SHARP KB6021M, KB-6021MS, KB-6021MK, KB-6021MW Service Manual

SERVICE MANUAL

KB-6021MS pictured

KB-6021MS KB-6021MK KB-6021MW

S77M284K6021M-D

MICROWAVE DRAWER

MODEL

KB-6021MS/MK/MW

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

WARNING TO SERVICE PERSONNEL:

This service manual is intended for use by persons having electrical and mechanical training and a level of knowledge of these subjects generally considered acceptable in the appliance repair trade. Sharp Electronics Corporation cannot be responsible, nor assume any liability, for injury or damage of any kind arising from the use of this manual.

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, High Voltage Rectiﬁer, Heat Sink, Magnetron and High Voltage Harness etc...)

TABLE OF CONTENTS

Page PRECAUTIONS TO BE OBSERVED BEFORE AND DURING SERVICING TO

AVOID POSSIBLE EXPOSURE TO EXCESSIVE MICROWAVE ENERGY ..................... INSIDE FRONT COVER

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

WARNING TO SERVICE PERSONNEL .................................................................................................................3

MICROWAVE MEASUREMENT PROCEDURE ..................................................................................................... 4

FOREWORD AND WARNING ............................................................................................................................... 5

PRODUCT SPECIFICATIONS ............................................................................................................................... 6

SCHEMATICS ...................................................................................................................................................... 10

TEST PROCEDURES .......................................................................................................................................... 11

TOUCH CONTROL PANEL ASSEMBLY .............................................................................................................. 19

MICROWAVE DRAWER DISASSEMBLY ............................................................................................................. 27

WIRING DIAGRAMS ............................................................................................................................................ 33

PRINTED WIRING BOARDS ............................................................................................................................... 34

PARTS LIST ......................................................................................................................................................... 38

PACKING AND ACCESSORIES .......................................................................................................................... 43

SHARP ELECTRONICS CORPORATION

This document has been published to be used for after sales service only. The contents are subject to change without notice.

KB-6021MS KB-6021MK KB-6021MW

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

(a) Do not operate or allow the oven to be operated with the door open. (b) Make the following safety checks on all ovens to be serviced before activating the magnetron 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.

ments, check the magnetron, wave guide or transmission line, and cavity for proper alignment, integrity, and connections.

(d) 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.

(e) A microwave leakage check to verify compliance with the Federal Performance Standard should be performed

on each oven prior to release to the owner.

BEFORE SERVICING

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 @1-800-237-4277.

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 Food and Drug Administration's Center for Devices and Radiological Health immediately.

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.

WARNING TO SERVICE PERSONNEL

Microwave Oven units contain circuitry capable of producing very high voltage and current, contact with following parts

(Example) High Voltage Capacitor, High Voltage Power Transformer, Magnetron, High Voltage Rectiﬁer

Assembly, High Voltage Harness, Heating Elements, etc.. Read the Service Manual carefully and follow all instructions.

Before Servicing

1. Disconnect the power supply cord , a n d t h en remove cabinet.

2. Open the drawer and keep it open.

3. Discharge high voltage capacitor.

WARNING: RISK OF ELECTRIC SHOCK.

DISCHARGE THE HIGH-VOLTAGE CAPACITOR BEFORE SERVICING.

may result in a severe, possibly fatal, electrical shock.

KB-6021MS KB-6021MK KB-6021MW

When the testing is completed,

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

2. Open the drawer and keep it open.

3. Discharge high voltage capacitor.

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

5. Reinstall the covers.

6. Reconnect the power supply cord.

7. Run the unit and check all functions.

The high-voltage capacitor remains charged about 60 seconds after the oven has been switched off. Wait for 60 seconds and then short-circuit the connection of the high-voltage capacitor (that is 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. It may, in some cases, be necessary to connect the power supply after the outer case has been removed, in this event:

1. Disconnect the power supply cord, and then remove neccessary covers.

2. Open the drawer and keep it open.

3. Discharge 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 insulation tape.

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

After repairing

1. Reconnect all leads removed from components during testing.

2. Reinstall the covers.

3. Reconnect the power supply cord.

4. 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 tray, close the drawer 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 that the water is now hot. If the water remains cold carry out Before Servicing procedure and re-examine the connections to the component being tested.

