SHARP R420BK, R-420BW Service Manual

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Page 1

R-420BK R-420BW

SHARF?

SERVICE MANUAL

S28M104R420BE

MICROWAVE OVEN MODELS

R-420BK / R-420BW

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

WARNING TO SERVICE PERSONNEL: Microwave ovens contain circuitry capable of producing very high voltage and current. Contact with the following parts may result in a severe, possibly fatal electrical shock.(High Voltage Capacitor, High Voltage Power Transformer, Magnetron, High Voltage Rectifier Assembly, High Voltage Harness etc..)

SECTION

PRECAUTIONS TO BE OBSERVED BEFORE AND DURING SERVICE TO AVOID POSSIBLE EXPOSURE TO EXCESSIVE MICROWAVE ENERGY.

Before Servicing .............................................................

Warning to Service Personnel

Forewordandwarning .......................................................................

Specifications

Generallnformation .........................................................................

KeyUnitLayout .............................................................................

Operation ..................................................................................

Servicing and Troubleshooting Guide TestProcedures

TouchControlOutline .......................................................................

Component Replacement and Adjustment Procedure

Microwave Measurement Procedure

Wiring/Schematic Diagram

Parts .....................................................................................

Packing and Accessories ....................................................................

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

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

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

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

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

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

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

SHARP ELECTRONICS CORPORATION

...........

PAGE

Inside Front Cover Inside Front Cover

1 2 3 4 5 6 9

11 21 25 35 36 41 46

Service Headquarters: Sharp Plaza, Mahwah, New Jersey, 07430-2135

Page 2

R-420BK R-420BW

Do not operate or allow the oven to be operated with the door open.

( )

Make the following safety checks on all ovens to be serviced before activating the magnetron

(b)

or other microwave source, and make repairs as necessary: (1) Interlock operation, (2) proper door closing, (3) seal and sealing surfaces (arcing, wear, and other damage), (4) damage to or loosening of hinges and latches, (5) evidence of dropping or abuse.

Before turning on microwave power for any service test or inspection within the microwave gen-

( )

erating compartments, check the magnetron, waveguide or transmission line, and cavity for proper alignment, integrity, and connections.

Any defective or misadjusted components in the interlock, monitor, door seal, and microwave

generation and transmission systems shall be repaired, replaced, or adjusted by procedures described in this manual before the oven is released to the owner.

A microwave leakage check to verify compliance with the Federal Performance Standard

( )

should be performed on each oven prior to releasing oven to the owner.

Before servicing an operative unit, perform a microwave emission check as per the Microwave Measurement Procedure outlined in this service manual. If microwave emissions level is in excess of the specified limit, contact SHARP ELECTRONICS CORPORATION immediately @ l-800-237-4277.

If the unit operates with the door open, service person should 1) tell the user not to operate the oven and 2) contact SHARP ELECTRONICS CORPORATION and DHHS immediately.

(RD21101U)

Service personnel should inform SHARP ELECTRONICS CORPORATION of any certified unit found with emissions in excess of 4mW/cm2. The owner of the unit should be instructed not to use the unit until the oven has been brought into compliance.

(RD81001 U)

Page 3

SERVICE MANUAL

SHARI?

R-420BK R-420BW

Microwave Ovens R=420BK/R=420BW

Foreword

This manual has been prepared to provide Sharp

Electronics Corporation personnel with complete operation and service information for Sharp microwave oven models R-420BWR-420BW.

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

Check interlock switches and the door seal carefully.

Special attention must be given to avoid electrical shock

and microwave radiation hazards.

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 are no other visible signs of damage to the

oven.

DANGER

Certain initial parts are intentionally not grounded and present a risk of electrical shock only during servicing. Service personnel - Do not contact the following parts while the appliance is energized; High Voltage Capacitor, Power Transformer, Magnetron, High Voltage Rectifier Assembly and High voltage Harness. If provided, Vent Hood, Fan Assembly and Cooling Fan motor.

All of the parts marked ages more than 25OV.

Removal of the outer case cabinet gives access to voltage above 250V.

All of the parts marked “A” on parts list may cause undue microwave exposure, by themselves, or when they are damaged, loosened or removed.

“*” on parts list are used at volt-

Specifications

General Information

Key Unit Layout

Operation

Troubleshooting /

Touch Control Panel

Component Replacement and Adjustment

Microwave Measurement

Wiring / Schematic

Diagram

Sharp Electronics Corporation

Sharp Plaza

Mahwah, New Jersey 07430-2135

Page 4

R-420BK R-420BW

WARNING TO SERVICE PERSONNEL

Microwave ovens contain circuitry capable of producing very high voltage and current. Contact with following parts may result in a severe, possibly fatal, electrical shock.

(EXAMPLE) High Voltage Capacitor, High Voltage Power Transformer, Magnetron, High Voltage Rectifier Assembly, High Voltage Harness etc.. Read the Service Manual carefully and follow all instructions.

Before Servicing

Rage

1. Disconnect the power supply cord and then remove outer case

2. Open the door and block it open.

3. Discharge the high voltage capacitor.

WARNING:RlSK QF ELECTRICAL SHOCK. DISCHARGE THE HIGH VOLTAGE CAPACITOR BEFORE SERVICING.

The high-voltage capacitor remains charged about 60 se- conds after the oven has been switched off. Wait for 60 se-

1 conds and then short-circuit the connection of the high volt- ~ age capacitor (that is the connecting lead of the high voltage

rectifier) against the chassis with the use of an insulated

screwdriver.

Whenever troubleshooting is performed, the power supply must be disconnected. In some cases it may be necessary to connect the power supply after the outer case has been removed, in this event:

Disconnect the power supply cord, and then remove outer case cabinet.

Open the door and block it open.

Discharge the high voltage capacitor.

Disconnect the leads to the primary of the power

transformer.

Ensure that the leads remain isolated from other

5. components and oven chassis by using insulation tape.

After the above procedure, reconnect the power sup-

ply cord.

When the testing is completed

1. Disconnect the power supply cord and then remove outer case cabinet.

2. Open the door and block it open.

3. Discharge the high voltage capacitor.

4. Reconnect the leads to the primary of the power transformer.

5. Re-install the outer case cabinet.

6. Reconnect the power supply cord after the outer case cabinet is installed.

7. Start the oven and check all functions.

After repairing

1. Reconnect all leads removed from components during testing.

2. Re-install the outer case (cabinet).

3. Reconnect the power supply cord after the outer case is installed.

4. Reconnect the power supply cord after the outer case is installed.

5. Run the oven and check all functions.

Microwave ovens should not be operated 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 power to HIGH and set the microwave timer for two (2) minutes. When the two minutes has

elapsed (timer at zero), carefully check to see if the water is hot. If the water remains cold, carry out Before

Servicing procedure and re-examine the connection 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 the microwave leakage test should be car-

ried out.

Page 5

SPECIFICATIONS

R-420BK R-420BW

Item

Power Requirements

Power Output 1100 watts (IEC-705 Test Procedure)

Case Dimensions

Cooking Cavity

1.3 Cu.Ft.

Control Complement

Description

120 Volts 14 Amperes 1650 Watts 60 Hertz Single phase, 3 wire grounded

Operating frequency of 2450 MHz

Width 2111&” Height 123/i’ (including feet) Depth 1731;’

Width 15” Height 8”/23”

Depth 163/i

Tray Size 141/8)’ Diameter

Touch Control System Clock (I:00 - 12:59) Timer (0 - 99 min. 99 sec.)

Microwave Power for variable cooking

Repetition Rate;

P-HI (HIGH) . . . . . . . . . Full power throughout the cooking time

P-90 . . . . . . . . . . . , . . . . . approx. 90% of full power

P-80 . . . . . . . . . . . . . . . . . approx. 80% of full power

P-70 (MED HIGH) . . . .

P-60 . . . . . . . . . . . , . . . . . approx. 60% of full power

P-50 (MED) . . . . . . . . . . approx. 50% of full power

P-40 . . . . . . . . . . . , . . . . . approx. 40% of full power

P-30 (MED LOW) . . . . .

P-20 . . . . . . , . . . . , . . . . . approx. 20% of full power

P-IO . . . . . . . . . . . , . . . . . approx. 10% of full power

P-O................... No power throughout the cooking time

approx. 70% of full power

approx. 30% of full power

Oven Cavity Light Safety Standard

FEATURES

Instant Action Compu Defrost Sensor Cook Minute Plus Kitchen Timer Variable Power (10) 4 Stage Cooking

Yes

UL Listed FCC Authorized DHHS Rules, CFR, Title 21, Chapter 1, Subchapter J

Page 6

R-420BK R-420BW

Grounding

GENERAL INFORMATION

Instructions

This

oven

must be appliance only, ommended appliance observe all

WARNING:

result

must be connected to a

Ampere

or more fused

that

provided. When installing

applicable

Improper

a risk

Where a two-pronged is

the personal tomer to placed

with pronged an

extension

responsibility

contact a

a properly

wall

receptacle cord must be used, it

15 ampere minimum

Oven Diagram

fully grounded at all

120

electrical

separate

codes

use of the

electric

circuit serving only

and

ordinances.

grounding

shock.

wall-receptacle is

and

obligation of

qualified

electrician and

polarized

use

and

a grounding adaptor. If

should be a

cord.

times.

volt,

This

Hz, AC

supply. It is rec-

this

this appliance,

plug

can

encountered,

the

cus-

have

re-

grounded three-

3-wire,

Grounded Receptacle

Box

Pronged

Grounded Receptacle

Plug

Box

Grounding Receptacle

Grounding

Pronged

Receptacle

Do not under any circumstances cut round grounding

prong

from this plug.

Screw

Tab

for

Grounding

Screw

’

remove

the

1. Digital display

2. Auto-Touch control panel

3. Door open button

4. Door latches

5. Removable turntable support

6. Removable turntable

7. Oven lamp

8. Oven door with see through window

9. Waveguide cover

10. Power Cord

Page 7

Key Unit Layout

a. Indicators. b. Lighted digital display. c. SENSOR COOK pad.

Touch to cook popular items using a pre-set time

constant.Instant Action pad.

d. INSTANT ACTION pad.

Pre-set time constant for some popular food items in everyday life style

e. COMPU DEFROST pad.

Touch to defrost certain foods.

f. Number selection pads.

g. AUTO START/CLOCK pad.

Touch to set clock or auto start time.

h. KITCHEN TIMER pad.

Touch to set minute function.

i. START pad.

Touch to start oven.

j. MINUTE PLUS pad.

Touch to cook for 1 minute at 100% power or to increase

cooking time.

k. STOP/CLEAR pad.

Touch to erase during programming.

Touch once to stop operation of oven during cooking. Touch twice to cancel cooking program.

I. POWER LEVEL pad.

Touch to select microwave power setting.

R-420BK R-420BW

SENSOR COOK

INSTANT ACTION

COMPU DEFROS

Page 8

R-420BK R-420BW

OPERATION

Description of Operating Sequence

The following is a description of component functions during oven operation:

interlock relay and is mechanically associated with

the door so that it functions as follows:

Off Condition

Closing the door activates the door sensing switch and secondary interlock switch. In this condition, the monitor switch contacts are opened. When the oven is plugged in, 120 volts AC is supplied to the control unit (see schematic diagram). The display flashes 88:88. To set any program or set the clock, first touch the STOP/ CLEAR pad. The display clears and “ : ” appears and the control unit counts every minute.

Cooking Condition

Program desired cooking time and Variable Cooking

Control by touching the NUMBER pads and the Power

Level pad of the Variable Cooking Control. When

START is touched, the following operations occur:

1. The relay contacts are closed and components connected to the relays (RY-1 and RY-2) are turned on. (For details, see table below.)

Relay Components

RY-1 RY-2

120 volts AC is supplied to the primary winding of the power transformer and is converted to approximately 3.4 volts AC on the filament winding and approximately 2400 volts AC on the high voltage winding.

