LG LMH2235ST Service Manual
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LG LMH2235ST Service Manual

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삼
삼
흥
흥
정
정
판
판

MICROWAVE OVEN

SERVICE MANUAL
MODEL: LMH2235ST
CAUTION
BEFORE SERVICING THE UNIT, READ THE SAFETY PRECAUTIONS IN THIS MANUAL.
P/NO : MFL06272534
Internal Use Only
Website: http://biz.lgservice.com
June, 2014
Printed in Korea

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  • Page 1: Microwave Oven

    삼 삼 흥 흥 정 정 판 판 Internal Use Only Website: http://biz.lgservice.com MICROWAVE OVEN SERVICE MANUAL MODEL: LMH2235ST CAUTION BEFORE SERVICING THE UNIT, READ THE SAFETY PRECAUTIONS IN THIS MANUAL. June, 2014 P/NO : MFL06272534 Printed in Korea...

  • Page 2: Safety Precautions

    CAUTION WARNING TO SERVICE TECHNICIANS PRECAUTIONS TO BE OBSERVED BEFORE AND DURING SERVICING TO AVOID POSSIBLE EXPOSURE TO EXCESSIVE MICROWAVE ENERGY a. Do not operate or allow the oven to be operated with the door open. b. Make the following safety checks on all ovens to be serviced before activating the magnetron or other microwave source, and make repairs as necessary;...

  • Page 3: Table Of Contents

    FOREWORD Read this manual carefully. Failure to adhere to or observe the information in this manual may result in exposing yourself to the microwave energy normally contained within the oven cavity. CONTENTS (Page) Safety Precautions .............................. 2 1. Specifications ..............................4 2.

  • Page 4: Specifications

    1. SPECIFICATIONS Rated Power Consumption ........ 1600W maximum (Microwave oven+Cook top lamps+Ventilation fan) Microwave Output ..........1000W (IEC60705) Frequency ............2450 MHz ±50 MHz Power Supply ............. 120 VAC, 60 Hz Rated Current ............ 14 Amp. (Microwave oven+Cook top lamps+Ventilation fan) Magnetron Cooling ..........

  • Page 5: Cautions

    2. 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 connected.

  • Page 6: Installation

    3. INSTALLATION BEFORE YOU BEGIN, READ THE FOLLOWING INSTRUCTIONS COMPLETELY AND CAREFULLY. PRECAUTIONS ON INSTALLATION A. Plug the power supply cord into a 120V AC, 60Hz, single-phase power source with a capacity of at least 20 amperes. B. Avoid placing the unit in a location where there is direct heat or splashing water.

  • Page 7: Operation

    4. OPERATION 4-1. Control Panel...

  • Page 8: Explanation Of Control Panel

    4-2. Explanation of Control Panel 1. DISPLAY The Display includes a clock and 14. TIMER indicators to tell you the time of day, cooking time 15. NUMBER Press this button to enter cooking settings and cooking functions selected. time, power level, quantities or weights. 2.

  • Page 9: Wiring Diagram / Key Matrix

    5. WIRING DIAGRAM / KEY MATRIX 5-1. Wiring Diagram CAPACITOR C. L. (LED) 21VAC...

  • Page 10: Key Matrix

    5-2. Key Matrix KEY MATRIX Clear Vent Hi/Low/Off Clock Energy Saving Add 30 Sec. Quick Defrost Soften Melt Timer Sensor Reheat Less time & weight Sensor Popcorn Sensor Cook More Defrost Start C/T Lamp On/Off Hold Warm Time Cook Power Level Turntable On/Off -10-...

  • Page 11: Troubleshooting

    6. TROUBLESHOOTING 6-1. General Information for Service GENERAL PRECAUTIONS IN USE FEATURES AND SPECIFICATIONS FEATURES A. Never operate the unit when it is empty. A. The safety systems incorporated in this model Operating the oven with no load may shorten the are: life of the magnetron.

  • Page 12: Safety Caution

    6-2. Safety Caution A. SINCE NEARLY 4,000 VOLTS EXISTS IN (3) Do not operate the unit until it is completely SOME CIRCUITS OF THIS UNIT REPAIRS repaired. If any of the following conditions exist, SHOULD BE CARRIED OUT WITH GREAT the unit must not be operated.

  • Page 13: Basic Check Summary

    6-3. Basic Check Summary Symptom: Dead Check: Open/Short CAPACITOR C. L. (LED) 21VAC Symptom #1(Door is closed): No key, Not started, Operating O.L, V.M, T.T.M. Symptom#1(Door is closed): Not Check: Open/Short when the door cooking, Not operating V.M, T.T.M. is closed. (Switch) Check: Open/Short when the door Symptom #2(Door is open): Not is closed.

