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LMVM2277ST

Door Interlock Switches

T-20

MONITOR SWITCH

Disconnect the wire lead from the switch.

Connect an ohmmeter to the COM (common) and NC
(normally closed) terminals of the switch.

With the door open, the meter should indicate a closed
circuit.

Closing the door should indicate an open circuit.
(See chart, next slide.)

Summary of Contents for LMVM2277ST

Page 1: ...1 LMVM2277ST Product Training LMVM2277ST Over The Range Microwave Oven Pres V 1 0 080124 ...

Page 2: ...r job descriptions in general Anyone found to be part of any such communication will immediately be dismissed from this class and will not be allowed to attend future events LG supplies this training class for the benefit of all in attendance We ask your assistance in keeping this a professional meeting and to remain focused only on the technical improvement and education of our service network No...

Page 3: ...3 LMVM2277ST IMPORTANT SAFETY NOTICE DISCLAIMER MODIFICATIONS ESD ISSUE REGULATORY INFORMATION Preliminary T 1 Slide Number Page in Training Manual ...

Page 4: ...4 LMVM2277ST COMPLIANCE The responsible party for this device s compliance is LG Electronics Alabama Inc PO Box 240007 Huntsville AL 35813 Preliminary T X ...

Page 5: ...T Safety Notices and Warnings 1 Contact Information 1 Contents 2 Specifications 4 Safety Notices 5 Serial Number Identification 6 Introduction 7 Controls 8 Installation 9 Accessories 10 Drying Rack 10 Contents T X ...

Page 6: ...6 LMVM2277ST Serial Number ...

Page 7: ...7 LMVM2277ST Serial Number ...

Page 8: ...8 LMVM2277ST Introduction T 1 ...

Page 9: ...9 LMVM2277ST Headline The LMVM2277ST is part of the new LG complete kitchen suite T 4 ...

Page 10: ...277ST Reminder Always run a microwave leak test If the oven is operational test it before and after the repair The Federal standard for leakage is less than 5 mW cm2 but LG s standard is less than 1 mW cm2 T 4 ...

Page 11: ...tions T 5 Rated Power Consumption 1 700 W max MWO lights fan Microwave Output 1 100 W IEC 60705 Frequency 2 450 MHz 50 MHz Power Supply 120 V AC 60Ø Rated Current 14 5 Amps MWO lights fan Magnetron Cooling Forced Air Cooling ...

Page 12: ...12 LMVM2277ST Switch Chart T 5 Switch Mode Primary Secondary Monitor Conditions COM N O COM N O COM N C Door Open OPEN OPEN CLOSE Door Closed CLOSE CLOSE OPEN ...

Page 13: ...13 LMVM2277ST WARRANTY T 6 ...

Page 14: ...le or repair it Never operate the microwave oven when it is empty When cooking very small amounts of food put a glass of water in the cooking compartment Do not operate the oven on a 2 wire extension cord during repair or use Use proper ESD precautions when handling the PCB ...

Page 15: ...T Safety and Warnings T 7 Never put anything into the latch holes and interlock switches Remove your watch before working on or around the magnetron Do not operate the oven without the glass tray turntable in place ...

Page 16: ...16 LMVM2277ST Safety and Warnings T 7 Be sure the magnetron gasket is properly installed around the dome of the tube whenever installing the magnetron See magnetron section page 21 ...

Page 17: ...T Safety and Warnings T 7 Always use a properly wired and grounded 3 wire dedicated outlet to power the oven 120 VAC 20 A Never cut the ground prong off the plug or otherwise defeat the grounding of this appliance ...

Page 18: ...T must be properly installed before operation Installation includes mounting the bracket on the wall with toggle bolts and or lag bolts and drilling holes in the cabinet above the oven to accommodate the electric cord and the upper mounting bolts ...

Page 19: ...he holes properly The ventilation fan can exhaust air in any of three directions through the back wall through the roof or recirculated through the charcoal filter into the kitchen If the air is vented through a duct to the outside the damper and flap must be installed ...

Page 20: ...20 LMVM2277ST Turntable Installation T 9 1 Round glass tray 2 Rotating ring 3 Rectangular glass tray 4 Turntable drive arm ...

Page 21: ...T 9 Follow these steps to install the turntable components and to ensure they function correctly 1 Install the turntable drive arm and position it securely on the drive cam 2 Install the rectangular glass tray and ensure it slides properly ...