The filament winding voltage heats the magnetron filament and the high voltage is sent to a voltage doubler circuit.

4. The microwave energy produced by the magnetron is channeled through the waveguide into the cavity feed-box and into the cavity where the food is cooked.

5. Upon completion of the cooking cycle, the power transformer, oven lamp and cooling fan are turned off and the generation of microwave energy is termi-

nated.

6 .

When the door is opened during a cook cycle, the

monitor switch, door sensing switch, secondary interlock switch and primary interlock relay are activated with the following results. The turntable motor, cooling fan motor and the high voltage components are de-energized. The oven lamp remains on and the digital readout displays the time still remaining in the cook cycle when the door was opened.

7. The monitor switch is electrically monitoring the operation of the secondary interlock switch and primary

Oven Lamp/Turntable Motor/Fan Motor Power Transformer

When the door opens from a closed position, the

( )

secondary interlock switch and primary interlock relay open their contacts, then the monitor switch contacts close.

When the door is closed from the open position,

(b)

the monitor switch contacts first open and the contacts of the secondary interlock switch close.

If the secondary interlock switch and the primary inter-

lock relay contacts are closed when the door is opened, the monitor switch contacts form a short circuit through the monitor fuse, secondary interlock switch and prima-

ry interlock relay causing the monitor fuse to blow.

Power Level P-O to P-90 Cooking

When Variable Cooking Power is programmed, 120 volts AC is supplied to the power transformer intermittently through the contacts of relay RY-2 which is operated by the control unit within a 32 second time base. Microwave power operation is as follows:

Vari-Mode On Time Off Time

P - HI (HIGH) (100% power)

P - 90 (approx. 90% power)

P - 80

(approx. 80% power) 26 sec. 6 sec. P - 70 (MED, HIGH)

(approx. 70% power) P - 60

(approx. 60% power)

P - 50 (MED)

(approx. 50% power)

P - 40

(approx. 40% power) 16 sec. 16 sec. P - 30 (MED, LOW)

(approx. 30 % power)

P - 20

(approx. 20% power)

P-IO

(approx. 10% power) 6 sec. 26 sec.

P-O

(0% power)

The ON/OFF time ratio does not correspond with the

percentage of microwave power, because approximate-

ly 2 seconds are needed for heating the magnetron fila-

ment.

32 sec. 0 sec.

30 sec. 2 sec.

24 sec.

22 sec.

18 sec.

12 sec.

8 sec.

0 sec. 32 sec.

8 sec.

IO sec.

14 sec.

20 sec.

24 sec.

Page 9

DESCRIPTION OF OPERATING SEQUENCE

R-420BK R-420BW

The following is a description during oven ope ration.

component functions

Sensor Cooking Condition

When using the SENSOR REHEAT function, the foods are cooked 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 the 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 is inputted into the

LSI The following is an example of how the AH Sensor Works:

3. Sensor detects moisture and h umidity and lates cooking time and va riable power level.

calcu-

Cooking Sequence

1. Touch SENSOR REHEAT pad.

Note: The oven should not be operated in either mode

immediately after plugging in the unit. Wait five minutes before cooking in sensor mode.

2. The coil to the shut off relay (RY-1) is energized, the

oven lamp, turntable motor and cooling fan motor are turned on and the power transformer remains off.

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

Heated potatoes . Moisture and humi rapidly.

You can

smell the aroma as it cooks.

dity is emitted

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 cooking is started.

Note: The 16 second delay is for cooling time required

to remove any vapor from the oven cavity and sensor. During this first stage, do not open the oven door or touch the STOP/CLEAR pad.

When the sensor detects the vapor emitted from the food, the display switches over the remaining cook-

ing time and the timer counts down to zero.

At this time, the door may be opened to stir food, turn

it or season, etc.

When the timer reaches zero, an audible signal

5. sounds. The shut-off relay and cook relay are de-energized and the power transformer, oven lamp, etc.

are turned off.

By opening the door or touching the STOP/CLEAR pad, the time of day will re-appear on the display and

the oven will revert to an OFF condition.

Page 10

R-420BK R-420BW

DESCRIPTION AND FUNCTION OF COMPONENTS

Cooling Fan Motor

The cooling fan motor drives a blade which draws external cool air. This cool air is directed through the air vanes surrounding the magnetron to cool 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 exhaust vents in the oven cavity.

Oven Temperature Fuse

The oven temperature fuse located on the top of the oven cavity is designed to prevent damage to the unit 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 temperature fuse re-

mains closed. However, when abnormally high temperatures are reached within the oven cavity, the fuse will open at 144OC, causing the oven to shut down.

Note: This is a fuse and it does not reset.

Magnetron Temperature Fuse

The magnetron temperature fuse located on top of the

magnetron duct is designed to prevent damage to the

magnetron if an over heated condition develops in the tube due to cooling fan failure, obstructed air ducts, dirty or blocked air intake, etc.

Under normal operation, the magnetron temperature fuse remains closed. However, when abnormally high temperatures are reached within the magnetron the fuse will open at 144OC, causing the oven to shut down.

Note: This is a fuse and it does not reset.

Monitor Switch

The monitor switch is activated (the contacts opened) by the latch head on the door while the door is closed. The switch is intended to render the oven inoperative by means of blowing the monitor fuse when the contacts of the primary interlock relay and secondary interlock switch fail to open when the door is opened.

Monitor Switch Functions

When the door is opened, the monitor switch contacts close (to the ON condition) due to their being normally closed. At this time the primary interlock relay and secondary interlock switch are in the OFF condition (contacts open) due to their being normally open contacts.

When the door is closed, the monitor switch contacts are first opened and then the door sensing switch and the secondary interlock switch contacts close.

Note: When opening the door, each of these

switches operate inversely.

If the door is opened and the primary interlock relay and secondary interlock switch contacts fail to open, the monitor fuse blows simultaneously with closing of the monitor switch contacts.

Before replacing a blown monitor fuse, test the primary interlock relay, door sensing switch, monitor switch

and secondary interlock switch for proper operation.

(Refer to section “Test Procedures”.)

Door Open Mechanism

The door is opened by pushing the open button on the control panel. When the open button is pushed, the open button pushes up the switch lever, and then the switch lever pushes up the latch heads. The latch heads are moved upward and released from the latch hook. Now the door will open.

Door Sensing / Secondary Interlock

Switches

The secondary interlock switch is mounted in the lower position of the latch hook and the door sensing switch in the primary interlock system is mounted in the upper position of the latch hook. They are activated by the

latch heads on the door. When the door is opened, the switches interrupt the circuit to all components, except the oven lamp. A cook cycle cannot take place until the door is firmly closed thereby activating both interlock switches. The primary interlock system consists of the door sensing switch and the primary interlock relay located on the control panel circuit board.

NOTE:

Latch Heads

Monitor Switch

Secondary Interlock Switch

MONITOR FUSE AND MONITOR SWITCH ARE REPLACED AS AN ASSEMBLY.

Page 11

R-420BK R-420BW

SERVICING

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.

Before replacing a blown monitor fuse, test the door sensing switch, primary interlock relay, sec- ondary interlock switch and monitor switch for proper operation. tion.)

Whenever troubleshooting is performed, the power supply must be disconnected. In some cases it may be necessary to connect the power supply after the outer case cabinet has been removed. In this event,

Disconnect the power supply cord, and then remove outer case cabinet.

2. Open the door and block it open.

3. Discharge the high voltage capacitor. Disconnect the leads to the primary of the power transformer.

5. Ensure that the leads remain isolated from other components and oven chassis by using insulated tape.

6. After the above procedure install the outer case cabinet, reconnect the power supply cord.

When the testing is completed

1. Disconnect the power supply cord, and then remove outer case

2. Open the door and block it open.

3. Discharge the high voltage capacitor. Reconnect the leads to the primary of the power transformer.

5. Re-install the outer case (cabinet).

6. Reconnect the power supply cord after the outer case is insta

7. Run the oven and check all functions.

led.

(Refer to “Test Procedure” sec-

Troubleshooting Guide

Off Condition

Problem

Home fuse blows when power cord is plugged into the wall receptacle.

Monitor fuse blows when power is applied.

Display does not illuminate when Shorted or open wiring

power cord is plugged in.

Display does not operate properly Primary interlock relay or door sens- Procedure E when STOP/CLEAR button is ing switch touched.

Oven lamp does not light with door Shorted or open wiring

opened.

Shorted power cord or wire harness

Shorted power cord or wire harness Secondary interlock or monitor

switch

Monitor switch or monitor fuse Oven temperature fuse

1 Control unit

Control unit

Key unit unit Procedure K

Monitor fuse Oven temperature fuse Oven lamp or socket

Control unit

Relay (RYI)

Possible Cause

Check or replace

Check or replace Procedure E

Check or replace Procedure E Procedure F

1 Procedure G

Procedure G

Check or replace

Procedure E Procedure F

Check or replace

Procedure G Procedure H

Test Procedure

Page 12

_---

R-420BK

R-420BW

Problem

Iven lamp does not light at all.

>ven lamp lights, but fan motor and urntable motor do not operate.

Iven does not go into cook cycle yhen START button is touched.

&en seems to be operating but ittle or no heat is produced in oven oad. (incompletely cooked or not zooked at all at the end of cook cycle.)

3ven goes into a cook cycle but extremely uneven heating is produced In oven load (food).

Oven does not cook properly when programmed for Cooking Power P-50 (MED.) mode. (Operates properly on Cooking Power P-HI (HIGH) mode.)

Oven goes into COMPU DEFROST

but food is not defrosted well

The oven is in the sensor cooking condition but AH sensor does not end or AH sensor turns off about a maxi-

mum of 30 minutes after start. When a cup of water is heated by sensor, the oven does not shut off when the water is boiling.

Troubleshooting Guide

Cook Condition Possible Cause

Shorted or open wiring Oven lamp or socket Control unit Shorted or open wiring

Cooling fan motor

Turntable motor

Shorted or open wiring Primary interlock system Monitor fuse Magnetron or oven temperature

fuse

qelay (RYI)

-’

Shorted or open wiring Vlagnetron ‘ower transformer qectifier assembly

-I .V. capacitor Primary interlock system Shorted or open wiring Turntable motor Low voltage Ditty oven cavity wrong operation Shorted or open wiring

Control unit

Magnetron

Wrong operation

Low voltage

Dirty oven check Compu Defrost Control Unit

AH Sensor

Test Procedure

Check or replace Check or replace Procedure G Check or replace Check or replace Check or replace Check or replace

Procedure E Procedure E Procedure F

Procedure H Check or replace Procedure A Procedure B Procedure C Procedure D Procedure E Check or replace Check or replace Check _ Check Check Check or replace

Procedure G

Procedure A

Check

Check Check Procedure J Procedure G

Procedure L

Page 13

TEST PROCEDURES

R-420BK

R-420BW

Procedure Letter

A. Magnetron Assembly Test

1. Disconnect the power supply cord, and then remove outercase cabinet.

2. Open the door and block it open.

3. Discharge the high voltage capacitor.

4. To test for an open filament, isolate the magnetron from the high voltage circuit. A continuity check across the magnetron filament leads should indicate less than IQ.

5. To test for a shorted magnetron, connect the ohmmeter leads between the magnetron filament leads and chassis ground. This test should indicate an infinite resistance. If there is little or no resistance, the magnetron is grounded (shorted) and must be replaced.

6. Reconnect all leads removed from components during testing.

7. Re-install the outercase cabinet.

8. Reconnect the power supply cord after installing the outer case cabinet.

9. Run the oven and check all functions.

MICROWAVE OUTPUT POWER

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

condition (outer case fitted).

