Dacor DMO2420 Parts And Service Manual

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DMO2420

Microwave

Parts and Service Manual

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DMO2420B DMO2420R DMO2420S

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 Trans-

former, Magnetron, High Voltage Rectifier Assembly, High Voltage Harness etc..

Read the Service Manual carefully and follow all instructions.

Before Servicing

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

2. Open the door and block it open.

3. Discharge high voltage capacitor.

WARNING:RISK OF ELECTRIC SHOCK.

DISCHARGE THE HIGH-VOLTAGE CAPACITOR BEFORE SERVICING.

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 highvoltage capacitor (that is the connecting lead of the highvoltage 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 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 the leads remain isolated from other components and oven chassis by using insulation tape.

6. After that procedure, 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 high voltage capacitor.

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

5. Reinstall the outer case (cabinet).

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

7. Run the oven and check all functions.

After repairing

1. Reconnect all leads removed from components during testing.

2. Reinstall the outer case (cabinet).

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

4. Run the oven and check all functions.

Microwave ovens should not be run empty. To test for the presence of microwave energy within a cavity, place a cup of cold water on the oven turntable, close the door and set the 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.

Don't Touch ! Danger High Voltage

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DMO2420B DMO2420R DMO2420S

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 and door sensing switch shall prevent microwave radiation emission in excess of the requirement as above mentioned, secondary interlock 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 oven tray in the oven cavity.

3) Place the load of 275±15 ml (9.8 oz) of tap water initially at 20±5½C (68½F) 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 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.

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

5) Close the door 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. Leakage test:

Closed-door leakage test (microwave measurement)

1) Grasp the probe of the survey instrument and hold it perpendicular to the gap between the door 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 door 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 door pull the door 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 secondary interlock switch does turn the oven OFF before any door movement.

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

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DMO2420B DMO2420R DMO2420S

SERVICE MANUAL

MICROWAVE OVEN

DMO2420B/DMO2420R/DMO2420S

FOREWORD

This Manual has been prepared to provide Dacor Service Personnel with Operation and Service Information for the DACOR MICROWAVE OVENS, DMO2420B, DMO2420R and DMO2420S.

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 no other visible damage with the oven.

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.

PRODUCT DESCRIPTION

GENERAL INFORMATION

OPERATION

TROUBLESHOOTING GUIDE AND TEST PROCEDURE

TOUCH CONTROL PANEL

COMPONENT REPLACEMENT AND ADJUSTMENT PROCEDURE

WIRING DIAGRAM

PARTS LIST

distinctive appliances

950 SOUTH RAYMOND AVE.

PASADENA, CA 91105

distinctive appliances

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DMO2420B DMO2420R DMO2420S

ITEM DESCRIPTION

Power Requirements 120 Volts / 13.8 Amperes

60 Hertz Single phase, 3 wire grounded

Power Output 1200 watts (IEC TEST PROCEDURE)

Operating frequency of 2450MHz

Case Dimensions Width 24"

Height 13-3/8" Depth 19-1/8"

Cooking Cavity Dimensions Width 17-3/8"

Height 10-1/2"

2.0 Cubic Feet Depth 18-5/8" Control Complement Touch Control System

Clock ( 1:00 - 12:59 ) Timer (0 - 99 min. 99 seconds)

Microwave Power for Variable Cooking Repetition Rate;

100 PERCENT............................. Full power throughout the cooking time

90 PERCENT............................................... approx. 90% of Full Power

80 PERCENT............................................... approx. 80% of Full Power

70 PERCENT............................................... approx. 70% of Full Power

60 PERCENT............................................... approx. 60% of Full Power

50 PERCENT............................................... approx. 50% of Full Power

40 PERCENT............................................... approx. 40% of Full Power

30 PERCENT.............................................. approx. 30% of Full Power

20 PERCENT............................................... approx. 20% of Full Power

10 PERCENT............................................... approx. 10% of Full Power

0 PERCENT.............................. No power throughout the cooking time

Sensor Cooking pads, Breakfast pad, Lunch pad 15 Minute Dinner pad, Auto Defrost pad, Microwave Recipes pad Beverage pad, Number selection pads, Timer/Clock pad Keep Warm Plus pad, Easy Minute pad, Power Level pad Stop/Clear pad, Start/Instant On pad

Oven Cavity Light Yes Safety Standard UL Listed FCC Authorized

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

SPECIFICATION

GENERAL INFORMATION

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.

A short power-supply cord is provided to reduce risks of becoming entangled in or tripping over a longer cord.

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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 the extension cord must be used, it should be a 3-wire, 15 amp. or higher rated cord. Do not drape over a countertop or table where it can be pulled on by children or tripped over accidentally.

CAUTION: DO NOT UNDER ANY CIRCUMSTANCES CUT OR RE-

MOVE THE ROUND GROUNDING PRONG FROM THIS PLUG.

OVEN DIAGRAM

1. One touch door open button. Push to open door.

2. Door latches. The oven will not operate unless the door is securely closed.

3. Removable turntable support.

4. Removable turntable. The turntable will rotate clockwise or counterclockwise.

5. Oven lamp. It will light when oven is operating or door is opened.

6. Oven door with see-through window.

7. Ventilation openings. (Rear)

8. Auto-Touch control panel.

9. Time display: Digital display, 99 minutes 99 seconds.

10.Coupling.

11.Wave guide cover.

12.Power supply cord.

NOTE: The directed features are disabled after three minutes 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.

TOUCH CONTROL PANEL

3-Pronged Plug

Grounded Receptacle Box

Grounding Pin

3-Pronged Receptacle

DMO2420R DMO2420B DMO2420S

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DMO2420B DMO2420R DMO2420S

OPERATION

DESCRIPTION OF OPERATING SEQUENCE

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

OFF CONDITION

Closing the door 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. (Figure O-1).

1. The display will show "Welcome". 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. 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 Figure O-2)

RELAY CONNECTED COMPONENTS RY-1 oven lamp/turntable 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 3.2 volts A.C. output on the filament winding, and approximately 2360 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 door 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 turntable 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

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

(1) When the door 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.

(2) When the door 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 door is opened, the closing of the monitor switch contacts will form a short circuit through the monitor fuse, secondary interlock switch, relay (RY1) and primary interlock relay (RY2), causing the monitor fuse to blow.

POWER LEVEL 0% TO 100% 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:

VARI-MODE ON TIME OFF TIME

100% power 32 sec. 0 sec.

approx. 90% power 30 sec. 2 sec.

approx. 80% power 26 sec. 6 sec.

approx. 70% power 24 sec. 8 sec.

approx. 60% power 22 sec. 10 sec.

approx. 50% power 18 sec. 14 sec.

approx. 40% power 16 sec. 16 sec.

approx. 30% power 12 sec. 20 sec.

approx. 20% power 8 sec. 24 sec.

approx. 10% power 6 sec. 26 sec.

0% power 0 sec. 32 sec.

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

Using the SENSOR function, the 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 increases gradually. When the resistance reaches the value set according to the menu, supplementary cooking is started.

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DMO2420B DMO2420R DMO2420S

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.

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

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

Cooking Sequence.

1. Touch one of the SENSOR pads and then touch the Start pad.

NOTE: The oven should not be operated on SENSOR

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

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

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

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

STOP/CLEAR pad.

4. When the sensor detects the vapor emitted from the food, the display switches over to the remaining cooking time and the timer counts down to zero. At this time, the door may be opened to stir, 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 door or touching the STOP/CLEAR pad, the time of day will reappear on the display and the oven will revert to an OFF condition.

MICROWAVE

AH SENSOR

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DMO2420B DMO2420R DMO2420S

Figure O-1. Oven Schematic-Off Condition

SCHEMATIC

NOTE: CONDITION OF OVEN

1. DOOR CLOSED.

2. CLOCK APPEARS ON DISPLAY.

SCHEMATIC

NOTE: CONDITION OF OVEN

1. DOOR CLOSED.

2. COOKING TIME PROGRAMMED.

3. VARIABLE COOKING CONTROL "P-HI/ 100 PERCENT".

4. "START" PAD TOUCHED.

Figure O-2. Oven Schematic-Cooking Condition

120V AC 60 Hz

OVEN LAMP

TURNTABLE MOTOR

FAN MOTOR

MONITOR SWITCH

H.V. RECTIFIER

MAGNETRON

SECONDARY INTERLOCK SWITCH

TTM

OL FM

MONITOR FUSE 20A

CAVITY TEMP. FUSE

MAGNETRON TEMP. FUSE

COM.

COM.N.O.

N.C.

N.O.

