURE........................................................... 22

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

WIRING DIAGRAM......................................................................................................................................... 29

PICTORIAL DIAGRAM ................................................................................................................................... 30

POWER UNIT CIRCUIT ..................................................................................................................................31

CPU UNIT CIRCUIT ........................................................................................................................................32

PRINTED WIRING BOARD .............................................................................................................................33

PARTS LIST ................................................................................................................................................... 34

S7108R480EPJ/

MICROWAVE OVEN

MODELS R-480E

R-480E(K)

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

SHARP CORPORATION

SERVICE MANUAL

S E

N S

O R

D E

F R

O S

C O

O K

HEL

SENSOR INSTANT REHEAT

SENSOR COOK

isp

EASY

PIE

PIZ

LESS

INSTANT COO

12345 67890

R-480E R-480E(K)

SERVICE MANUAL

MICROWAVE OVEN

R-480E/ R-480E(K)

GENERAL IMPORTANT INFORMATION

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

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

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.

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

PRODUCT SPECIFICATIONS

APPEARANCE VIEW

OPERATING SEQUENCE

FUNCTION OF IMPORTANT COMPONENTS

SERVICING AND TROUBLESHOOTING CHART

TEST PROCEDURE

TOUCH CONTROL PANEL ASSEMBLY

COMPONENT REPLACEMENT AND ADJUSTMENT PROCEDURE

MICROWAVE MEASUREMENT

WIRING DIAGRAM

PARTS LIST

R-480E R-480E(K)

PRODUCT SPECIFICA TIONS

ITEM DESCRIPTION

Power Requirements 230 - 240 Volts

50 Hertz

Single phase, 3 wire earthed Power Consumption 1.65 kW Power Output 1150 watts nominal of RF microwave energy (IEC Test Procedure)

Operating frequency 2450 MHz

Case Dimensions Width 550 mm

Height 315 mm

Depth 446 mm Cooking Cavity Dimensions Width 401 mm

Height 237 mm

Depth 425 mm Turntable diameter 360mm Control Complement Touch Control System

Clock ( 1:00 - 12:59)

Timer (0 - 99 minutes 99 seconds)

Microwave Power for Variable Cooking

Repetition Rate;

HIGH ...............................................Full power throughout the cooking time

MEDIUM HIGH ..................................................approx. 70% of Full Power

MEDIUM .............................................................approx. 50% of Full Power

MEDIUM LOW ....................................................approx. 30% of Full Power

LOW....................................................................approx. 10% of Full Power

HELP pad

SENSOR INSTANT REHEAT pads

SENSOR COOK pads

SLOW COOK pad

EXPRESS DEFROST pad

EASY DEFROST pad

MORE, LESS pads

QUICK & EASY pad

NUMBER pads

POWER LEVEL pad

CLOCK pad

TIMER pad

STOP/CLEAR pad

INSTANT COOK/START pad Weight Approx. 19 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-480E R-480E(K)

APPEARANCE VIEW

1. Ventilation openings

2. Oven lamp

3. Door hinges

4. Door safety latches

5. See through door

6. Door seals and sealing surfaces

7. Coupling

8. Door open button

9. Touch control panel

10.Digital readout

11.Waveguide cover

12.Power supply cord

13.Rating label

14.Menu label

15.Turntable

16.Roller stay

TOUCH CONTROL PANEL

NOTE: The directed features are disabled after three minutes when the oven is not in use. These feature are automatically enabled when the door is opened and closed or the STOP/ CLEAR pad is pressed.

SENSOR DEFROST COOK

HELP

SENSOR INSTANT REHEAT

SENSOR COOK

Info Display

HELP

SOUP

CASSEROLE

DINNER

PLATE

EXPRESS

DEFROST

EASY

DEFROST

PIERICEPIZZA

VEGETABLES

RICE/PASTA

MEAT

SLOW COOK

QUICK &

EASY

DESSERTS

LESS MORE

STOP

CLEAR

INSTANT COOK

START

CLOCK

POWEER

LEVEL

TIMER

12345 67890

STOP/CLEAR PAD Press to clear during programming. Press once to stop operation of oven during cooking; press twice to cancel cooking programme.

POWER LEVEL PAD Press to select microwave power setting. If not pressed, HIGH is automatically selected.

INSTANT COOK/START PAD Press once to cook for 1 minute on HIGH or increase in 1 minute increments each time this pad is pressed during cooking. Press to start the oven after setting programmes.

(See NOTE.)