HIGH VOLTAGES ARE PRESENT DURING THE COOK CYCLE, SO EXTREME CAUTION SHOULD BE OBSERVED

Power output of the magnetron can be measured by performing a water temperature rise test. This test should only be used if above tests do not indicate a faulty magnetron and there is no defect in the following components or wiring: high voltage rectifier, high voltage capacitor and power transformer. This test will require a 16 oz. (453~~) measuring cup and an accurate mercury thermometer or thermocouple type temperature tester. For accurate results, the following procedure must be fol-

lowed:

Fill the measuring cup with 16 oz. (453~~) of tap water and measure the temperature of the water

1. with a thermometer or thermocouple temperature tester. Stir the thermometer or thermocouple through the water until the temperature stabilizes. Record the temperature of the water.

Place the cup of water in the oven. Operate oven on HIGH selecting 62 seconds cook time. Allow

2. the water to heat.

Remove the cup from the oven and again measure the temperature, making sure to stir the ther-

mometer or thermocouple through the water until the maximum temperature is recorded.

Subtract the cold water temperature from the hot water temperature. The normal result should be 38” to 78°F (21 O to 42.6”C) rise in temperature. If the water temperatures are accurately measured and are tested for the required time period the test results will indicate if the magnetron tube has low power output (low rise in water temperature) which would extend cooking time or high power output (high rise in water temperature) which would reduce cook time. Because cooking time can be adjusted to compensate for power output, the magnetron tube assembly should be

replaced only if the water temperature rise test indicates a power output well beyond the normal

limits. The test is only accurate if the power supply line voltage is 120 volts and the oven cavity

Component Test

. Power Transformer

1. Disconnect the power supply cord, and then remove outer case cabinet.

2. Open the door and block it open.

3. Discharge the high voltage capacitor.

4. Disconnect the primary input terminals and measure the resistance of the transformer with an ohmmeter. Check for continuity of the coils with an ohmmeter. On the R X 1 scale, the resistance of

the primary coil should be less than 1 Q and the resistance of the high voltage coil should be approx-

imately 1 OOQ; the resistance of the filament coil should be less than IQ.

5. Reconnect all leads removed from components during testing.

6. Re-install the outercase cabinet.

7. Reconnect the power supply cord after installing the outer case cabinet.

8. Run the oven and check all functions.

Note: High voltages are present at the high voltage terminal, so do not attempt to measure the fila-

ment and high voltage.

Page 14

R-420BK R-420BW

Procedure Letter Component Test

C . High Voltage Rectifier Test

I. Disconnect the power supply cord, and then remove outer case cabinet.

2. Open the door and block it open.

3. Discharge the high voltage capacitor.

4. Isolate the rectifier from the circuit. Using the highest ohm scale of the meter, read the resistance across the terminals and observe, reverse the leads to the rectifier terminals and observe meter

reading. If a short is indicated in both directions, or if an infinite resistance is read in both directions,

the rectifier is probably defective and should be replaced.

5. Reconnect all leads removed from components during testing.

6. Re-install the outer case cabinet.

7. Reconnect the power supply cord after installing the outer case cabinet.

8. Run the oven and check all functions.

Note: Be sure to use an Ohm-Meter that will supply a forward bias voltage of more than 6.30 Volts.

High Voltage Capacitor Test

(Discharge the high voltage capacitor before touching any oven components or wiring.)

1. Disconnect the power supply cord, and then remove outercase.

2. Open the door and block it open.

3. Discharge the high voltage capacitor. 4 If the capacitor is open, no high voltage will be available to the magnetron. Disconnect input leads

and check for short or open between the terminal using an ohmmeter. Checking with a high ohm scale, if the high voltage capacitor is normal, the meter will indicate continuity initially and once the capacitor is charged an open circuit.

If the above is not the case, check the capacitor with an ohmmeter to see if it is shorted between

each terminal and case. If it is shorted, replace the capacitor.

5. Reconnect all leads removed from components during testing.

6. Re-install the outercase (cabinet).

7. Reconnect the power supply cord after the outer case is installed.

8. Run the oven and check all functions.

Secondary Interlock Switch Test

1. Disconnect the power supply cord, and then remove outercase.

2. Open the door and block it open. Discharge the high voltage capacitor. Isolate the switch and connect the ohmmeter to the common (COM) and normally open (NO) terminal of the switch. The meter should indicate an open circuit with the door open and a closed circuit with the door closed. If improper operation is indicated, replace the secondary interlock switch.

Reconnect all leads removed from components during testing. Re-install the outercase (cabinet).

,‘. Reconnect the power supply cord after the outer case is installed.

8. Run the oven and check all functions.

Primary Interlock System Test

Door Sensing Switch

Disconnect the power supply cord, and then remove outercase.

Open the door and block it open.

Discharge the high voltage capacitor.

Isolate the switch and connect the ohmmeter to the common (COM) and normally open (NO) terminal of the switch. The meter should indicate an open circuit with the door open and a closed circuit with the door closed. If improper operation is indicated, replace the door sensing switch. Reconnect all leads removed from components during testing.

5. Re-install the outercase (cabinet).

/. Reconnect the power supply cord after the outer case is installed.

8. Run the oven and check all functions.

Page 15

Procedure Letter Component Test

R-420BK R-420BW

Continued

Primary Interlock Relay CRY-2)

1. Disconnect the power supply cord, and then remove outer case cabinet.

2. Open the door and block it open.

3. Discharge the high voltage capacitor.

4. Disconnect two (2) wire leads from the relay on the printed circuit board in the control panel assembly. The relay is located on the bottom portion of the circuit board on the backside of the control panel assembly. Connect an ohmmeter to the male terminals and observe the meter reading. The

relay contacts should be open. If the relay contacts are closed, replace the primary interlock relay

or the circuit board.

5. Reconnect all leads removed from components during testing.

6. Re-install the outer case cabinet.

7. Reconnect the power supply cord after installing the outer case cabinet.

8. Run the oven and check all functions.

Monitor Switch Test

1. Disconnect the power supply cord, and then remove outer case cabinet.

2. Open the door and block it open. Discharge the high voltage capacitor.

Disconnect the oven from the power supply. Before performing this test, make sure that the secondary interlock switch and primary interlock relay are operating properly referring to the above Switch Test Procedure. Disconnect the wire lead from the monitor switch (NC) terminal. Check the monitor switch operation by using the ohmmeter as follows: When the door is open, the meter should indicate a closed circuit. With the door open, take a screw driver and push in the monitor switch actuator located through the lower latch hole on the faceplate of the cavity. The meter should indicate a open circuit.

If improper operation is indicated, the monitor switch may be defective and should be replaced. After testing the monitor switch, reconnect the wire lead to the monitor switch (NC) terminal and check continuity of the monitor circuit. Reconnect all leads removed from components during testing.

5. Re-install the outer case cabinet.

6. Reconnect the power supply cord after installing the outer case cabinet.

8. Run the oven and check all functions.

Red Wire Connected to Normally Closed Terminal

Note1 : Connect ohmmeter

probes here.

Note2: Use screwdriver to engage

monitor switch actuator.

WhiteWires Connected to Common Terminal

Monitor Switch

Page 16

R-420BK R-420BW

Procedure Letter Component Test

E .

Continued

Open Monitor Fuse

1, Disconnect the power supply cord, and then remove outer case cabinet.

2. Open the door and block it open.

3. Discharge the high voltage capacitor. 4 If the monitor fuse is open, perform the tests for the primary interlock system, secondary interlock

switch and the monitor switch according to the procedure outlined in this section. Adjust or replace the secondary interlock and door sensing switches.

5. Reconnect all leads removed from components during testing.

6. Re-install the outer case cabinet.

7. Reconnect the power supply cord after installing the outer case cabinet.

8. Run the oven and check all functions.

F . Temperature Fuses

Disconnect the power supply cord, and then remove outer case cabinet.

Open the door and block it open.

Discharge the high voltage capacitor.

A continuity check across either of the temperature fuse terminals should indicate a closed circuit

unless the temperature of the magnetron temperature fuse reaches 144°C or the oven cavity fuse reaches 144°C. An open magnetron temperature fuse indicates overheating of the magnetron assembly while an open oven fuse indicates overheating of the oven cavity. If a temperature fuse indicates an open circuit, exchange that temperature fuse and check for a restricted air duct, stricted air flow to the magnetron and oven cavity through the vent holes of the oven cavity, especially the air duct and cooling fan assembly. Reconnect all leads removed from components during testing.

5 c

6: Re-install the outercase cabinet.

7. Reconnect the power supply cord after installing the outer case cabinet.

8. Run the oven and check all functions.

When replacing a monitor fuse, make sure that the monitor switch is also

replaced at that time. Replace monitor fuse and monitor switch with Part#

FFS-BAO16/KIT

re-

. Touch Control Panel Assembly Test

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

fore, unlike conventional microwave ovens, proper maintenance can not be performed with only a

voltmeter and ohmmeter. In this service manual, the touch control panel assembly is divided into two control units, Control Unit and Key Unit. Troubleshooting by unit replacement is described according to the symptoms indicated.

Before testing

1. Disconnect the power supply cord, and then remove outer case cabinet.

2. Open the door and block it open.

3. Discharge the high voltage capacitor.

4. Disconnect the leads to the primary of the power transformer.

5. Ensure that these leads remain isolated from other components and oven chassis by using insulated tape.

6. After that procedure, re-connect the power supply cord.

Page 17

TEST PROCEDURES

R-420BK R-420BW

Procedure Letter

G n Continued

Touch Control Panel Assembly Test

1. Key Unit I. Disconnect the power supply cord, and then remove outer case cabinet

2. Open the door and block it open.

3. Discharge the high voltage capacitor.

4. Check unit ribbon connection before replacement.

5. Reconnect all leads removed from components during testing.

6. Re-install the outercase (cabinet).

7. Reconnect the power supply cord after the outer case is installed.

8. Run the oven and check all functions. 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.

If the key unit is defective.

1. Disconnect the power supply cord, and then remove outercase cabinet.

2. Open the door and block it open.

3. Discharge the high voltage capacitor.

4. Replace the key unit.

5. Reconnect all leads removed from components during testing.

6. Re-install the outercase cabinet.

7. Reconnect the power supply cord after the outer case is installed.

8. Run the oven and check all functions.

2. Control Unit The following symptoms indicate a defective control unit. Before Replacing the control unit, perform the Key unit test (Procedure K) 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) All the segments of a digit flicker.

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

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

When testing is completed,

1. Disconnect the power supply cord, and then remove outer case cabinet.

2. Open the door and block it open.

3. Discharge the high voltage capacitor.

4. Reconnect all leads removed from components during testing.

5. Re-install the outercase cabinet.

6. Reconnect the power supply cord after installing the outer case cabinet.

7. Run the oven and check all functions.

Component Test

Page 18

R-420BK R-420BW

Procedure Letter

H . Relay Test

1. Disconnect the power supply cord, and then remove outer case cabinet.

2. Open the door and block it open.

3. Discharge the high voltage capacitor.

4. Disconnect the leads to the primary of the power transformer.

5. Ensure that the leads remain isolated from other components and oven chassis by using insulated tape.

6. After the above procedure , reconnect the power supply cord.

7. Check voltage between Pin No. 1 of the 2 pin connector (A) and the common terminal of the

relay RY2 on the control unit with A.C. voltmeter. The meter should indicate 120volts. If not, check

oven circuit.

RY-1 and RY-2 Relay Test

These relays are operated by D.C. voltage.

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

DC. voltage indicated . . . . . . . . . . . . . . . . . . . . . .

DC. voltage not indicated . . . . . . . . . . . . . . . . . . .

~RelaySymbolIOperationaVoltageF ~ ~ /Connected Components

RY 1

RY2

Component Test

1 Approx. 24.0 V DC 1 Approx. 23.0 V DC

Defective relay. Check diode which is connected to the relay coil. If diode is good, control unit is defective.

1 Oven lamp/Turntable motor/Cooling fan motor

Power transformer

1 I

8. Disconnect the power supply cord.

9. Open the door and block it open.

IO. Discharge the high voltage capacitor.