When all service work is completed and the oven is fully assembled, the microwave power output should be checked and a microwave leakage test should be carried out.

KB-6021MS KB-6021MK KB-6021MW

MICROWAVE MEASUREMENT PROCEDURE

A. Requirements:

1) Microwave leakage limit (Power density limit): The power density of microwave radiation emitted by a microwave oven should not exceed 1mW/cm2 at any point 5cm or more from the external surface of the oven, measured prior to acquisition by a purchaser, and thereafter (through the useful life of the oven), 5 mW/cm2 at any point 5cm or more from the external surface of the oven.

2) Safety interlock switches:

Primary interlock relay switch shall prevent microwave radiation emission in excess of the requirement as above mentioned. Secondary interlock relay and door sensing switch shall prevent microwave radiation emission in excess of

5 mW/cm2 at any point 5cm or more from the external surface of the oven.

B. Preparation for testing: Before beginning the actual measurement of leakage, proceed as follows:

1) Make sure that the actual instrument is operating normally as speciﬁed in its instruction booklet.

Important: Survey instruments that comply with the requirement for instrumentation as prescribed by the performance standard for microwave ovens, 21 CFR 1030.10(c)(3)(i), must be used for testing.

2) Place the load of 275±15 ml (9.8 oz) of tap water initially at 20±5

The water container shall be a low form of 600 ml (20 oz) beaker with an inside diameter of approx. 8.5 cm (3-1/2 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.

3) Set the cooking control on Full Power Cooking Mode.

4) Close the drawer and select a cook cycle of several minutes. If the water begins to boil before the survey is completed, replace it with 275 ml of cool water.

C (68OF) in the center of the oven cavity.

C. Leakage test:

Closed-drawer leakage test (microwave measurement):

1) Grasp the probe of the survey instrument and hold it perpendicular to the gap between the drawer and the body of the oven.

2) Move the probe slowly, not faster than 1 in./sec. (2.5 cm/sec.) along the gap, watching for the maximum indication on the meter.

3) Check for leakage at the drawer screen, sheet metal seams and other accessible positions where the continuity of the metal has been breached (eg., around the switches, indicator, and vents).

While testing for leakage around the drawer, pull the drawer away from the front of the oven as far as is permitted by

the closed latch assembly.

4) Measure carefully at the point of highest leakage and make sure that the highest leakage is no greater than 4mW/cm2, and that the primary interlock switch/secondary interlock relay does turn the oven OFF before any door movement.

NOTE: After servicing, record data on service invoice and microwave leakage report.

SERVICE MANUAL

MICROWAVE DRAWERS

PRODUCT DESCRIPTION

KB-6021MS KB-6021MK KB-6021MW

KB-6021MS / KB-6021MK / KB-6021MW

FOREWORD

This Manual has been prepared to provide Sharp Electronics Corp. Service Personnel and Service Information for the MICROWAVE DRAWERS, KB-6021MS, KB-6021MK, KB-6021MW.

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

Check the interlock switches and the door seal carefully. Special attention should be given to avoid electrical shock and microwave radiation hazard.

WARNING

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

SCHEMATICS

TEST PROCEDURE

TOUCH CONTROL PANEL

MICROWAVE DRAWER DISSASSEMBLY AND ADJUSTMENT PROCEDURE

WIRING DIAGRAM

PARTS LIST

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

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, High Voltage Harness; If provided, Vent Hood, Fan assembly, Cooling Fan Motor.

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

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

All the parts marked “ ” on parts list may cause undue microwave

∆

exposure, by themselves, or when they are damaged, loosened or removed.

