Sharp R-350D Service Manual

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Page 1

R-350D

SHARP CORPORATION

SERVICE MANUAL

S7005R350DPJ/

MICROWAVE OVEN

MODEL R-350D

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

TABLE OF CONTENTS

Page

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

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

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

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

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

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

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

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

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

TOUCH CONTROL PANEL .............................................................................................................................14

COMPONENT REPLACEMENT AND ADJUSTMENT PROCEDURE ........................................................... 18

MICROWAVE MEASUREMENT .................................................................................................................... 24

WIRING DIAGRAM ......................................................................................................................................... 25

PICTORIAL DIAGRAM ................................................................................................................................... 26

POWER UNIT CIRCUIT ..................................................................................................................................27

CPU UNIT CIRCUIT ........................................................................................................................................28

PRINTED WIRING BOARD .............................................................................................................................29

PARTS LIST ................................................................................................................................................... 30

DINNER PLATE

PASTA MEAL

FROZEN DINNER

CASSEROLE

SOUP

PIE

PIZZA

POWER LEVEL

LESS MORE

STOP CLEAR

INSTANT COOK

START

CLOCK

TIMER

EASY

DEFROST

EXPRESS

DEFROST

BEVERAGE

MEAT

VEGETABLES

RICE/

PASTA

CONVENIENCE MEALS

REHEAT MENU

INFORMATION COOK

1234 6789

5 0

DEFROST COOK

HELP

Info Display

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R-350D

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R-350D

SERVICE MANUAL

MICROWAVE OVEN

R-350D

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

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R-350D

ITEM DESCRIPTION

Power Requirements 230 - 240 Volts

50 Hertz

Single phase, 3 wire earthed Power Consumption 1.6kW Power Output 1100 watts nominal of RF microwave energy (IEC Test Procedure)

Operating frequency 2450 MHz Case Dimensions Width 520 mm

Height 302 mm including foot

Depth 436 mm Cooking Cavity Dimensions Width 374 mm

Height 227 mm

Depth 399 mm Turntable diameter 335 mm Control Complement Touch Control System

Clock ( 1:00 - 12:59)

Timer (0 - 99 minutes 99 seconds)

Microwave Power for Variable Cooking

Repetition Rate;

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

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

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

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

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

INSTANT ACTION pads

EXPRESS DEFROST pad

EASY DEFROST pad

NUMBER pads

POWER LEVEL pad

TIMER/CLOCK pad

STOP/CLEAR pad

INSTANT COOK/START pad Set Weight Approx. 17 kg

PRODUCT SPECIFICA TIONS

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

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R-350D

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 handle

9. Touch control panel

10.Digital readout

11.Waveguide cover

12.Power supply cord

13.Rating label

14.Turntable tray

15.Turntable support

TOUCH CONTROL PANEL

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

DINNER

PLATE

PASTA MEAL

FROZEN DINNER

CASSEROLE

SOUP

PIZZA

POWER

LEVEL

LESS MORE

STOP

CLEAR

INSTANT COOK

START

CLOCK

TIMER

EASY

DEFROST

EXPRESS

DEFROST

BEVERAGE

PIE

MEAT

VEGETABLES

RICE/

PASTA

CONVENIENCE MEALS

REHEAT MENU

INFORMATION COOK

12345 6789

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 to start the oven after setting programmes. Press once to cook for 1 minute on HIGH or increase in 1 minute increments each time this pad is pressed during cooking. (See note.)

HELP PAD Press to select auto start, child lock or demonstration modes. Press to display preset menu cooking information.

CONVENIENCE MEALS PADS Press to select Convenience Meals menus.

INFORMATION COOK PADS Press to select information Cook mode.

EASY DEFROST PAD Press to select Easy Defrost menu.

REHEAT MENU PADS Press to select a reheat menu.

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

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

EXPRESS DEFROST PAD Press to select Express Defrost menu.

TIMER PAD Press to set Timer.

CLOCK PAD Press to set Clock.

Indicator

Display

DEFROST COOK

HELP

Info Display

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R-350D

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 noise filter and the control unit.