11. Reconnect all leads removed from components during testing.

12. Re-install the outer case cabinet.

13. Reconnect the power supply cord after installing the outer case cabinet.

14. Run the oven and check all functions.

I . Foil pattern on the printed wiring board Test

To protect the electronic circuits, this model is provided with a fine foil pattern added to the primary

on the PWB, which acts as a fuse. 1 Foil Pattern check and repairs

I. Disconnect the power supply cord, and then remove outer case cabinet.

2. Open the door and block it open.

3. Discharge the high voltage capacitor.

4. Follow the troubleshooting guide given below for repair.

1 Steps 1 Occurrence

1 ( Only pattern at “a” is broken.

2 ( Pattern at “a” and “b” are broken

1 Cause or Correction / * Insert jumper wire Jl and solder. ( * Insert the coil RCILF~ OO~YAZZ between “c” and “d”. (

Page 19

R-420BK R-420BW

Procedure Letter

I . Continued

Procedures to be taken when the foil is open

5. Make a visual inspection of the varistor burn

damage and test the transformer with an ohm-

meter for the presence of layer short-circuit (check the primary coil resistance which is

approximately 227 Q & 15%). If any abnormal

condition is detected, replace the defective pan(s) *

6. Reconnect all leads removed from components during testing.

7. Re-install the outercase (cabinet).

8. Reconnect the power supply cord after installing the outer case cabinet.

9. Run the oven and check all functions.

2. Follow the troubleshooting guide given below. If indicator does not light up after above check and repairs are finished.

1. Disconnect the power supply cord, and then remove outer case cabinet.

2. Open the door and block it open.

3. Discharge the high voltage capacitor.

4. Disconnect the leads to the primary of the power transformer.

5. Ensure that the leads remain isolated from other components and oven chassis by using insulated tape.

6. After the above procedure, reconnect the power supply cord.

7. Follow the troubleshooting guide given below for repair.

Component Test

pattern of the printed wiring

board (PWB)

1 Steps 1 Occurrence

The rated AC voltage is not present between Check supply voltage and oven power cord

Pin No. 1 of the 2-pin connector (A) and the

I I

8. Disconnect the power supply cord, and then remove the outer case.

9. Open the door and block it open.

10. Discharge the high voltage capacitor.

11. Reconnect all leads removed from components during testing.

12. Re-install the outer case cabinet.

. 13.Reconnect the power supply cord after the outer case cabinet is installed.

14.Run the oven and check all functions.

common terminal of the relay RYI .

2 The rated AC voltage is present at primary

side of low voltaae transformer.

1 Cause or Correction

Low voltage transformer or secondary circuit defective. Check and repair.

Page 20

R-420BK R-420BW

Procedure Letter

J Compu Defrost Test

1. Place one cup of water in the center of the turntable tray in the oven cavity.

2. Close the door, touch the “Stakes/chops” pad once.

3. The oven is in Compu Defrost condition.

4. The oven will operate as follows:

Weight 1st Stage 2nd Stage

Level Time Level Time

0.5

60% 47sec. 40%

5. If improper operation is indicated, the control unit is probably defective and should be checked.

K . Key Unit Test

1. Disconnect the power supply cord, and then remove outer case cabinet.

2. Open the door and block it open.

3. Discharge the high voltage capacitor.

4. If the display fails to clear when the STOP/CLEAR pad is depressed, first verify the flat ribbon is making good contact and verify that the door sensing switch operates properly (contacts are closed when the door is closed and open when the door is open). If the door sensing 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 repIaced.lf a specific pad does not respond, the above method may be used (after clearing the control unit) to determine if the control unit or pad is at fault.

5. Reconnect all leads removed from components during testing.

6. Re-install the outer case cabinet.

7. Reconnect the power supply cord after installing the outer case cabinet

8. Run the oven and check all functions.

Component Test

37 sec.

G-8 G-7 G-6 G-5

-I

- G-9 -

- G-10 -

- G-11 - MINUTE Chicken

- G-12 - START

PLUS

Pieces

Auto-Start

Clock

Key Unit

Chicken

breast

Frozen

Roll/

Muff in

G-4

Rice

FROZEN

Vegetable

Steaks/ Frozen

Chops

entrees

G-3 G-2

Reheat Popcorn

Baked Potato

Fresh ! Ground meat

seafood (INSTANT)

Ground meat

(COMPU) DEFROST

Fresh

Vegetables

ACTION

Fresh Roll/ Muffin

G-l

KITCHEN

TIMER

Power

Level

STO

CLEAR

Page 21

TEST PROCEDURES

R-420BK R-420BW

Procedure Letter

L. AH Sensor Test

Checking the initial sensor cooking condition

1. The oven should be plugged in at least five minutes before sensor cooking.

2. Room temperature should not exceed 95” F (35” C).

3. The unit should not be installed in any areas where heat and steam are generated. The unit should not be installed, for example, next to a conventional surface unit.

4. Exhaust vents are provided on the bottom of the unit for proper cooling and air flow in the cavity. To permit adequate ventilation, be sure to install so as not to block these vents. There should be some space for air circulation.

5. Be sure the exterior of the cooking container and the interior of the oven are dry. Wipe off any moisture with a dry cloth or paper towel.

6. The sensor works with food at normal storage temperature. For example, chicken pieces would be at refrigerator temperature and canned soup at room temperature.

7. Avoid using aerosol sprays or cleaning solvents near the oven while using Sensor settings. The sensor will detect the vapor given off by the spray and turn off before the food is properly cooked.

8. If the sensor has not detected the vapor of the food, ERROR will appear and the oven will shut off.

Water load cooking test

Note: The cabinet should be installed and screws tightened. Make sure the oven has been plugged in at lease five minutes before checking sensor cook opera-

tion.

1. Fill approximately 200 milliliters (7.2 oz.) of tap water in a 1000 milliliter measuring cup.

2. Place the container on the center of tray in the oven cavity.

3. Close the door.

4. Touch SENSOR REHEAT pad once. Now, the oven is in the sensor cooking condition and “SEN-

SOR REHEAT“ will appear in the display.

5. Now the oven will operate for the first 16 seconds without generating microwave energy. Note: ERROR will appear if the door is opened or STOP/CLEAR button is touched during first stage

of sensor cooking.

6. After approximately 16 seconds, microwave energy is produced, the oven should turn off when water is boiling (bubbling).

If the oven does not turn off, replace the AH sensor or check the control unit.

Testing Method for AH Sensor and/or Control Unit

To determine if the sensor is defective, the simplest method is to replace it with a new sensor.

1. Disconnect the power supply cord, and then remove outer case cabinet.

2. Open the door and block it open.

3. Discharge the high voltage capacitor.

4. Remove the AH sensor.

5. Install the new AH sensor. 6 Reconnect all leads removed from components during testing.

7. Re-install the outer case.

8. Reconnect the power supply cord and check the sensor cook operation, proceed as follows: A. Fill approximately 200 milliliters (7.2 oz.) of tap water in a 1000 milliliter measuring cup. B. Place the container on the center of tray in the oven cavity. C. Close the door.

D. Touch SENSOR REHEAT pad. E. The control panel is in automatic Sensor operation. F. The oven will turn off automatically when the water is boiling (bubbling).

If the new sensor does not operate properly, the problem is with the control unit.

Checking the Control Unit

1. Disconnect the power supply cord, and then remove outer case cabinet.

2. Open the door and block it open.

3. Discharge the high voltage capacitor.

4. Disconnect the sensor connector that is mounted to control panel.

5. Then connect the dummy resistor circuit (see fig. A) to the sensor connector of control panel.

Component Test

Page 22

R-420BK R-420BW

Procedure Letter

Checking the Control Unit (CoWwed)

6. Disconnect the wire leads to the primary of power transformer.

7. Ensure that these leads remain isolated from other components and oven chassis by using insu-

lated tape.

8. After that procedure, reconnect the power supply cord.

9. Check the sensor cook operation proceed as follows:

10. Disconnect the power supply cord, and then remove outer case cabinet.

11. Open the door and block it open.

12. Discharge the high voltage capacitor.

13. Disconnect the dummy resistor circuit from the sensor connector of control panel. 14Carry out the necessary repair. 15Reconnect all leads removed from components during testing and repairing.

16. Re-install the outer case cabinet.

17.Reconnect the power supply cord after the outer case is installed. tions.

18.Cart-y out the

Component Test

A. Touch SENSOR REHEAT pad once.

B. The control panel is in the sensor cooking operation.

C. After approximately 20 seconds, push plunger of select switch for more than 3 seconds. This

condition is the same as judgment by AH sensor.

D. After approximately 3 seconds, the display shows “XX. XX” which is the remaining cooking

time, and the display counts down.

If the above is not the case, the control unit is probably defective. If the above checks positive, the AH sensor is probably defective.

Run the oven and check all func-

‘Water load cooking test” again and ensure that the oven works properly.

F-l +

TO CONNECTOR (F)

ON CONTROL UNIT

CONNECTOR

PLUNGER

A A I

RI, R2: 2252 + 1% 1/2w

R3: 4.3kQ +, 5% 1/4W R4: 1 Ma + 5% ll4W

r--NO1

Figure A. Sensor Dummy Resistor Circuit

NC NO

COM

Page 23

OUTLINE OF TOUCH CONTROL PANEL

R-420BK R-420BW

The touch control section consists of the following units as shown in the touch control panel circuit: (1) Key Unit (2) Control Unit (The Control Unit consist of Power Unit and LSI Unit)

The principal functions of these units and their related signals 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 P20 - P27. When a key pad is touched, a signal is completed through the key unit and passed back to the LSI through

P43 - P46 perform the function that was requested.

Control Unit

The Control unit consists of the following:

1. 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.

2. ACL Circuit A circuit to generate a signal which resets the LSI to the initial state when power is applied.

3. Buzzer Circuit The buzzer is responsive to signals from the LSI to

emit Audible sounds (key touch sound and completion sound).

Door Sensing Switch

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

Relay Circuit

5. To drive the magnetron, fan motor, turntable motor and oven lamp.

Indicator Circuit

This circuit consists of 25 segmenets and 4 com-

mon electrodes using a liquid Crystal Display.

Back Light Circuit

A circuit to drive the back light (Light emmitting

diodes LDI -LD5). It incorporates a very small error because it works on commercial frequency.

Power Source Circuit

This circuit generates voltage 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.

1 Symbol / Voltage / Application

vc - 5v / LSI (ICI),

9. Absolute Humidity Sensor Circuit

This circuit detects the humidity of the food which is being cooked, to control automatic cooking.

Page 24

R-420BK R-420BW

DESCRIPTION OF LSI

The I/O signals of the LSI (IZA865DR) is detailed in the following table.

Pin No. Signal

I-2 VLi-VLI IN

3-6

II-13

AN7-AN4 IN

AN3 OUT Terminal not used.

8 AN2 IN

AN1

AN0

P57-P55

15 16

P54 OUT Signal to sound Buzzer (2.0 kHz).

P53 P52

I/O

OUT

OUT OUT

Description

Power source voltage input terminal

Standard voltage for LCD.

Terminal to change functions according to the Model.

By using the A/D converter contained in the LSI, DC voltage in accordance with the Model in operation is applied to set up its cooking constant.

To Input signal which communicates the door open/close information to the LSI.

Door closed; “H” level signal (OV). Door opened “L” level signal (-5V).

AH Sensor input. This is an analog input terminal from the AH sensor circuit and is connected to the A/D converter built in to the LSI.

Used for Initial balancing of the bridge circuit (absolute humidity sensor). This input is an analog input terminal from the AH sensor circuit, and connected to the A/D converter built into the LSI.

Terminal not used.

0.1 sec.