DOOR SENSING SWITCH

(RY-1)

(RY-2)

CONTROL UNIT

PRIMARY INTERLOCK RELAY

B1 B2

GRN

POWER TRANSFORMER

CAPACITOR 1.0µF AC 2300V

AH SENSOR

120V AC 60 Hz

OVEN LAMP

TURNTABLE MOTOR

FAN MOTOR

MONITOR SWITCH

H.V. RECTIFIER

MAGNETRON

SECONDARY INTERLOCK SWITCH

TTM

OL FM

CAVITY TEMP. FUSE

COM.

COM.N.O.

N.C.

N.O.

DOOR SENSING SWITCH

(RY-1)

(RY-2)

CONTROL UNIT

PRIMARY INTERLOCK RELAY

B1 B2

GRN

POWER TRANSFORMER

CAPACITOR 1.0µF AC 2300V

MONITOR FUSE 20A

MAGNETRON TEMP. FUSE

NOTE: Indicates components with potential above 250 V.

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DMO2420B DMO2420R DMO2420S

DESCRIPTION AND FUNCTION OF COMPONENTS

DOOR OPEN MECHANISM

The door is opened by pushing the open button on the control panel, refer to the Figure D-1. When the open button is pushed, the open button pushes up the switch lever, and then the switch lever pushes up the latch head. The latch heads are moved upward and released from latch hook. Now the door will open.

Figure D-1. Door Open Mechanism

DOOR SENSING AND 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 power to all high voltage components. 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 primary interlock relay located on the control circuit board.

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 (RY2) and secondary interlock switch fail to open when the door is opened.

Functions:

1. When the door is opened, the monitor switch contact close (to the ON condition) due to their being normally closed. At this time the primary interlock relay (RY2) and secondary interlock switch are in the OFF condition (contacts open) due to their being normally open contact switches.

2. As the door goes to a closed position, the monitor switch contacts are first opened and then the door sensing switch and the secondary interlock switch contacts close. (On opening the door, each of these switches operate inversely.)

3. If the door is opened, and the primary interlock relay (RY2) and secondary interlock switch contacts fail to

open, the monitor fuse blows simultaneously with closing of the monitor switch contacts.

CAUTION: BEFORE REPLACING A BLOWN MONITOR

FUSE TEST THE DOOR SENSING SWITCH, PRIMARY INTERLOCK RELAY (RY2), RELAY (RY1), SECONDARY INTERLOCK SWITCH AND MONITOR SWITCH FOR PROPER OPERATION. (REFER TO CHAPTER "TEST PROCEDURE").

NOTE: MONITOR FUSE AND MONITOR SWITCH ARE

REPLACED AS AN ASSEMBLY.

TURNTABLE MOTOR

The turntable motor rotates the turntable located on the bottom of the oven cavity, so that the foods on the turntable cook evenly during cooking. The turntable may turn in either direction.

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 and cools the magnetron. This air is channelled through the oven cavity to remove steam and vapors given off from the heating foods. It is then exhausted through the exhausting air vents at the oven cavity.

MONITOR FUSE

1. The monitor fuse blows when the contacts (COM-NO) of the primary interlock relay (RY2) and secondary interlock switch remain closed with the oven door open and when the monitor switch closes.

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

CAVITY TEMPERATURE FUSE

The cavity temperature fuse located on the top of the oven cavity, is designed to prevent damage to the oven by fire. If the food load is overcooked, by either error in cook time or defect in the control unit, the cavity temperature fuse will open. Under normal operation, the cavity temperature fuse remains closed. However, when abnormally high temperatures are reached within the oven cavity, the cavity temperature fuse will open at 302½F(150½C) causing the oven to shut down. NOTE: This is a fuse. It does not reset.

MAGNETRON TEMPERATURE FUSE

The magnetron temperature fuse located near the magnetron is designed to prevent damage to the magnetron if an over heated condition develops in the tube due to cooling fan failure, obstructed air guide, dirty or blocked air intake, etc. Under normal operation, the magnetron temperature fuse remains closed. However, when abnormally high temperatures are reached within the magnetron, the magnetron temperature fuse will open at 302½F(150½C) causing the oven to shut down. NOTE: This is a fuse. It does not reset.

Door Sensing Switch

Monitor Switch

Switch Lever

Secondary Interlock Switch

Latch Heads

Door

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DMO2420B DMO2420R DMO2420S

TROUBLESHOOTING GUIDE

Never touch any part in the circuit with your hand or an uninsulated tool while the power supply is connected.

When troubleshooting the microwave oven, it is helpful to follow the Sequence of Operation in performing the checks. Many of the possible causes of trouble will require that a specific test be performed. These tests are given a procedure letter which will be found in the "Test Procedure "section.

IMPORTANT: If the oven becomes inoperative because of a blown monitor fuse, check the monitor switch, relay (RY1)

primary interlock relay (RY2), door sensing switch and secondary interlock switch before replacing the monitor fuse. If the monitor fuse is replaced, the monitor switch must also be replaced. Use part FFS-BA016/ KIT as an assembly.

IMPORTANT: Whenever troubleshooting is performed with the power supply cord disconnected. It may in, some cases, be

necessary to connect the power supply cord after the outer case has been removed, in this event,

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 the leads remain isolated from other components and oven chassis by using insulation tape.

6. After that procedure, 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 high voltage capacitor.

4. Reconnect all leads removed from components during testing.

5. Reinstall the outer case (cabinet).

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

7. Run the oven and check all functions.

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DMO2420B DMO2420R DMO2420S

CK = Check / RE = Replace

SHORT IN POWER CORD

SHORT OR OPENED WIRING

MAGNETRON

POWER TRANSFORMER

H.V. RECTIFIER ASSEMBLY

HIGH VOLTAGE CAPACITOR

CAVITY TEMPERATURE FUSE

MAGNETRON TEMPERATURE FUSE

PRIMARY INTERLOCK SYSTEM

SECONDARY INTERLOCK SWITCH

MONITOR SWITCH

MONITOR FUSE

OVEN LAMP OR SOCKET

COOLING FAN MOTOR

TURNTABLE MOTOR

TOUCH CONTROL PANEL

WRONG OPERATION

LOW VOLTAGE

DIRTY OVEN CAVITY

KEY UNIT

RELAY (RY1)

DEFROST CENTER

FOIL PATTERN ON PWB.

AH SENSOR

Home fuse or circuit breaker blows when power cord is plugged into wall receptacle.

Monitor fuse blows when power cord is plugged into wall receptacle.

Any letters or indicators do not appear in display when power cord is first plugged into wall outlet.

Display does not operate properly when STOP/CLEAR key is touched. (Buzzer should sound and ":" or time of day should appear in display.)

Oven lamp does not light when door is opened.

Oven lamp does not go out when door is closed.

Oven lamp lights but fan motor and turntable motor do not operate.

Oven does not go into cook cycle when START pad is touched

Oven seems to be operating but little or no heat is produced in oven load. (Food incompletely cooked or not cooked at all at end of cook cycle.)

Oven goes into a cook cycle but extremely uneven heating is produced in oven load (food).

Oven does not cook properly when programmed for P-50/ 50 PERCENT mode. (Operates properly on P-HI/ 100 PERCENT mode.)

Oven goes into Defrost Center but food is not defrosted well.

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

Oven stops at 16 sec. after starting.

RE RE

ABCDEEFFGH

RE RE CKICK CK CK

JKLMN

TEST PROCEDURE

POSSIBLE CAUSE

AND

DEFECTIVE PARTS

COOKING

CONDITION

PROBLEM

OFF

CONDITION

SENSOR

COOKING

CONDITION

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DMO2420B DMO2420R DMO2420S

B POWER TRANSFORMER 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 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 ohm and the resistance of the high voltage coil should be approximately 90 ohms; the resistance of the filament coil should be less than 1 ohm.

5. Reconnect all leads removed from components during testing.

6. Reinstall the outer case (cabinet).

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

8. Run the oven and check all functions.

TEST PROCEDURES

PROCEDURE

LETTER

COMPONENT 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. 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 1 ohm.

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 and must be replaced.

6. Reconnect all leads removed from components during testing.

7. Reinstall the outer case (cabinet).

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

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 assembled 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: silicon rectifier, high voltage capacitor and power transformer. This test will require a 16 ounce (453cc) measuring cup and an accurate mercury thermometer or thermocouple type temperature tester. For accurate results, the following procedure must be followed carefully:

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

2. Place the cup of water in the oven. Operate oven at 100 PERCENT POWER/ P-HI selecting more than 60 seconds cook time. Allow the water to heat for 60 seconds, measuring with a stop watch, second hand of a watch or the digital read-out countdown.

3. Remove the cup from the oven and again measure the temperature, making sure to stir the thermometer or thermocouple through the water until the maximum temperature is recorded.

4. Subtract the cold water temperature from the hot water temperature. The normal result should be 33 to 62½F(18.6 to 34.5½C) rise in temperature. If the water temperatures are accurately measured and 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 cooking 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 is clean.

