Sharp R-420EK Service Manual
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Sharp R-420EK Service Manual

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R-420EK
BEFORE SERVICING ..................................................................................................... INSIDE FRONT COVER
WARNING TO SERVICE PERSONNEL .............................................................................................................. 1
MICROWAVE MEASUREMENT PROCEDURE .................................................................................................. 2
FOREWORD AND WARNING ............................................................................................................................. 3
PRODUCT SPECIFICATIONS ............................................................................................................................. 4
GENERAL INFORMATION ................................................................................................................................. 4
OPERATION ........................................................................................................................................................ 6
TROUBLESHOOTING GUIDE ............................................................................................................................. 10
TEST PROCEDURE ............................................................................................................................................ 11
TOUCH CONTROL PANEL .................................................................................................................................. 21
COMPONENT REPLACEMENT AND ADJUSTMENT PROCEDURE .................................................................. 27
PICTORIAL DIAGRAM ........................................................................................................................................ 33
POWER UNIT CIRCUIT ....................................................................................................................................... 34
CPU UNIT CIRCUIT ............................................................................................................................................. 35
PRINTED WIRING BOARD ................................................................................................................................. 36
PARTS LIST ........................................................................................................................................................ 37
PACKING AND ACCESSORIES ......................................................................................................................... 41
SHARP ELECTRONCS CORPORATION
Service Headquarters: Sharp Plaza, Mahwah, New Jersey, 07430-2135
SERVICE MANUAL
MODELS
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 con-
tain circuitry capable of producing very high voltage and
current, contact with following parts may result in a severe,
possibly fatal, electrical shock. (High Voltage Capacitor, High
Voltage Power Transformer, Magnetron, High Voltage Recti-
fier Assembly, High Voltage Harness etc..)

TABLE OF CONTENTS

This document has been published to be used for after
sales service only.
The contents are subject to change without notice.
S61M167R420EE
MICROWAVE OVEN
R-420EK
R - 420EK
Page

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  • Page 1: Table Of Contents

    PARTS LIST ................................ 37 PACKING AND ACCESSORIES ......................... 41 This document has been published to be used for after sales service only. SHARP ELECTRONCS CORPORATION The contents are subject to change without notice. Service Headquarters: Sharp Plaza, Mahwah, New Jersey, 07430-2135...

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

    Before servicing an operative unit, perform a microwave emission check as per the Microwave Measurement Procedure outlined in this service manual. If microwave emissions level is in excess of the specified limit, contact SHARP ELECTRONICS CORPORATION immediately @1-800-237-4277. If the unit operates with the door open, service person should 1) tell the user not to operate the oven and 2) contact SHARP ELECTRONICS CORPORATION and Food and Drug Administration's Center for Devices and Radiological Health immediately.

  • Page 3: Warning To Service Personnel

    R-420EK 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

    R - 4 2 0 E K 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 by a purchaser, and thereafter (through the useful life of the oven), 5 mW/cm at any point 5cm or more from the external surface of the oven.

  • Page 5: Foreword And Warning

    MICROWAVE OVEN R-420EK GENERAL INFORMATION FOREWORD This Manual has been prepared to provide Sharp Electronics Corp. Service Personnel with Operation and Service Information for the SHARP OPERATION MICROWAVE OVEN, R-420EK. It is recommended that service personnel carefully study the entire text...

  • Page 6: Product Specifications

    R - 4 2 0 E K SPECIFICATION ITEM DESCRIPTION Power Requirements 120 Volts / 13.8 Amperes/1650Watts 60 Hertz Single phase, 3 wire grounded Power Output 1200 watts (IEC TEST PROCEDURE) Operating frequency of 2450MHz Case Dimensions Width 21-21/32" Height 12-3/8"...
  • Page 7 R-420EK 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.