:f$ s.;* :y$,q *z$

~~~ B ~

Used for Initial balancing of the bridge circuit (absolute humidity sensor).

Oven lamp, fan motor and turntable motor driving signal.

To turn on and off shut off relay RYI. The square waveform voltage is delivered to the RY-1 driving circuit and RY-2 control circuit.

#$ f&s :::y,:: *.a #< y<:; $$+i f$:$

$5 $;g :m vy&

Sk ;F<$$ ;& v:::.:

$j & $$ &

,y z$$$ :p>,< ..,, x

B: completion sound

17 18

P51 P50

19 P47

20 P46

P45

ii rl n i_-____, 1 n R-____H

I I

OUT

Used for Initial balancing of the bridge circuit (absolute humidity sensor) OUT Terminal not used. OUT

Magnetron high-voltage circuit driving signal.

To turn on and off cook relay RY2. In high operation, the signals holds “H” level during micro-

wave cooking and ‘I” level while not cooking. In other cooking modes (variable cooking) the

signal turns to “H” level and “L” level in repetition according to the power level.

--------------------

P-HI

PTkl 24 sec. +Tc ii’

Signal coming from touch-key.

When either G-12 line on key matrix is touched, a corresponding signal out of P20-P27 will be

input into P46. When no key is touched, the signal is held at “H” level.

Signal similar to P46.

When either Gil line on key matrix is touched, a corresponding signal will be inputted into P45.

16.7 msec.

During Cooking

H: GND

I I

Page 25

R-420BK R-420BW

1 Pin No. / Signal 1 I/O

22 P44

24 INTO IN

1 25 1 P41 1 OUT 1 Terminal not used. 1 26 1 P40 1 IN 1 Connected to VC.

P43

RESET

I I

1 28-29 1 P70-P71 1 OUT 1 Terminal not used.

XIN

I 31 I XoUT I OUT I

1 32 / VSS 1 IN / Power source voltage: -5V.

r-T=-

36 P24

38 P22

39 P21

40 P20

41-44

P26

P25

P23

PI 7-PI 4

1 Description

Signal similar to P46.

When either GIO line on key matrix is touched, a corresponding signal will be inputted into P44.

Signal similar to P46.

When either GO9 line on key matrix is touched, a corresponding signal will be inputted into P43.

Signal synchronized with commercial power source frequency.

This is the basic timing for time processing of LSI.

IN Auto-clear terminal.

Signal is input to reset the LSI to the initial state when power is supplied. Temporarily set to “L” level the moment power is supplied, at this time the LSI is reset. Thereafter set at “H” level.

Internal clock oscillation frequency setting input.

The internal clock frequency is set by applying the ceramic filter oscillatior circuit with respect to XIN terminal.

Internal clock oscillation frequency control output.

Output to control oscillation input of XOUT.

VC voltage of power source circuit input.

OUT

OUT Key strobe signal.

OUT

OUT Key strobe signal.

OUT

OUT Key strobe signal.

OUT

Key strobe signal.

Signal applied to touch-key section. A pulse signal is inputted to P43 - P46 terminal while one of G8 line keys on key matrix is touched.

Key strobe signal.

Signal applied to touch-key section. A pulse signal is inputted to P43 - P46 terminal while one of G7 line keys on key matrix is touched.

Signal applied to touch-key section. A pulse signal is inputted to P43 - P46 terminal while one of G6 line keys on key matrix is touched.

Key strobe signal.

Signal applied to touch-key section. A pulse signal is inputted to P43 - P46 terminal while one

of G5 line keys on key matrix is touched.

Signal applied to touch-key section. A pulse signal is inputted to P43 - P46 terminal while one of G4 line keys on key matrix is touched.

Signal applied to touch-key section. A pulse signal is inputted to P43 - P46 terminal while one of G3 line keys on key matrix is touched.

Key strobe signal.

Signal applied to touch-key section. A pulse signal is inputted to P43 - P46 terminal while one of G2 line keys on key matrix is touched.

Signal applied to touch-key section. A pulse signal is inputted to P43 - P46 terminal while one of Gl line keys on key matrix is touched.

I Terminal not used.

~~~~

H: +5V

L: GND

16.7 msec.

Page 26

Fb420BK R-420BW

Pin No. Signal

45-5 1

SEG27-SEG21

I/O Description

OUT Segment data signal.

Connected to LCD. The relation between signals are as follows:

LSI signal (Pin No.) LCD (Pin No.) LSI signal (Pin No.) LCD (Pin No.)

SEG27(45) . . . . . . . . . . . . S16(25) SEG 13 (59) . . . . . . . . . . . . S20 (12)

SEG26(46) . . . . . . . . . . . . S15(24)

SEG 25 (47) . . . . . . . . . . . . S14 (23) SEG IO (62) . . . . . . . . . . . . S22 (10)

SEG 24 (48) . . . . . . . . . . . . S13 (22) SEG 9 (63) . . . . . . . . . . . . S23 (9)

SEG 23 (49) . . . . , . . . . . . . S12 (21) SEG 8 (64) . . . . . . . . . . . . S24 ( 8)

SEG 22 (50) . . . . . . . . . . . . Sll (20)

SEG21 (51) . . . . , . . . . . . . Slo(19) SEG 6 (66) . . . . . . . . . . . . S26 ( 6)

SEG 19 (53) . . . . . . . . . . . . . S9 (18)

SEG 18 (54) . . . . . . . . . . . . . S8 (17) SEG 3 (69) . . . . . . . . . . . . . S3 ( 4)

SEG 17 (55) . . . . . . . . . . . . . S7 (16)

SEG 16 (56) . . . . . . . . . . . . . S6 (15) SEG l(71) . . . . . . . . . . . . . Sl (2)

SEG 15 (57) . . . . , . . . . . . . . S5 (14) SEG 0(72) . . . . . . . . . . . . . SO (1)

SEG 14 (58) . . . . , . . . . . . . S19 (13)

53 - 59

SEG20 OUT Terminal not used.

SEG19-SEG13

OUT Segment data signal

Signal Similar to SEG27.

60 SEG12 OUT Terminal not used.

61 -67

SEGli-SEG5

OUT Segment data signal

Signal Similar to SEG27.

69 - 72

SEG4 OUT Terminal not used.

SEG3-SEGO

OUT Segment data signal

Signal Similar to SEG27.

73/74

VCC/VREF

75 AVSS IN

Connected to GND. Connected to VC.

76 COM3 OUT Common data signal: COM3.

Connected to LCD signal C3 (Pin No. 29).

COM2 OUT Common data signal: COM2.

Connected to LCD signal C3 (Pin No. 28).

COMI

OUT

Common data signal: COMI.

Connected to LCD signal C3 (Pin No. 27).

79 COMO OUT Common data signal: COMO.

Connected to LCD signal C3 (Pin No. 26).

VL3

Power source voltage input terminal

Standard voltage for LCD.

SEG 11 (61) . . . . . . . . . . . . S21 (11)

SEG 7 (65) . . . . . . . . . . . . S25 (7)

SEG 5 (67) . . . . . . . . . . . . . S4 (5)

SEG 2 (70) . . . . . . . . . . . . . S2 ( 3)

Page 27

Precautions for Handling Electronic Components

This unit uses CMOS LSI in the integral part of the circuits. When handling these parts, the following precautions should be strictly followed: CMOS LSI have extremely high impedance at its input and output terminals. For this reason, it is easily influenced by surrounding high voltage power sources, static electricity charge in clothes, etc. and sometimes

it is not fully protected by the built-in protection circuit. In order to protect CMOS LSI, practice the following

guidelines:

1. When storing and transporting LSI, thoroughly wrap them in aluminum foil. Also wrap all PW boards in aluminum foil.

2. When soldering, the technician should use a grounding strap as shown in the figure and use a grounded soldering iron and work table.

Approx. 1 MQ

Shapes of Electronic Components

[

Transistor 2SB1238

Transistor

KRC243M

Servicing of Touch Control Panel

We describe the procedures to permit servicing of the touch control panel of the microwave oven and the pre-

cautions you must take when doing so.

To perform the servicing, power to the touch control pan-

el is available either from the power line of the oven itself or from an external power source.

Servicing The Touch Control Panel With The Oven Power Supply

The high voltage transformer of the microwave oven

is still live during servicing and presents a hazard.

When checking the performance of the touch control panel, put the outer cabinet on the oven to avoid touching the high voltage transformer or unplug the primary terminal (connector) of the high voltage transformer to turn it off; the end of such connector must be insulated with an insulating tape. After servicing, be sure to reconnect the leads to their original locations.

1. On some models, the power supply cord between the touch control panel and the oven itself is so short that

SERVICING

the two can’t be separated. For those models, check

and repair all the controls (sensor-related ones in-

cluded) of the touch control panel while keeping it

connected to the oven.

2. On some models, the power supply cord between the touch control panel and the oven proper is long

enough that they may be separated from each other. For those models, therefore, it is possible to check and repair the controls of the touch control panel while keeping it apart from the oven proper: in this case you must short both ends of the door sensing switch (on PWB) of the touch control panel with a jumper, which brings about an operational state that is equivalent to the oven door being closed. As for the sensor-related controls of the touch control panel, checking them is possible if dummy resistor (s) with resistance equal to that of the controls are used.

Servicing The Touch Control Panel With An

External Power Supply

Disconnect the touch control panel completely from the oven proper, and short both ends of the door sensing switch (on PWB) of the touch control panel, which activates an operational state that is equivalent to the oven

door being closed. Connect an external power source to the power input terminal of the touch control panel, then it is possible to check and repair the controls of the touch control panel; it is also possible to check the sen-

sor-related controls of the touch control panel by using the dummy resistor (s).

Servicing Tools

Tools required to service the touch control panel assem-

bly.

1. Soldering iron: 30W (It is recommended to use a soldering iron with a grounding terminal.)

2. Oscilloscope: Single DC-IOMHz type or more

3. Hand tools.

Other Precautions

1. Before turning on the power source of the control unit, remove the aluminum foil applied for preventing static electricity.

2. Connect the connector of the key unit to the control

unit being sure that the lead wires are not twisted.

3. After aluminum foil is removed, be careful that abnor-

mal voltage due to static electricity etc. is not applied

to the input or output terminals.

4. Attach connectors, electrolytic capacitors, etc. to

PWB, making sure that all connections are tight.

5. Be sure to use specifi

cision is required.

beam, frequency

advanced model.

ed components

R-420BK R-420BW

range:

where high pre-

Page 28

R-420BK R-420BW

COMPONENT REPLACEMENT/ADJUSTMENT PROCEDURE

Microwave ovens contain circuitry capable of producing very high voltage and current, contact with the following parts may result in severe, possibly fatal, electric shock.

Example High Voltage Capacitor, Power Transformer, Magnetron, High Voltage Rectifier Assembly, High Voltage Harness

etc..

oid possible exposure to microwave energy. Please follow the

instructions below before operating the oven.

1. Disconnect the power supply cord.

2. Visually check the door and cavity face plate for damage (dents, cracks, signs of arcing etc.).

Carry out any remedial work that is necessary before

operating the oven.

Do not operate the oven if any of the following conditions exist;

1. Door does not close firmly.

2. Door hinge, support or latch hook is damaged.

3. The door gasket or seal is damaged.

4. The door is bent or warped.

5. There are defective parts in the door interlock systern.

6. There are defective parts in the microwave generating and transmission assembly.

7. There is visible damage to the oven.

Do not operate the oven:

1. Without the RF gasket (Magnetron).

2. If the wave guide or oven cavity are not intact.

3. If the door is not closed.

4. If the outer case cabinet is not fitted.

To prevent electric shock, take the following pre-

cautions.

1. Before wiring.

1) Disconnect the power supply cord.

2) Open the door and block it open.

3) Discharge the high voltage capacitor and wait for 60 seconds.

2. Don’t let the wire leads touch the following parts;

1) High voltage parts: Magnetron, High voltage Transformer, High voltage capacitor and High voltage rectifier assembly.

2) Hot parts: Oven lamp, Magnetron, High voltage Transform-

er and oven cavity.