A MAGNETRON ASSEMBLY TEST

Page 14

DMO2420B DMO2420R DMO2420S

TEST PROCEDURES

PROCEDURE

LETTER

COMPONENT 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. 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 terminals using an ohmmeter. Checking with a high ohm scale, if the high voltage capacitor is normal, the meter will indicate continuity for a short time and should indicate an open circuit once the capacitor is charged. If the above is not the case, check the capacitor with an ohmmeter to see if it is shorted between either of the terminals and case. If it is shorted, replace the capacitor.

5. Reconnect all leads removed from components during testing.

6. Reinstall the outer case (cabinet).

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

8. Run the oven and check all functions.

D HIGH VOLTAGE CAPACITOR TEST

E CAVITY TEMPERATURE FUSE 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. A continuity check across the cavity temperature fuse terminals should indicate a closed circuit unless the temperature of the cavity temperature fuse reaches approximately 302½F(150½C). An open cavity temperature fuse indicates overheating of the oven, exchange the cavity temperature fuse and check inside of oven cavity and for improper setting of cooking time or operation of control unit. Check for restricted air flow through the vent holes of the oven cavity, especially the cooling fan and air guide.

5. Reconnect all leads removed from components during testing.

6. Reinstall the outer case (cabinet).

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

8. Run the oven and check all functions.

MAGNETRON TEMPERATURE FUSE 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. A continuity check across the magnetron temperature fuse terminals should indicate a closed circuit unless the temperature of the magnetron temperature fuse reaches approximately 302½F(150½C). An open magnetron temperature fuse indicates overheating of the magnetron. Check for restricted air flow to the magnetron, especially the cooling fan air guide.

C HIGH VOLTAGE RECTIFIER 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. 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. Reinstall the outer case (cabinet).

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

8. Run the oven and check all functions.

NOTE: Be sure to use an ohmmeter that will supply a forward bias voltage of more than 6.3 volts.

(HIGH VOLTAGES ARE PRESENT AT THE HIGH VOLTAGE TERMINAL, SO DO NOT ATTEMPT TO MEASURE THE FILAMENT AND HIGH VOLTAGE.)

Page 15

DMO2420B DMO2420R DMO2420S

TEST PROCEDURES

PROCEDURE

LETTER

COMPONENT 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. Before performing this test, make sure that the secondary interlock switch and the primary interlock relay are operating properly, according to the above Switch Test Procedure. Disconnect the wire lead from the monitor switch (COM) terminal. Check the monitor switch operation by using the ohmmeter as follows. When the door is open, the meter should indicate a closed circuit. When the monitor switch actuator is pushed by a screw driver through the lower latch hole on the front plate of the oven cavity

5. Reconnect all leads removed from components during testing.

6. Reinstall the outer case (cabinet).

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

8. Run the oven and check all functions.

CAUTION: IF THE TEMPERATURE FUSE INDICATES AN OPEN CIRCUIT AT ROOM TEMPERA-

TURE, REPLACE TEMPERATURE FUSE.

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. 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.

5. Reconnect all leads removed from components during testing.

6. Reinstall the outer case (cabinet).

7. 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

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

2. Open the door and block it open.

3. Discharge high voltage capacitor.

5. Reconnect all leads removed from components during testing.

6. Reinstall the outer case (cabinet).

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

8. Run the oven and check all functions.

NOTE: If the door sensing switch contacts fail in the open position and the door is closed, the cooling fan,

turntable and oven light will be activated by RY1.

PRIMARY INTERLOCK RELAY (RY2)

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 two (2) wire leads from the male tab terminals of the Primary Interlock Relay. Check the state of the relay contacts using a ohmmeter. The relay contacts should be open. If the relay contacts are closed, replace the circuit board entirely or the relay itself.

5. Reconnect all leads removed from components during testing.

6. Reinstall the outer case (cabinet).

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

8. Run the oven and check all functions.

F SECONDARY INTERLOCK SWITCH TEST

G MONITOR SWITCH TEST

Page 16

DMO2420B DMO2420R DMO2420S

H BLOWN MONITOR FUSE TEST

TEST PROCEDURES

PROCEDURE

LETTER

COMPONENT 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. If the monitor fuse is blown when the door is opened, check the primary interlock relay, secondary interlock switch and monitor switch according to the "TEST PROCEDURE" for those switches before replacing the blown monitor fuse.

CAUTION: BEFORE REPLACING A BLOWN MONITOR FUSE, TEST THE PRIMARY INTERLOCK

RELAY, SECONDARY INTERLOCK SWITCH, DOOR SENSING SWITCH AND MONITOR

SWITCH FOR PROPER OPERATION. If the monitor fuse is blown by improper switch operation, the monitor fuse and monitor switch must be replaced with "monitor fuse and monitor switch assembly" part number FFS-BA016/KIT, even if the monitor switch operates normally. The monitor fuse and monitor switch assembly is comprised of a 20 ampere fuse and switch.

5. Reconnect all leads removed from components during testing.

6. Reinstall the outer case (cabinet).

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

8. Run the oven and check all functions.

The touch control panel consists of circuits including semiconductors such as LSI, ICs, etc. Therefore, unlike conventional microwave ovens, proper maintenance cannot be performed with only a voltmeter and ohmmeter. In this service manual, the touch control panel assembly is divided into two units, Control Unit and Key Unit, and also the Control Unit is divided into two units, LSI 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 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.

1. Key Unit. NOTE ;

1) Check Key unit ribbon connection before replacement.

2) Reconnect all leads removed from components during testing.

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

I TOUCH CONTROL PANEL ASSEMBLY TEST

with the door opened (in this condition the plunger of the monitor switch is pushed in), the meter should indicate an open circuit. If improper operation is indicated, the switch may be defective. After testing the monitor switch, reconnect the wire lead to the monitor switch (COM) terminal and check the continuity of the monitor circuit.

5. Reconnect all leads removed from components during testing.

6. Reinstall the outer case (cabinet).

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

8. Run the oven and check all functions.

Monitor Switch

Secondary Interlock Switch

Screw Driver

Ohmmeter

RED

WHT/WHT

Page 17

DMO2420B DMO2420R DMO2420S

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

5) Run the oven and check all functions. The following symptoms indicate a defective 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 outer case.

2) Open the door and block it open.

3) Discharge high voltage capacitor.

4) Replace the Key unit.

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.

2. Control Unit The following symptoms indicate a defective control unit. Before replacing the control unit, perform the Key unit test (Procedure J) to determine if control unit is faulty.

2-1 In connection with pads.

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

2-2 In connection with indicators

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

2-3 Other possible 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.

2) Open the door and block it open.

3) Discharge high voltage capacitor.

4) Reconnect all leads removed from components during testing.

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

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

7) Run the oven and check all functions.

J KEY UNIT 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. If the display fails to clear when the STOP/CLEAR pad is depressed, first verify the flat ribbon cable

is making good contact, verify that the door sensing switch (stop switch) operates properly; that is the contacts are closed when the door is closed and open when the door is open. If the door sensing switch (stop switch) is good, disconnect the flat ribbon cable that connects the key unit to the control unit and make sure the door sensing switch is closed (either close the door or short the door sensing switch 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 a faulty and must be replaced. If a specific pad does not respond, the above method

TEST PROCEDURES

PROCEDURE

LETTER

COMPONENT TEST

Page 18

DMO2420B DMO2420R DMO2420S

TEST PROCEDURES

PROCEDURE

LETTER

COMPONENT TEST

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.

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 No. 1 of the 2 pin connector (A) and the common terminal of the relay RY1 on the control unit with an A.C. voltmeter. The meter should indicate 120 volts, if not check oven circuit.

RY1 and RY2 Relay Test

These relays are operated by D.C. voltage Check voltage at the relay coil with a D.C. voltmeter during the microwave cooking operation.

DC. voltage indicated ......................... Defective relay.

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

is good, control unit is defective.

RELAY SYMBOL OPERATIONAL VOLTAGE CONNECTED COMPONENTS

RY1 Approx. 24.0V D.C. Oven lamp / Turntable motor / Cooling fan motor RY2 Approx. 23.0V D.C. Power transformer

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

9.Open the door and block it open.

10.Discharge 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 is installed.

14.Run the oven and check all functions.

K RELAY TEST

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

(1) Place one cup of water in the center of the turntable tray in the oven cavity. (2) Close the door, touch the Auto Defrost pad and touch the number pad 5. And touch the number pad

5 again. And then touch the Start pad. (3) The oven is in Auto Defrost cooking condition. (4) The oven will operate as follows.