HELP PAD Press to select auto start, child lock, demonstration modes or info on pads. Press to get cooking information.

SENSOR INSTANT REHEAT PADS Press once to reheat 1 of 6 popular menus. (See NOTE.)

SENSOR COOK PADS Press to select Sensor Cook menus.

EASY DEFROST PAD Press to defrost frozen food by entering quantity.

QUICK AND EASY PAD Press to select Quick and Easy manus.

MORE( ), LESS ( ) PADS Press to increase/ decrease the time in one minute increments during cooking or alter the cooking result for automatic operations.

NUMBER PADS Press to enter cooking times, clock time, weight or quantity of food.

TIMER PAD Press to set Timer

CLOCK PAD Press to set Clock.

SLOW COOK PAD Press to cook slowly and for a long time.

EXPRESS DEFROST PAD Press to select the Express Defrost menus.

Indicator

Display

R-480E R-480E(K)

OPERATION SEQUENCE

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. latch switch and 2nd. interlock relay.

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

cycle of a cooking program, the 1st. latch switch and 2nd. interlock relay control switch must open their contacts first. After that the contacts (COM-NC) of the monitor switch can be closed.

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

NC) of the monitor switch must be opened first. After that the contacts of the 1st. latch switch and 2nd. interlock relay control switch are closed.

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

1st. latch switch and 2nd. interlock relay remain closed. The fuse M10A will blow, because the monitor switch is closed and a short circuit is caused.

VARIABLE COOKING

When the microwave oven is preset for variable cooking power. Rated voltage is supplied to the power transformer intermittently within a 32-second time base through the relay contact which is coupled with the relay (RY2). The following levels of microwave power are given.

SETTING;

OFF CONDITION

Closing the door activates all door interlock switches (1st. latch switch, 2nd. interlock relay control 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 noise filter and the control unit.

Figure O-1 on page 28

1. The display shows SHARP, MICRO-WAVE and OVEN.

2. To set any programs or set the clock, you must first touch the STOP/CLEAR pad.

3. “ : “ appears in the display.

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

comes on at this time.

MICROWAVE COOKING CONDITION

HIGH COOKING

Enter a desired cooking time with the touching Number pads 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 power transformer. The voltage is converted to about

3.3 volts A.C. output on the filament winding and high voltage of approximately 2000 volts A.C. on the secondary winding.

2. The filament winding voltage (3.3 volts) heats the magnetron filament and the high voltage (2000 volts) is sent to the voltage doubling circuit, where it is doubled to negative voltage of approximately 4000 volts D.C..

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

4. When the cooking time is up, a signal tone is heard and the relays (RY1+RY2) go back to their home position (off condition)º. 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

(NO COOKING) 1st. latch switch COM-NO Closed Open 2nd. interlock relay

control switch COM-NO Closed Open Monitor switch COM-NC Open Closed

The circuits to the power transformer, fan motor and turntable motor are cut off when the 1st. latch switch and 2nd. interlock relay control switch are made open. The oven lamp remains on even if the oven door is opened after the cooking cycle has been interrupted,

NOTE: The ON/OFF time ratio does not exactly correspond

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

SENSOR COOKING CONDITION

Using the SENSOR COOK or SENSOR INSTANT REHEAT function, the foods are cooked or reheated without figuring time, power level or quantity. When the oven senses enough steam from the food, it relays the information to its microprocessor which will calculate the remaining cooking time and power level needed for best results. When the food is cooked, water vapor is developed. The sensor “senses” the vapor and its resistance increases gradually. When the resistance reaches the value set according to the menu, supplementary cooking is started. The time of supplementary cooking is determined by experiment with each food category and inputted into the LSI.

An example of how sensor works:

HIGH

32 sec. ON

MEDIUM HIGH Approx. 70%

24 sec. ON 8 sec. OFF

14 sec. OFF

20 sec. OFF

26 sec. OFF

MEDIUM Approx. 50%

18 sec. ON

MEDIUM LOW Approx. 30%

12 sec. ON

LOW Approx. 10%

6 sec. ON

R-480E R-480E(K)

2. Heat potatoes. Moisture and humidity is emitted rapidly. You can smell the aroma as it cooks.

3. Sensor detects moisture and humidity and calculates cooking time and variable power.

Cooking Sequence.

1. Touch each SENSOR COOK or SENSOR INSTANT REHEAT function pad to operating the sensor cooking.

NOTE: The oven should not be operated on SENSOR

COOK or SENSOR INSTANT REHEAT immediately after plugging in the unit. Wait two minutes before cooking on SENSOR COOK or SENSOR INSTANT REHEAT.

