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LG MS-194A Service Manual

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MICROWAVE OVEN
SERVICE MANUAL
MODEL: MS-194A
CAUTION
BEFORE SERVICING THE UNIT, READ THE
SAFETY PRECAUTIONS IN THIS MANUAL.

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Summary of Contents for LG MS-194A

  • Page 1 MICROWAVE OVEN SERVICE MANUAL MODEL: MS-194A CAUTION BEFORE SERVICING THE UNIT, READ THE SAFETY PRECAUTIONS IN THIS MANUAL.

  • Page 2: Safety Precautions

    SAFETY PRECAUTIONS This device is to be serviced only by properly qualified service personnel. Consult the service manual for proper service procedures to assure continued safety operation and for precautions to be taken to avoid possible exposure to excessive microwave energy. PRECAUTIONS TO BE OBSERVED BEFORE AND DURING SERVICING TO AVOID POSSIBLE EXPOSURE TO EXCESSIVE MICROWAVE ENERGY...

  • Page 3: Table Of Contents

    CONTENTS (Page) SAFETY PRECAUTIONS - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - Inside front cover SPECIFICATIONS - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - 1-1 CAUTIONS - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - 2-1 INSTALLATIONS - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - 3-1...

  • Page 4: Specifications

    SPECIFICATIONS ITEM DESCRIPTION MS-194A MODEL 230 Volts AC 60 Hz Power Requirement 1,200 Watts Single phase, 3 wire grounded Power Output 800 Watts full microwave power (IEC705) 2,450 MHz Microwave Frequency Magnetron 2M214 - 39F, 2M218J, 2M254J 0 ~ 99 min. 90 sec.

  • Page 5: Cautions

    CAUTIONS Unlike other appliances, the microwave oven is MICROWAVE RADIATION high-voltage and high-current equipment. Personnel should not be exposed to the Though it is free from danger in ordinary use, microwave energy which may radiate from the extreme care should be taken during repair. magnetron or other microwave generating device if it is improperly used or connection.

  • Page 6: Installations

    INSTALLATIONS BEFORE YOU BEGIN, READ THE FOLLOWING INSTRUCTIONS COMPLETELY AND CAREFULLY. INSTALLING EARTHING INSTRUCTIONS 1. Empty the microwave oven and clean inside it with This microwave oven is designed to be used in a fully a soft, damp cloth. Check for damage such as earthed condition.

  • Page 7: Operating Instructions

    OPERATING INSTRUCTIONS FEATURES Oven Frot Plate Window Door Screen Door Seal Display Window Control Panel Safety Door Lock System Turntable Rotating Ring CONTROL PANEL 1. INDICATORS 2. SET CLOCK: Used to set the time of day. 3. AUTO COOK: Used to cook the foods listed by one touch.

  • Page 8: Operating Sequence

    OPERATING SEQUENCE The following is a description of component functions 5. MULTI-STAGE MICROWAVE during oven operation. COOKING 1. SETTING THE CLOCK STAGE 1 Desired Desired Stop Set the power level cooking time Stop clock clock correct time STAGE 2 ex) To set 4:35, Press 10 min four times. Press 1 min three times.

  • Page 9: Schematic Diagram

    SCHEMATIC DIAGRAM...

  • Page 10: Circuit Description

    CIRCUIT DESCRIPTION • A high voltage of approximately 2100 volts AC is GENERAL DETAILS generated in the secondary of the high voltage • The low voltage transformer supplies the necessary transformer which is increased by the action of the high voltage to the micom controller when power cord is voltage diode and charging of the high voltage plugged in.

  • Page 11: Service Information

    SERVICE INFORMATION TOOLS AND MEASURING INSTRUMENTS NECESSARY TOOLS NECESSARY MEASURING INSTRUMENTS Tools normally used for TV servicing are sufficient. • TESTER(VOLTS-DC, AC., Ohmmeter) Standard tools are listed below. • Microwave survey meter • Diagonal pliers - Holaday HI-1500 • Long nose pliers HI-1501 •...
  • Page 12 MEASUREMENT WITH OUTER CASE NOTES WHEN MEASURING REMOVED • Do not exceed meter full scale deflection. • The test probe must be removed no faster than • When you replace the magnetron, measure for 1 inch/sec (2.5 cm/sec) along the shaded area, microwave energy leakage before the outer case is otherwise a false reading may result.