L COMPU DEFROST TEST

G 1 G 2 G 3 G 4 G 5 G 6 G 7 G 8

G 9 G10 G11 G12 G13 G14

FRESH

VEGETABLES

BEVERAGE

BREAKFAST

LUNCH

POPCORN

SNACKS

MICROWAVE

RECIPES

START

INSTANT ON

FISH

SEAFOOD

POWER

LEVEL

KEEP

WARM

15 MINUTE DINNER

AUTO

DEFROST

HELP

GUIDE

BAKED

POTATOES

REHEAT

EASY

MINUTE

VEGETABLES

RICE

POULTRY

GROUND

MEAT

ENTREES

TIMER

CLOCK

STOP

CLEAR

Page 19

DMO2420B DMO2420R DMO2420S

To protect the electronic circuits, this model is provided with a fine foil pattern added to the primary on the PWB, this foil pattern acts as a fuse.

1. Foil pattern check and repairs.

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) Follow the troubleshooting guide given below for repair.

STEPS OCCURRENCE CAUSE OR CORRECTION

1 Only pattern at "a" is broken. *Insert jumper wire J1 and solder. 2 Pattern at "a" and "b" are broken. *Insert the coil RCILF2003YAZZ between "c" and "d".

5) Make a visual inspection of the varistor. Check for burn damage and examine the transformer with a tester for the presence of layer short-circuit (check the primary coil resistance which is approximately 210ý ± 15%). If any abnormal condition is detected, replace the defective parts.

6) Reconnect all leads removed from components during testing.

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

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

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.

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, reconnect the power supply cord.

7) Follow the troubleshooting guide given below for repair.

STEPS OCCURRENCE CAUSE OR CORRECTION

The rated AC voltage is not present between

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

common terminal of the relay RY1.

The rated AC voltage is present at primary Low voltage transformer or secondary circuit defective. side of low voltage transformer. Check and repair.

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

9) Open the door and block it open.

M FOIL PATTERN ON THE PRINTED WIRING BOARD TEST

MENU 1ST STAGE 2ND STAGE

Steaks, chops or fish LEVEL TIME LEVEL TIME

0.5lb 70% 30sec. 40% 15sec.

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

TEST PROCEDURES

PROCEDURE

LETTER

COMPONENT TEST

VRS1

OMIF

CN - A

(J1)

Page 20

DMO2420B DMO2420R DMO2420S

TEST PROCEDURES

PROCEDURE

LETTER

COMPONENT TEST

10) Discharge 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 is installed.

14) Run the oven and check all functions.

N 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 95½F (35½C). (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.

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 door. (4) Touch the Timer/Clock pad once, the Power Level pad twice, the Start pad once and the number pad

1 once. Now, the oven is in the sensor cooking condition and "TEST", “SENSOR” and "COOK" 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, replace the AH sensor or check the control unit, refer to explanation below. If the oven stops after 5 minutes and ERROR is displayed, check the parts except for 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 remove outer case. (2) Open the door 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 outer case (cabinet). (8) Reconnect the power supply cord after the outer case is 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. 9-2. Place the container on the center of tray in the oven cavity.

Page 21

DMO2420B DMO2420R DMO2420S

TEST PROCEDURES

PROCEDURE

LETTER

COMPONENT TEST

9-3. Close the door. 9-4. Touch the Timer/Clock pad once, the Power Level pad twice, the Start pad once and the number

pad 1 once. 9-5. The control panel is in automatic Sensor operation. 9-6. And then the oven will turn off automatically, and the time for detecting moisture will be displayed.

If new sensor dose not operate properly, the problem is with the control unit, and refer to explanation below.

CHECKING CONTROL UNIT

(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 sensor connector that is mounted to control panel. (5) Then connect the dummy resistor circuit (see fig.) to the sensor connector of control panel. (6) Disconnect the leads to the primary of the power transformer. (7) Ensure that these leads remain isolated from other components and oven chassis by using insulation tape. (8) After that procedure, re-connect the power supply cord. (9) Check the sensor cook operation proceed as follows:

9-1. Touch the Timer/Clock pad once, the Power Level pad twice, the Start pad once and the number

pad 1 once. 9-2. The control panel is in the sensor cooking operation. 9-3. After approximately 25 seconds, push plunger of select switch for more than 3 seconds. This

condition is same as judgement by AH sensor.

9-4. After approximately 3 seconds, the oven will turn off automatically, and the display shows “ X

X . X X “ which is the time for detecting moisture. If the above is not the case, the control unit is probably defective. If the above is proper, the AH sensor is probably defective.

(10) Disconnect the power supply cord, and then remove outer case. (11) Open the door and block it open. (12) Discharge high voltage capacitor. (13) Disconnect the dummy resistor circuit from the sensor connector of control panel. (14) Carry out necessary repair. (15) Reconnect 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. Run the oven and check all functions. (18) Carry out "Water load cooking test" again and ensure that the oven works properly.

R1, R2 :22

((

(ohm) ± 1% 1/2W

R3 :4.3k

((

(ohm) ± 5% 1/4W

R4 :1M

((

(ohm) ± 5% 1/4W

Sensor Dummy Resistor Circuit

Plunger

NC NO

COM

R3 R4

1 2 3

F-1 F-2

F-3

To connector (F) on Control Unit.

CONNECTOR

Page 22

DMO2420B DMO2420R DMO2420S

TOUCH CONTROL PANEL ASSEMBLY

OUTLINE OF TOUCH CONTROL PANEL

4) Relay Circuit

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

5) Buzzer Circuit

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

6) Synchronizing Signal Circuit

The power source synchronizing signal is available in order to compose a basic standard time in the clock circuit. It accompanies a very small error because it works on commercial frequency.

7) Door Sensing Switch

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

8) Back Light Circuit

A circuit to drive the back light (Light emitting diodes LD10- LD15).

9) Absolute Humidity Sensor Circuit

This circuit detects moisture of the cooking food to allow its automatic cooking.

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

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

and LSI Unit).

The principal functions of these units and the signals communicated among them are explained below.

Key Unit

The key unit is composed of a matrix, signals generated in the LSI are sent to the key unit through P00-P07. When a key pad is touched, a signal is completed through the key unit and passed back to the LSI through P14-P17, AIN6 and AIN7 to perform the function that was requested.

Control Unit

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

1) ACL

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

2) Indicator Circuit

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

3) Power Source Circuit

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

Symbol Voltage Application

VC -5V LSI(IC1)

Page 23

DMO2420B DMO2420R DMO2420S

LSI(IXA098DR)

The I/O signal of the LSI(IXA098DR) is detailed in the following table.

Pin No. Signal I/O Description

1 COM5 OUT

Common data signal : COM11.

Connected to LCD signal COM11.

2 COM4 OUT Common data signal : COM12.

Connected to LCD signal COM12.

3 COM3 OUT

Common data signal : COM13.

Connected to LCD signal COM13.

4 COM2 OUT

Common data signal : COM14.

Connected to LCD signal COM14.

5 COM1 OUT Common data signal : COM15.

Connected to LCD signal COM15.

6 COM0 OUT Common data signal : COM16.

Connected to LCD signal COM16.

7-10 VL1-VL4 IN Power source voltage input terminal.

Standard voltage for LCD.

11 VL5 IN Power source voltage input terminal.

Standard voltage for LCD. Connected to GND.

12-14 C3-C1 IN Terminal not used.

15 VLIN IN Terminal not used. 16 VREG OUT Terminal not used. 17 NC

Terminal not used.

18 VSS IN Power source voltage : -5.0V.

The power source voltage to the LSI is input to VSS terminal. Connected to VC. 19-21 P27-P25 OUT Terminal not used. 22-26 P24-P20 IN Used for initial balancing of the bridge circuit (absolute humidity sensor).

27 P47 IN To input signal which communicates the door open/close information to LSI.

Door close "H" level signal (0V). Door open "L" level signal (-5V).

28 P46 OUT Terminal not used. 29 P45 OUT Oven lamp, fan motor and turntable motor driving signal.

To turn on and off shut off relay (RY1). The

square waveform voltage is delivered to the

RY1 driving circuit and RY2 control circuit.

30 P44 OUT Magnetron high-voltage circuit driving signal.

To turn on and off the cook relay (RY2). The

signals holds "L" level during microwave cook-

ing and "H" 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.

(ON and OFF times for other power level.) 31 P43 OUT Terminal not used. 32 CNTR0 OUT Signal to sound buzzer (2.0 kHz).

A: key touch sound. B: Completion sound.

33 P41 OUT Terminal not used.

16.7 msec.

During cooking

H : GND

L : -5V

100 PERCENT

70 PERCENT

H : GND

L : -5V H : GND

L : -5V

OFF

OFF OFF

24 sec.

8 sec.

0.1 sec.

2.0 sec.

H : GND

L : -5V H : GND

L : -5V

Page 24

DMO2420B DMO2420R DMO2420S

34 INT0 IN Signal synchronized with commercial power source frequency.

This is the basic timing for time processing of LSI.

35 P07 OUT Key strobe signal.

Signal applied to touch-key section. A pulse signal is input to AIN7, P14, P15, P16 and P17 terminal while one of G1 line keys on key matrix is touched.