SHARP ELECTRONICS CORPORATION

SHARP PLAZA, MAHWAH,

NEW JERSEY 07430-2135

KB-6021MS KB-6021MK KB-6021MW

MICROWAVE DRAWER SPECIFICATION

ITEM DESCRIPTION

Power Requirements 120 Volts

14.5 Amperes, 1000 watts 60 Hz Single phase, 3 wire grounded

Power Output 1000 watts (IEC TEST PROCEDURE) Operating frequency of 2450MHz

Cooking Cavity Dimensions Width 17-11/32 Height 5-7/8"

1.0 Cubic Feet Depth 17-1/8"

Outside Dimensions Width 23-7/8" Height 15-9/32" (Including drawer handle) Depth 26-1/16"

Control Complement Touch Control System Clock ( 1:00 - 12:59 ) Timer (0 - 99 min. 99 seconds)

Microwave Power for Variable Cooking

Repetition Rate;

P-HI .................................................. Full power throughout the cooking time

P-90 ..................................................................... approx. 90% of Full Power

P-80 ..................................................................... approx. 80% of Full Power

P-70 ..................................................................... approx. 70% of Full Power

P-60 ..................................................................... approx. 60% of Full Power

P-50 ..................................................................... approx. 50% of Full Power

P-40 ..................................................................... approx. 40% of Full Power

P-30 .................................................................... approx. 30% of Full Power

P-20 ..................................................................... approx. 20% of Full Power

P-10 ..................................................................... approx. 10% of Full Power

P-0 ..................................................... No power throughout the cooking time

START/MINUTE PLUS pad, Defrost pad, Number selection pad, Keep-warm pad, Power Level pad, Timer/Clock pad, Stop/Clear pad, Sensor Reheat, Sensor Popcorn, Sensor Cook, Open pad, Close pad, Setup/Custom Help, On/Off, Control Lock, Reheat.

Oven Cavity Light Yes

Safety Standard UL Listed FCC Authorized

DHHS Rules, CFR, Title 21, Chapter 1, Subchapter J

KB-6021MS

3-Pronged Plug

Grounded Receptacle Box

Grounding Pin

3-Pronged Receptacle

GENERAL INFORMATION

KB-6021MK KB-6021MW

GROUNDING INSTRUCTIONS

This oven is equipped with a three prong grounding plug. It must be plugged into a wall receptacle that is properly installed and grounded in accordance with the National Electrical Code and local codes and ordinances. In the event of an electrical short circuit, grounding reduces the risk of electric shock by providing an escape wire for the electric current.

WARNING: Improper use of the grounding plug can result in a risk of electric shock.

Electrical Requirements The electrical requirements are a 120 volt 60 Hz, AC only, 15 or 20 amp. fused electrical supply. It is recommended that a separate circuit serving only this appliance be provided. When installing this appliance, observe all applicable codes and ordinances.

Where a two-pronged wall-receptacle is encountered, it is the personal responsibility and obligation of the customer to contact a qualiﬁed electrician and have it replaced with a properly grounded three-pronged wall receptacle or have a grounding adapter properly grounded and polarized. If an extension cord must be used, it should be a 3-wire, 15 amp. or higher rated cord. Do not drape over a counter top or table where it can be pulled on by children or tripped over accidentally.

CAUTION: DO NOT UNDER ANY CIRCUMSTANCES CUT OR REMOVE THE ROUND GROUNDING PRONG FROM

THIS PLUG.

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

KB-6021MS

(Colors may vary)

KB-6021MS KB-6021MK KB-6021MW

OPERATION

DESCRIPTION OF OPERATING SEQUENCE

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

OFF CONDITION

Closing the drawer activates the door sensing switch and secondary interlock switch. (In this condition, the monitor switch contacts are opened.) When oven is plugged in, 120 volts A.C. is supplied to the control unit. (Page 10).

1. The display will show ﬂashing "Enjoy Your Drawer Touch Clear and Touch Clock".

To set any program or set the clock, you must ﬁrst touch

the STOP/CLEAR pad. The display will clear, and " : " will appear.