  • Page 13: Measurement Of Microwave Power Output

    MEASUREMENT OF MICROWAVE POWER OUTPUT • Microwave power output measurement is made with • The microwave power output P in watts is calculated the microwave oven supplied at its rated voltage and from the following formula : operated at its maximum microwave power setting with 4187 x (∆T) a load of (1000±5) g of potable water.
  • Page 14 D. DOOR GROSS ASSEMBLY REMOVAL E. HIGH VOLTAGE TRANSFORMER 1) Open the door. REMOVAL 2) Remove the choke cover cap very carefully with a 1) Discharge the high voltage capacitor. flat-blade screwdriver. 2) Disconnect the leadwire from magnetron, high voltage CAUTION : Be careful not to damage door seal plate transformer, and capacitor.
  • Page 15 H. AIR DUCT ASSEMBLY REMOVAL L. REMOVING THE TURNTABLE MOTOR 1) Remove the turntable. 1) Disconnect the leadwire from the lamp. 2) Remove the turntable shaft VERY CAREFULLY. 2) Remove the mounting screw to the latch board. 3) Lay the unit down on its back. 4) Remove the turntable motor cover.
  • Page 16 K. PCB ASSEMBLY REMOVAL L. INTERLOCK SYSTEM 1) Remove the control panel assembly from the 1) INTERLOCK MECHANISM cavity. (Refer to control panel assembly removal The door lock mechanism is a device which has on previous page.) been specially designed to eliminate completely 2) Remove screws which hold the PCB SUB ASS’Y to microwave activity when the door is opened during the control panel.

  • Page 17: Interlock Continuity Test

    INTERLOCK CONTINUITY TEST WARNING : FOR CONTINUED PROTECTION AGAINST EXCESSIVE RADIATION EMISSION, REPLACE ONLY WITH IDENTICAL REPLACEMENT PARTS. TYPE NO. SZM-V 16-FA-63 OR VP-533A-OF FOR PRIMARY SWITCH TYPE NO. SZM-V 16-FA-62 OR VP-532A-OF FOR MONITOR SWITCH TYPE NO. SZM-V 16-FA-63 OR VP-533A-OF FOR SECONDARY SWITCH B.

  • Page 18: Component Test Procedure

    COMPONENT TEST PROCEDURE CAUTIONS 1. DISCONNECT THE POWER SUPPLY CORD FROM THE OUTLET WHENEVER REMOVING THE OUTER CASE FROM THE UNIT. PROCEED WITH THE TEST ONLY AFTER DISCHARGING THE HIGH VOLTAGE CAPACITOR AND REMOVING THE WIRE LEADS FROM THE PRIMARY WINDING OF THE HIGH VOLTAGE TRANSFORMER.
  • Page 19 COMPONENTS TEST PROCEDURE RESULTS Antenna Gasket Chassis Filament Terminals NOTE: When testing the magnetron, be sure to install the magnetron gasket in the correct position and be sure that the gasket is in good condition. HIGH VOLTAGE Measure the resistance. Normal: Momentarily indicates CAPACITOR (Ohm-meter scale: Rx1000)
  • Page 20 COMPONENTS TEST PROCEDURE RESULTS Check for continuity of relay 2 with an RELAY 2 POWER ohm-meter. LEVEL (Remove wire leads from relay 2 and operate the unit.) 6 sec 16 sec 10 sec 12 sec Relay 1 14 sec 8 sec Relay 2 18 sec 4 sec...