36 P06 OUT Key strobe signal.

Signal applied to touch-key section. A pulse signal is input to AIN7, P14, P15, P16 and P17 terminal while one of G2 line keys on key matrix is touched.

37 P05 OUT

Key strobe signal.

Signal applied to touch-key section. A pulse signal is input to AIN7, P14, P15, P16 and P17 terminal while one of G3 line keys on key matrix is touched.

38 P04 OUT

Key strobe signal.

Signal applied to touch-key section. A pulse signal is input to AIN7, P14, P15, P16 and P17 terminal while one of G4 line keys on key matrix is touched.

39 P03 OUT Key strobe signal.

Signal applied to touch-key section. A pulse signal is input to AIN7, P14, P15, P16 and P17 terminal while one of G5 line keys on key matrix is touched.

40 P02 OUT Key strobe signal.

Signal applied to touch-key section. A pulse signal is input to AIN6, AIN7, P14, P15, P16 and P17 terminal while one of G6 line keys on key matrix is touched.

41 P01 OUT Key strobe signal.

Signal applied to touch-key section. A pulse signal is input to AIN7, P14, P15, P16 and P17 terminal while one of G7 line keys on key matrix is touched.

42 P00 OUT Key strobe signal.

Signal applied to touch-key section. A pulse signal is input to AIN7, P14, P15, P16 and P17 terminal while one of G8 line keys on key matrix is touched.

43 P17 OUT Signal coming from touch key.

When either G9 line on key matrix is touched, a corresponding signal out of P00-P07 will be input into P17. When no key is touched, the signal is held at "H" level.

44 P16 IN Signal similar to P17.

When either G10 line on key matrix is touched, a corresponding signal will be input into P16.

45 P15 IN Signal similar to P17.

When either G11 line on key matrix is touched, a corresponding signal will be input into P15.

46 P14 IN Signal similar to P17.

When either G12 line on key matrix is touched, a corresponding signal will be input into P14.

47 AIN7 IN Signal similar to P17.

When either G13 line on key matrix is touched, a corresponding signal will be input into AIN7.

48 AIN6 IN Input terminal to judge the model.

The signal out of P02 will be input into AIN6 through G6 line on key matrix. The LSI will judge the model by this signal.

49 AIN5 IN AH sensor input.

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

50 AIN4 IN 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.

51 RESET IN Auto clear terminal.

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

Pin No. Signal I/O Description

16.7 msec.

H : GND

L : -5V

Page 25

DMO2420B DMO2420R DMO2420S

52 NC

Terminal not used. 53 XCOUT OUT Terminal not used. 54 XCIN IN Connected to VC. 55 NC

Terminal not used. 56 VCC IN Power source voltage: GND(0V).

The power source voltage to drive LSI is input to VCC terminal. 57 OSCSEL IN Connected to VC(-5V). 58 XOUT OUT Internal clock oscillation output.

Output to control oscillation input of XIN. 59 VSS IN Power source voltage: -5.0V.

The power source voltage to the LSI is input to VSS terminal. Connected to VC. 60 NC Terminal not used. 61 XIN IN Internal clock oscillation frequency control input setting.

The internal clock frequency is set by inserting the ceramic filter oscillation circuit with

respect to XOUT terminal. 62 NC

Terminal not used.

63-66 AIN3-AIN0 IN Terminal to change cooking input 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. 67 COM8 OUT Common data signal : COM8.Connected to LCD signal COM8. 68 COM9 OUT Common data signal : COM7.Connected to LCD signal COM7. 69 COM10 OUT Common data signal : COM6. Connected to LCD signal COM6. 70 COM11 OUT Common data signal : COM5. Connected to LCD signal COM5. 71 COM12 OUT Common data signal : COM4. Connected to LCD signal COM4. 72 COM13 OUT Common data signal : COM3. Connected to LCD signal COM3. 73 COM14 OUT Common data signal : COM2. Connected to LCD signal COM2. 74 COM15 OUT Common data signal : COM1. Connected to LCD signal COM1.

75-102

SEG67-SEG40

OUT Terminal not used.

103-142

SEG39-SEG0

OUT Segment data signal.

Connected to LCD.

The relation between signals and LCD are as follows:

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

SEG 39 (103).......................... SEG 1 SEG 19 (123) .........................SEG 21

SEG 38 (104).......................... SEG 2 SEG 18 (124) .........................SEG 22

SEG 37 (105).......................... SEG 3 SEG 17 (125) .........................SEG 23

SEG 36 (106).......................... SEG 4 SEG 16 (126) .........................SEG 24

SEG 35 (107).......................... SEG 5 SEG 15 (127) .........................SEG 25

SEG 34 (108).......................... SEG 6 SEG 14 (128) .........................SEG 26

SEG 33 (109).......................... SEG 7 SEG 13 (129) .........................SEG 27

SEG 32 (110).......................... SEG 8 SEG 12 (130) .........................SEG 28

SEG 31 (111).......................... SEG 9 SEG 11 (131) .........................SEG 29

SEG 30 (112).......................... SEG 10 SEG 10 (132) ......................... SEG 30

SEG 29 (113).......................... SEG 11 SEG 9 (133) .........................SEG 31

SEG 28 (114).......................... SEG 12 SEG 8 (134) .........................SEG 32

SEG 27 (115).......................... SEG 13 SEG 7 (135) .........................SEG 33

SEG 26 (116).......................... SEG 14 SEG 6 (136) .........................SEG 34

SEG 25 (117).......................... SEG 15 SEG 5 (137) .........................SEG 35

SEG 24 (118).......................... SEG 16 SEG 4 (138) .........................SEG 36

SEG 23 (119).......................... SEG 17 SEG 3 (139) .........................SEG 37

SEG 22 (120).......................... SEG 18 SEG 2 (140) .........................SEG 38

SEG 21 (121).......................... SEG 19 SEG 1 (141) .........................SEG 39

SEG 20 (122).......................... SEG 20 SEG 0 (142) .........................SEG 40

Pin No. Signal I/O Description

Page 26

DMO2420B DMO2420R DMO2420S

ABSOLUTE HUMIDITY SENSOR CIRCUIT

(1)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 in the open vessel. Each sensor is provided with the protective cover made of metal mesh to be protected from the external airflow.

(2)Operational Principle of Absolute Humidity Sensor

The figure below shows the basic structure of an absolute humidity sensor. A bridge circuit is formed by two thermistors and two resistors (R1 and R2). The output of the bridge circuit is to be amplified by the operational amplifier. Each thermistor is supplied with a current to keep it heated at about 150½C (302½F), the resultant heat is dissipated in the air and if the two thermistors are placed in different humidity conditions they show different degrees of heat conductivity leading to a potential difference between them causing an output voltage from the bridge circuit, the intensity 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.

(3)Detector Circuit of Absolute Humidity Sensor Circuit

This detector circuit is used to detect the output voltage of the absolute humidity circuit to allow the LSI to control sensor cooking of the unit. When the unit is set in the sensor cooking mode, 16 seconds clearing cycle occurs than the detector circuit starts to function and the LSI observes the initial voltage available at its AIN5 terminal. 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 R98 ~ R102. Changing the resistance values results in that there is the same potential at both F-3 terminal of the absolute humidity sensor and AIN4 terminal of the LSI. The voltage of AIN5 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 AIN5 terminal of the LSI. Then the LSI observes that voltage at AIN5 terminal and compares it with its initial value, and when the comparison rate reaches the preset value (fixed for each menu to be cooked), the LSI causes the unit to stop sensor cooking; thereafter, the unit goes in the next operation automatically. When the LSI starts to detect the initial voltage at AIN5 terminal 16 seconds after the unit has been put in the Sensor Cooking mode, if it is not possible to balance the bridge circuit due to disconnection of the absolute humidity sensor, ERROR will appear on the display and the cooking is stopped.

1) Absolute humidity sensor circuit

Pin No. Signal I/O Description

143 COM7 OUT Common data signal : COM9.Connected to LCD signal COM9. 144 COM6 OUT Common data signal : COM10. Connected to LCD signal COM10.

ventilation opening for sensing

Sensing part (Open vessel)

Sensing part (Closed vessel)

Thermistors

Operational amplifier

Output voltage

S : Thermistor open vessel

C : Thermistor closed vessel

Absolute humidity (g/m )

Output voltage

Absolute humidity vs, output voltage characteristic

SW1 SW2

SW3 SW4 SW5

P20 P21 P22 P23 P24

LSI (IC1)

AIN4

AIN5

620k

300k 150k

75k

37.4k

23 22

47k

10k

1234

8765

0.01uF

0.015uF

0.01uF

VA : -15V

R90

C90

C91

C93

C92

F-2

1.8k

IC2

F-1

F-3

3.57k

3.32k

VC : -5V

0.1

C. Thermistor in closed vessel S. Thermistor in open vessel

R98 R99

R96

R91

360k

R93

R92

R94

R95

D91

D90

R100 R101

R102

R97

Page 27

DMO2420B DMO2420R DMO2420S

1. 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 the surrounding high voltage power source, 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.