COOKING CONDITION

Program desired cooking time by touching the NUMBER pads. Program the power level by touching the POWER LEVEL pad and then a Number pad. When the START pad is touched, the following operations occur:

1. The contacts of relays are closed and components connected to the relays are turned on as follows.

(For details, refer to Page 10)

the secondary interlock switch and secondary interlock relay and is mechanically associated with the drawer so that it will function in the following sequence.

8. When the drawer opens from the closed position, the primary interlock relay (RY2) and secondary interlock switch open their contacts. And contacts of the relay (RY1) remains closed. Then the monitor switch contacts close.

9. When the drawer is closed from the open position, the monitor switch contacts open ﬁrst. Then the contacts of the secondary interlock switch and door sensing switch close. And contacts of the relay (RY1) open.

If the secondary interlock switch and primary interlock relay (RY2) fail with the contacts closed when the drawer is opened, the closing of the monitor switch contacts will form a short circuit through the fuse, secondary interlock switch, relay (RY1) and secondary interlock relay (RY2), causing the fuse to blow.

POWER LEVEL P-0 TO P-90 COOKING

When Variable Cooking Power is programmed, the 120 volts A.C. 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:

RELAY CONNECTED COMPONENTS

RY-1 oven lamp/stir fan motor/fan motor

RY-2 power transformer

2. 120 volts A.C. is supplied to the primary winding of the power transformer and is converted to about 3.3 volts A.C. output on the ﬁlament winding, and approximately 2370 volts A.C. on the high voltage winding.

3. The ﬁlament winding voltage heats the magnetron ﬁlament and the H.V. winding voltage is sent to a voltage doubler circuit.

4. The microwave energy produced by the magnetron is channelled through the waveguide into the cavity feedbox, and then into the cavity where the food is placed to be cooked.

5. Upon completion of the cooking time, the power transformer, oven lamp, etc. are turned off, and the generation of microwave energy is stopped. The oven will revert to the OFF condition.

6. When the drawer is opened during a cook cycle, the monitor switch, door sensing switch, secondary interlock switch, relay (RY1) and primary interlock relay are activated with the following results. The circuits to the stir fan motor, the cooling fan motor, and the high voltage components are de-energized, the oven lamp remains on, and the digital read-out displays the time still remaining in the cook cycle when the door was opened.

7. The monitor switch electrically monitors the operation of

VARI-MODE ON TIME OFF TIME

Power 10(P-HI) 32 sec. 0 sec. (100% power)

Power 9(P-90) 30 sec. 2 sec. (approx. 90% power)

Power 8(P-80) 26 sec. 6 sec. (approx. 80% power)

Power 7(P-70) 24 sec. 8 sec. (approx. 70% power)

Power 6(P-60) 22 sec. 10 sec. (approx. 60% power)

Power 5(P-50) 18 sec. 14 sec. (approx. 50% power)

Power 4(P-40) 16 sec. 16 sec. (approx. 40% power)

Power 3(P-30) 12 sec. 20 sec. (approx. 30% power)

Power 2(P-20) 8 sec. 24 sec. (approx. 20% power)

Power 1(P-10) 6 sec. 26 sec. (approx. 10% power)

Power 0(P-0) 0 sec. 32 sec. (0% power)

Note: The ON/OFF time ratio does not correspond with the

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

SENSOR COOKING CONDITION

MICR

OWAV

MICROWAVE

AH SENSOR

Using the SENSOR function, food is 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 power level needed for best results. When the food is cooked, water vapor is developed. the sensor "senses" the vapor and its resistance increase gradually. When the resistance reaches the value set according to the menu, supplementary cooking is started. The time of supplementary cooking is determined by experiment with each food category and inputted into the LSI. An example of how sensor works: (Potatoes)

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

KB-6021MS KB-6021MK KB-6021MW

2. The coil of shut-off relay (RY-1) is energized, but the power transformer is not turned on.

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

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

touch STOP/CLEAR pad.

4. When the sensor detects the vapor emitted from the food, the display switches over to the remaining cooking time and the timer counts down to zero.

At this time, the drawer may be opened to stir, turn or

season food.