  • Page 8: Operation

    (2) When the door is closed from the open position, the control unit. (Figure O-1). monitor switch contacts open first. Then the contacts of 1. The display will show "SHARP SIMPLY THE BEST the secondary interlock switch and door sensing switch PRESS CLEAR AND PRESS CLOCK".
  • Page 9 R-420EK 2. The coil of shut-off relay (RY-1) is energized, the turntable motor are turned on, but the power transformer SENSOR COOKING CONDITION is not turned on. 3. After about 16 seconds, the cook relay (RY-2) is Using the SENSOR function, food is cooked without figuring energized.
  • Page 10 R - 4 2 0 E K Note:* Indicates components, with potential above 250v SCHEMATIC NOTE: CONDITION OF OVEN 1. DOOR CLOSED 2. CLOCK APPEARS ON DISPLAY MAGNETRON MONITOR TEMP. FUSE 20A FUSE COM. N.O. CAPACITOR 1.0µF AH SENSOR AC 2300V (RY-2) (RY-1) PRIMARY...
  • Page 11 R-420EK DESCRIPTION AND FUNCTION OF COMPONENTS DOOR OPEN MECHANISM open, the monitor fuse blows simultaneously with closing of the monitor switch contacts. The door is opened by pushing the open button on the control CAUTION: BEFORE REPLACING A BLOWN MONITOR panel, refer to the Figure D-1.

  • Page 12: Troubleshooting Guide

    R - 4 2 0 E K 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: Test Procedure

    R-420EK CK = Check / RE = Replace RE RE A B C D E E F F G H RE RE CK I CK CK CK J K L TEST PROCEDURE POSSIBLE CAUSE DEFECTIVE PARTS PROBLEM CONDITION Home fuse or circuit breaker blows...
  • Page 14 R - 4 2 0 E K TEST PROCEDURES PROCEDURE COMPONENT TEST LETTER 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.
  • Page 15 R-420EK 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 R - 4 2 0 E K TEST PROCEDURES PROCEDURE COMPONENT TEST LETTER CAUTION: IF THE TEMPERATURE FUSE INDICATES AN OPEN CIRCUIT AT ROOM TEMPERA- TURE, REPLACE TEMPERATURE FUSE. SECONDARY INTERLOCK SWITCH TEST 1. Disconnect the power supply cord, and then remove outer case. 2.
  • Page 17 R-420EK TEST PROCEDURES PROCEDURE COMPONENT TEST LETTER 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 Screw Driver functions.
  • Page 18 R - 4 2 0 E K TEST PROCEDURES PROCEDURE COMPONENT TEST LETTER 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.
  • Page 19 R-420EK 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. CHICKEN PIECES STEAKS BAKED POPCORN POTATOES CHOPS...
  • Page 20 R - 4 2 0 E K TEST PROCEDURES PROCEDURE COMPONENT TEST LETTER (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 R-420EK TEST PROCEDURES PROCEDURE COMPONENT TEST LETTER 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.
  • Page 22 R - 4 2 0 E K TEST PROCEDURES PROCEDURE COMPONENT TEST LETTER 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.

  • Page 23: Touch Control Panel

    R-420EK TOUCH CONTROL PANEL ASSEMBLY OUTLINE OF TOUCH CONTROL PANEL The touch control section consists of the following units. 3) Power Source Circuit This circuit generates voltages necessary in the control (1) Key Unit unit from the AC line voltage.
  • Page 24 R - 4 2 0 E K Pin No. Signal Description RESET 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"...
  • Page 25 R-420EK Pin No. Signal Description P114 Key strobe signal. Signal applied to touch-key section. A pulse signal is input to ANI7, P100, P101, P102 and P103 terminal while one of G4 line keys on key matrix is touched. P115 Key strobe signal.
  • Page 26 R - 4 2 0 E K Pin No. Signal Description 0.1 sec. Signal to sound buzzer (2.0 kHz). H : GND A: key touch sound. L : -5V 2.0 sec. B: Completion sound. H : GND L : -5V To input signal which communicates the door open/close information to LSI.
  • Page 27 R-420EK ABSOLUTE HUMIDITY SENSOR CIRCUIT (1) Structure of Absolute Humidity Sensor With this voltage given, the switches SW1 to SW5 in the The absolute humidity sensor includes two thermistors LSI are turned on in such a way as to change the as shown in the illustration.
  • Page 28 R - 4 2 0 E K TOUCH CONTROL PANEL SERVICING 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. circuits.