1) When storing and transporting, thoroughly wrap them in aluminium foil. Also wrap all PW boards containing them in aluminium foil.

2) When soldering, ground the technician as shown in the figure and use grounded soldering iron and work table.

2. Shapes of Electronic Components

3. Servicing of Touch Control Panel

We describe the procedures to permit servicing of the touch control panel of the microwave oven and the precautions you must take when doing so. To perform the servicing, power to the touch control panel is available either from the power line of the oven itself or from an external power source.

(1)Servicing the touch control panel with power supply

of the oven: CAUTION: THE HIGH VOLTAGE TRANSFORMER OF THE MICROWAVE OVEN IS STILL LIVE DURING SERVICING AND PRESENTS A HAZARD.

Therefore, before checking the performance of the touch control panel,

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. After checking the performance of the touch control panel,

1) Disconnect the power supply cord.

2) Open the door and block it open.

3) Re-connect the leads to the primary of the power

transformer.

TOUCH CONTROL PANEL SERVICING

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

5) Re-connect the power supply cord after the outer case is installed.

6) Run the oven and check all functions.

A. On some models, the power supply cord between the

touch control panel and the oven itself is so short that the two can’t be separated. For those models, check and repair all the controls (sensor-related ones included) of the touch control panel while keeping it connected to the oven.

B. 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, 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 activates 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.

(2)Servicing the touch control panel with power supply

from an external power source:

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

4. Servicing Tools

Tools required to service the touch control panel assembly.

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

2) Oscilloscope: Single beam, frequency range: DC-10MHz type or more advanced model.

3) Others: Hand tools

5. Other Precautions

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

2) Connect the connectors of the key unit to the control unit being sure that the lead wires are not twisted.

3) After aluminium foil is removed, be careful that abnormal 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 specified components where high precision is required.

approx. 1M ohm

Transistor 2SB1238

Transistor KRC243M

Page 28

DMO2420B DMO2420R DMO2420S

To remove the outer case, proceed as follows.

1. Disconnect the power supply cord.

2. Open the oven door and block it open.

3. Remove the two (2) screws from the lower portion of the rear cabinet using a T20H Torx type or GTXH20-100 screw driver.

4. Remove the remaining two (2) screws from rear and four (4) screws along the right side of outer case.

5. Slide the entire outer case back out about 1 inch (3 cm) to free it from retaining clips on the cavity face plate.

6. Lift entire outer case from the unit.

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

WARNING:

Avoid possible exposure to microwave energy. Please follow the instructions below before operating the oven.

W ARNING AGAINST HIGH VOLTAGE:

OUTER CASE REMOVAL

COMPONENT REPLACEMENT AND ADJUSTMENT PROCEDURE

To prevent an electric shock, take the following precautions.

1. Before wiring,

1) Disconnect the power supply cord.

2) Open the door block it open.

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

2. Don’t let the wire leads touch to 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 transformer and Oven cavity.

WARNING FOR WIRING

1. Disconnect the power supply cord.

2. Make sure that a definite” click” can be heard when the microwave oven door is unlatched. (Hold the door in a closed position with one hand, then push the door open button with the other, this causes the latch leads to rise, it is then possible to hear a “click’ as the door switches operate.)

3. 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 system.

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.

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, Open button.

3. Do not catch the wire leads in the outer case cabinet.

4. 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.

5. To prevent an error function, connect the wire leads correctly, referring to the Pictorial Diagram.

Please refer to ‘OVEN PARTS, CABINET PARTS, CONTROL PANEL PARTS, DOOR PARTS’, when carrying out any of the following removal procedures:

Page 29

DMO2420B DMO2420R DMO2420S

POWER TRANSFORMER REMOVAL

Reinstallation

1. Rest transformer on the bottom plate with its primary terminals toward the oven face plate.

Secure transformer with four screws to bottom plate.

3. Re-connect wire leads (primary and high voltage) to power transformer and filament leads of transformer to magnetron and high voltage capacitor. Refer to "PICTORIAL DIAGRAM" on page 35.

4. Re-install outer case and check that oven is operating properly.

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

2. Open the oven door and block it open.

3. Discharge high voltage capacitor.

4. Disconnect wire leads (primary and high voltage) from power transformer and the filament leads from the magnetron and capacitor terminals.

5. Remove four (4) screws holding transformer to bottom plate.

6. Remove transformer from bottom plate.

CAUTION: 1. DISCONNECT OVEN FROM POWER SUP

PLY BEFORE REMOVING OUTER CASE.

2. DISCHARGE THE HIGH VOLTAGE CAPACITOR BEFORE TOUCHING ANY OVEN COMPONENTS OR WIRING.

NOTE: When replacing the outer case, the 2 special

Torx screws must be reinstalled in the same locations.

HIGH VOLTAGE RECTIFIER AND HIGH VOLTAGE CAPACITOR REMOVAL

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 high voltage wire A from the high voltage capacitor.

5. Disconnect the high voltage wire of high voltage rectifier assembly from the magnetron.

6. Disconnect the filament lead (short one) of the power transformer from the high voltage capacitor.

7. Remove one (1) screw holding capacitor holder with the high voltage rectifier to the base plate.

8. Disconnect rectifier terminal from capacitor. High voltage rectifier assembly is now free.

9. Remove capacitor holder. Capacitor is now free.

CAUTION: WHEN REPLACING HIGH VOLTAGE RECTI-

FIER AND HIGH VOLTAGE CAPACITOR, GROUND SIDE TERMINAL OF THE HIGH VOLTAGE RECTIFIER MUST BE SECURED FIRMLY WITH A GROUNDING SCREW.

MAGNETRON REMOVAL

Removal

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 wire leads from magnetron.

5. Remove the two (2) screws holding the chassis support to the magnetron and the oven cavity front flange.

6. Slide the magnetron duct slightly so that the two (2) screws at left hand side of the magnetron appear.

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

8. Remove the magnetron with care so that the magnetron antenna is not hit by any metal object around the antenna.

9. Now, the magnetron is free.

Reinstallation

1. Re-install the magnetron to waveguide flange with care to prevent damage to the magnetron antenna.

2. Secure the magnetron with the four (4) screws.

3. Hold the chassis support to the oven cavity front plate and the magnetron with the two (2) screws.

4. Reconnect the wire leads to the magnetron. Refer to "PICTORIAL DIAGRAM" on page 35.

5. Re-install outer case and check that the oven is operating properly.

CAUTION: WHEN REPLACING MAGNETRON, BE SURE

THE R.F. GASKET IS IN PLACE AND MOUNTING SCREWS ARE TIGHTENED SECURELY

pecial screw

Screw Driver (Type: TORX T20 H or GTXH20-100)

Page 30

DMO2420B DMO2420R DMO2420S

CONTROL PANEL ASSEMBLY REMOVAL

POSITIVE LOCK® CONNECTOR (NO-CASE TYPE) REMOVAL

Figure C-2. Positive lock® connector

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. Push the lever of positive lock® connector.

5. Pull down on the positive lock® connector.

CAUTION: WHEN CONNECTING THE POSITIVE LOCK

CONNECTORS TO THE TERMINALS, CONNECT THE POSITIVE LOCK® SO THAT THE LEVER FACES YOU.

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 wire leads from panel components.

5. Make one (1) tab of the oven cavity front plate straight holding the control panel assembly to the oven cavity front plate.

6. Slide the control panel assembly upward and remove it.

7. Now, individual components can be removed.

NOTE: 1. Before attaching a new key unit, wipe off remaining

adhesive on the control panel frame surfaces completely with a soft cloth soaked in alcohol.

2. 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 control panel frame.

3. Stick the key unit firmly to the control panel frame by rubbing with soft cloth so not to scratch.

LSI UNIT NOTE: Handle the LSI unit carefully so that there is no

excessive force applied to the ribbon connection.

Oven lamp socket

Terminal

Wire lead

Terminal hole

Flat type small screw driver

Terminal

Push

Pull down

Lever

Positive lock® connector

LSI unit

1. Disconnect the power supply cord.

2. Remove turntable and turntable support from oven cavity.

3. Lay the oven on it's backside. Remove the turntable motor cover by snipping off the material in four corners.

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

TURNTABLE MOTOR REMOVAL

5. Disconnect wire leads from turntable motor. (See "Positive lock connector removal")

6. Remove one (1) screw holding turntable motor to oven cavity.

7. Now the turntable motor is free.

8. After replacement use the one (1) screw to fit the turntable motor cover.

Disconnect the power supply cord and remove outer case.