3) Sharp edge: Bottom plate, oven cavity, waveguide, flange,

chassis support and other metallic plate.

4) Movable parts (to prevent a fault) Fan blade, Fan motor, Switch , Switch lever, and

Open button.

Do not catch the wire leads in the outer case cabi-

3. net.

Insert the positive lock connector until its pin is locked and make sure that the wire leads do not come off even if the wire leads are pulled.

To prevent an error function, connect the wire leads

5. correctly, referring to the Wiring Diagram.

Page 29

Please refer to “OVEN PARTS, CABINET PARTS, CONTROL PANEL PARTS, DOOR PARTS” When carrying out any of the following removal procedures:

Outer Case Removal

1. Disconnect power supply cord before removing outer case cabinet.

2. Discharge the high voltage capacitor before touching any oven components or wiring.

To remove the outer case, proceed as follows.

1. Disconnect the power supply cord.

2. Open the oven door and block it open. Remove the two screws (2) from the upper and lower

Power Transformer Removal

left portion of rear cabinet using a T20H Torx type OI GTXH20-100 screw driver.

Remove the two screws (2) from the rear of outer

case.

Slide the entire case back about 1 inch (3cm) to free

it from retaining clips on the cavity face plate.

Lift entire case from the unit.

the same locations.

R-420BK R-420BW

1. Disconnect the power supply cord and remove outer case cabinet. Open the oven door and block it open.

Discharge high voltage capacitor.

Disconnect wire leads of the main wire harness and H.V. wire from power transformer. Disconnect the lead from magnetron filament.

Disconnect the leads of the power transformer from

high voltage capacitor.

Remove the four (4) screws holding the transformer

7. to base plate.

Remove the transformer.

High Voltage Rectifier and High Voltage

Capacitor Removal

When replacing the high voltage rectifier and high volt-

age capacitor, the ground side terminal of the high

voltage rectifier must be secured firmly with a ground-

ina screw.

Disconnect the power supply cord and remove outer

case cabinet.

Open the oven door and block it open.

Discharge high voltage capacitor.

Remove one (1) screw holding the capacitor band and the high voltage rectifier assembly to the base

9. Now the power transformer is free. Re-install

Rest transformer on baseplate with its primary termi-

nals toward oven face plate.

Secure transformer with four (4) screws to baseplate.

Reconnect the wire leads (primary and high volt-

age) to transformer and filament leads of transformer to magnetron and high voltage capacitor. Refer to “Wiring Diagram”.

Re-install outercase cabinet and check that oven is

operating properly.

plate.

5. Disconnect the wire lead of high voltage rectifier as-

sembly from the magnetron. Disconnect terminals of rectifier assembly from ca-

pacitor and magnetron. High voltage rectifier assembly is now free.

Do not replace only high voltage rectifier. When replacing it, replace the entire high voltage rectifier assembly.

(RDA1504U)

Magnetron Removal

Disconnect the power supply cord and remove outer

1. case cabinet.

Open the oven door and block it open. Discharge high voltage capacitor.

3. Disconnect wire leads from the magnetron.

4. Remove the one (1) screw holding chassis support

5. to magnetron and magnetron duct. Slide the magnetron duct slightly so that two (2) screws at left hand

side of the magnetron appear.

6. Carefully remove the four (4) screws holding magnetron to waveguide flange.

7. Remove the magnetron with care so that the magnetron antenna is not hit by any metal objects around the tube.

8. Now, the magnetron is free.

Page 30

R-420BK R-420BW

COMPONENT REPLACEMENT / ADJUSTMENT PROCEDURE

Magnetron Installation

Install magnetron assembly to the waveguide flange

with care to prevent damage to the magnetron tube.

Secure the magnetron with four (4) screws.

Hold the chassis support to the magnetron and magnetron duct with one (1) screw.

Connect wire leads to the magnetron .

Re-install outer case and check that the oven is oper-

Control Panel Assembly Removal

1. Disconnect the power supply cord and remove outer case cabinet.

Open the oven door and block it open.

Discharge high voltage capacitor.

Disconnect wire leads from panel components.

Remove the one (1) screw holding the control panel.

Re-adjust the clip holding panel assembly to oven

flange.

Remove control panel assembly by sliding it upward.

Now, individual components can be removed.

Oven Lamp and Lamp Socket Removal

Disconnect the power supply cord and remove outer case cabinet.

Open the oven door and block it open. Discharge high voltage capacitor.

Pull the wire leads from the oven lamp socket with the flat type small screw driver.

Remove the oven lamp socket from the magnetron

duct by turning the socket counterclockwise. Push-

ing the small tab of magnetron locating the left hand blue mark on the lamp socket.

Turntable Motor Removal

Do not drop the turntable motor cover into the oven after cutting the bridges. Because it will damage the wire leads of the motor and it is difficult to remove it out of the oven.

Disconnect the power supply cord.

Remove turntable and turntable support from oven cavity. Lay the oven on its backside. Remove the turntable

ating properly.

gasket is in place and that the mounting screws are

tightened securely.

NOTE:

Before attaching a new key unit, remove remaining

adhesive on the control panel frame surface com-

pletely with alcohol. When attaching the key unit to the control panel frame, adjust the upper edge and right edge of the

key unit to the correct position of the control panel.

Stick the key unit firmly to the control panel frame by

rubbing with soft cloth.

side of lamp socket.

6. Pull the wire leads from the oven lamp socket by pushing the terminal hole of the oven lamp socket with the small flat type screw driver.

7. Remove the oven lamp from the oven lamp socket by

turning the oven lamp.

8. Now, the oven lamp and lamp socket are free.

Note: (orange) wires must be connected to the terminal with

motor cover by snipping off the material in four corners.

When the corners have been snipped off, bend the corner areas flat. No sharp edges must be evident after removal of the turntable motor cover.

Disconnect wire leads from turntable motor.

5. Remove two (2) screws holding turntable motor to

6. oven cavity. Now turntable motor is free.

(RDA1305U)

TURNTABLE

MOTOR COVER

+ CUTTING PLIER f’j ’ _

f7!3d=d

Turntable motor cover removal

f--\ ROTATE

- DOOR

BASE PLATE

TURNTABLE

MOTOR COVER

SCREW

I 1

Turntable motor cover re-install

DOOR

Page 31

COMPONENT REPLACEMENT / ADJUSTMENT PROCEDURE

Turntable Motor Re-install

Remove any sharp edges on the turntable motor cover and the base plate with cutting pliers.

Insert the edge of motor cover into tab on the base plate.

Cooling Fan Motor Removal

Disconnect the power supply cord and remove outer case cabinet.

Open the oven door and block it open.

Discharge the high voltage capacitor.

Disconnect the wire leads from the fan motor.

Remove two (2) screws holding the fan motor to the back plate of the oven cavity. Remove the fan blade from the fan motor shaft ac-

6. cording to the following procedure.

a) Hold the edge of the rotor of the fan motor by using

a pair of groove joint pliers.

3. Secure motor cover with one (1) screw to base plate.

INSTALLATION

Install the fan blade to the fan motor shaft according to the following procedure Hold the center of the bracket which supports the shaft of the fan motor on the flat table. Apply the screw lock tight into the hole (for shaft) of the fan blade.

Install the fan blade to the shaft of the fan motor by pushing the fan blade with a small, light weight, ball peen hammer or rubber mallet.

R-420BK R-420BW

Make sure that any pieces do not enter the gap between the rotor and the stator of the fan motor because the rotor is easily shaven by pliers and metal pieces

may be produced. Do not touch the pliers to the coil

of the fan motor because the coil may be cut or injured.

Do not disfigure the bracket by touching with the pliers.

b) Remove the fan blade from the shaft of the fan mo-

tor by pulling and rotating the fan blade with your hand.

c) Now, the fan blade will be free.

Do not use this removed fan blade again because the

hole (for shaft) may become bigger than a standard

one.

P+

Coil

Groove joint pliers

Me View

Axis

Do not hit the fan blade strongly when installed be-

cause the bracket may be disfigured.

Make sure that the fan blade rotates smooth after installation. Make sure that the axis of the shaft is not slanted.

2. Install the fan motor to the back plate of the oven cavity with two (2) screws.

3. Connect the wire leads to the fan motor, referring to the wiring diagram.

0 0

These are the positions which should be pinched with pliers

Page 32

R-420BK R-420BW

COMPONENT REPLACEMENT/ADJUSTMENT PROCEDURE

Door Sensing Switch /Secondary Interlock Switch and Monitor Switch Adjustments

Disconnect the power supply cord and remove outer

case cabinet.

Open the oven door and block it open.

Discharge the high voltage capacitor.

If the door sensing switch, secondary interlock switch and monitor switch do not operate due to a misadjustment, the following adjustment should be made.

Loosen the two the oven cavity front flange.

With the door closed, adjust the

it back and forth, and

In and out play of the door allowed by the upper and

lower position of the latch heads should be less than

0.5mm. The vertical position of the latch hook should be placed where the door sensing switch and the secondary interlock switch have activated with the door closed.

Secure the screws with washers firmly.

3 4:

Make sure of the door sensing switch operation. If

the door sensing switch has not activated with the

door closed, loosen the screw and adjust the latch hook position. Check operation of all switches. If each switch has

not activated with the door closed, loosen screw and

adjust the latch hook position. Note: After adjustments, make sure of the following: I. In and out play of the door remains less than 0.5mm

when in the latched position.

Check the upper position of the latch hook by push-

ing and pulling the upper portion of the door.

(2) screws holding the

latch hook by moving

and down.

properly

latch hook to

Then check lower portion

the lower

pulling

and oven face. Both results (play of the door) should be

less than 0.5mm.

2. The door sensing and secondary interlock interrupt the circuit before the door

Monitor switch contacts close when door is opened. Re-install outer case and check for microwave leakage around the door with an approved microwave survey meter. (Refer to “Microwave Measurement Procedure.“)

of the latch hook, by pushing

portion

of the door toward the

switches

can be

opened.

Door Sensing Switch /Secondary Interlock

Switch and Monitor Switch

power supply cord and remove outer

Disconnect case cabinet. The door sensing and secondary interlock switches

2. interrupt the circuit before the door can be opened. Discharge high voltage capacitor.

Disconnect wire leads from switches, fuse and connectors from control panel. Remove one (1) screw holding control panel to oven

5. cavity faceplate. Slide control panel assembly upward and remove

6. from cavity faceplate.

Open oven door.

Remove two (2) screws holding the latch hook to oven flange.

Remove latch hook from oven flange by lifting up on

9. flexible tab and pushing latch hook back.

IO. Locate the flexible retaining tabs on the latch hook.

11. Push tab inward and rotate switch counterclockwise to release switch.

Note: For monitor switch, lift switch over boss while ro-

tating counterclockwise.

12Switch is now free.

the

Removal

Page 33

DOOR DISASSEMBLY

R-420BK R-420BW

Removal

Disconnect the power supply cord.

Push the open button and open the door slightly.

Insert a putty knife (thickness of about 0.5mm) into the gap between the choke cover and corner portion of door panel as shown in the figure below to free engaging parts .

Pry the lever and lift up the choke cover by inserting

a putty knife in the order as shown in the figure below.

Release choke cover from door panel.

Now choke cover is free from door panel.

Release two(2) pins of door panel from two (2) hole of upper and lower door hinges by lifting up.

. 8.

Now, door panel is free from oven cavity.

Release door panel from eight (8) tabs of door frame and remove door frame.

1 O.Now, door panel with sealer film is free.

11. Tear sealer film from door panel.

12.Now, door panel is free. 13Slide latch head upward and remove it from door

frame and latch head.

14. Now latch head and latch spring are free.

15. Remove door screen from door frame.

16.Now, door screen is free.

-- .

Re-Install

1. Re-install door screen to door frame.

2. Re-install latch spring to the head. Re-install latch spring to the door frame.

3. Re-install door panel to door frame by fitting eight (8)

tabs of door frame to eight (8) holes of door panel.

