LG LMVH1750SB Service Manual Download Page 10 | Manualshive

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5-2

MATRIX CIRCUIT FOR TOUCH KEY BOARD

5-SPEED

LEVEL

POWER

CUSTOM

POPCORN

SET

ON/OFF

(VENT)

N.C

1

TIME SET

AUTO

CLOCK

STOP/

CLEAR

N.C

ENTER

START/

ON/OFF

LIGHT

ON/OFF

TURNTABLE

REHEAT

COOK

AUTO

COOK

(VENT)

AUTO

TIMER

DEFROST

N.C

8

9

0

AUTO

MORE

COMBI.

SPEED

SOFTEN

N.C

LESS

MELT

CONV.

COOK

CUSTOM

N.C

2

3

MICRO.

4

N.C

5

6

COMBI.

7

EZ-ON

12

13

11

10

8

9

1

2

3

4

5

6

7

KEY MATRIX

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9
10
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12
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Summary of Contents for LMVH1750SB

Page 1: ...OVEN SERVICE MANUAL MODEL LMVH1750SB LMVH1750ST LMVH1750SW CAUTION BEFORE SERVICING THE UNIT READ THE SAFETY PRECAUTIONS IN THIS MANUAL Website http us lgservice com P NO 3828W5S6189 August 2005 Printed in Korea ...

Page 2: ...roper 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 ea...

Page 3: ...RALL CIRCUIT DIAGRAM 5 1 SCHEMATIC DIAGRAM 5 1 MATRIX CIRCUIT FOR TOUCH KEY BOARD 5 2 GENERAL INFORMATION FOR SERVICE 6 1 GENERAL PRECAUTIONS IN USE 6 1 TRIAL OPERATION 6 1 FEATURES AND SPECIFICATIONS FEATURES 6 1 SERVICE INFORMATION 7 1 PRECAUTIONS AND REPAIR SERVICE TIPS 7 1 MICROWAVE LEAKAGE TEST 7 2 POWER OUTPUT MEASUREMENT 7 3 DISASSEMBLY INSTRUCTIONS 7 4 INTERLOCK SYSTEM 7 12 INTERLOCK CONTI...

Page 4: ...ary Interlock Switch Interlock Monitor Switch Magnetron 2M246 Cook top Lamp 130 V 35 W Cavity Lamp 130 V 35 W Timer Digital up to 99 min 99 sec in each cooking stage Tray Tempered Safety Glass Overall Dimensions 2915 16 W x167 16 H x153 8 D Oven Cavity Size 211 4 W x97 16 H x143 16 D Effective Capacity of Oven Cavity 1 7 Cu ft Accessories Use Care Guide Cooking Guide Installation Manual Exhaust Ad...

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 this 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 ...

Page 6: ...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 electrical 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 type the unit will be grounde...

Page 7: ...4 1 OPERATING INSTRUCTIONS CONTROL PANEL ...

Page 8: ... Fresh Roll Muffin Frozen Roll Muffin Beverage Chicken Pieces and Hot Cereal 12 MICRO Touch this pad when setting Microwave cooking 13 CONV Touch this pad when setting Convection cooking 14 COMBI Touch this pad when setting combination cooking or preheat 15 NUMBER Touch number pads to enter cooking time power level quantities weights or cooking temperature 16 EZ ON Touch this pad to set and start ...

Page 9: ...5 1 OVERALL CIRCUIT DIAGRAM SCHEMATIC DIAGRAM ...

Page 10: ...F VENT N C 1 TIME SET AUTO CLOCK STOP CLEAR N C ENTER START ON OFF LIGHT ON OFF TURNTABLE REHEAT COOK AUTO COOK VENT AUTO TIMER DEFROST N C 8 9 0 AUTO MORE COMBI SPEED SOFTEN N C LESS MELT CONV COOK CUSTOM N C 2 3 MICRO 4 N C 5 6 COMBI 7 EZ ON 12 13 11 10 8 9 1 2 3 4 5 6 7 KEY MATRIX ...

Page 11: ...ll 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 Touch the START ENTER key each time the door is closed E Continue operating the unit Two short and a long beep sound signal is heard when the time is up The unit will s...

Page 12: ...w the limit of 5 mW cm2 All service adjustments should be made for minimum microwave energy leakage readings 3 Do not operate the unit until it is completely repaired if any of the following conditions exist The unit must not be operated a The door does not close firmly 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 th...

Page 13: ...rvicing The power density of the microwave radiation leakage emitted by the microwave oven should not exceed 1mW cm2 sq And 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 TESTE...

Page 14: ...sed 3 At least once a year have the electromagnetic energy leakage monitor checked for calibration by its manufacturer POWER OUTPUT MEASUREMENT 1 Microwave power output measurement is made with the microwave oven supplied at its rated voltage and operated at its maximum microwave power setting with a load of 1000 5 g of potable water 2 The water is contained in a cylindrical borosilicate glass ves...

