LG LMH2235ST Service Manual Download Page 1

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MICROWAVE OVEN

SERVICE MANUAL

MODEL: LMH2235ST

CAUTION

BEFORE SERVICING THE UNIT, READ THE SAFETY PRECAUTIONS IN THIS MANUAL.

P/NO : MFL06272534

June, 2014

Printed in Korea

Website: http://biz.lgservice.com

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Internal Use Only

Summary of Contents for LMH2235ST

Page 1: ...VE OVEN SERVICE MANUAL MODEL LMH2235ST CAUTION BEFORE SERVICING THE UNIT READ THE SAFETY PRECAUTIONS IN THIS MANUAL P NO MFL06272534 June 2014 Printed in Korea Website http biz lgservice com 삼 흥 정 판 Internal Use Only ...

Page 2: ... proper alignment integrity and connections d Any defective or misadjusted components in the interlock monitor door seal and microwave generation and transmission systems shall be repaired replaced or adjusted by procedures described in this manual before the oven is released to the owner e A microwave leakage check to verify compliance with the federal performance standard should be performed on ...

Page 3: ...7 4 1 Control Panel Features 7 4 2 Explanation of Control Panel 8 5 Wiring Diagram Key Matrix 9 5 1 Wiring Diagram 9 5 2 Key Matrix 10 6 Troubleshooting 11 6 1 General Information for Service 11 6 2 Safety Caution 12 6 3 Basic Check Summary 13 6 4 Troubleshooting 14 7 Microwave Leakage Test 24 8 Power Output Measurement 26 9 Interlock System 27 9 1 Interlock Mechanism 27 9 2 Interlock Continuity T...

Page 4: ...h Magnetron 2M246 050GP Cook Top Lamp DC 12V LED Lamp Cavity Lamp 125 V 30 W or 40 W Timer Digital up to 99 min 99 sec in each cooking stage Tray Tempered Safety Glass Overall Dimensions 2914 16 W x 17 13 18 H x 15 12 16 D Oven Cavity Size 22 W x 115 8 H x 14 5 8 D Effective Capacity of Oven Cavity 2 2Cu ft Accessories Owner s Manual Cooking Guide Installation Manual Exhaust Adapter Exhaust Damper...

Page 5: ...ng operation BEFORE TOUCHING any parts of the oven always remove the power plug from the outlet Remove your watches whenever working close to or replacing the magnetron DO NOT touch any parts of the control panel circuit A resulting static electric discharge may damage the P C B NEVER operate the oven with no load NEVER injure the door seal and front plate of the oven cavity NEVER put iron tools o...

Page 6: ...dio etc to prevent interference GROUNDING INSTRUCTIONS For personal safety this appliance must be fully grounded at all times In the event of an electrical short circuit grounding reduces the risk of electric shock The plug must be plugged into an outlet that is properly installed and grounded CAUTION This unit is equipped with a 3 prong plug for your safety If the wall outlet is a grounded 3 hole...

Page 7: ... 7 4 OPERATION 4 1 Control Panel 2 1 9 12 10 20 23 18 6 5 4 11 21 24 25 16 7 8 15 19 14 13 17 22 3 ...

Page 8: ...fault setting for sound clock disply speed and defrost weight 11 POWER LEVEL Press this button to select a cooking power level 12 CLOCK Press this button to enter the time of day 13 COOK TIME Press this button to set a cooking time 14 TIMER 15 NUMBER Press this button to enter cooking time power level quantities or weights 16 START ENTER Press this button to start a function If you open the door a...

Page 9: ...iagram BK C L RD BN YL YL 21VAC CAPACITOR BK PK WH BN GY WH RD WH RD BN YL H W WH H W H V FUSE 180 60 356 140 WH WH YL PK LED YL W O L H G I H O B R U T VL 1 2 3 4 5 6 7 8 SLOW WH OG YL BL YL PK PK GY BL RD 7 4 10 RD BN BL 1 2 3 4 5 6 7 8 BK WH ...

Page 10: ... Warm C T Lamp On Off Start 13 More Sensor Cook time weight Defrost N A N A N A N A SensorPopcorn 12 Less Sensor Reheat Timer 0 9 8 7 11 Melt 6 5 4 3 2 1 10 Soften Quick Defrost Add 30 Sec Energy Saving Clock Vent Hi Low Off Clear 9 8 7 6 5 4 3 2 1 2st KEY MATRIX ...