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

6. Opening the drawer or touching the STOP/CLEAR pad, the time of the day will reappear on the display and the oven will revert to an OFF condition. When the timer reaches zero, an audible signal sounds.

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

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

Cooking Sequence.

1. Touch one of the SENSOR pads.

NOTE: The oven should not be operated on sensor

immediately after plugging in the unit. Wait two minutes before cooking on SENSOR.

KB-6021MS

HUMIDITY

SENSOR

NOISESUPRESSIONCO

RESISTOR 470k? 1/2W

LINE

CROSSCAPA

CITOR1.0? F 275

LINE BYPASS CAPACIT

0.0033?F250V

FUSE 20A

FAN

OVENLAM

NITORSWITC

PRIMARY INTERLOCK RELAY

H.V. R

IFIER

MAGNET

RON

POWER TRANSFORMER

CAPACITOR

1.00?F A

C2300

STIRRER MOTOR

C ONT R OL U NIT

MICROWAVE DRAWER

S WIT C HIN G R E GU LAT OR

OVEN

THERMAL

CUT-OUT

THERMAL

CUT-OUT

SECONDARY INTELOCK SWITCH

MICROWAVE DRAWER

DOOR OPEN-CLOSE

MOTOR

DOOR

POSITION

SWITCH

FRONT

DOOR

POSITION

SWITCH

REAR

DOOR

SENSING

SWITCH

N.O.

COM

RY4

RY3

RY1

RY2

N.O.

COM

INE BYPASS

PACITO

0.00

33 ? F250V

NO IS E F ILT E R

120 VAC

60 H z.

LO W VO LT AG E

F M

S M

N. C.

COM

C OM

N. O.

WHT

RED

GND

G RN

WH T

R E D

OR G

BL K

OR G

WHT

B LK

C N501

RY5

TR A NS FO R MER

C N502

R E D

BL K

R E

OR G

YL W

BL U

R N

GR N

WH T

GR N

R E D

E D

R E

OR G

R Y

BL K

OR G

BLK

WH T

G RY

WH T

GRY

NOT E S :

1. C irc uits / Wire C olo rs s u bje ct to c ha nge w ithout n oti ce .

2. T ermi na l that is lo ca ted to the r igh t s id e on the l amp s oc ke t's b a ck view

mu s t be c on nec ted to n eutr a l w ire .

3. Only c er tain m odels us e the a bs ol ute h umidi ty s ens o r

4. P ower T ra ns fo rm er ( Fin is h L ea d) te rm inal m u s t be c o nnec ted to H OT wire ( R E D)

GR N

"TO SOURCE"

"TOLOAD"

"TO LOAD

H11

R E D

KB-6021MK KB-6021MW

SCHEMATIC (OFF CONDITION)

KB-6021MS KB-6021MK

TEST PROCEDURES

PROCEDURE LETTER A TOUCH CONTROL PANEL ASSEMBLY TEST

COMPONENT TEST

KB-6021MW

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

unlike conventional microwave ovens, proper maintenance cannot be performed with only a voltmeter and ohmmeter. In this service manual, the touch control panel assembly is divided into three units, Control Unit, Keyboard Unit and Power Unit, and troubleshooting by unit replacement is described according to the symptoms indicated.

Before testing,

1) Disconnect the power supply cord, and then disassemble as per "MICROWAVE DRAWER DISASSEMBLY" page 27.

2) Open the drawer and block it open.

3) Discharge 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 insulation tape.

1. Keyboard Unit. NOTE ;

1) Check Keyboard unit connection before replacement.

2) Reconnect all leads removed from components during testing.

3) Re-install the covers.

4) Reconnect the power supply cord after the covers are installed.

5) Run the oven and check all functions.

The following symptoms indicate a defective keyboard 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 Keyboard unit is defective.

1) Disconnect the power supply cord, and then remove covers.

2) Open the drawer and block it open.

3) Discharge high voltage capacitor.

4) Replace the Keyboard unit.

5) Reconnect all leads removed from components during testing.