Page 15: ...IALLY SWITCHES AND HIGH VOLTAGE CIRCUIT A REMOVING POWER AND CONTROL CIRCUIT BOARD Figures 1 2 and 3 1 Remove a screw securing the control panel assembly to the oven cavity 2 Remove the control panel with pushing it upward 3 Remove the five connectors CN1 CN2 CN4 CN5 and wire leads Relay8 Relay10 from the circuit board 4 Remove 4 screws securing the circuit board Circuit Board 7 4 DISASSEMBLY INST...

Page 16: ...sert the F P C connector into the terminal socket securely with the fingers 2 Hold the plastic fastener with thumb and forefinger of the other hand and push it slowly into the terminal socket Figure 6 NOTE When reconnecting the F P C connector make sure that the holes on the F P C connector are properly engaged with the hooks on the plastic fastener 3 Lock the level of the plastic fastener into th...

Page 17: ... the screws 1 or 2 screws securing it to the out case 4 Remove two screws on the left central edge and one screw on the right central edge of Base plate Remove the Mount All from the outside case by removing one screw securing it to the outside case 5 Remove six screws of the rear cavity 6 Remove the outside case Controller 3 screws Door Mounting Plate 1 or 2 screws Out Case Mount All Vent Grille ...

Page 18: ...securing the Latch Board 3 Make necessary replacements and check microwave energy leakage according to ADJUSTMENT PROCEDURES on page 7 12 Latch Board Primary Interlock Switch Monitor Interlock Switch Secondary Interlock Switch Latch Board Primary Interlock Switch Monitor Interlock Switch Secondary Interlock Switch Figure 9 Figure 10 ...

Page 19: ...it any adjacent parts or it may be damaged When replacing 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 Check microwave energy leakage must be below the limit of 5 mW cm2 All service adjustments should be made for minimum microwave en...

Page 20: ...e to check that the primary interlock switch the secondary interlock switch and the interlock monitor switch is in good operating normally After replacing the door check for microwave energy leakage with a survey meter Microwave energy leakage must be below the limit of 5mW cm2 With a 275 ml water load G DISASSEMBLING DOOR Figure 17 1 Remove the dielectric choke by using knife blade or small screw...

Page 21: ... 1 Remove the mounting plate by loosening mounting plate screws 1 or 2 screws securing it to the back plate See Figure 18 2 Remove MOUNT ALL by loosening one screw securing the ventilation Motor and back plate See Figure 19 a 3 Carefully pull the ventilation motor ASS Y out of the microwave oven See Figure 19 b J REPLACING THE HUMIDITY SENSOR For sensor model only 1 Remove the sensor by removing t...

Page 22: ...nnector not the wires when removing L REMOVING CONVECTION HEATER AND THERMISTOR Figure 23 1 Remove the out case 2 Remove the air duct by removing six screws securing it to the oven front plate guide air and glasswool L cover 3 Disconnect the wire leads of air duct 4 Remove the magnetron 5 Remove the latch board assembly 6 Remove the bottom plate by removing four screws 7 Remove the four net screws...

Page 23: ...microwave oven on its side so that you can see the latch board and the switches as shown in Figure 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 sequence of the sw...

Page 24: ...ro 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 achieve the prope...

Page 25: ...When the secondary switch operation is abnormal make the necessary adjustment or replace the switch only 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 closed circuit in the door open condition When the door is closed meter shoul...

Page 26: ...TRON 1 Remove 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 resis...

Page 27: ...ate infinite resistance 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 1 Measure continuity ohm meter scale Rx1 2 Remove the lead wires and operate oven at Convection Cooking 1 Remove wire leads 2 Measure resistance ohm meter scale Rx1 RELAY 8 Power Level 1 2 3 4 5 6 7 8 9 10 4 Sec 6 Sec 8 Sec 10 Sec 12 S...

Page 28: ...M TURNTABLE MOTOR T M STIRRER MOTOR S M THERMISTOR HEATER ELEMENT SENSOR 1 Remove wire leads 2 Measure resistance ohm meter scale Rx1 1 Remove wire leads 2 Measure resistance ohm meter scale Rx1000 1 Remove the connector from PCB 2 Measure resistance across pins 1 3 ohm meter scale Rx1 1 Remove wire leads 2 Measure resistance ohm meter scale Rx1 1 Remove the 3 pin connector from PCB 2 Measure resi...

Page 29: ...NNECTOR Top 1 2 3 4 5 6 7 8 9 10 11 12 13 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 5 SPEED LEVEL POWER CUSTOM POPCORN SET ON OFF VENT N C 1 TIME SET AUTO CLOCK STOP CLEAR N C ENTER START ON OFF LIGHT ON ...

Page 30: ...JUSTMENT PROCEDURES on page 7 12 when the primary interlock secondary interlock switches and or the interlock monitor switches are adjusted or replaced Fuse blows immediately after the door is closed Fuse blows immediately after the door is opened Fuse blows when the door is closed and START ENTER key is touched Improper operation of the primary interlock secondary interlock switches and or the in...

