Dacor DMT2420S Service Manual
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Dacor DMT2420S Service Manual

Microwave oven
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In the interest of user-safety the oven should be restored to its original condition and only parts identical to those specified should
be used.
WARNING TO SERVICE PERSONNEL: Microwave ovens contain circuitry capable of producing very high voltage
and current. Contact with the following parts may result in a severe, possibly fatal, electrical shock. (Inverter unit
that includes High Voltage Capacitor, High Voltage Power Transformer, High Voltage Rectifier and Heat sink etc.,
and Magnetron, High Voltage Harness etc..)
BEFORE SERVICING ...................................................................................................... INSIDE FRONT COVER
WARNING TO SERVICE PERSONNEL ................................................................................................................1
MICROWAVE MEASUREMENT PROCEDURE .....................................................................................................2
FOREWORD AND WARNING ................................................................................................................................3
PRODUCT SPECIFICATIONS ...............................................................................................................................4
GENERAL INFORMATION ...................................................................................................................................5
OPERATION .........................................................................................................................................................6
TROUBLESHOOTING GUIDE ............................................................................................................................. 10
TEST PROCEDURE ............................................................................................................................................ 11
TOUCH CONTROL PANEL ASSEMBLY ............................................................................................................. 26
COMPONENT REPLACEMENT AND ADJUSTMENT PROCEDURE .................................................................. 27
PICTORIAL DIAGRAM ........................................................................................................................................ 33
POWER UNIT CIRCUIT ....................................................................................................................................... 34
LSI UNIT CIRCUIT ............................................................................................................................................... 35
PRINTED WIRING BOARD ................................................................................................................................. 36
PARTS LIST ........................................................................................................................................................ 37
PACKING AND ACCESSORIES ......................................................................................................................... 41
dis tinctive appliances
SERVICE MANUAL
MICROWAVE OVEN
MODELS

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This document has been published to be used for after
sales service only.
The contents are subject to change without notice.
S12M201DMT24E
DMT2420B
DMT2420R
DMT2420S
DMT2420B
DMT2420R
DMT2420S
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  • Page 1: Table Of Contents

    DMT2420B DMT2420R DMT2420S SERVICE MANUAL S12M201DMT24E MICROWAVE OVEN DMT2420B MODELS DMT2420R DMT2420S In the interest of user-safety the oven should be restored to its original condition and only parts identical to those specified should be used. WARNING TO SERVICE PERSONNEL: Microwave ovens contain circuitry capable of producing very high voltage and current.

  • Page 2: Precautions To Be Observed Before And During Servicing To Avoid Possible Exposure To Excessive Microwave Energy

    2) contact DACOR and Food and Drug Administration's Center for Devices and Radiological Health immediately. Service personnel should inform DACOR of any certified unit found with emissions in excess of 4mW/cm The owner of the unit should be instructed not to use the unit until the oven has been brought into compliance.

  • Page 3: Warning To Service Personnel

    DMT2420B DMT2420R DMT2420S WARNING TO SERVICE PERSONNEL Microwave ovens contain circuitry capable of pro- ducing 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 Assem- bly, High Voltage Harness etc..

  • Page 4: Microwave Measurement Procedure

    DMT2420B DMT2420R DMT2420S 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/cm at any point 5cm or more from the external surface of the oven, measured prior to acquisition...

  • Page 5: General Information

    MICROWAVE OVEN DMT2420B/DMT2420R/DMT2420S GENERAL INFORMATION FOREWORD This Manual has been prepared to provide Dacor Service Personnel OPERATION with Operation and Service Information for the DACOR MICRO- WAVE OVENS, DMT2420B, DMT2420R and DMT2420S. It is recommended that service personnel carefully study the entire text...
  • Page 6 DMT2420B DMT2420R DMT2420S SPECIFICATION ITEM DESCRIPTION Power Requirements 120 Volts / 14.3 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"...

  • Page 7: Oven Diagram

    DMT2420B DMT2420R DMT2420S Where a two-pronged wall-receptacle is encountered, it is the personal Grounded responsibility and obligation of the customer to contact a qualified Receptacle Box electrician and have it replaced with a properly grounded three-pronged wall receptacle or have a grounding adapter properly grounded and polarized.