Figure O-1 on page 25

1. The display shows "SHARP MICRO-WAVE OVEN".

2. To set any programmes 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 pad and start the oven with touching START pad.

Function sequence

Figure O-2 on page 25

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 channeled 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. 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. 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 When the oven door is opened during or after the

cycle of a cooking program, the 1st. latch switch, 2nd. latch switch and stop 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. 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 M10A 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;

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

to the percentage of microwave power, because approx. 2 seconds are needed for heating up the magnetron filament.

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%

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R-350D

FUNCTION OF IMPORTANT COMPONENTS

OVEN THERMAL CUT-OUT

The thermal cut-out, located on the top of the oven cavity, is designed to prevent damage to the oven by fire. If the foods load is overcooked, by either error in cook time or defect in the control unit, the thermal cut-out will open. Under normal operation, the oven thermal cut-out remains closed. However, when abnormally high temperatures are reached within the oven cavity, the oven thermal cut-out will open at 125˚C, causing the oven to shut down. The defective thermal cut-out must be replaced with new one.

MAGNETRON THERMAL CUT-OUT

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 95˚C causing the oven to shut down, when the magnetron has cooled to 75˚C, the thermal cut-out closes and cook cycle will resume.

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 channeled 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

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

DOOR OPEN MECHANISM

The door is opened by pulling the door, refer to the Figure D-1.

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. 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. latch switch 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. LATCH SWITCH MONITOR SWITCH AND MONITOR RESISTOR FOR PROPER OPERATION.

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.

HIGH VOLTAGE FUSE

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

FUSE M10A

1. The fuse M10A blows when the contacts (COM-NO) of the 1st. latch switch and 2nd. latch switch remain closed with the oven door open and when the monitor switch closes.

2. If the wire harness or electrical components are shortcircuited, this fuse M10A blows to prevent an electric shock or fire hazard.

Latch Hook

Stop Switch

2nd. Latch

Switch Latch Heads

Door

Monitor Switch

1st. Latch

Switch

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R-350D

SERVICING

WARNING TO SERVICE PERSONNEL

Microwave ovens contain circuitry capable of producing very high voltage and current, contact with following parts 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 the 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.

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 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.

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

IMPORTANT: If the oven becomes inoperative because

of a blown fuse M10A in the 1st. latch switch - 2nd. latch switch - monitor switch

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

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R-350D

MAGNETRON

POWER TRANSFORMER

H.V. RECTIFIER ASSEMBLY

HIGH VOLTAGE CAPACITOR

1ST. LATCH SWITCH

2ND. LATCH SWITCH

STOP SWITCH

MONITOR SWITCH

MONITOR RESISTOR

THERMAL CUT-OUT 95˚C /125˚C

FAN MOTOR

TURNTABLE MOTOR

FUSE M10A

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

HIGH VOLTAGE FUSE

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 then the STOP/ CLEAR pad is touched the oven stops.)

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

TEST PROCEDURE

CK = Check / RE = Replace

ABCDEEEEGFH HILMNO

RECK CK RE CK CKCKCK CK

CONDITION

PROBLEM

POSSIBLE CAUSE

AND

DEFECTIVE PARTS

ON CONDITION

OFF CONDITION

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R-350D

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)

(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.............................. 38 sec. Mass of container (mc) ......................... 330 g

T2............................ Final Temperature P = 110 x ∆T + 0.55 x mc (T2-T0)/38

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 heatup 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.

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.

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R-350D

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

Temperature after (38 + 2) = 40 sec. ................................................................ T2 = 21°C

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

Measured output power

The equation is “P = 110 x ∆T” ........................................... P = 110 x 10°C = 1100 Watts

TEST PROCEDURES

PROCEDURE

LETTER

COMPONENT TEST

1000g

T1˚C

T2˚C

Heat up for 40 sec.

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

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

CAUTION: 1°C CORRESPONDS TO 110 WATTS REPEAT MEASUREMENT IF THE POWER IS

INSUFFICIENT.

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R-350D

CARRY OUT 3D CHECKS. Disconnect the leads from the monitor resistor. Using an ohmmeter and set on a low range. Check

between the terminals of the monitor resistor.

