Dacor MMD24S Service Manual
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Dacor MMD24S Service Manual

Microwave drawer
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MMD24S
In the interest of user-safety the unit should be restored to its original condition and only parts identical to those specified should
be used.
WARNING TO SERVICE PERSONNEL:
This service manual is intended for use by persons having electrical and mechanical training and a level of
knowledge of these subjects generally considered acceptable in the appliance repair trade. Sharp Electronics
Corporation cannot be responsible, nor assume any liability, for injury or damage of any kind arising from the
use of this manual.
Microwave ovens contain circuitry capable of producing very high voltage and current. Contact with the
following parts may result in a severe, possibly fatal, electrical shock. (High Voltage Capacitor, High Voltage
Power Transformer, High Voltage Rectifier and Heat sink etc., and Magnetron, High Voltage Harness etc..)
BEFORE SERVICING ....................................................................................................... INSIDE FRONT COVER
WARNING TO SERVICE PERSONNEL ................................................................................................................. 3
MICROWAVE MEASUREMENT PROCEDURE ..................................................................................................... 4
FOREWORD AND WARNING ............................................................................................................................... 5
PRODUCT SPECIFICATIONS ............................................................................................................................... 6
SCHEMATICS ...................................................................................................................................................... 0
TEST PROCEDURES .......................................................................................................................................... 
TOUCH CONTROL PANEL ASSEMBLY .............................................................................................................. 9
MICROWAVE DRAWER DISASSEMBLY ............................................................................................................. 27
WIRING DIAGRAMS ............................................................................................................................................ 33
PRINTED WIRING BOARDS ............................................................................................................................... 34
PARTS LIST ......................................................................................................................................................... 38
PACKING AND ACCESSORIES .......................................................................................................................... 43
SERVICE MANUAL
MICROWAVE DRAWER
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.
MMD24B

MMD24S
MMD24B
S38M289MMD24S
Page

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  • Page 1: Table Of Contents

    MMD24S MMD24B SERVICE MANUAL S38M289MMD24S MICROWAVE DRAWER MODELS MMD24S MMD24B In the interest of user-safety the unit should be restored to its original condition and only parts identical to those specified should be used. WARNING TO SERVICE PERSONNEL: This service manual is intended for use by persons having electrical and mechanical training and a level of knowledge of these subjects generally considered acceptable in the appliance repair trade.

  • 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/ . The owner of the unit should be instructed not to use the unit until the oven has been brought into...

  • Page 3: Warning To Service Personnel

    MMD24S MMD24B WARNING TO SERVICE PERSONNEL Microwave Oven units contain circuitry capable of producing very high voltage and current, contact with following parts may result in a severe, possibly fatal, electrical shock. (Example) High Voltage Capacitor, High Voltage Power Transformer, Magnetron, High Voltage Rectifier Assembly, High Voltage Harness, Heating Elements, etc..

  • Page 4: Microwave Measurement Procedure

    MMD24S MMD24B MICROWAVE MEASUREMENT PROCEDURE A. Requirements: ) Microwave leakage limit (Power density limit): The power density of microwave radiation emitted by a microwave oven should not exceed mW/cm at any point 5cm or more from the external surface of the oven, measured prior to...

  • Page 5: Foreword And Warning

    PRODUCT DESCRIPTION MICROWAVE DRAWER MMD24S / MMD24B SCHEMATICS FOREWORD This Manual has been prepared to provide Dacor Service Personnel TEST PROCEDURE with Operation and Service Information for the DACOR MICROWAVE DRAWER. It is recommended that service personnel carefully study the entire...

  • Page 6: Product Specifications

    MMD24S MMD24B MICROWAVE DRAWER SPECIFICATION ITEM DESCRIPTION Power Requirements Canada - 7 Volts / 3.0 Amperes / 500 Kw / 60 Hz (CUL) U.S.A. - 20 Volts / 3.6 Amperes / 500 Kw / 60 Hz (UL) Single phase, 3 wire grounded...
  • Page 7 MMD24S GENERAL INFORMATION MMD24B 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.
  • Page 8 MMD24S MMD24B OPERATION DESCRIPTION OF OPERATING SEQUENCE The following is a description of component functions dur- the secondary interlock switch and secondary interlock ing oven operation. relay and is mechanically associated with the drawer so that it will function in the following sequence.
  • Page 9 MMD24S MMD24B SENSOR COOKING CONDITION Using the SENSOR function, food is cooked without figur- 2. The coil of shut-off relay (RY-) is energized, but the power transformer is not turned on. ing time, power level or quantity. When the oven senses 3.
  • Page 10 MMD24S MMD24B SCHEMATIC (OFF CONDITION)