  • Page 8: Operation

    DMT2420B DMT2420R DMT2420S OPERATION DESCRIPTION OF OPERATING SEQUENCE The following is a description of component functions during 4. The microwave energy produced by the magnetron is oven operation. channelled through the waveguide into the cavity feed- box, and then into the cavity where the food is placed to OFF CONDITION be cooked.
  • Page 9 DMT2420B DMT2420R DMT2420S Note: The ON/OFF time ratio does not correspond with the Cooking Sequence. percentage of microwave power, because approx. 2 1. Touch one of the SENSOR pads and then touch the Start seconds are needed for heating of the magnetron pad.
  • Page 10 DMT2420B DMT2420R DMT2420S SCHEMATIC NOTE: CONDITION OF OVEN 1. DOOR CLOSED. NOTE: Indicates components with potential above 250 V. 2. CLOCK APPEARS ON DISPLAY. FUSE N.O. HUMIDITY SENSOR (RY2) (RY1) POWER PRIMARY TRANSFORMER INTERLOCK RELAY 120V AC 60Hz CONTROL UNIT N.O.

  • Page 11: Description And Function Of Components

    DMT2420B DMT2420R DMT2420S DESCRIPTION AND FUNCTION OF COMPONENTS DOOR OPEN MECHANISM 3. If the door is opened, and the primary interlock relay (RY2) and secondary interlock switch contacts fail to open, the The door is opened by pushing the open button on the control C/T fuse blows simultaneously with closing of the monitor panel, refer to the Figure D-1.

  • Page 12: Troubleshooting Guide

    DMT2420B DMT2420R DMT2420S 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.
  • Page 13 DMT2420B DMT2420R DMT2420S CK = Check / RE = Replace TEST PROCEDURE A B C D E E F F G H J K L M N RE RE RE RE CK CK CK CK POSSIBLE CAUSE DEFECTIVE PARTS PROBLEM...

  • Page 14: Test Procedure

    DMT2420B DMT2420R DMT2420S TEST PROCEDURES PROCEDURE COMPONENT TEST LETTER 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.
  • Page 15 DMT2420B DMT2420R DMT2420S TEST PROCEDURES PROCEDURE COMPONENT TEST LETTER 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.
  • Page 16 DMT2420B DMT2420R DMT2420S TEST PROCEDURES PROCEDURE COMPONENT TEST LETTER CAUTION: BEFORE REPLACING A BLOWN C/T FUSE, TEST THE PRIMARY INTERLOCK RELAY, SECONDARY INTERLOCK SWITCH, DOOR SENSING SWITCH AND MONITOR SWITCH FOR PROPER OPERATION. If the C/T fuse is blown by improper switch operation, the C/T fuse and monitor switch must be replaced with "C/T fuse and monitor switch assembly"...
  • Page 17 DMT2420B DMT2420R DMT2420S TEST PROCEDURES PROCEDURE COMPONENT TEST LETTER MONITOR SWITCH 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.
  • Page 18 DMT2420B DMT2420R DMT2420S TEST PROCEDURES PROCEDURE COMPONENT TEST LETTER 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.
  • Page 19 DMT2420B DMT2420R DMT2420S TEST PROCEDURES PROCEDURE COMPONENT TEST LETTER 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. RELAY TEST 2. Open the door and block it open.
  • Page 20 DMT2420B DMT2420R DMT2420S TEST PROCEDURES PROCEDURE COMPONENT TEST LETTER WEIGHT 1ST STAGE 2ND STAGE LEVEL TIME LEVEL TIME 0.5lb 30sec. 15sec. (5) If improper operation is indicated, the control unit is probably defective and should be checked. FOIL PATTERN ON THE PRINTED WIRING BOARD TEST To protect the electronic circuits, this model is provided with a fine foil pattern added to the primary on the PWB, this foil pattern acts as a fuse.
  • Page 21 DMT2420B DMT2420R DMT2420S TEST PROCEDURES PROCEDURE COMPONENT TEST LETTER 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.
  • Page 22 DMT2420B DMT2420R DMT2420S TEST PROCEDURES PROCEDURE COMPONENT TEST LETTER 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.

  • Page 23: Touch Control Panel Assembly

    DMT2420B DMT2420R DMT2420S TOUCH CONTROL PANEL ASSEMBLY OUTLINE OF TOUCH CONTROL PANEL unit from the AC line voltage. The touch control section consists of the following units. In addition, the synchronizing signal is available in order to compose a basic standard time in the clock (1) Key Unit circuit.
  • Page 24 DMT2420B DMT2420R DMT2420S LSI(IXA029DR) The I/O signal of the LSI(IXA029DR) is detailed in the following table. Pin No. Signal Description TIOCA2 Terminal not used. Terminal not used. Power source voltage : +5.0V. The power source voltage to drive LSI is input to Vcc terminal. Connected to Vcc.
  • Page 25 DMT2420B DMT2420R DMT2420S Pin No. Signal Description Power source voltage : GND(0V). The power source voltage to drive LSI is input to VSS terminal. Key strobe signal. Signal applied to touch screen section. A pulse signal is input to PB1-PB5 terminal while one of G10 line keys on key matrix is touched.
  • Page 26 DMT2420B DMT2420R DMT2420S Pin No. Signal Description 75-76 MD0-MD1 Connected to VCC. Connected to GND. Avcc A/D converter power source voltage : +5V. The power source voltage to drive the A/D converter. Connected to VCC. Vref A/D converter power source voltage : +5V.
  • Page 27 DMT2420B DMT2420R DMT2420S ABSOLUTE HUMIDITY SENSOR CIRCUIT With this voltage given, the switches SW1 to SW5 in the (1) Structure of Absolute Humidity Sensor LSI are turned on in such a way as to change the The absolute humidity sensor includes two thermistors resistance values in parallel with R98 ~ R102.