2. The coil of shut-off relay (RY-1) is energized, the turntable motor, oven lamp and cooling fan motor are turned on, but the power transformer is not turned on.

3. After about 16 seconds, the cook relay (RY-2) is energized. The power transformer is turned on, microwave energy is produced and first stage is started. The 16 seconds is the cooling time required to remove any vapor from the oven cavity and sensor.

NOTE: During this first stage, do not open the door or

touch STOP/CLEAR pad.

4. When the sensor detects the vapor emitted from the food, the display switches over to the remaining cooking time and the timer counts down to zero. At this time, the door may be opened to stir food, turn it or season, etc.

5. When the timer reaches zero, an audible signal sounds. The shut-off relay and cook relay are de-energized and the power transformer, oven lamp, etc. are turned off.

6. Opening the door or touching the STOP/CLEAR pad, the time of day will reappear on the display and the oven will revert to an OFF condition.

POWER OUTPUT REDUCTION

After 100% power cooking mode is carried out more than 40 minutes, the power output is automatically reduced to 70%.

1. Potatoes at room temperature. Vapor is emitted very slowly.

MICROWAVE

AH SENSOR

R-480E R-480E(K)

Figure D-1. Door Open Mechanism

1ST. LATCH SWITCH AND 2ND. INTERLOCK RELAY CONTROL SWITCH

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

2. When the oven door is opened, the contacts (COMNO) 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 (COMNC) must be closed.

3. If the oven door is opened and the contacts (COM-NO) of the 1st. latch switch and 2nd. interlock relay fail to open, the fuse (M10A) blows simultaneously with closing the contacts (COM-NC) of the monitor switch.

CAUTION: BEFORE REPLACING A BLOWN FUSE

(M10A) TEST THE 1ST. LATCH SWITCH, 2ND. INTERLOCK RELAY, MONITOR SWITCH AND MONITOR RESISTOR FOR PROPER OPERATION. (REFER TO CHAPTER "TEST PROCEDURE".)

MONITOR RESISTOR (0.8Ω 20W)

The monitor resistor prevents the fuse (M10A) bursting when the fuse (M10A) blows due to the operation of the monitor switch.

FUSE (M10A)

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

2. The fuse also blows when 1st. latch switch and 2nd. interlock relay remains closed with the oven door open and when the monitor switch closes.

FUNCTION OF IMPORTANT COMPONENTS

DOOR OPEN MECHANISM

The door can be opened by pushing the door open button on the control panel. When the door open button is pushed, the latch lever is moved upward, operating the latch head. The latch head is moved upward, and released from latch hook. Now the door can be opened.

HIGH VOLTAGE FUSE 0.75A

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

THERMAL CUT-OUT 145˚C (OVEN)

The thermal cut-out located on the top of the oven cavity is designed to prevent damage to the oven if the foods in the oven catch fire due to over heating produced by improper setting of cook time or failure of control unit. Under normal operation, the oven thermal cut-out remains closed. However, when abnormally high temperature is 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 replaced with new one.

THERMAL CUT-OUT 145˚C (MAGNETRON)

The thermal cut-out located near the magnetron is designed to prevent damage to the magnetron if an over heated condition develops in the tube due to cooling fan failure, obstructed air guide, dirty or blocked air intake, etc. Under normal operation, the thermal cut-out remains closed. However, when abnormally high temperatures are reached within the magnetron, the thermal cut-out will open at 145˚C causing the oven to shut down. The defective thermal cut-out must be replaced with new one.

TURNTABLE MOTOR

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

FAN MOTOR

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

NOISE FILTER

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

Latch Hook

1st. Latch Switch

Monitor Switch

Switch Lever

Latch Heads

Door

2nd. Interlock Relay Control Switch

R-480E R-480E(K)

SERVICING

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 fuse, 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 connection of the high-voltage capacitor (that is, of the connecting lead of the high-voltage rectifier) against the chassis with the use of an insulated screwdriver.

Sharp recommend that wherever possible fault-finding is carried out with the supply disconnected. It may, in some cases, be necessary to connect the supply after the outer case has been removed, in this event carry out 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.

WARNING TO SERVICE PERSONNEL

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 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 3D checks and reexamine 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.