Page 11: ...ay window will show the time counting down by seconds D After about 5 minutes make sure the primary interlock switch the secondary interlock switch and the interlock monitor switch operate properly by opening and closing the door several times Press the START button each time the door is closed E Continue operating the unit Two short beeps and one long beep will sound when the time is up The unit ...

Page 12: ...rmly b The hinge is broken c The door seal is damaged d The door is bent or warped or there is any other visible damage on the unit that may cause microwave energy leakage NOTE Always keep the seal clean e Make sure that there are no defective parts in the interlock mechanism f Make sure that there are no detective parts in the microwave generating and transmission assembly especially waveguide 4 ...

Page 13: ... is open Switch Symptom 1 Door is closed No key Not started Operating O L V M T T M Check Open Short when the door is closed Switch Symptom 2 Door is open Not turned on O L Check Open Short when the door is open Switch BK C L RD BN YL YL 21VAC CAPACITOR BK PK WH BN GY WH RD WH RD BN YL H W WH H W H V FUSE 180 60 356 140 WH WH YL PK LED YL W O L H G I H O B R U T VL 1 2 3 4 5 6 7 8 SLOW WH OG YL BL...

Page 14: ...heck Open Short Symptom No display Check connection BK C L RD BN YL YL 21VAC CAPACITOR BK PK WH BN GY WH RD WH RD BN YL H W WH H W H V FUSE 180 60 356 140 WH WH YL PK LED YL W O L H G I H O B R U T VL 1 2 3 4 5 6 7 8 SLOW WH OG YL BL YL PK PK GY BL RD 7 4 10 RD BN BL 1 2 3 4 5 6 7 8 BK WH ...

Page 15: ...the connector Is there any beeping sound in the continuity test between the power cord and the connector Code L to Pin1 Code N to Pin3 No Yes Check PCB Go to No 6 of this flow chart Go to No 6 of this flow chart Is there any beeping sound in the continuity test between the ends of the fuse Yes No Replace the Fuse 5 Is there any beeping sound in the continuity test between the ends of the noise fil...

Page 16: ... 16 Keypad Failure ...

Page 17: ... Door should be closed Power ON Yes No Adjust latch board Refer to section 9 1 9 2 Check PWB Go to No 4 of this flow chart 3 When the door is opened is the voltage of the door sensing part over 4 V CN3 Pin1 and Pin2 Yes No Replace the PCB EBR75341201 Reconnect or repair the connector Replace the PCB EBR75341201 4 Is the connector connected to the PCB disconnected or disassembled No Yes Replace the...

Page 18: ...D BN YL YL 21VAC CAPACITOR BK PK WH BN GY WH RD WH RD BN YL H W WH H W H V FUSE 180 60 356 140 WH WH YL PK LED YL W O L H G I H O B R U T VL 1 2 3 4 5 6 7 8 SLOW WH OG YL BL YL PK PK GY BL RD 7 4 10 RD BN BL 1 2 3 4 5 6 7 8 BK WH ...

Page 19: ...and TAB2 No Yes PCB no problem Alternate explanation refer to the Note 3 While the product is operating under EZ ON start is the voltage of both ends of the D35 over 8 V No Yes Replace the Relay 2 4 Replace the PCB EBR75341201 Note If something is caught in the door or in the sealing area the microwave oven cannot operate safely The latch switches and monitor switch will prevent operation ...

Page 20: ...efer to section 9 1 9 2 7 Is the resistance of the high voltage Transformer out of range Test Point 1 Primary winding 0 2 0 5 Ohm 2 Secondary 50 120 Ohm 3 Filament winding 0 Ohm No Yes Replace the High Voltage Transformer 6 Is the connector connected to High Voltage Transformer assembly disconnected or disassembled No Yes Reconnect or repair the connector ...

Page 21: ... the high voltage diode assembly disconnected or disassembled No Yes Reconnect or repair the connector Case ground 12 Is the connector connected to the magnetron assembly disconnected or disassembled Yes Case ground 11 Is the resistance of the high voltage diode out of range refer to section 10 Yes No Replace the high voltage Diode Forward Forward Forward Forward Forward Forward Forward Forward Fo...

Page 22: ... the Primary latch board refer to section 9 1 9 2 Replace the turntable motor Power ON 3 Push the EZ ON button operate Is the voltage of both ends of the D37 over 8 V Yes No Replace the PCB EBR75341201 4 Is there any beeping sound in the continuity test between the ends of two Pin of RY1 Yes No Replace the PCB EBR75341201 5 PCB No Problem ...