  • Page 11: Test Procedures

    MMD24S MMD24B TEST PROCEDURES PROCEDURE COMPONENT TEST LETTER TOUCH CONTROL PANEL ASSEMBLY TEST The touch control panel consists of circuits including semiconductors such as LSI, ICs, etc. Therefore, unlike conventional microwave ovens, proper maintenance cannot be performed with only a voltmeter and ohmmeter.
  • Page 12 MMD24S MMD24B TEST PROCEDURES PROCEDURE COMPONENT TEST LETTER 4) Reconnect all leads removed from components during testing. 5) Re-install the covers. 6) Reconnect the power supply cord after the covers are installed. 7) Run the oven and check all functions.
  • Page 13 MMD24S MMD24B TEST PROCEDURES PROCEDURE COMPONENT TEST LETTER 2. Re-install the outer case (cabinet). 3. Reconnect the power supply cord after the outer case is installed. 4. Run the oven and check all function. DEFROST TEST WARNING : The oven should be fully assembled before following procedure.
  • Page 14 MMD24S MMD24B TEST PROCEDURES PROCEDURE COMPONENT TEST LETTER ) Discharge high voltage capacitor. 2) Reconnect all leads removed from components during testing. 3) Re-install the outer case (cabinet). 4) Reconnect the power supply cord after the outer case is installed.
  • Page 15 MMD24S MMD24B TEST PROCEDURES PROCEDURE COMPONENT TEST LETTER 9-2. Place the container on the center of tray in the oven cavity. 9-3. Close the drawer. 9-4. Touch the TIMER/CLOCK pad once, the POWER LEVEL pad twice and the START pad once. And touch the number pads  once and the number pad 4 once.
  • Page 16 MMD24S MMD24B TEST PROCEDURES PROCEDURE COMPONENT TEST LETTER Refer to the disassembly instructions found on Page 27. MAGNETRON ASSEMBLY TEST Disconnect the power supply cord. 2. Open the drawer and keep it open. 3. To discharge high voltage capacitor, wait for 60 seconds.
  • Page 17 MMD24S MMD24B TEST PROCEDURES PROCEDURE COMPONENT TEST LETTER SECONDARY INTERLOCK SWITCH TEST . Disconnect the power supply cord. 2. Open the drawer and keep it open. 3. To discharge high voltage capacitor, wait for 60 seconds. 4. Isolate the switch and connect the ohmmeter to the common (COM.) and normally open (NO) terminal of the switch.
  • Page 18 MMD24S MMD24B TEST PROCEDURES PROCEDURE COMPONENT TEST LETTER BLOWN MONITOR FUSE TEST . Disconnect the power supply cord. 2. Open the drawer and block it open. 3. To discharge high voltage capacitor, wait for 60 seconds. 4. If the monitor fuse is blown when the drawer is opened, check the primary interlock switch, secondary interlock switch and monitor switch according to the "TEST PROCEDURE"...

  • Page 19: Touch Control Panel Assembly

    MMD24S MMD24B TOUCH CONTROL PANEL ASSEMBLY OUTLINE OF TOUCH CONTROL PANEL The touch control section consists of the following units. 6) Power Source Circuit This circuit generates voltages necessary in the control () Key unit unit from the AC line voltage.
  • Page 20 MMD24S MMD24B DESCRIPTION OF LSI (IC-1) The I/O signal of the LSIis detailed in the following table. Pin No. Signal Description  - 3 AN5- AN3 Terminal to change cooking input according to the Model. By using A/D converter contained in the LSI, DC voltage in accordance with the Model in operation is applied to set up its cooking constant.
  • Page 21 MMD24S MMD24B Pin No. Signal Description COM0 Common data signal. Connected to LCD signal C4. Connected VC (+5V). 29 - 3 P27- P25 Terminal not used. SEG20 Segment data signal. Connected to LCD segment S24. Signal coming from touch key.
  • Page 22 MMD24S MMD24B Pin No. Signal Description Magnetron high-voltage circuit driving signal. Microwave cooking mode Other cooking mode To turn on and off the cook relay(RY2). In 00% VARI MODE ON TIME OFF TIME ON TIME OFF TIME 00% power 32 sec.
  • Page 23 MMD24S MMD24B HUMIDITY SENSOR CIRCUIT (1) Structure of Humidity Sensor the resistance values results in that there is the same The humidity sensor includes two thermistors as shown potential at both F-3 terminal of the absolute humidity in the illustration. One thermistor is housed in the closed sensor and AN6 terminal of the LSI.
  • Page 24 MMD24S MMD24B TOUCH CONTROL PANEL SERVICING A. On some models, the power supply cord between the 1. Precautions for Handling Electronic Components touch control panel and the oven itself is so short that This unit uses CMOS LSI in the integral part of the circuits.
  • Page 25 MMD24S MMD24B PRECAUTIONS FOR USING LEAD-FREE SOLDER 1. Employing lead-free solder The "Main PWB" of this model employs lead-free solder. This is indicated by the "LF" symbol printed on the PWB and in the service manual. The suffix letter indicates the alloy type of the solder.