2. Open the door and block it open.

3. Discharge high voltage capacitor.

4. Remove the oven lamp from the oven lamp socket.

5. 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.

6. Remove the oven lamp socket from the magnetron duct by turning the socket counterclockwise.

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

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

OVEN LAMP AND LAMP SOCKET REMOVAL

Figure C-1. Oven lamp socket

Printed wiring board

of LSI unit

Liquid Crystal

Display (LCD)

Ribbon cable

Page 31

DMO2420B DMO2420R DMO2420S

COOLING FAN MOTOR REMOVAL

REMOVAL

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 wire leads from the fan motor.

5. Remove the two (2) screws holding the fan motor to the oven cavity back plate.

6. Remove the fan blade from the fan motor shaft according to the following procedure.

7. Hold the edge of the rotor of the fan motor by using a pair of groove joint pliers.

CAUTION: * Make sure that no metal pieces 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 damaged.

* Do not disfigure the bracket by touching with the

pliers.

8. Remove the fan blade from the shaft of the fan motor by pulling and rotating the fan blade with your hand.

9. Now, the fan blade and the fan motor will be free.

CAUTION: * Do not reuse the removed fan blade because the hole

(for shaft) may be larger than normal.

INSTALLATION

1. Install the fan blade to the fan motor shaft according to the following procedure.

2. Hold the center of the bracket which supports the shaft of the fan motor on the flat table.

3. Apply the screw lock tight into the hole (for shaft) of the fan blade.

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

CAUTION: * Do not hit the fan blade hard when installing because

the bracket may be damaged.

* Make sure that the fan blade rotates smoothly after

installation.

* Make sure that the axis of the shaft is not slanted.

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

6. Connect the wire leads to the fan motor, referring to the pictorial diagram.

Side ViewRear View

Disconnect the power supply cord and remove outer case.

2. Open the door and block it open.

3. Discharge high voltage capacitor.

4. Disconnect wire leads from the switches.

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

6. Remove latch hook assembly from oven flange.

7. Push outward on the two (2) retaining tabs holding switch in place.

8. Switch is now free. At this time switch lever will be free, do not lose it.

Reinstallation

1. Re-install each switch in its place. The secondary interlock/

DOOR SENSING SWITCH/SECONDARY INTERLOCK SWITCH AND MONITOR SWITCH REMOVAL

AH SENSOR REPLACEMENT

Removal

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. Remove the two (2) screws holding the AH sensor to the sensor duct.

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

6. AH sensor is now free.

Reinstallation

1. Insert the new AH sensor into the sensor duct.

2. Install two (2) screws to secure the AH sensor.

3. Route the AH sensor harness across the oven cavity top plate and through the large opening.

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

5. Re-install the outer case cabinet and check for proper operation.

Gap

Rotor

Bracket

Stator

Groove joint pliers

Coil

Shaft

Axis

Stator

Rotor

These are the positions that should be pinched with pliers

Shaft

Table

Center of bracket

Page 32

DMO2420B DMO2420R DMO2420S

DOOR REPLACEMENT

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

2. Open the door and block it open.

3. Discharge high voltage capacitor.

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

4. Loosen the two (2) screws holding latch hook to the oven cavity front flange.

5. With door closed, adjust latch hook by moving it back and forth, and up and down. In and out play of the door allowed by the upper and lower position of the latch hook should be less than 0.5mm. The vertical position of the latch hook should be adjusted so that the door sensing switch and secondary interlock switch are activated with the door closed. The horizontal position of the latch hook should be adjusted so that the plunger of the monitor switch is pressed with the door closed.

6. Secure the screws with washers firmly.

7. Check the operation of all switches. If each switch has not activated with the door closed, loosen screw and adjust the latch hook position.

After adjustment, check the following.

1. In and out play of door remains less than 0.5mm when in the latched position. First check upper position of latch hook, pushing and pulling upper portion of door toward the oven face. Then check lower portion of the latch hook,

pushing and pulling lower portion of the door toward the oven face. Both results (play in the door) should be less than 0.5mm.

2. The door sensing switch and secondary interlock switch interrupt the circuit before the door can be opened.

3. Monitor switch contacts close when door is opened.

4. Re-install outer case and check for microwave leakage around door with an approved microwave survey meter. (Refer to Microwave Measurement Procedure.)

Figure C-3. Latch Switch Adjustments

REMOVAL

1. Disconnect the power supply cord.

2. Push the open button and open the door slightly.

3. Insert a putty knife (thickness of about 0.5mm) into the gap between the choke cover and door frame as shown in Figure C-4 to free engaging parts.

4. Pry the choke cover by inserting a putty knife as shown in Figure C-4.

5. Release choke cover from door panel.

6. Now choke cover is free.

NOTE: When carrying out any repair to the door, do not

bend or warp the slit choke (tabs on the door panelassembly) to prevent microwave leakage.

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

8. Now, door panel with door frame is free from oven cavity.

Figure C-4. Door Disassembly

9. Release the door panel from ten (10) tabs of door frame.

10.Remove the door panel from the door frame.

11.Now, door panel with sealer film is free.

12.Tear sealer film from door panel.

Door Sensing Switch

Monitor Switch

Switch Lever

Secondary Interlock Switch

Latch Heads

Door

Choke Cover

Door Frame

Putty Knife

monitor switches are in the lower position and the door sensing switch is in the upper position.

2. Re-connect wire leads to each switch. Refer to pictorial diagram.

3. Secure latch hook (with two (2) mounting screws) to oven flange.

4. Make sure that the monitor switch is operating properly and check continuity of the monitor circuit. Refer to chapter "Test Procedure" and Adjustment procedure.

DOOR SENSING SWITCH/SECONDARY INTERLOCK SWITCH AND MONITOR SWITCH ADJUSTMENT

Page 33

DMO2420B DMO2420R DMO2420S

Note: The door on a microwave oven is designed to act as

an electronic seal preventing the leakage of microwave energy from oven cavity during cook cycle. This function does not require that door be airtight, moisture (condensation)-tight or light-tight. Therefore, occasional appearance of moisture, light or sensing of gentle warm air movement around oven door is not abnormal and do not of themselves indicate a leakage of microwave energy from oven cavity.

Figure C-5. Door Replacement

SEALER FILM

Installation

1. Put the adhesive tape on the backing film of the sealer film as shown in Fig. C-6.

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

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

Figure C-6. Sealer film

13.Now, door panel is free.

14.Slide latch head upward and remove it from door frame by releasing latch spring from door frame and latch head.

15.Now, latch head and latch spring are free.

16.Remove one (1) screw holding the door glass stopper to the door frame.

17.Remove door glass stopper from door frame.

18.Slide the door glass rightwards and then slide upwards to release the door glass from the tabs holding it.

19.Remove the door glass from the door frame.

20.Now, door frame is free.

REINSTALLATION

1. Re-install door glass to door frame as follows.

1-1. Insert the upper edge of the door glass into the five (5)

tabs of the door frame.

1-2. Slide the door glass downwards and insert the lower

edge of door glass into the five (5) tabs of the door frame.

1-3. Slide the door glass leftwards and insert the left edge

of door glass into the two (2) tabs of the door frame.

2. Re-install the door glass stopper to the door frame so that the two (2) holes of the door glass stopper fit to the two (2) pins of the door frame. And hold the door glass stopper with one (1) screw.

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

4. Re-install door panel to door frame by catching ten (10) tabs of door frame on the edges of door panel.

5. Put sealer film on door panel. Refer to “Sealer Film” about how to handle new one.

6. Catch two (2) pins of door panel on two (2) hole of upper and lower oven hinges.

7. Re-install choke cover to door panel by pushing.

Note: After any service to the door; (A) Make sure that door sensing switch and secondary

interlock switch are operating properly. (Refer to chapter “Test Procedures”.).

(B) An approved microwave survey meter should be

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

After any service, make sure of the following :

1. Door latch heads smoothly catch latch hook through latch holes and that latch head goes through center of latch hole.

2. Deviation of door alignment from horizontal line of cavity face plate is to be less than 1.0mm.

3. Door is positioned with its face pressed toward cavity face plate.

4. Check for microwave leakage around door with an approved microwave survey meter. (Refer to Microwave Measurement Procedure.)

Sealer film

Backing film

Adhesive tape

Upper Oven Hinge

Lower Oven

Hinge

Lower Oven Hinge

Choke Cover

Page 34

DMO2420B

DMO2420R

DMO2420S

Figure S-1. Pictorial Diagram

HIGH VOLTAGE CAPACITOR

HIGH VOLTAGE WIRE A

H.V. RECTIFIER

POWER SUPPLY CORD 120V 60Hz

HIGH VOLTAGE COMPONENTS

OVEN LAMP AND SOCKET

MAGNETRON

COM.

MONITOR SWITCH

COM.