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 M10A in the 1st. latch switch - 2nd. interlock relay - monitor switch

- monitor resistor circuit, check the 1st. latch switch, 2nd. interlock relay, monitor switch and monitor resistor before replacing the fuse M10A.

R-480E R-480E(K)

CK = Check / RE = Replace

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

FUSE M10A blows when power supply cord is plugged into wall outlet.

Display does not show anything when power supply cord is plugged into wall outlet.

Display does not operate properly 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)

Oven lamp does not light (Display appears.)

Fan motor does not operate. (Display appears.)

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

Oven or any electrical parts does not stop when cooking time is 0 or STOP/CLEAR pad is touched.

Oven seems to be operating but little or no heat is produced in oven load. (Microwave power level is set at HIGH)

Oven does not seems to be operating properly when MEDIUM HIGH, MEDIUM, MEDIUM LOW or LOW is set. (Oven operates properly at HIGH and when the STOP/CLEAR pad is touched the oven stops.)

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

Oven stops as soon as when the START pad is touched.

AH sensor does not end during Sensor Cooking condition. (Oven does not shut off after a cup of water is boiling by sensor cooking.)

Oven stops at 16 sec. after starting.

MAGNETRON

POWER TRANSFORMER

H.V. RECTIFIER ASSEMBLY

HIGH VOLTAGE CAPACITOR

1ST. LATCH SWITCH

2ND. N D. INTERLOCK RELAY

CONTROL SWITCH

MONITOR SWITCH

NOISE FILTER

MONITOR RESISTOR

THERMAL CUT-OUT (MAGNETRON)

THERMAL CUT-OUT (OVEN)

FAN MOTOR

TURNTABLE MOTOR

FUSE M10A

HIGH VOLTAGE FUSE

TOUCH CONTROL PANEL

KEY UNIT

RELAY (RY-1, RY-2)

FOIL PATERN ON P.W.B.

POWER SUPPLY CORD

OVEN LAMP OR SOCKET

SHORTED WIRE HARNESS

OPENED WIRE HARNESS

WALL OUTLET

HOME FUSE OR BREAKER

WRONG OPERATION

MISADJUSTMENT SWITCH

BLOCKED COOLING FAN

BLOCKED VENTILATION OPENING

AH SENSOR

ABCDEEEFG HHIIJKLMNO

RE RE CK CK CK CK CK CK CK CK P

POSSIBLE CAUSE

AND

DEFECTIVE PARTS

TEST PROCEDURE

PROBLEM

SENSOR COOKING CONDITION

CONDITION

OFF CONDITION

ON CONDITION

R-480E R-480E(K)

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 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 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 IEC test procedure, i.e. it can be measured by using water load how much it can be absorbed by the water load. To measure the microwave output power in the microwave oven, the relation of calorie and watt is used. When P(W) heating works for t(second), approximately P x t/4.187 calorie is generated. On the other hand, if the temperature of the water with V(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)/

4.187P (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.............................. 36 sec. Mass of container (mc)......................... 330 g

T2............................ Final Temperature P = 115 x ∆T + 0.55 x mc (T2-T0)/36

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±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 an accurate thermometer.

7. The water load must be (1000±5) g.

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

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

up time.

Measuring method:

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

2. Add the 1 litre water to the vessel.

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

4. Operate the microwave oven at HIGH for the temperature of the water rises by a value ∆ T of 10 ˚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.

R-480E R-480E(K)

TEST PROCEDURES

PROCEDURE

LETTER

COMPONENT TEST

Room temperature .................. To = 21˚C Initial temperature ................. T1 = 11°C

Temperature after (36 + 3) = 39 sec. ................................................................ T2 = 21°C

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

Measured output power

The equation is “P = 115 x ∆T” ........................................... P = 115 x 10°C = 1200 Watts

Heat up for 39 sec.

1000g

T1˚C

T2˚C

B POWER TRANSFORMER TEST

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

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

CARRY OUT 3D CHECKS. Disconnect the leads to the primary winding of the power transformer. Disconnect the filament and

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

a. Primary winding .................. approx. 1.0 Ω

b. Secondary winding .............. approx. 87 Ω

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

If the reading obtained are not stated as 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 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.

HIGH VOLTAGE RECTIFIER

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

CAUTION: 1°C CORRESPONDS TO 115 WATTS REPEAT MEASUREMENT IF THE POWER IS

INSUFFICIENT.

+ 28 hidden pages

Sharp R-480E, R-480E(K) Service Manual

Specifications and Main Features

Frequently Asked Questions

User Manual