The resistance of monitor resistor is approx. 0.8 ohms.

G MONITOR RESISTOR TEST

TEST PROCEDURES

PROCEDURE

LETTER

COMPONENT TEST

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. 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.

Table: Terminal Connection of Switch

Plunger Operation COM to NO COM to NC COM; Common terminal

Released Open circuit Short circuit NO; Normally open terminal Depressed Short circuit Open circuit NC; Normally close terminal

If incorrect readings are obtained, make the necessary switch adjustment or replace the switch. CARRY OUT 4R CHECKS.

CARRY OUT 3D CHECKS. Disconnect the leads from the terminals of the temperature fuse or thermal cut-out. Then using an

ohmmeter, make a continuity test across the two terminals as described in the table below. CARRY OUT 4R CHECKS.

Table: Temperature fuse and 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 125˚C This is not resetable type. Above 125˚C Closed circuit. Thermal cut-out 95˚C Below 75˚C Above 95˚C Closed circuit.

If incorrect readings are obtained, replace the temperature fuse or thermal cut-out. An open circuit thermal cut-out 95˚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 125˚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.

F TEMPERATURE FUSE AND THERMAL CUT-OUT TEST

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R-350D

TEST PROCEDURES

PROCEDURE

LETTER

COMPONENT 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.

Table: Resistance of Motor

Motors Resistance Fan motor Approximately 390 Ω Turntable motor Approximately 12 kΩ

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

H MOTOR WINDING TEST

CARRY OUT 3D CHECKS.

1. If the fuse M10A 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 M10A is blown when the door is opened, check the 1st. latch switch, 2nd. latch switch, monitor switch and monitor resistor. If the fuse M10A is blown by incorrect door switching replace the defective switch(s) and the fuse M10A.

CARRY OUT 4R CHECKS. CAUTION: ONLY REPLACE FUSE M10A WITH THE CORRECT VALUE REPLACEMENT

I BLOWN FUSE M10A

J NOISE FILTER TEST

CARRY OUT 3D CHECKS. Disconnect the leads from the terminals of the noise filter. Using an ohmmeter, check between the terminals as described in the following table.

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

If incorrect readings are obtained, replace the noise filter unit. CARRY OUT 4R CHECKS.

WHT

RED

L (min) Cx ± 20% Cy ± 20% 600µH 0.068µF 0.0022µF

CARRY OUT 3D CHECKS. If the high voltage fuse is blown, there could be a short in the high voltage rectifier or the magnetron.

Check them and replace the defective parts and high voltage fuse. CARRY OUT 4R CHECKS. CAUTION: ONLY REPLACE THE HIGH VOLTAGE FUSE WITH THE CORRECT VALUE RE-

PLACEMENT

K HIGH VOLTAGE FUSE TEST

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

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R-350D

TEST PROCEDURES

PROCEDURE

LETTER

COMPONENT TEST

M KEY UNIT TEST

If the display fails to clear when the STOP/CLEAR pad is depressed, first verify the flat ribbon cable is making good contact, verify that the door sensing switch (stop switch) operates properly; that is the contacts are closed when the door is closed and open when the door is open. If the door sensing switch (stop switch) is good, disconnect the flat ribbon cable 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 door sensing switch connector). Use the key unit matrix indicated on the control panel schematic and place a jumper wire between the pins that correspond to the STOP/CLEAR pad making momentary contact. If the control unit responds by clearing with a beep the key unit is faulty and must be replaced. If the control unit does not respond, it is faulty and must be replaced. If a specific 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. CARRY OUT 3D CHECKS.

L 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 also the Control Unit is divided into two units, CPU Unit and Power Unit, and troubleshooting by unit replacement is described according to the symptoms indicated.

1. Key Unit. Note: Check key unit ribbon connection before replacement. 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 Unit. The following symptoms indicate a defective control unit. Before replacing the control unit, perform the Key unit test (Procedure M) to determine if control unit is faulty.

2-1 In connection with pads.

a) When touching the pads, a certain group of pads do not produce a signal. b) When touching the pads, no pads produce a signal.