N.O.

N.C.

DOOR SENSING SWITCH

SECONDARY INTERLOCK SWITCH

TURNTABLE MOTOR

NOTE: Hot (ORG) wire must be connected to the terminal with blue mark on the oven light socket.

POWER TRANSFORMER

COM.

NOTE: The neutral (WHT/GRY) wire must be connected to the terminal with "N" mark on the power supply cord.

RED

WHT

RED

WHT

ORG

WHT

PNK

GRN

to Oven cavity

WHT

RED

BLK

WHT

BLUE MARK

WHT

RED

WHT

CAVITY TEMP. FUSE

MAGNETRON TEMP. FUSE

FAN MOTOR

MONITOR

FUSE

HOLDER

RED

WHT

GRY

WHT

GRN

ORG ORG

CN-A

NOTE: The grounding conductor of the power supply cord has been grounded by power supply cord fixing screw. The screw must always be kept tight.

GRY

PNK

GRN

2 1

CN-B

BRN

WHT

BLK

BLU

ORG

B LU

BRN

RED

BLK

AH SENSOR

RED

WHT

1 2 3

CN-F

N.O.

COM.

RY2

PRIMARY INTERLOCK RELAY

CN-A

CONTROL PANEL

(LSI UNIT)

(POWER UNIT)

CN-F

CN-C

CN-G

Page 35

DMO2420B DMO2420R DMO2420S

Figure S-2. Power Unit Circuit

–

A 1

CN-A

R4 27

VRS1

(J1)

D7D8

1SS270A1SS270A

10G471K

C1 0.1µ/50v

C3 0.1µ/50v

ZD1

HZ16-1

C5 10µ/35v

C2 1000µ/35v

C4 10µ/35v

R1 2.4k

1SS270A1SS270A

D1-D4 11ES1

R5 4.7k

R2 680 1/2w

R3 510 1/2w

R6 3.3k

Q2 2SB1238

SP1 PKM22EPT

Q1 2SB1238

RY1

RY2

Q3 KRC243M

CN-C 12PIN LEAD WIRE HARNESS

LED

GND

VA INT VR

BUZZER

MICRO

NC DOOR

SENSING SWITCH

OVEN LAMP TURNTABLE MOTOR FAN MOTOR

MICRO

DOOR SENSING SWITCH

OVEN LAMP TURNTABLE MOTOR FAN MOTOR

C10

C 2

C 3

C 1 C 4 C 9

C 5

C 6

C 7

C 8

C11

C12

A 2

COM

B 2

Page 36

DMO2420B

DMO2420R

DMO2420S

FRESH

VEGETABLES

BEVERAGE

BREAKFAST

LUNCH

POPCORN

SNACKS

MICROWAVE

RECIPES

START

INSTANT ON

FISH

SEAFOOD

POWER LEVEL

KEEP

WARM

15 MINUTE DINNER

AUTO

DEFROST

HELP

GUIDE

BAKED

POTATOES

REHEAT

EASY

MINUTE

VEGETABLES

RICE

POULTRY

GROUND

MEAT

ENTREES

TIMER

CLOCK

STOP

CLEAR

C-10

C-9 C-1

C-8

C-12

F-1 F-2 F-3

G 1 G 2 G 3 G 4 G 5 G 6 G 7 G 8

G 9 G10 G11 G12 G13 G14

C-11

C-3

C-4

C-2

CN-C

GND

INT

VC LED

OVEN LAMP TURNTABLE MOTOR FAN MOTOR

BUZZERR

MICRO

NC DOOR

SENSING SWITCH

AH SENSOR

NOTE

: IF NOT SPECIFIED 1/10W ± 5%

CN-F

CN-G

Q20 DTA143EAK

Q30 DTA143EAK

R90 330 1w

IC-2 BA4558

CF1 CST4.00MGW

IC-1 IXA098DR

7237

144 109

108

R94

4.7k

R69 15k

R97 15k

R41 15k

R92 1.8kF R93 360kF

R91

3.32kD

R96

3.57kD

R40

4.7k

R74 270k

876

123

R95

15k

Q21 DTA123JKA

D40 1SS355

D90

Q11 DTA143EAK

LD10 LD11 LD12 LD13

LD15 LD14

C10 47µ/16v

C11 0.1µ/50v

C90 0.1µ/50v

C91 0.1µ/50v

C40 0.01µ/25v

C60 330p/50v

C20

0.1µ/50v

C13 0.01µ/25v

AIN0

AIN1

AIN2

AIN3

C14 0.01µ/25v

C15

0.1µ/50v

VL4

VL3

VL2

P44

P45

P20

P07 P06 P05 P04 P03 P02 P01 P00

P17 P16

P15 P14

AIN7 AIN6

AIN5AIN4

P21 P22 P23 P24

CNTRO

VL1

C16

0.1µ/50v C17

0.1µ/50v C18

0.1µ/50v

R12 15k

D20 1SS355

(J11) 4.7k (J10)

(J12)

(J14)

(J16)

(J13) 4.7k

(J15) 4.7k

(J17) 4.7k

R11 15k

R10 1k

R15

4.7k

R16

4.7k

R17

4.7k

R18

4.7k

R98

620k

R99

300k

R100

150kF

R101

75kF

R102

37.4kF

R19

4.7k

C12

0.1µ/50v

C92

0.01µ/25v

C93

0.01µ/25v

ZD10

UDZ4.3B

Q10

2SA1037AK

C61 330p/50v

C62 330p/50v

C63 330p/50v

C64 330p/50v

C65 330p/50v

–

R75 270k

R60 15k

R61 15k

R62 15k

R63 15k

R64 15k

R65 15k

R66 15k

R67 15k

R76 270k

R77 270k

R78 270k

R79 270k

R70 15k R71 15k R72 15k R73 15k

R68 15k

C-6

C-5

C-7

COM14

COM15

COM5

COM6

COM16

COM15

COM14

COM13

COM12

COM11

COM10

COM9

SEG40

SEG39

SEG38

SEG37

SEG36

SEG35

SEG34

SEG33

SEG32

SEG31

SEG30

SEG29

SEG28

SEG27

SEG26

SEG25

SEG24

SEG23

SEG22

SEG21

SEG20

SEG19

SEG18

SEG17

SEG16

SEG15

SEG14

SEG13

SEG12

SEG11

SEG10

SEG9

SEG8

SEG7

SEG6

SEG5

SEG4

SEG3

SEG2

SEG1

COM1

COM2

COM3

COM4

COM5

COM6

COM7

COM8

COM0

COM5

COM15

COM8

SEG34

SEG39

P05

P04

P03

P02

P01

P00

P17

P16

P15

P14

AIN7

AIN6

AIN5

AIN4

RESET

XCOUT

XCIN

VCC

OSCSEL

XOUT

VSS

XIN

AIN3

AIN2

AIN1

AIN0

COM8

COM9

COM10

COM11

COM12

COM13

COM7

SEG0

SEG1

SEG2

SEG3

SEG4

SEG5

SEG6

SEG7

SEG8

SEG9

SEG10

SEG11

SEG12

SEG13

SEG14

SEG15

SEG16

SEG17

SEG18

SEG19

SEG20

SEG21

SEG22

SEG23

SEG24

SEG25

SEG26

SEG27

SEG28

SEG29

SEG30

SEG31

SEG32

SEG33

COM4 COM3 COM2 COM1 COM0

VL1 VL2 VL3 VL4 VL5 C3 C2

C1 VLIN VREG

NC VSS

P27

P26

P25

P24

P23

P22

P21

P20

P47

P46

P45

P44

P43

CNTR0

P41 INT0

P07

P06

SEG67

SEG66

SEG65

SEG64

SEG63

SEG62

SEG61

SEG60

SEG59

SEG58

SEG57

SEG56

SEG55

SEG54

SEG53

SEG52

SEG51

SEG50

SEG49

SEG48

SEG47

SEG46

SEG45

SEG44

SEG43

SEG42

SEG41

SEG40

SEG39

SEG38

SEG37

SEG36

SEG35

SEG34

SENSOR DEFROST TURNTABLE OFF COOK HELP

MA152WA

Figure S-3 LSI Unit Circuit

Page 37

DMO2420B DMO2420R DMO2420S

Figure S-4. Printed Wiring Board of Power Unit

WH - 1

SH - B

SH - A

C3 C4

10 D4 D2 D1

(J1)

(D10)

RY3

(CN - D)

ZD1

VRB

SP1

RY2

VRS1

OMIF

RY1

TTM

B Q3

(CN - C)

CN - C

CN - B

CN - A

Page 38

Technical Service

950 S. Raymond Ave.

Pasadena, CA 91105

800-353-2267

Part # 85927

Dacor DMO2420 Parts And Service Manual

Specifications and Main Features

Frequently Asked Questions

User Manual