Page 22: ...22 LMVM2277ST Turntable Installation T 9 3 Place the rotating ring on top of the rectangular glass tray 4 Be sure the drive arm can rotate in the hollow area on the bottom of the rectangular tray ...

Page 23: ...y on top of the rotating ring Put a cup of water on the turntable and operate the oven for a minute to ensure that the tray mechanism is seated properly and works as it should There should be rotation on the turntable AND lateral motion involving the rectangular tray ...

Page 24: ...24 LMVM2277ST Operating Instructions T 10 ...

Page 25: ...wer and 7 minutes thirty seconds at a power level of 70 press 3 0 0 and COOK TIME to set the 3 minutes at full power then press 7 3 and 0 to set the second cooking time of seven minutes thirty seconds then press POWER LEVEL and 7 to set the power level of the second cooking period to 70 and then press START ...

Page 26: ...irst plugged in or after a power failure the display will flash the message PLEASE SET THE TIME OF DAY If the time is not set the colon will display until you touch CLOCK To set the clock touch CLOCK the numbers 0 through 9 to set the time START and START again ...

Page 27: ...e the ventilation fan touch VENT ON OFF then touch or to adjust the speed To run the fan for a set period turn it on and set the desired speed as illustrated above Then touch AUTO TIME SET several times to increase the time before the fan is turned off ...

Page 28: ...28 LMVM2277ST Operating Instructions T 11 To toggle the CHILD LOCK feature ON or OFF touch and hold the START CHILD LOCK button for 5 seconds until a beep sounds ...

Page 29: ...29 LMVM2277ST Operating Instructions T 11 The EZ ON button turns the oven on at full power for 30 seconds To cook for 2 minutes press it four times ...

Page 30: ...2277ST Operating Instructions T 11 To use the timer without operating the oven press TIMER ON OFF the numbers of the time to set and TIMER ON OFF The timer will count down and beep at the end of the set period ...

Page 31: ...e On Time Off Time 0 magnetron is off 10 2 sec 2 sec 18 sec 20 2 sec 4 sec 16 sec 30 2 sec 6 sec 14 sec 40 2 sec 8 sec 12 sec 50 2 sec 10 sec 10 sec 60 2 sec 12 sec 8 sec 70 2 sec 14 sec 6 sec 80 2 sec 16 sec 4 sec 90 2 sec 18 sec 2 sec 100 magnetron is on ...

Page 32: ...32 LMVM2277ST Care and Cleaning T 13 Cleaning the oven is easy Always unplug the oven before cleaning the control panel to avoid touching too many buttons at once and damaging the microprocessor ...

Page 33: ...f the oven use a soft cloth and spray glass cleaner Spray the glass cleaner onto the cloth rather than onto the oven DO NOT USE abrasive cleanser steel wool scrubbing pads gritty washcloths rough paper towers and those sorts of things They can damage the finish on your oven ...

Page 34: ... that it is easiest if you wipe out the oven and clean any spatters as soon as the cooking is completed This prevents the spatters from being baked onto the oven surfaces during subsequent cooking Be especially careful to clean the area where the door closes and touches the frame of the oven ...

Page 35: ...f water in the oven and run the oven for 10 minutes A 2 cup microwave safe glass measuring cup works well for this The steam will soften soils and allow them to be wiped away with a damp towel If you cut up a lemon and put it into the water during the cooking your oven and entire kitchen will be citrusy fresh ...

Page 36: ...d be removed and cleaned monthly Push the tab backward and allow the filters to drop out of their holders Clean them by swishing them in hot soapy water and rinsing them Shake them to dry them and replace them in their holders DO NOT OPERATE the oven without the grease filters in place ...

Page 37: ...not cause a problem If the oven recirculates the air back into the kitchen the charcoal filter should be replaced every 6 12 months It is not washable and must be replaced DO NOT OPERATE the oven without the charcoal filter in place unless of course the oven is vented to the outside The charcoal filter part number is 5230W1A0003A ...

Page 38: ...7ST Charcoal Filter T 14 Remove the two screws at the top of the oven housing These are the two middle screws If the oven is properly installed these screws will be accessible in front of the edge of the cabinet ...

Page 39: ...39 LMVM2277ST Charcoal Filter T 14 Remove the wire cover It is a small plastic guide that fits with the vent grille on the left end It can be pulled out through the top when the door is closed ...