  • Page 28: Touch Control Panel Assembly

    DMT2420B DMT2420R DMT2420S TOUCH CONTROL PANEL SERVICING 4) Re-install the outer case (cabinet). 1. Precautions for Handling Electronic Components 5) Re-connect the power supply cord after the outer This unit uses CMOS LSI in the integral part of the case is installed.

  • Page 29: Component Replacement And Adjustment Procedure

    DMT2420B DMT2420R DMT2420S COMPONENT REPLACEMENT AND ADJUSTMENT PROCEDURE WARNING AGAINST HIGH VOLTAGE: 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..

  • Page 30: Pictorial Diagram

    DMT2420B DMT2420R DMT2420S CAUTION: 1. DISCONNECT OVEN FROM POWER SUP PLY BEFORE REMOVING OUTER CASE. 2. DISCHARGE THE HIGH VOLTAGE CA- PACITOR BEFORE TOUCHING ANY OVEN COMPONENTS OR WIRING. Special screw NOTE: When replacing the outer case, the 2 special Torx screws must be reinstalled in the same locations.
  • Page 31 DMT2420B DMT2420R DMT2420S OVEN LAMP AND LAMP SOCKET REMOVAL 1. Disconnect the power supply cord and remove outer case. Oven lamp socket 2. Open the door and block it open. 3. Discharge high voltage capacitor. 4. Remove the oven lamp from the oven lamp socket.
  • Page 32 DMT2420B DMT2420R DMT2420S COOLING FAN MOTOR REMOVAL REMOVAL CAUTION: 1. Disconnect the power supply cord and then remove * Do not reuse the removed fan blade because the outer case. hole (for shaft) may be larger than normal. 2. Open the door and block it open.

  • Page 33: Door Replacement

    DMT2420B DMT2420R DMT2420S 3. Secure latch hook (with two (2) mounting screws) to oven and check continuity of the monitor circuit. Refer to chapter flange. "Test Procedure" and Adjustment procedure. 4. Make sure that the monitor switch is operating properly DOOR SENSING SWITCH/SECONDARY INTERLOCK SWITCH AND MONITOR SWITCH ADJUSTMENT 1.
  • Page 34 DMT2420B DMT2420R DMT2420S 13.Now, door panel is free. Note: The door on a microwave oven is designed to act as 14.Slide latch head upward and remove it from door frame by an electronic seal preventing the leakage of microwave releasing latch spring from door frame and latch head.
  • Page 35 CONTROL UNIT CN-F AH SENSOR CN-C CN-F (CPU UNIT) CN-C CN-B PRIMARY INTERLOCK RELAY CN-A Figure S-1. Pictorial Diagram...
  • Page 36 DMT2420B DMT2420R DMT2420S R2 91 1w R3 91 1w CN-A Q1 KTC1027 S1NB10 – AC120V 60Hz BZ/EN SP30 BUZZR OVEN LAMP OVEN LAMP FAN MOTOR FAN MOTOR TURNTABLE TURNTABLE MOTOR MOTOR MICRO MICRO DOOR SENSING DOOR SWITCH SENSING CN-C SWITCH...

  • Page 37: Lsi Unit Circuit

    R10 470 1/2w Q10 KTC1027 WH-1 WH-1 KTC1027 LED1 LED2 C91 0.1µ/25v 4.7k – – C92 0.1µ/25v CPU UNIT C93 0.1µ/25v KRC101S C94 0.1µ/25v R13 4.7k AH SENSOR C95 0.1µ/25v (R101) 4.7k C40 0.1µ/50v R41 3.32kD (J10) 4.7k (J11) (J12) (J13) 4.7k 0.1µ...

  • Page 38: Printed Wiring Board

    DMT2420B DMT2420R DMT2420S CN - C VRS1 (J1) QKITPB033MREO CN - A Figure S-4. Printed Wiring Board of Power Unit...

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