  • Page 26: Component Replacement And Adjustment Procedure

    MMD24S MMD24B COMPONENT REPLACEMENT AND ADJUSTMENT PROCEDURE WARNING AGAINST HIGH VOLTAGE: Microwave ovens contain circuitry capable of producing very high voltage and current. Contact with the following parts may result in severe, possibly fatal, electric shock. (Example) High Voltage Capacitor, Power Transformer, Magnetron, High Voltage Rectifier Assembly, High Voltage Harness etc..

  • Page 27: Microwave Drawer Disassembly

    MMD24S MMD24B MICROWAVE DRAWER DISASSEMBLY WARNING: Follow all safety precautions as stated at the beginning of this Service Manual before proceeding! . Before removing Microwave Drawer, take measures to protect the Drawer louver by either removing the louver or by letting the louver over hang off flat protected surface (Fig 1).
  • Page 28 MMD24S MMD24B 7. To remove the Control Panel Frame Assembly, remove the 9 screws holding the C/P frame to the cavity. (Fig 3). With the C/P frame assembly now loose, you can unplug all wires. Fig. 3 At this point, you will have access to all parts of the Microwave Drawer.
  • Page 29 MMD24S MMD24B STOP SWITCH, SECONDARY INTERLOCK SWITCH AND MONITOR SWITCH REMOVAL . Follow the Microwave Drawer disassembly as previously stated 2. Open the drawer and keep it open. in the top position, located on the left side of the unit.
  • Page 30 MMD24S MMD24B DRAWER/SLIDE RAIL REMOVAL DRAWER ASSEMBLY AND CHOKE REMOVAL . Follow the Microwave Drawer disassembly as previously NOTE: stated Fig. D-1 To remove only the 2. Open the drawer and keep it open. Microwave Drawer, follow steps 3. To discharge the high voltage capacitor, wait for 60 , 2, 5, 8, 9 &...
  • Page 31 MMD24S MMD24B SWITCH ANGLE REMOVAL/ADJUSTMENT SWITCH ANGLE REMOVAL Fig. S-1 (Locate either the right or left switch angle) . Follow the Microwave Drawer disassembly as previously stated 2. Open the drawer and keep it open. 3. To discharge the high voltage capacitor, wait for 60 seconds.
  • Page 32 MMD24S MMD24B AUTO DRAWER GEAR REMOVAL/INSTALLATION (This procedure requires a 4" or greater phillips screwdriver) . Disengage any power going to the unit. 2. Open the drawer and keep it open. 3. Remove the top cover and right side cabinet.

  • Page 33: Wiring Diagrams

    MMD24S MMD24B Power Supply cord 120V 60Hz NOISE FILTER BOARD to Back Plate CN502 (SWITCHING POWER SUPPLY) BLK or CN502 CN501 MAGNETRON OVEN THERMAL THERMAL CUT-OUT CUT-OUT YLW or N.O. RED or YLW or N.C. THIRD DOOR SWITCH MONITOR COOLING...

  • Page 34: Printed Wiring Boards

    MMD24S MMD24B CN-A PA154DR D1 -- D4 2.5A 1N4002L x4 CN-H FUSE AC 120V VRS1 60Hz 10G471K SW Reg . 502-3 H- 9 SW Reg. OUT +24V H-11 N.O. MICRO N.O. (O.L) <NOTE> : IF NOT SPECIFIED, 1SS270A ( ) : NOT INSERT PARTS...
  • Page 35 MMD24S MMD24B COM3 COM2 COM1 COM0 SEG23 SEG22 SEG21 SEG20 SEG19 SEG19 SEG18 SEG18 SEG17 SEG17 R121 SEG16 SEG16 XOUT SEG15 SEG15 SEG14 SEG14 SEG13 SEG13 SEG12 SEG12 4.7K SEG11 SEG11 RESET SEG10 SEG10 CNVSS SEG9 SEG9 SEG8 SEG8 SEG7...
  • Page 36 MMD24S MMD24B N.O. COM. N.O. COM. FUSE 2.5A Figure S-4. Printed Wiring Board of Power Unit...
  • Page 37 MMD24S MMD24B C101 C100 R113 R112 C102 R114 C103 R115 R104 R105 R106 R100 R101 R102 R103 R107...

  • Page 38: Parts List

    MMD24S MMD24B COPYRIGHT © 2008 BY DACOR, INC. ALL RIGHTS RESERVED. No part of this publication may be reproduced, stored in retrieval systems, or transmitted in any form or by any means, electronic, mechanical, photocopying, recording, or otherwise, without prior written permission...

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