  • Page 14: Troubleshooting

    6-4. Troubleshooting No Display or Dead Symptom: Dead Check: Open/Short Symptom: Dead Check: Open/Short CAPACITOR Symptom: No display Check: connection C. L. (LED) 21VAC -14-...
  • Page 15 Is there any beeping sound Replace the Does the display operate? in the continuity test between Fuse. the ends of the fuse? Go to No. 6 of When you push any Key, is this flow chart. there any beeping sound? Power Off 2 Is the connector connected Reconnect or...
  • Page 16 Keypad Failure -16-...
  • Page 17 3 When the door is opened, Do the keys operate? Replace the PCB is the voltage of the door (EBR75341201) sensing part over 4 V? (CN3 Pin1 and Pin2) Power ON 1 Do only the START key and Check PWB EZ-ON keys operate? Go to No.
  • Page 18 No Heat / No Cook CAPACITOR C. L. (LED) 21VAC -18-...
  • Page 19 3 While the product is After power on, does the Replace the product operate? operating under EZ-ON start, Relay 2 is the voltage of both ends of the D35 over 8 V? 1 Repeat Door Open and close Alternate at least three times. explanation Does product operate? (refer to the...
  • Page 20 Power Off 7 Is the resistance of the high Replace the 5 Is there any beeping sound High Voltage Adjust the latch voltage Transformer out of board Transformer. in the continuity test between range? (Refer to section the ends of the latch board? 9-1,9-2) (Door should be closed) Test Point...
  • Page 21 8 Is the connector connected 11 Is the resistance of the high Reconnect or Replace the to High Voltage capacitor repair voltage diode out of range? high voltage assembly disconnected or the connector. (refer to section 10) Diode. disassembled? Forward Forward Forward Forward...
  • Page 22 3 Push the EZ-ON button Turntable Motor Does Not Work Replace the PCB (operate).Is the voltage of (EBR75341201) both ends of the D37 over 8 Power ON 1 Does the turntable motor Replace the operate? turntable motor. 2 When door is closed, Adjust the Primary latch does the oven lamp turn on?
  • Page 23 4 When the door is opened, Is Turns on automatically Replace the PCB the voltage of the door (EBR75341201) sensing part over 4 V? Does the product turn on (Pin 11 to Pin 12) automatically without pushing the start key? 1 Repeat door open and close Alternate at least three times.

  • Page 24: Microwave Leakage Test

    7. MICROWAVE LEAKAGE TEST CAUTION EQUIPMENT- • Be sure to check microwave leakage prior to • TESTER ((VOLTS-DC, AC, Ohmmeter) servicing the oven if the oven is operating prior to • Microwave survey meter servicing. - Holaday HI-1500 • Service personnel should inform the HI-1501 manufacturer, importer, or assembler of any - Narda...
  • Page 25 MEASUREMENT WITH THE OUTER NOTE WHEN MEASURING CASE (1) Do not exceed meter full scale deflection. (2) The test probe must be removed no faster than REMOVED 1 inch/sec (2.5cm/sec)along the shaded area, (1) When you replace the magnetron, measure for otherwise a false reading may result.

  • Page 26: Power Output Measurement

    8. POWER OUTPUT MEASUREMENT (1) Microwave power output measurement is made 4.187 Mw(T2 –T1)+0.55Mc(T2 –T0) with the microwave oven supplied at its rated voltage and operated at its maximum microwave power setting is measured while the microwave generator is with a load of (1000 ± 5) g of potable water. operating at full power.

  • Page 27: Interlock System

    9. INTERLOCK SYSTEM 9-1. Interlock Mechanism The door lock mechanism is a device which has been specially designed to eliminate completely microwave activity when the door is opened during cooking and thus to prevent the danger resulting from microwave leakage. ADJUSTMENT PROCEDURES CHECK THE DOOR LATCH AND SWITCH To avoid possible exposure to microwave energy...
  • Page 28 SPECIFICATIONS TEST THE LATCH AND SWITCH SEQUENCE fuse. (7) When you achieve the proper sequence of (5) Open the oven door slowly. Watch the door latch switches in Steps 5 and 6, tighten the latch board and the Secondary Switch. Release the rod and screws at that point.

  • Page 29: Interlock Continuity Test

    9-2. Interlock Continuity Test A. PRIMARY INTERLOCK SWITCH TEST B. SECONDARY INTERLOCK SWITCH TEST When the door is opened slowly, an audible click Disconnect the wire lead from the secondary should be heard at the same time or successively switch. at intervals and the latches should activate the Connect the ohmmeter leads to the common switches with an audible click.