  • Page 21: Trouble Shooting

    TROUBLE SHOOTING WHEN YOU GET A COMPLAINT FROM YOUR CUSTOMER, EVALUATE THE COMPLAINT CAREFULLY. IF THE FOLLOWING SYMPTOMS APPLY, PLEASE INSTRUCT THE CUSTOMER IN THE PROPER USE OF THE MICROWAVE OVEN. THIS CAN ELIMINATE AN UNNECESSARY SERVICE CALL. CAUTIONS 1. Check grounding before checking for trouble. 2.
  • Page 22 (TROUBLE 1) The following visual conditions indicate a probable defective control circuit. 1. Incomplete segments. • Segment missing. • Partial segment missing. • Digit flickering (NOTE:Slight flickering is normal.) 2. Colon does not turn on or blink. 3. A distinct change in the brightness of one or more numbers in display. 4.
  • Page 23 (TROUBLE 2) Oven does not operate at all; Display window does not display any figures, and no input is accepted. CONDITION CHECK RESULT CAUSE REMEDY Malfunction of the Replace fuse, Check continuity 1. Fuse blows. Continuity. monitor switch. primary, monitor of monitor switches, and switch (with...
  • Page 24 (TROUBLE 3) Display shows all figures set, but oven does not start cooking while desired program times are set and START pad is touched. CONDITION CHECK RESULT CAUSE REMEDY Defective Replace Check continuity 1. Setting time No continuity. secondary switch. secondary switch.
  • Page 25 (TROUBLE 5) No microwave oscillation even though oven lamp and fan motor run. (Display operates properly) CONDITION CHECK RESULT CAUSE REMEDY No microwave Defective PCB Replace PCB Disconnect the No continuity. oscillation. assembly. assembly. wire leads from relay 2 and check continuity Continuity.
  • Page 26 (TROUBLE 5) No microwave oscillation even though oven lamp and fan motor run. (Display operates properly) CONDITION CHECK RESULT CAUSE REMEDY Defective PCB Replace PCB Output is full power Disconnect the Abnormal. assembly. assembly. when you set lower wire leads from power level.