4. Put sealer film on door panel. Refer to “Sealer Film Installation” and on how to handle the new film.

5. Catch two (2) pins of door panel on two (2) holes of upper and lower door hinge.

6. Re-install choke cover to door panel by snapping on

to the door panel.

Note: After any service to the door

(A)Make sure that door sensing switch, secondary

Interlock switch, primary Interlock relay and monitor switch are operating properly. (Refer to section “Test Procedures”.)

(B)An approved microwave survey meter should be

used to assure compliance with proper microwave radiation emission limitation standards.

After adjustment, make sure of the following:

Door latch heads smoothly catch latch hook through latch holes, and also latch head goes through the center of the hole.

Deviation of door alignment from horizontal line of cavity face plate is less than 1 .O mm.

Door is positioned with its face depressed toward cav-

ity face plate.

Install the outer case cabinet and check for micro-

wave leakage around the door with an approved mi-

crowave survey meter.

(Refer to “Microwave Measurement Procedure”.)

Note: The door on a microwave oven is designed to act as an electronic seal preventing the leakage of microwave energy from the oven cavity during the cooking cycle. This function does not require that the door be air tight, moisture tight, or light tight. Therefore, the occasional appearance of moisture, light or sensing of gentle warm air movement around the oven door

is not abnormal and does not indicate leakage of microwave energy from the cavity.

Sealer Film Installation

1. Put adhesive tape on the backing film of the sealer film as shown below.

2. Tear the backing film by pulling the adhesive tape.

3. Put the pasted side of the sealer film on the door panel.

Sealer film / Backing film

Page 34

R-420BK R-420BW

ABSOLUTE HUMIDITY SENSOR CIRCUIT

Structure of Absolute Humidity Sensor

The absolute humidity sensor includes two thermistors as shown in the illustration. One thermistor is housed in the closed vessel filled with dry air while another is in an open vessel. Each sensor is provided with a protective cover made of metal to protect it from the external airflow. The open vessel cover has two small holes in it to allow moisture laden air from the oven cavity to surround

it.

Sensing part

ventilation openings for sensing

(Open vessel)

Operational Principle of AH Sensor

The figure below shows the basic structure of an abso-

lute humidity sensor. A bridge circuit is formed by two thermistors and two resistors (RI and R2). The output of the bridge circuit is amplified by an operational amplifier.

Each thermistor is supplied with a current to keep it

heated to about 150” C (302” F) and the resultant heat

is dissipated in the air, if the two thermistors are placed

in different humidity conditions they show different hu-

midity conditions and different degrees of heat conductivity leading to a potential difference between them

causing an output voltage from the bridge circuit, the in-

tensity of which is increased as the absolute humidity of

the air increases. Since the output is very minute, it is

amplified by the operational amplifier.

Thermistors

Absolute humidity vs. output voltage characteristic

Sensing part (Closed vessel)

the sensor cooking of the unit. When the unit is set in the sensor cooking mode, 16 seconds later the detector circuit starts to function and the

LSI observes the initial voltage available at its AN1 ter-

minal. With this voltage given, the switches SW1 to SW5 in the LSI are turned on in such a way as to change the resistance values in parallel with RI 07-RI 11 of IC2. Changing the resistance values results in that there is the same potential at both the F-3 terminal of the abso-

lute humidity sensor and the AN0 terminal of the LSI. The voltage of AN1 terminal will indicate about -2.5V. This initial balancing is set up about 16 seconds after the

unit is put in the Sensor Cooking mode. As the sensor cooking proceeds, the food is heated to

generate moisture by which the resistance balance of the bridge circuit is deviated to increase the voltage

available at the AN1 terminal of the LSI. Then the LSI

observes that voltage at AN1 terminal and compares it

with its initial value. When the comparison rate reaches

the preset value (fixed for each menu to be cooked), the

LSI caused the unit to stop sensor cooking; thereafter, the unit goes into the next operation automatically. When the LSI starts to detect the initial voltage at AN1 terminal 16 seconds after the unit has been put in the Sensor Cooking mode, if it is impossible to take a balance of the bridge circuit due to disconnection of the absolute humidity sensor, ERROR will reappear on the dis-

play and cooking is stopped.

Absolute Humidity Sensor Circuit

------__-----

R107 620k Q

R108 300k Q

0 \/LNc

RllO 75kLI

R11137.4k Q

I l2

I I

P57-c-9

P56-O-9,

P55-o-y

P51 --o-QJ

l5 P53T

SW1

SW2

SW3

SW4

SW5

L-----J 6: Thermistor ’

closed vessel

Absolute humidity (g/m3) )

Detector Circuit of AH Sensor Circuit

This detector circuit is used to detect the output voltage of the absolute humidity circuit to allow the LSI to control

Va: -15V

---

------

Va: -15V

S: Thermistor open vessel

._ -..

vc: -5v C: Thermistor closed vessel

Page 35

AH SENSOR DUCT REMOVAL

Disconnect the power supply cord.

Open the oven door and block it open.

Remove screws from the rear of the outercase cabinet. Slide the entire case back about 1 inch (3cm) to free it from retaining clips on the cavity faceplate.

Discharge the high voltage capacitor. Lift entire outer case cabinet from unit.

Remove ground screw mounted into the sensor duct.

Sensor Ground

screw

Sensor Duct

7. Slide the two tabs of the sensor duct to the right.

8. Sensor duct is now free.

Discharge the high voltage capacitor before touching

any oven components or wiring.

Slide

R-420BK R-420BW

AH SENSOR REPLACEMENT

Removal

Disconnect power supply cord .

1. Open the oven door and block it open.

2. .

Remove screws from the rear of the outercase cabi-

net. Slide the entire case back about 1 inch (3cm) to

free it from retaining clips on the cavity faceplate.

Lift the entire outercase cabinet from the oven unit.

Discharge high voltage capacitor.

5. Remove two (2) screws holding the AH sensor

Refer to Figures 1-16 & 2-16.

Disconnect the AH sensor harness from connector CN-F on control unit.

AH sensor is now free.

Installation

Insert new AH sensor into AH sensor duct. Refer to Figures I-16 & 2-16 for proper sensor

orientation.

Install two (2) screws to secure AH sensor. Route the AH sensor harness above emboss on AH

sensor duct.

Refer to Figures l-l 6 & 2-16.

Continue to route AH sensor harness across the oven cavity top plate and through the large opening.

Refer to Figure 2-16.

Connect AH sensor harness to CN-F on the control unit.

Re-install the outercase cabinet and check for prop-

6. er operation.

Page 36

R-420BK R-420BW

Sensor

AH Orientation

Mounting, Screw

ORIENTATION & HARNESS ROUTING

AH densor

MoGnting Screw

AH Sensor Duct

Figure 1-I 6

Oven Left Side View

Figure 2-I 6

Oven Top View

Page 37

MICROWAVE MEASUREMENT PROCEDURE

After adjustment of the door, interlock and monitor switches are completed individually or collectively, a INTERLOCK SWITCH TEST and MICROWAVE LEAKAGE TEST must be performed to assure compliance with DHHS (CDRH) Performance Standards for Microwave Ovens.

Interlock Switch Test

Make sure that the door sensing switch, secondary in-

terlock switch and monitor switch are operating properly

by checking with an ohmmeter. Refer to the “Test Procedure” of the door sensing switch, secondary interlock switch and monitor switch.

Microwave Leakage Test

Requirements

Microwave leakage limit (Power density limit).

The power density of microwave radiation emitted by

a microwave oven shall not exceed 1 mW/cm* at any point 5cm or more from the external surface of the oven, measured prior to acquisition by the purchaser, and thereafter (through the useful life of the oven) 5mW/cm* at any point 5cm or more from the external surface of the oven.

Safety interlock switches.

Primary interlock relay and door sensing switch will prevent microwave radiation emissions in excess of

the requirement as above mentioned, secondary

interlock switch shall prevent microwave radiation emission in excess of 5 mW/cm* at any point 5cm or more from the external surface of the oven.

Preparation For Testing

Before beginning the actual measurement of leakage,

proceed as follows:

1. Make sure that the actual i mally as specified

in its in struction booklet.

nstrument is operati

ng nor-

R-420BK R-420BW

Place the oven tray in the oven cavity. Place the load of 275 + 15ml(9.8 oz.) of tap water ini-

tially at 20 & 5*C (68*F) in the center of the oven cavity. The water container shall be a low form of 600 ml (20 oz.) beaker with an inside diameter of approximately

8.5 cm (3 % in.) and made of an electrically nonconductive material such as glass or plastic. The placing of this standard load in the oven is important not only to protect the oven, but also to insure that any leakage is measured accurately. Set the cooking control on High.

“. Close the door and put the oven into a cook cycle for

several minutes. If the water begins to boil before the survey is completed, replace it with 275ml of cool water.

Leakage Test

Closed-d oor leakage

Grasp the probe of the survey instrument and hold it perpendicular to the gap between the door and the body of the oven,

Move the probe slowly, not faster than lin./sec (2.5cm/sec.) along the gap, watching for the maximum indication of the meter.

Check for leakage at the door screen, sheet metal seams and other accessible positions where the continuity of the metal has been breached (es., around switches, indicator and vents). While testing for leakage around the door pull the door away from the front of the oven as far as is per-

mitted by the closed latch assembly.

4. Measure carefully at the point of the highest leakage and make sure that the highest leakage is no greater

than 4 mW/cm* to allow for measurement uncertainty,

and that the secondary interlock switch does turn the oven OFF before any door movement.

test (microwave measurement).

Note: Survey instruments that comply with the require-

ment for instrumentation 21 CFRI 030.1 O(c)(3)(i), as prescribed by the performance standard for

microwave ovens must be used for testing.

Note: After servicing, record data on service invoice

and microwave leakage report.

Page 38

FUSE Note 5

TEMP.

1 I

MAGNETRON

RED

H.V.

AH SENSOR

-r

CAPACITOR

RY-2

PRIMARY

RELAY

INTERLOCK

I MAGNETRON

TRANSFORMER

IECTIFIER

i.V.

RED

DOOR

SENSING

N.C.

SWITCH

Note 2

WHT

COM.

0 0 Ix1

FUSE

MONITOR

Door Closed, Cook Off Condition

BLK

I I

RED

I I

_ - - - _

L cl

- -

RY-1

GRND

Nf7-7

60Hz

12OVAC

-k2

TEMP.

CAVITY

FUSE

ORG

m‘

2. Wire color code applies to primary circuits only, not to low-voltage or secondary circuits.

3. Power supply cord terminal marked “N” must be connected to the neutral (Gray & white) wire.

Schematic Diagram

6. Terminal with blue mark on lamp socket must be connected to the (orange) wire.

5. The hot (red) wire must be connected to the upper (finish lead) terminal of the power transformer.

4. Power supply cord grounding screw must be kept tight at all times.

WHT

GRYNVHT

N.O.

WHT

WHT WHT

INTERLOCK

SWITCH

SECONDARY

1. Circuits subject to change without notice.

NOTES:

-1

Page 39

Fb420BK R-420BW

- - - - -

c.2

00’

-1

- -

Page 40

R-420BK R-420BW

TURNTABLE

MOTOR OVEN LAMP FAN MOTOR

MICRO

IA2t_

I I T

ii >

., v *

3 T1 0

3 4

LDI-LD5 ;

LDl LD2

LD3 LD4

LD5

GND

’

R2 680 112~

-p41

SPl

. I

INT

BUZZER

TURNTABLE MOTOR OVEN LAMP FAN MOTOR

MICRO

Q3 KRC243M

DOOR SWITCH

NOTE

- : IF NOT SPECIFIED, 1/4w f 5% v---#---

: IF NOT SPECIFIED, lSS270A

Power Unit Circuit

Page 41

Cal

CJ 0

1 LIQUID CRYSTAL DISPLAY 1

I I I I I I I I I

I I I I

IC-1 IZA865DR

: IF NOT SPECIFIED l/low f 5%

: IF NOT SPECIFIED lSS355

: IF NOT SPECIFIED O.OlpF / 25~

m u

-it--

Control Panel Circuit

I II I I I II

J ’

‘. .