  • Page 30: Component Testing Information

    10. COMPONENT TESTING INFORMATION CAUTION 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 LEAD WIRES FROM THE PRIMARY WINDING OF THE HIGH VOLTAGE TRANSFORMER. 2.
  • Page 31 COMPONENTS TEST RESULTS 1. Remove wire leads. CAPACITOR 2. Measure resistance. (ohm meter scale: Rx1000) • Terminal to terminal Normal: Momentarily Infinite and then soon reach 10 mega. ohms • Terminal to case Normal: Infinite. 1. Measure continuity. Forward. Normal: Below 100 ohms DIODE (ohm meter scale: Rx1000) Abnormal:Infinite...
  • Page 32 COMPONENTS TEST RESULTS 1. Remove wire leads. Normal: TURNTABLE MOTOR 2. Measure resistance. Approximately (ohm meter scale: Rx1000) 2.5 to 3.5 Kohms Abnormal: Infinite or several. Nmornal: 1. Unplug microwave oven or disconnect power. NOISE FILTER L(1)-L(2)(coil):Less than 2. Remove wire 1 ohm 3.
  • Page 33 COMPONENTS TEST RESULTS Measure the resistance between terminal TOUCH KEY BOARD When When not pins of connector KEY CONNECTOR. touched touched NOTE: Resistance When reconnecting the FPC connector, value More than Less than make sure that the holes on the FPC 1 megaohm 400 ohms connector are properly engaged with hooks...

  • Page 34: Disassembly Instructions

    11. DISASSEMBLY INSTRUCTIONS IMPORTANT NOTES: (4) Remove 5 screws securing the circuit board. THE UNIT MUST BE DISCONNECTED FROM THE ELECTRICAL OUTLET WHEN MAKING REPAIRS, REPLACEMENTS, ADJUSTMENTS AND CONTINUITY CHECKS. WHEN RECONNECTING THE WIRE LEADS TO ANY PART, MAKE SURE THE WIRING CONNE- CTIONS AND LEAD COLORS ARE CORRECTLY MATCHED ACCORDING TO THE OVERALL CIR- CUIT DIAGRAM.
  • Page 35 B. REMOVING THE OUTER CASE(Figure 8) (1) Remove the vent grille by removing the two screws securing it to the outer case. (2) Remove the two screws securing it to the air duct. (3) Remove the mounting plate by loosening the screws (1 or 2 screws) securing it to the outer case.
  • Page 36 C. REMOVING THE DOOR INTERLOCK SWITCHES (Figures 9, 10) (1) Disconnect the wire leads from the interlock switches. (2) Remove the two screws securing the Latch Board. (3) Make any necessary replacements and check for microwave energy leakage according to ADJUSTMENT PROCEDURES on page 7-12.
  • Page 37 D. REMOVING MAGNETRON E. REMOVING STIRRER FAN (Figures 11 Through 12) (Figures 13 and 14) (1) Remove the vent grill by loosening the one (1) Remove one rivet assembly securing it to the screws.(Figure 11) oven upper plate by using a knife blade. (2) Remove fan bracket and outer case.
  • Page 38 F. REMOVING DOOR (Figure 15) H. ASSEMBLING DOOR (1) Remove the vent grille by loosening the two (1) When mounting the door assembly to the oven screws securing it to the outer case. assembly, be sure to adjust the door assembly (2) Lift up and draw out the door.
  • Page 39 J. REMOVING THE TURNTABLE MOTOR (1) Remove the glass tray and rotating ring. (2) Remove the turntable shaft VERY CAREFULLY with one hand. (Figure 18) (3) Remove the base plate by removing the 8 screws securing it to the oven cavity. (Figure 19) (4) Disconnect the lead wire from the turntable motor terminals.

  • Page 40: Exploded View

    #EV# 12. EXPLODED VIEW INTRODUCTION Customer Model Product Code SVC Model OVEN CAVITY PARTS INTERIOR PARTS DOOR PARTS LATCH BOARD PARTS CONTROL PANEL PARTS -40-...

  • Page 41: Door Parts

    #EV# DOOR PARTS 1004 1005 1002 1000 1381 W262 1006 1007 1009 -41-...

  • Page 42: Controller Parts

    #EV# CONTROLLER PARTS 2004 2006 2008 2381 W262 -42-...
  • Page 43 #EV# OVEN CAVITY PARTS 3010 3024 3029 303L 3029 3036 3001 303R 3036 3034 3018 -43-...
  • Page 44 #EV# LATCH BOARD PARTS 4000 4002 W102 4001 4003 4004 4002 -44-...
  • Page 45 #EV# INTERIOR PARTS(I) 3002 5016 3012 5014 3008 5009 5030 3037 5023 5049 W101 5002 3009 5000 5008 5018 5116 5034 5022 -45-...
  • Page 46 #EV# INTERIOR PARTS(II) 3027 5015 5074 5010 5011 5038 5041 5001 5412 5006 5102 5068 5012 W140 5037 5073 5075 5004 5206 5069 5007 5103 W265 W248 5024 5058 5043 5044 3004 -46-...
  • Page 47 #EV# BASE PLATE PARTS 3250 3110 3055 W297 W311 3231 3053 3401 3110 3053 3093 3093 W311 3402 W311 3107 3109 3241 3230 W311 3026 6017 3108 3107 3109 5337 6381 W299 3251 3026 3108 3240 4100 6001 W299 3075 5036 3005 W311...
  • Page 48 #EV# INSTALLATION PARTS 6008 6011 6010 6009 VINYL -48- -48-...

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