6) Re-install the covers.

7) Reconnect the power supply cord after the covers are 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 Keyboard unit test (Procedure B) to determine if control unit is faulty.

2-1 In connection with indicators

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

2-2 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.

3. Power Unit or Touch Control Transformer a) Fan motor, stirrer motor, oven lamp or electrical parts do not turn on or do not turn off. b) Digital display on the control unit does not show anything.

When testing is completed,

1) Disconnect the power supply cord, and then disassemble as per "MICROWAVE DRAWER

DISASSEMBLY" page 27.

2) Open the drawer and block it open.

3) Discharge high voltage capacitor.

KB-6021MS

STOP/ CLEAR

REHEAT

START/MINUTE

PLUS

SENSOR

COOK

SENSOR REHEAT

DEFROST

OPEN

SENSOR

POPCORN

KEEP

WARM

TIMER

CLOCK

POWER

LEVEL

SET UP

CUSTOM

HELP

CONTROL

LOCK

ON/OFF

J-1

J-2

J-3

J-4

J-5

J-6

J-7

J-8

J-9

J-12

J-11

J-10

KB-6021MK KB-6021MW

PROCEDURE LETTER

TEST PROCEDURES

COMPONENT TEST

4) Reconnect all leads removed from components during testing.

5) Re-install the covers.

6) Reconnect the power supply cord after the covers are installed.

7) Run the oven and check all functions.

B KEY UNIT TEST

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

2. Open the drawer and block it open.

3. Discharge high voltage capacitor.

4. If the display fails to clear when the STOP/CLEAR pad is depressed, ﬁrst verify the ﬂat ribbon cable is making good contact, verify that the door sensing switch (stop switch) operates properly; that is the contacts are closed when the drawer is closed and open when the drawer is open. If the door sensing switch (stop switch) is good, disconnect the ﬂat ribbon cable that connects the key unit to the control unit and make sure the drawer sensing switch is closed (either close the drawer or short the door sensing switch connecter). Use the Key unit matrix indicated on the control panel schematic and place a jumper wire between the pins that correspond to the STOP/CLEAR pad making momentary contact. If the control unit responds by clearing with a beep the key unit is faulty and must be replaced. If the control unit does not respond, it is faulty and must be replaced. If a speciﬁc pad does not respond, the above method may be used (after clearing the control unit) to determine if the control unit or key pad is at fault.

5. Reconnect all leads removed from components during testing.

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

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

8. Run the oven and check all functions.

C RELAY TEST

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

2. Open the door and block it open.

3. Discharge 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 insulation tape.

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

7. Remove the outer case and check voltage between Pin Nos. 5 and 7 of the 4 pin connector (CN-A) on the power unit with an A.C. voltmeter.

The meter should indicate 120 volts, if not check oven circuit. RY1, RY2, RY3 and RY4 Relay Test These relays are operated by D.C. voltage Check voltage at the relay coil with a D.C. voltmeter during the microwave cooking operation.

DC. voltage indicated Defective relay. DC. voltage not indicated Check diode which is connected to the relay coil. If diode is good,

RELAY SYMBOL OPERATIONAL VOLTAGE CONNECTED COMPONENTS

RY1 Approx. 26V D.C. Oven lamp / Common

control unit is defective.

RY2 Approx. 25V D.C. Power transformer

RY3 Approx. 26V D.C. Stirrer motor

RY4 Approx. 26V D.C. Fan motor

RY5 Approx. 26V D.C. Switching regurator for drawer motor

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

9. Open the door and block it open.

10. Discharge high voltage capacitor.

PROCEDURE LETTER

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

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

13. Run the oven and check all function.

D DEFROST TEST

WARNING : The oven should be fully assembled before following procedure.