Page 40: ...40 LMVM2277ST Charcoal Filter T 14 Open the door and tip the vent grille forward Lift it out to remove it ...

Page 41: ...41 LMVM2277ST Charcoal Filter T 14 Remove the old filter and replace it with a new one It is not reusable ...

Page 42: ...42 LMVM2277ST Oven Light T 15 Push the metal tab of the lampholder off the plastic tab and pull the lamp and holder out Replace the bulb and reinstall the holder ...

Page 43: ...43 LMVM2277ST Oven Light T 15 The lampholder tab rests against a plastic tab on the oven vent housing It is a simple snap fit Push it aside to remove or replace the lamp assembly ...

Page 44: ... Oven Light T 15 Lift out the lamp holder which includes the bulb and the socket which is attached to the reflector with two bolts Do not touch the bulb with your fingers Use a clean protective cloth or paper towel ...

Page 45: ...replaced by pulling it out and replacing it with a new one The bulb is not equipped with a filament anchor so there is no top or bottom The socket pigtail is attached to the lamp holder by two bolts The socket need not be removed to change the bulb ...

Page 46: ...46 LMVM2277ST Disassembly and Repair T 16 ...

Page 47: ...47 LMVM2277ST Main Board and Power Board T 16 The main board and power board can be serviced without dismounting the oven ...

Page 48: ...Board T 16 Release the main board and pull it down You ll have to roll it to the right a little bit to make it clear easily Note The photo is in the lab but this can be achieved while the microwave is mounted on the wall ...

Page 49: ...49 LMVM2277ST Main Board T 17 This drawing shows the location of the main board upper item and the ventilation duct inside the microwave oven case The latch board is the lower item ...

Page 50: ...50 LMVM2277ST Main Board T 17 Remove the wires and connectors from the main board Remove the screws that hold it in the case to change the board ...

Page 51: ...51 LMVM2277ST Outer Case Removal T 18 ...

Page 52: ...t has been installed If it is a new oven be sure to remove two screws and the mounting bracket from the back of the oven before proceeding Remove the two vent grille screws Remove the four screws securing the oven case to the oven Four on the top one on the right side Remove two screws on each side of the base plate ...

Page 53: ...VM2277ST Outer Case Removal T 18 Remove the four screws holding the outer case to the back of the oven Lift the outer case carefully from the oven Store it to prevent damage while you are working on the oven ...

Page 54: ...54 LMVM2277ST Door Interlock Switches T 19 Disconnect the interlock switches You ll need a Torx T 20T Tamperproof bit ...

Page 55: ...55 LMVM2277ST Door Interlock Switches T 19 The connectors are keyed to prevent improper connection It is still a good idea to check the wire colors especially where there are multiple connectors ...

Page 56: ...56 LMVM2277ST Door Interlock Switches T 19 Left side switch ...

Page 57: ...57 LMVM2277ST Door Interlock Switches T 19 Right side switch ...

Page 58: ...oor Interlock Switches T 20 INTERLOCK SWITCH CONTINUITY TEST The door interlock switches should click audibly when the door is opened or closed If the latches do not activate the switches properly they can be adjusted ...

Page 59: ...HES Disconnect the wire lead from the switch Connect an ohmmeter to the COM common and NO normally open terminals of the switch With the door open the meter should indicate an open circuit Closing the door should indicate a closed circuit See chart couple of slides later ...

Page 60: ... Disconnect the wire lead from the switch Connect an ohmmeter to the COM common and NC normally closed terminals of the switch With the door open the meter should indicate a closed circuit Closing the door should indicate an open circuit See chart next slide ...

Page 61: ...61 LMVM2277ST Door Interlock Switches T 20 ...

Page 62: ...place switches ONLY with identical replacement parts PRIMARY Type SZM V16 FA 63 or VP 533A OF or V5230Q SECONDARY Type SZM V16 FA 63 or VP 533A OF or V5230Q MONITOR Type SZM V16 FA 62 or VP 532A OF or V5220Q NOTE After repairing the door interlock system or switches these continuity tests must be performed ...

Page 63: ...63 LMVM2277ST Magnetron T 21 Remove the outer case Remove the damper bracket Disconnect the transformer lead wire Remove the four screws securing the transformer Remove two screws securing the fan motor ...

Page 64: ...4 LMVM2277ST Magnetron T 21 Remove four screws securing the magnetron and lift it out carefully When removing or replacing the magnetron ensure the woven metal gasket is undamaged and properly positioned ...