Page 23: ... any beeping sound in the continuity test between the ends of the latch board Secondary switch Door should be closed Yes No Adjust latch board refer to section 9 1 9 2 Power ON 4 When the door is opened Is the voltage of the door sensing part over 4 V Pin 11 to Pin 12 Yes No Replace the PCB EBR75341201 4 Is there any beeping sound in the continuity test between the ends of the two pins of RY1 No Y...

Page 24: ...icing The power density of the microwave radiation leakage emitted by the microwave oven should not exceed 1mW cm2 sq Always start measuring of an unknown field to assure safety for operating personnel from radiation leakage NOTE The standard is 5mW cm2 sq while in the customer s home 1mW cm2 sq stated here is manufacturer s own voluntary standard for units in customer s home EQUIPMENT TESTER VOLT...

Page 25: ...meter full scale deflection 2 The test probe must be removed no faster than 1 inch sec 2 5cm sec along the shaded area otherwise a false reading may result 3 The test probe must be held with the grip portion of the handle A false reading may result if the operator s hand is between the handle and the probe 4 When testing near a corner of the door keep the probe perpendicular to the surface making ...

Page 26: ...10 1 K is measured where t is the time in seconds and T is the temperature rise The initial and final water temperatures are selected so that the maximum difference between the final water temperature and the ambient temperature is 5 K 6 The microwave power output P in watts is calculated from the following formula 4 187 Mw T2 T1 0 55Mc T2 T0 t is measured while the microwave generator is operatin...

Page 27: ...removed 1 Set the microwave oven on its side so that you can see the latch board and the switches as shown inFigure 23 a 2 Close the door tightly and check gaps A and B to be sure they are no more than 1 64 0 5 mm See Figure 23 b for close up view of gaps A and B door latches If all gaps are less than 1 64 0 5 mm adjustment of the latch board may not be necessary Go to Steps 5 and 6 to check the s...

Page 28: ...they are zero to the body of the switches in the following sequence Interlock Monitor Switch Primary Interlock Switch Secondary Interlock Switch NOTE The Interlock Monitor Switch is an added safety check on the Primary and Secondary Interlock Switches If the Primary and Secondary Interlock Switches allow the oven to operate with the door open the Monitor Switch will blow the fuse 7 When you achiev...

Page 29: ...ndicate a closed circuit If the secondary switch operation is abnormal make the necessary adjustment or replace the switch making sure to replace it with the same type of switch C MONITOR SWITCH TEST Disconnect the wire lead from the monitor switch Connect the ohmmeter leads to the common COM and normally closed NC terminals of the switch The meter should indicate a closed circuit in the door open...

Page 30: ... wire leads 2 Measure resistance ohm meter scale Rx1 Primary winding Secondary winding Filament winding 3 Measure resistance ohm meter scale Rx1000 Primary winding to ground Filament winding to ground 1 Remove wire leads Install the magnetron seal in the correct position Check that the seal is in good condition 2 Measure resistance ohm meter scale Rx1 Filament terminal 3 Measure resistance ohm met...

Page 31: ...ance in both directions 1 Measure continuity ohm meter scale Rx1 2 Remove the lead wires and operate oven at power level 1 through power level 10 RELAY 2 1 Remove lead wires 2 Measure resistance ohm meter scale Rx1 Turbo speed White and Brown High speed White and Blue Low speed White and Violet Slow speed white and Yellow Normal Turbo speed Approximately 20 25ohms High speed Approximately 40 45ohm...

Page 32: ...or L 2 N 1 or N 2 resistor 1 5M ohms Abnormal 0 ohms Normal under 10ohm Abnormal infinite 1 Remove wire leads 2 Measure resistance ohm meter scale Rx1000 1 Unplug microwave oven or disconnect power 2 Remove wire 3 Measure resistance ohmmeter scale Rx1 test 1 Depart from other components 2 Measure Resistance ohm meter scale Rx1 TURNTABLE MOTOR NOISE FILTER HIGH VOLTAGE FUSE L 1 L 2 N 2 N 1 ...