(1) Place one cup of water in the center of the tray in the oven cavity. (2) Close the drawer, touch the Defrost pad. Then select Steaks/Chops by touching the number pad

2. And touch the number pad 5. (Now, weight 0.5lb is set.) And then touch the start pad. (3) The oven is in Defrost cooking condition. (4) The oven will operate as follows

WEIGHT 1ST STAGE 2ND STAGE 3RD. STAGE

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

TEST PROCEDURES

COMPONENT TEST

LEVEL TIME LEVEL TIME LEVEL TIME

0.5lb 60% 20sec. 40% 20sec. 30% 45sec.

KB-6021MS KB-6021MK KB-6021MW

E PROCEDURES TO BE TAKEN WHEN THE FUSE ON THE PRINTED WIRING BOARD (PWB) IS OPEN.

To protect the electronic circuits, this model is provided with a fuse added to the primary on the PWB.

1. Fuse check and repairs.

1) Disconnect the power supply cord.

2) Remove the outer case cabinet.

3) Open the door and block it open.

4) Discharge high voltage capacitor.

5) If the Fuse is blown, replace power unit.

6) Make a visual inspection of the varistor. Check for burned damage. If the varistor has been burned, replace the power unit.

7) Examine the touch control transformer with a tester for the presence of layer short-circuit (check the primary coil resistance which is approximately 151.6Ω ± 10%). If any abnormal condition is detected, replace the touch control transformer.

8) Reconnect all leads removed from components during testing.

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

10) Reconnect the power supply cord after the outer case is installed.

11) 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.

2) Remove the outer case cabinet.

3) Open the door and block it open.

4) Discharge high voltage capacitor.

5) Disconnect the leads to the primary of the power transformer.

6) Ensure that these leads remain isolated from other components and oven chassis by using

insulation tape.

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

8) Follow the troubleshooting guide given below for repair.

STEPS OCCURRENCE CAUSE OR CORRECTION

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

Pin Nos. 5 and 7 of the 4-pin connecter (CN-A).

2 The rated AC voltage is present at primary Touch control transformer or secondary circuit defective. side of touch control transformer. Check and replace touch control transformer or power unit .

KB-6021MS KB-6021MK KB-6021MW

TEST PROCEDURES

PROCEDURE LETTER

9) Discharge high voltage capacitor.

10) Reconnect all leads removed from components during testing.

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

12) Reconnect the power supply cord after the outer case is installed.

13) Run the oven and check all functions.

F AH SENSOR TEST

Checking the initial sensor cooking condition

WARNING : The oven should be fully assembled before following procedure.

(1) The oven should be plugged in at least two minutes before sensor cooking. (2) Room temperature should not exceed 95οF (35οC). (3) The unit should not be installed in any area where heat and steam are generated. The unit should not be

installed, for example, next to a conventional surface unit. Refer to the “INSTALLATION INSTRUCTIONS” of the operation manual.

(4) Exhaust vents are provided on the back 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 of by the spray and turn off before 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.

COMPONENT TEST

Water load cooking test WARNING : The oven should be fully assembled before following procedure.

Make sure the oven has been plugged in at least two minutes before checking sensor cook operation. The cabinet should be installed and screws tightened. (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 drawer. (4) Touch the TIMER/CLOCK pad once, the POWER LEVEL pad twice and the START pad once. And touch

the number pad 1 once and the number pad 4 once. Now, the oven is in the sensor cooking condition,

and "AH20" and "ON" will appear in the display. (5) 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 pad is touched during ﬁrst stage of sensor

cooking. (6) After approximately 16 seconds, microwave energy is produced. If ERROR is displayed or the oven does not turn off, replace the AH sensor or check the control unit, refer to explanation below. If the oven stops after 5 minutes and no ERROR code is displayed, then the AH sensor is normal. Check other parts except the AH sensor.

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 replacement

sensor. (1) Disconnect the power supply cord, and

then disassemble as per "MICROWAVE DRAWER

DISASSEMBLY" page 27.

(2) Open the drawer and block it open. (3) Discharge 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 covers. (8) Reconnect the power supply cord after the covers are installed. (9) Reconnect the oven to the power supply and check the sensor cook operation as follows:

9-1. Fill approximately 200 milliliters (7.2 oz) of tap water in a 1000 milliliter measuring cup.

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