  • Page 29: Component Replacement And Adjustment Procedure

    4. If the outer case (cabinet) is not fitted. WARNING FOR WIRING To prevent an electric shock, take the following pre- 3) Sharp edge: cautions. Bottom plate, Oven cavity, Waveguide flange, 1. Before wiring, Chassis support and other metallic plate.
  • Page 30 R - 4 2 0 E K CAUTION: 1. DISCONNECT OVEN FROM POWER SUP PLY BEFORE REMOVING OUTER CASE. 2. DISCHARGE THE HIGH VOLTAGE CA- PACITOR BEFORE TOUCHING ANY OVEN Special screw COMPONENTS OR WIRING. NOTE: When replacing the outer case, the 2 special Torx screws must be reinstalled in the same locations.
  • Page 31 4. Where the corners have been snipped off bend corner 7. Now the turntable motor is free. areas flat. No sharp edges must be evident after removal 8. After replacement use the one (1) screw to fit the turntable of the turntable motor cover.
  • Page 32 R - 4 2 0 E K COOLING FAN MOTOR REMOVAL REMOVAL CAUTION: 1. Disconnect the power supply cord and then remove outer * Do not reuse the removed fan blade because the hole case. (for shaft) may be larger than normal. 2.
  • Page 33 R-420EK 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 R - 4 2 0 E K RE-INSTALL 1. Re-install door screen to door frame. Figure C-5. Door Replacement 2. 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.

  • Page 35: Pictorial Diagram

    NOTE: The grounding conductor of the power supply cord has been grounded by power supply cord fixing screw. CAVITY TEMP. FUSE The screw must always be MAGNETRON TEMP. FUSE kept tight. CN-F AH SENSOR POWER SUPPLY CORD 120V 60Hz DOOR CONTROL PANEL N.O.

  • Page 36: Power Unit Circuit

    R - 4 2 0 E K D1-4 11ES1 CN-A – OVEN LAMP FAN MOTOR BUZZER TURNTABLE MOTOR OVEN LAMP FAN MOTOR TURNTABLE MOTOR (CN-D) MICRO MICRO DOOR SENSING SWITCH CN-C (CN-B) 12PIN LEAD WIRE DOOR SENSING HARNESS SWITCH...

  • Page 37: Cpu Unit Circuit

    LIQUID CRYSTAL DISPLAY CPU UNIT DTA143EKA COOK SENSOR LBS DEF HELP – – 1037AK R3 510 Q1 KTA1661 1/2w R2 680 1/2w MA152WA 1SS355 x 2 C-10 D5 D6 R94 10k R95 47k IC2 BA4558 SEG21 1 2 3 4 R92 1.8kF 330 1w R4 27 1/4w...

  • Page 38: Printed Wiring Board

    R - 4 2 0 E K (CN - C) CN - C CN - B CN - A (J1) (CN - D) (D10) Figure S-4 . Printed Wiring Board of Power Unit...

  • Page 39: Parts List

    R-420EK PARTS LIST Note: The parts marked “∆” may cause undue microwave exposure. The parts marked “*” are used in voltage more than 250V. "§" MARK: PARTS DELIVERY SECTION. REF. NO. PART NO. § DESCRIPTION Q'TY CODE ELECTRIC PARTS 1- 1...
  • Page 40 To have your order filled promptly and correctly, please furnish the following information. 1. MODEL NUMBER 2. REF. NO. 3. PART NO. 4. DESCRIPTION Order Parts from the authorized SHARP parts Distributor for your area. Defective parts requiring return should be returned as indicated in the Service Policy.
  • Page 41 R-420EK OVEN AND CABINET PARTS 4-11 1-15 7-10 1-10 1-14 7-11 1-11 4-10 1-12 1-13 7-10 7-11 4-12...
  • Page 42 R - 4 2 0 E K CONTROL PANEL PARTS DOOR PARTS 5-1-1 5-1-2 MISCELLANEOUS Actual wire harness may be different from illustration.

  • Page 43: Packing And Accessories

    R-420EK PACKING AND ACCESSORIES TOP PAD ASSEMBLY DOOR PROTECTION SHEET PLASTIC BAG TRAY HOLDER 6-5 TURNTABLE TRAY 6-8 OPERATION MANUAL 6-4 TURNTABLE SUPPORT BOTTOM PAD ASSEMBLY TRAY PACK SPADPB038MRE0 PACKING CASE Non-replaceable items.
  • Page 44 No part of this publication may be repro- duced, stored in retrieval systems, or trans- mitted in any form or by any means, elec- tronic, mechanical, photocopying, recording, or otherwise, without prior written permission of the publisher. '01 SHARP CORP. (6M2.61E) Printed in U.S.A...

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