Page 33: ...ched More than 1 megaohm FPC CONNECTOR Top NOTES A MICROWAVE ENERGY TEST MUST ALWAYS BE PERFORMED WHEN THE UNIT IS SERVICED FOR ANY REASON MAKE SURE THE WIRE LEADS ARE IN THE CORRECT POSITION WHEN REMOVING THE WIRE LEADS FROM THE PARTS BE SURE TO GRASP THE CONNECTOR NOT THE WIRES KEY MATRIX TurntableOn Off PowerLevel TimeCook HoldWarm C TLampOn Off Start 13 More SensorCook time weight Defrost N A ...

Page 34: ... POWER AND CONTROL CIRCUIT BOARD Figures 1 2 and 3 1 Remove the a screw securing the control panel assembly to the oven cavity 2 Remove the control panel by pushing it upward 3 Remove the connectors cn1 cn3 cn5 and wire leads RY1 RY2 from the circuit board 4 Remove 5 screws securing the circuit board CN1 Relay 2 White Relay 5 Blue Relay 2 Relay 1 Circuit Board FPC Connector S1 Control Bracket 5 Re...

Page 35: ... by loosening the screws 1 or 2 screws securing it to the outer case 4 Remove two screws on the left central edge and one screw on the right central edge of the base plate Remove the fan bracket from the outer case by removing one screw securing it to the outer case 5 Remove six screws of the rear cavity 6 Remove the outer case Fan Bracket Door Outer Case Vent Grill Control Panel Power Cord Figure...

Page 36: ...securing the Latch Board 3 Make any necessary replacements and check for microwave energy leakage according to ADJUSTMENT PROCEDURES on page 7 12 YL YL from HVT BR from HVT PK RD from T T mot or Figure 9 Figure 10 WIRE COLOR SYMBOL COLOR WH WHITE BK BLACK BR BROWN RD RED YL YELLOW PK PINK BL BLUE GY GREY GN GREEN N P Not Provided 36 ...

Page 37: ...g the magnetron be sure to install the magnetron gasket in the correct position and be sure that the gasket is in good condition After replacing the magnetron check for microwave energy leakage with a survey meter Checked microwave energy leakage must be below the limit of 5 mW cm2 All service adjustments should be made for minimum microwave energy leakage readings E REMOVING STIRRER FAN Figures 1...

Page 38: ...ver etc 2 Remove the two screws securing it to the door handle CAUTION Be careful not to damage the door seal plate with the screwdriver H ASSEMBLING DOOR 1 When mounting the door assembly to the oven assembly be sure to adjust the door assembly parallel to the chassis Also adjust it so the door has no play between the inner door surface and oven frame assembly If the door assembly is not mounted ...

Page 39: ...by removing the 8 screws securing it to the oven cavity Figure 19 4 Disconnect the lead wire from the turntable motor terminals 5 Remove the 1 screw securing the turntable motor to the oven cavity assembly Figure 20 NOTES Remove the lead wire from the turntable motor VERY CAREFULLY Be sure to grasp the connector not the wires when removing Figure 18 Figure 19 Figure 20 ...

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

Page 41: ... 41 DOOR PARTS 1004 1000 1002 1005 1381 1009 1007 1006 W262 EV ...

Page 42: ... 42 2004 2381 2008 2006 W262 EV CONTROLLER PARTS ...

Page 43: ... 43 OVEN CAVITY PARTS 3010 3001 3034 3036 303R 3018 3036 303L 3024 3029 3029 EV ...

Page 44: ... 44 W102 4000 4001 4004 4002 4003 4002 LATCH BOARD PARTS EV ...

Page 45: ... 45 INTERIOR PARTS I EV 3037 3009 5014 3002 3012 3008 5016 5030 5002 5000 5116 5023 5009 5049 5008 5034 5022 5018 W101 ...

Page 46: ... 46 INTERIOR PARTS II EV 3027 5010 5012 5073 5007 5412 5103 5206 5075 5004 5037 5102 5068 5001 5038 5006 5074 5015 5011 5069 5041 5058 W248 5044 5043 5024 W265 W140 3004 ...

Page 47: ...ARTS EV 6001 4100 3251 3107 3109 3026 3075 3240 W299 3026 3108 3108 5337 6017 5036 4005 3025 3005 W311 6015 3241 W311 W311 W299 3109 3230 3401 3110 3053 3093 3402 3093 3055 3231 3110 3250 3107 W311 W297 3053 W311 6381 ...

Page 48: ... 48 48 INSTALLATION PARTS EV 6011 6010 6009 6008 VINYL BAG ...

Page 49: ......

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