  • Page 27: Exploded View

    EXPLODED VIEW INTRODUCTION OVEN CAVITY PARTS INTERIOR PARTS BASE PLATE PARTS DOOR PARTS LATCH BOARD PARTS CONTROL PANEL PARTS...
  • Page 28 DOOR PARTS 13581A 15006A 13536A 13552A 13213A 13720D 13352A 14026A 14970A...
  • Page 29 CONTROL PANEL PARTS 24781M 24930D 268711 23550D 23572A WTP018 26638A...
  • Page 30 OVEN CAVITY PARTS WTT021 33112U 33052M 340511 33390G 34960A 35889A 34036W 36549S WTP013...
  • Page 31 LATCH BOARD PARTS 43501A 43500A WSZ085 466001 466003 466002 44510A...
  • Page 32 INTERIOR PARTS 568771 WSZ062 50FZZA 56411A 56930V 56201A WTT028 56549F 54974S WSZ002 55900A WTT037 WSZ002 56851D 56912B WSZ002 50CZZH 56851C 55262A WTT028 54810C 56324A WSZ002 56201B...
  • Page 33 BASE PLATE PARTS 56170D 63302A 63303A WTT021 65006B WSZ002...
  • Page 34 2-1. Function & Type (1/2) 1. How a Microwave Oven Works The microwave oven is one of the great inventions of the 20th century - millions of homes in world have one. Microwave ovens are popular because they cook food incredibly quickly. They are also extremely efficient in their use of electricity because a microwave oven heats only the food - nothing else.
  • Page 35 2-1. Function & Type (2/2) 2) GRILL COOKING This is a method of cooking with radiant heat from the grill heater on the top of the oven. This is a traditional way of cooking which quickly seals and browns food evenly.
  • Page 36 2-2. Installation & Utensils (1/2) 1. Installation 5. Fill a microwave safe container 1. Unpack your oven and place it on a flat level surface. with 300 ml (1/2 pint) of water. 2. Place your oven in the level location of tour choice with more Place on the GLASS TRAY and than 85cm height but make sure there is at least 30cm of space close the oven door.
  • Page 37 2-2. Installation & Utensils (2/2) 2.COOKING UTENSILS 3.Plastic dishes, cups, freezer bags, and plastic wraps may be Utensils should be checked to ensure that they are suitable for use used in the microwave oven. Follow the manufacturer’s in the microwave oven. instructions or the information given in the cookbook when The following chart summaries the proper use of cooking utensils using plastics in the microwave oven.
  • Page 38 3-1. What’s the microwave? (1/2) 1. History of dielectric heating In 1945, Dr. Spencer working for RAYTHEON Co. in the U.S.A found out a pieces of chocolate in his pocket melting suddenly by the electric wave (ultra high frequency wave using for radar) on his experiment for radar. then began research in heating matters by the electric wave.
  • Page 39 3-1. What’s the microwave? (2/2) 3. The safety of microwave oven Since the microwave oven can’t make the native fire like gas, you have no use for worrying about the fire. Because it doesn’t become hot like the ordinary electric range. It has been used in the dinner car of the trains etc. Microwave oven has the shielded structure strictly with metal case not to leak electric wave at once not only using but on opening the door.
  • Page 40 3-2. Conventional heating vs. dielectric heating 2. Dielectric heating 1. Conventional heating 1) The heating is uniform. FIRE! FIRE! FIRE! 2) The temperature rise is fast (high). 3) If you break the electric power: The microwave oven stops FIRE! FIRE! HEAT! heating at once, so you can’t heat something with the heat of their surroundings.
  • Page 41 4-1. Construction of microwave oven Cavity Cabinet locking in microwave and holding food. Door Gate coming in and out food. Magnetron It has window Inject microwave and seal to oven. structure OVEN CAVITY PARTS Controller INTERIOR PARTS Control and supervise BASE PLATE PARTS DOOR PARTS operating state...
  • Page 42 4-2. How does the microwave oven operate? After plugging your oven into a standard household socket, press start button or turn the timer. And then switches (primary, secondary, timer) close the circuit. Eventually the input power will be applied to turntable motor, timer motor, fan motor, oven lamp and high voltage transformer. A high voltage of 2,100 volts AC is generated in the second winging of H.V.Transformer.
  • Page 43 4-3. WARNING - High voltage circuit ( 4,000 volt ) * The half-wave voltage doubler circuit consists of the secondary winding of the high voltage transformer, H.V. diode (rectifier), and H.V. capacitor. The H.V. diode allows alternating current (AC) to flow in one direction only and INPUT INPUT rectifies it to pulsating direct current (DC).
  • Page 44 4-4. Microwave generation system_Magnetron (1/2) GASKET ANTENNA (OUTPUT) FILAMENT (CATHODE) MAGNET (MAGNETIC CIRCUIT) ANODE MAGNET (FERRITE) VANE FILAMENT TERMINALS FEED THROUGH CAPACITOR FILTER CASE FILTER * The magnetron is the energy source for the microwave oven. The magnetron is a vacuum tube of special construction. ANTENNA It is basically a diode with addition of a magnetic field.
  • Page 45 4-4. Microwave generation system_Magnetron (2/2) * In order to create an electron flow from cathode to anode, the cathode must be heated and a potential difference must exist between the two. 2,450 MHz. This is accomplished by heating the cathode with 3, 4 to 3,5 V AC. ( from the ANTENNA filament winding of the high voltage transformer) and applying a negative 4000 V DC (from the voltage doubler circuit) to the cathode.
  • Page 46 5-1. Multiwave system What is Multi-Wave • The multi-Wave system heats food more evenly than convectional microwave ovens. - 20 -...
  • Page 47 LG microwave oven reduce cooking time. Our revolutionary Infrared sensor makes it 3 times faster than the ordinary microwave. Infrared eye tracks the exact temperature of food and regulates the power of the microwave so that the temperature reaches you actually set.
  • Page 48 We changed the old way. LG heater is moving when you choose grill, the heater goes down. The angle of heater varies as to each menu. You don’t have to worry about safety. The heater moves back to it’s position automatically after grilling.

  • Page 49: Schematic Diagram Of P.c.b

    SCHEMATIC DIAGRAM OF P.C.B...

  • Page 50: Printed Circuit Board

    PRINTED CIRCUIT BOARD...

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