7-l m

+F$

- %

GND

I II I m=L>

INT

BUZZER

0.1 p/5ov

_.J

ICS)

RYl

I I

RY2

DOOR

SWITCH

NOTE

AH SENSOR

,-,-I

T-l

Page 42

R-420BK R-420BW

Printed Wiring Board of Power Unit

Page 43

Contact your nearest SHARP Parts Distributor to order.

For location of SHARP Parts Distributor, Please call Toll-Free;

I-800-BE-SHARP

R-420BK R-420BW

Ref No.

Part No. Q Description Qty Code

Electrical

l- 1 l- 2 FH-DZBOO8MRYO M H.V. Diode assembly 1

l- 3 QSOCLBOOGMREO M Oven lamp socket 1

l- 4 l- 5 RMOTEA346WREO M Fan motor 1

l- 6 QFSHDBOO3MREO M Fuse block 1 l- 7

l- 8 l- 9 QFS-TBOO6MREO M Temperature fuse (144OC)

l-10 RV-MZA255WREO M Magnetron 1 l-11 RMOTDAl82/KIT M T.T. Motor 1-12 RTRN-BO6OMREO M Power transformer 1 BF

1-13 FACCDB003MREO M Power cord 1

‘k

1-14 QW-QZBO16MREO M H.V. wire A (Transformer - Capacitor) 1 AC 1-15

1-16 FW-VZB125MREO M Stop switch harness 1 1-17 FDTCTAl77WRKO M AH sensor 1 AQ

RC-QZBO18MREO M H.V. Capacitor 1

RLMPTAO3OWREO M Oven lamp

FFS-BAOlG/KIT M Monitor switch (V-16G-2C25) & Fuse assembly

QSW-MAllOWREO M Sec.

FW-VZB147MREO

(2OA-25OVAC)

interlock & Door sensing switch (V-16G-3C25) 2 AE

M Main wire harness 1 AU

Oven

2- 1 LBNDKBOO7MRPO M H.V. Capacitor band 1 AB

2- 2 LANGTBO28MRPO M Chassis support 1 AF

2- 3 PHOK-BOl3MRFO M Latch hook 1 AG

2- 4 GDAI-BO5OMRPO M Base plate 1 AQ 2- 5 GLEGPBOO3MRFO M Foot 4

2- 6 MLEVPBO16MRFO M Latch lever 1 AD 2- 7 PDUC-B073MRPO M Magnetron duct 1 AF 2- 8 NFANPBOOlMREO M Fan blade 1 AC 2- 9 PDUC-BO43MRFO M Fan duct 1 AD 2-10 _____--____---_---_ - Oven cavity (Not a reolaceable Dart) 1 -

2-11 PCOVPB037MRPO M Waveguide cover 1 AD 2-12 GCABUBO64MRPO M Outer case cabinet 2-12 2-13 2-14 NTNT-AO95WREO M T.T. Tray 1 2-15 PPACGBOl4MRFO M T.T. Motor packing 1

2-16 PCUSGBO33MRPO M Base plate cushion 1 2-17 2-18 PCUSUBO42MRPO M Air flow cushion 2 2-19 PCUSGBO28MRPO M cavity cushion 1

GCABUBO58MRPOA M Outer case cabinet (R-420BW)

FROLPBO24MRKO

PDUC-BO74MRPO M AH sensor duct

M T.T. Roller assembly 1

(R-420BK)

1 AE

AR AD

1 AF

2 AF

1 AP

1 AV 1

AV AK

Page 44

R-420BK R-420BW

Ref No. Part No. Q

Description

Control Panel

3-l

3-1A 3-1B 3-1c 3-1D FW-VZB14lMREO M Lead wire harness

Cl c2 c3 c4-5 Dl-4

D5-8 VHDlSS27OA/-1 J Diode (lSS27OA) LDl-5

Ql-Q2 Q3

Rl R2

R3 R4 R5 R6

RYl RRLY-AO75DREO J Relay RY2

SPl RALM-AOl4DREO J Buzzer Tl VRSl RH-VZAO32DREO J Varistor

ZD1

3-2

3-3

3-3 FPNLCB203MRKO M Control panel assembly (R-420BW)

3-4

3-5

3-6 MSPRTAO5OWREO M Button Spring

3-7 PSHEPBO23MREO M LED sheet

3-8 XEPSD3OPlOXSO M Screw; Control unit mtg.

CPWBFB009MRUO M Control unit l' lQCNCMA394DREO J 2-pin connector (CN-A) 1 AD QCNCMA275DREO J 2-pin connector (CN-B) QCNCMA422DREO J g-pin connector (CN-C) 1

(WH-1)

RC-KZAO87DREO J Capacitor

VCEAB31EW108M J Capacitor

RC-KZAO87DREO J Capacitor VCEAB3lVWlO6M J Capacitor VHDllESl///-1 J Diode (11ESl) 4

VHPSLZ381A9-3 J Light emitting diode 5 VS2SB1238//-3 J Transistor

VSKRC243M//-3 J Transistor VRD-B12EF242J J Resistor

VRD-B12HF681J J Resistor VRD-B12HF511J J Resistor VRD-B12EF270J J Resistor VRD-B12EF472J J Resistor VRD-B12EF332J J Resistor

RRLY-BOO2MREO M Relay (DU24Dl-lP(M))

RTRNPBOOgMREO M Transformer

VHEHZ161///-1 J Zener diode (HZ16-1)

LHLD-BOO4MRFO M LED holder FPNLCB202MRKO M Control panel assembly (R-42OBK)

FUNTKB15OMREO M Key unit FUNTKB151MREO M Key unit

JBTN-BO65MRFO M Open Button JBTN-BO68MRFO M Open Button (R-420BW)

O.lpF 50V 1 AB

1000pF 35V 1 AD

O.lpF 50V

10pF 35V

(2SB1238) (KRC243M) 1 AB

2.4kQ1/@ 68OQl/,W

510@/2w

27Q&w 1

4.7kQ 1/4w

3.3ka l/,w 1

(OJE-SS-124LM) 1

(PKM22EPT) 1

(104G471K)

(R-420BK) 1 (R-420BW) 1

(R-420BK) 1

Qty Code

1 AB

1 AC

1 2

1 1

1 AH

1 1 AE

1 1 1 1 AX

1 AE

1 AR

AB AB AB

AR AR

Page 45

R-420BK R-420BW

Ref No.

Part No. 5

Description

Door

4- 0 4- 0 4- 1 4- 1 4- 2

4- 3 4- 4 4- 5 4- 6 4- 7

4-7

CDORFB213MRKO

CDORFB214MRKO FCOV-BlOlMRKOA FCOV-BlO3MRKOA

FDORFBO62MRTO PSHEPB021MREO

GCOVHBO34MRFO

LSTPPBO21MRFO

MSPRTAO46WREO

HPNL-BO77MREO HPNL-BO78MREO

Door assembly(R-420BK) Door assembly (R-420BW) Door screen assembly (R-420BK) Door screen assembly (R-420BW) Door panel

Sealer film Choke cover Latch head Latch spring Door Screen

Door Screen (R-420BW)

(R-420BK)

Miscellaneous

5- 1 TCAUABO15MRRO 5- 2 TCAUABO27MRRO 5- 3 TCAUABO33MRRO 5- 4 TINSEB179MRRO

M Monitor caution label M DHHS caution label M UL SCREW label M Operation manual

Fasteners

6- 1 LX-BZAO41WREO 6- 2 LX-CZOO52WREO

6- 3 XHTSD4OP12RVO 6- 4 LX-BZ0081YBEO 6- 5 XOTSD4OP12000 M Screw; Power transformer mtg., Chassis support &

6- 6 XCPSD30P08000 6- 7 XCBSD3OPO8000 6- 8 XHTSD40P08000 6- 9 LX-CZAO38WREO 6-10 XHTSD4OPO8RVO

6-11

LX-CZBOllMREO

M Screw; Base plate mtg. M Screw;

M Screw; Power cord mtg. M Screw; H.V. Capacitor mtg.&

Base plate.

M Screw; M Screw; Temperature fuse mtg. M Screw; Magnetron duct mtg. M Screw; O.C. Cabinet grnd. M Screw;

M Screw; UL O.C. Cabinet

Latch hook mtg. & AH sensor duct mtg.

T.T. Motor mtg. & AH sensor mtg.

Fan motor mtg.

Magnetron mtg.

Qty Code

1 BE 1 1 AS 1 AU 1 AW

1 AE 1 AG 1 AE 1 AB 1 AK

1 AK

1 1 1 1

3 3 1 5

4 2 2 2 2

Page 46

R-420BK R-420BW

Cavity Assembly

2 3 4

5 6

Page 47

R-420BK R-420BW

1 2

Control Panel

Assembly

5 6

I I \

Door

r----

----------

_--__-------1__________----------------.

--------- -----

\ ’

l-__---________

I H

Page 48

R-420BK R-420BW

Wire Harnesses

Packing and Accessories

* Actual harnesses may be different than

illustrations.

TRAY HOLDER

@TURNTABLE TRAY

a OPERATlON MANUAL 0

* TRAY PACK

* Non-replaceable items.

I I I

‘980 SHARP CORP. (3M505E) Printed in U.S.A.

SHARP R420BK, R-420BW Service Manual

TABLE OF CONTENTS

WARNING TO SERVICE PERSONNEL

Before Servicing

After repairing

SPECIFICATIONS

GENERAL INFORMATION

Oven Diagram

Key Unit Layout

OPERATION

Description of Operating Sequence

Off Condition

Cooking Condition

Power Level P-O to P-90 Cooking

Sensor Cooking Condition

Cooking Sequence

DESCRIPTION AND FUNCTION OF COMPONENTS

Cooling Fan Motor

Oven Temperature Fuse

Magnetron Temperature Fuse

Monitor Switch

Monitor Switch Functions

Door Open Mechanism

Off Condition

TEST PROCEDURES

A. Magnetron Assembly Test

C . High Voltage Rectifier Test

F . Temperature Fuses

H . Relay Test

I . Foil pattern on the printed wiring board Test

K . Key Unit Test

L. AH Sensor Test

OUTLINE OF TOUCH CONTROL PANEL

Key Unit

Control Unit

DESCRIPTION OF LSI

Precautions for Handling Electronic Components

Shapes of Electronic Components

Servicing of Touch Control Panel

Servicing The Touch Control Panel With The Oven Power Supply

SERVICING

Servicing Tools

Other Precautions

COMPONENT REPLACEMENT/ADJUSTMENT PROCEDURE

Outer Case Removal

Power Transformer Removal

Magnetron Removal

Magnetron Installation

Control Panel Assembly Removal

Oven Lamp and Lamp Socket Removal

Turntable Motor Removal

Turntable Motor Re-install

Cooling Fan Motor Removal

Door Sensing Switch /Secondary Interlock Switch and Monitor Switch Adjustments

DOOR DISASSEMBLY

Removal

Re-Install

Sealer Film Installation

ABSOLUTE HUMIDITY SENSOR CIRCUIT

Structure of Absolute Humidity Sensor

Operational Principle of AH Sensor

Absolute Humidity Sensor Circuit

Detector Circuit of AH Sensor Circuit

AH SENSOR DUCT REMOVAL

AH SENSOR REPLACEMENT

Removal

Installation

MICROWAVE MEASUREMENT PROCEDURE

Interlock Switch Test

Microwave Leakage Test

Schematic Diagram

Power Unit Circuit

Control Panel Circuit

Printed Wiring Board of Power Unit

Electrical

Oven

Control Panel

Door

Miscellaneous

Fasteners