2-2 In connection with indicators.

a) At a certain digit, all or some segments do not light up. b) At a certain digit, brightness is low. c) Only one indicator does not light. d) The corresponding segments of all digits do not light up; or they continue to light up. e) Wrong figure appears. f) A certain group of indicators do not light up. g) The figure of all digits flicker.

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

a) Buzzer does not sound or continues to sound. b) Clock does not operate properly. c) Cooking is not possible.

09876

BEVERAGE

POWER

LEVEL

FROZEN

DINNER

MEAT CLOCK TIMER

HELP

LESS

DINNER

PLATE

RICE/

PASTA

MEAL

EASY

DEFROST

EXPRESS

DEFROST

STOP

CLEAR

VEGETABLES

INSTANT

COOK

START

G 8

G 9

G10

G11

G12

G13

G14

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

SOUP

CASSEROLE

PIE PIZZA

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R-350D

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. CARRY OUT 3D CHECKS.

STEPS OCCURRENCE CAUSE OR CORRECTION

The rated AC voltage is not present between

1 Pin No. 1 of the 2-pin connector (A) and the Check supply voltage and oven power cord.

normal open terminal of the relay RY1.

The rated AC voltage is present to 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. 4 Pattern at "a" and "b" are broken. *Insert the coil RCILF2003YAZZ between "c" and "d".

NOTE: *At the time of making these repairs,

make a visual inspection of the varistor. Check for burned damage and examine the transformer with a tester for the presence of layer short-circuit (check the primary coil resistance). If any abnormal condition is detected, replace the defective parts.

CARRY OUT 4R CHECKS.

TEST PROCEDURES

PROCEDURE

LETTER

COMPONENT TEST

N RELAY TEST

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

(PWB) IS OPEN

Remove the outer case and check voltage between Pin No 1 of the 2-pin connector (A) and the normal open terminal of the relay RY1 on the power unit with an A.C. voltmeter. The meter should indicate 230 - 240 volts, if not check oven circuit.

RY1 and RY2 Relay Test These relays are operated by D.C. voltage. 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. 24.0V D.C. Oven lamp / Turntable motor / Cooling fan motor RY2 APPROX. 23.0V D.C. Power transformer

CARRY OUT 4R CHECKS.

RY1

VRS1

RY3

(J1)

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R-350D

TOUCH CONTROL PANEL ASSEMBLY

OUTLINE OF TOUCH CONTROL PANEL

The touch control section consists of the following units. (1) Key Unit

(2) Control Unit (The Control Unit consists of Power Unit

and LSI 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 P10-P17. When a key pad is touched, a signal is completed through the key unit and passed back to the LSI through AN11, AN10, AN9, P42, P41 and AN8 to perform the function that was requested.

Control Unit

Control unit consists of LSI, ACL circuit, indicator circuit, power source circuit, relay circuit, buzzer circuit, synchronizing signal circuit and back light circuit.

1) ACL

This circuit generates a signal which resets the LSI to the initial state when power is supplied.

2) Indicator Circuit

This circuit consists of 40 segments and 16 common electrodes using a Liquid Crystal Display. The Liquid Crystal Display (LCD) is drived by LCD driver IC3.

3) Power Source Circuit

This circuit generates voltages necessary in the control unit from the AC line voltage. In addition, the synchronizing signal is available in order to compose a basic standard time in the clock circuit.

Symbol Voltage Application

VC -5V LSI(IC1)

4) Relay Circuit

A circuit to drive the magnetron, fan motor, turntable motor and light the oven lamp.

5) Buzzer Circuit

The buzzer is responsive to signals from the LSI to emit audible sounds (key touch sound and completion sound).

6) 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.

7) Door Sensing Switch

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

8) Back Light Circuit

A circuit to drive the back light (Light emitting diodes LD10-LD19).

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R-350D

1 AN10 IN Signal coming from touch key.

When either G10 line on key matrix is touched, a corresponding signal out of P10 - P17 will be input into AN10. When no key is touched, the signal is held at "H" level.

2 AN11 IN Signal similar to AN10.

When either G9 line on key matrix is touched, a corresponding signal will be input into

AN11. 3 AVSS IN Connected to VC. 4 P10 OUT Key strobe signal.