Page 31: ...ithout touching START ENTER key when the door is closed GOOD Remove the mate connector of I O CON from the circuit board Does the unit still operate Defective Wire Assembly Replace the circuit board Replace Wire Assembly NO NO YES YES GOOD Measure the voltage at pin NO 1 10 of CN1 Voltage reading 120 V AC Replace the circuit board Defective FAN motor YES NO NO YES Replace FAN motor PROBLEM B Oven ...

Page 32: ...usly operates 3 Proper temperature measurement is not obtained 4 The buzzer does not sound or continues to sound 5 Some segments of one or more digits do not light up or they continue to light up or segments light when they should not 6 Wrong figures appear 7 The figures of all digits 8 Some of the indicators do no flicker light up 9 The clock does not keep time properly NOTE A MICROWAVE ENERGY LE...

Page 33: ...while working on this panel to discharge any static charge built up in your body Micom model only CONDITION Microwave oven does not work Inserting many plugs into one outlet and using them at the same time blown fuse or breaker Plug is not inserted tightly Output power is too low Low AC input voltage Food temperature is too low Using metallic ware and allowing it to touch the oven wall Sparks occu...

Page 34: ...ly 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 One or more digits in the display are not lighting 5 Display indicates a number different...

Page 35: ... of the monitor switch Replace fuse primary monitor switches and RELAY RY8 of P C B Assembly Check continuity of monitor switch with door closed Check continuity of primary switch with door opened No continuity Disconnect one side of the wire lead connected from transformer to the high voltage capacitor and operate the unit No continuity Continuity Shorted contact at the primary switch Replace fus...

Page 36: ...ion then tightly Output is low Lower than 90 of rating voltage Normal Decrease in power source voltage with load Suggest customer contact local electric power utility co or qualified electrician Check the power source voltage Disconnect the wire leads from relay 8 and check on and off time with multitester Abnormal Normal Abnormal Defective magnetron Replace magnetron Defective P C B assembly Repl...

Page 37: ...capacitor Replace high voltage capacitor Check high vol tage capacitor Abnormal Defective magnetron Replace magnetron Check Magnetron TROUBLE 5 No microwave oscillation even though oven lamp and fan motor run Display operates properly Output is full power when you set lower power level Abnormal Defective PCB assembly Replace PCB assembly Disconnect the wire leads from relay 8 and check continuity ...

Page 38: ...ly Check the Relay 10 of P C B assembly Temperature in the oven cavity is lower or higher than preset Abnormal Normal Abnormal Check the convection heater element Defective Relay 10 Replace Relay 10 Defective convection heater Replace convection heater Check the Relay 10 of P C B assembly Abnormal Check the circulation motor Defective circulation motor Replace circulation motor Cook on the glass t...

Page 39: ...51B 14760A 13213A 13552A 14026A 14970A 14890A 13650A WTP004 WTT028 14760A 13581A 13551A 14760A 13213A 13552A 14026A 14970A 14890A WTP004 WMP027 WTT028 14760A WWS005 13650A 148902 148901 EV FOR MODEL LMVH1750SB LMVH1750SW FOR MODEL LMVH1750ST ...

Page 40: ...8 2 CONTROLLER PARTS 23506A 23572A 23551A 24781M 24810P WTP015 268711 24781M 24810P WTP015 268711 07 07 EV FOR MODEL LMVH1750SB LMVH1750SW FOR MODEL LMVH1750ST ...

Page 41: ...750ST LMVH1750SW For Model For Model LMVH1750SB LMVH1750SW LMVH1750ST For Model WTT027 WTT029 WTP013 WMP004 WTT022 WNH001 34960A 33550P 33112U 33809A 63303A 34931A 36912H 33740A 34890C 35230A 34810T 948501 330342 63302A 34810Q 36549S 33530A 33531A EV ...

Page 42: ...8 4 LATCH BOARD PARTS 43500A 43501A WSZ084 466001 466003 466001 44510A EV ...

Page 43: ...D 36549H WWP008 WWP008 WWS005 WWS005 WNH003 348101 WTT028 WTT022 WTT022 WTT022 WTT021 WTT022 WTP013 WTP013 WTP013 WTP013 WTP005 WNH002 WSZ002 WSZ002 WSZ002 WTT028 WTT037 WTT028 WNH002 348102 56549B 56322A 55012A 53300S 36549C 568772 53300B 56170D 54810A 56930M 56324A 54810C 55900A 54974S 56549F 55238A 56851D 50CZZH 33390G WTT028 WTT011 34930W EV ...

Page 44: ...PARTS II 56501A 352641 56930V WTT028 WTT028 WTT028 WTP005 WTP007 WTP007 WTT028 WTT028 352642 55231C 36549V 330341 53550L 36912H 50CZZM 55262A 56411A 55012U 568771 50FZZA 54931A WTP005 WSZ002 WTT030 56201A WTP018 EV ...

Page 45: ...8 7 INSTALLATION PARTS 65862D 65862B 63300M VINYL BAG 63861A 01 OWNERS MANUAL 02 SERVICE MANUAL 06 1 UPPER TEMPLATE 06 2 WALL TEMPLATE 04 INSTALLATION MANUAL 05 COOKING GUIDE LABEL EV ...

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