Page 65: ...ir fan cover is in the top of the oven It is held in place by one screw and three tabs This cover must be in place to operate the microwave oven safely Remove the screw and pull the cover out of the tabs being careful not to bend or break the cover ...

Page 66: ...66 LMVM2277ST Stirrer Fan and Cover T 21 The stir fan presses onto the shaft The cover is secured by three tabs and a single screw ...

Page 67: ...67 LMVM2277ST Door Removal T 22 Remove the two vent grille mounting screws Remove the door hinge screws Remove the wire cover and open the hinge covers ...

Page 68: ...68 LMVM2277ST Door Removal T 22 Open the door Remove the vent grille Disconnect the two flat cables at the face plate connectors ...

Page 69: ...69 LMVM2277ST Door Removal T 22 Use a small screwdriver to remove the clip on the end of the pneumatic damper and take the spring out of the oven USE CAUTION The damper could expand without notice ...

Page 70: ...door off the hinges and remove it Set it on a protective surface like a blanket to prevent scratches or damage When replacing the door always check the interlock switches and perform a microwave leakage test See page 33 in the training manual ...

Page 71: ...71 LMVM2277ST Door Disassembly T 23 Remove the four screws securing the choke cover to the door Separate them carefully using a small screwdriver or a knife ...

Page 72: ...72 LMVM2277ST Door Disassembly T 23 Remove the two screws securing the handle Remove the door frame Remove the two screws securing the PCB Printed Circuit Board ...

Page 73: ...73 LMVM2277ST Door Disassembly T 23 Disconnect the flat plastic connector See page 24 in the training manual ...

Page 74: ...door adjust it to be parallel to the chassis There should be no play between the inner door surface and the oven frame If the door is not mounted properly microwaves may leak between the door and oven or the monitoring and safety switches will prevent usage ...

Page 75: ...75 LMVM2277ST Door Disassembly T 23 Always perform a microwave leakage test whenever the door is adjusted or repaired photo goes here ...

Page 76: ... Flat Plastic Connector T 23 The flat plastic connector FPC is opened and closed by moving the plastic slide at the top to release or secure the flat cable To release the cable pull the latch away from the connector ...

Page 77: ...77 LMVM2277ST Flat Plastic Connector T 23 Lift the flat cable out It is held in place by two hooks that fit into the two square holes on the cable ...

Page 78: ...tor T 23 To replace the flat cable be sure the latch is pulled up away from the connector Insert the flat cable and secure the hooks in the two square holes Press the latch into place and gently tug on the cable to be sure it is secure ...

Page 79: ...79 LMVM2277ST Ventilation Fan Motor T 25 If the oven has not been installed be sure the mounting bracket has been removed from the back of the oven ...

Page 80: ...80 LMVM2277ST Ventilation Fan Motor T 25 Remove the two screws securing the blower plate cover One on the top and one on the back ...

Page 81: ...ut and turn it to face the proper direction front top or back for venting Replace the screws in the top and back to secure it against vibration Replace the top plate unless you are venting the oven through the roof Attach the adapter and duct work for venting ...

Page 82: ...82 LMVM2277ST Turntable Motor T 26 Remove the base This can be done with the oven mounted on the wall ...

Page 83: ...83 LMVM2277ST Turntable Motor T 26 The turntable motor is attached to the base with a tab and a screw ...

Page 84: ...84 LMVM2277ST Humidity Sensor T 26 With the outer case removed remove one screw and lift out the humidity sensor Unplug the connector at the main board and replace the defective sensor ...

Page 85: ...85 LMVM2277ST Component Test Procedures T 27 Test procedures are listed to help the servicer determine which parts are defective by doing as little disassembly as possible ...

Page 86: ...86 LMVM2277ST Transformer Test T 27 ...

Page 87: ...ke it out of the circuit Measure the resistance between the following points Meter scale Rx1 Primary A B High 0 2 1 0 Ω Primary A C Low 0 2 1 5 Ω HV Secondary G GND 50 120 Ω Filament E F 0 5 2 0 Ω Meter scale Rx1000 Primary to ground Normal infinity Filament to ground Normal infinity ...

Page 88: ...88 LMVM2277ST Magnetron Test T 27 ...

Page 89: ...est T 27 To test the magnetron remove the connector to take it out of the circuit Measure the resistance between the following points Meter scale Rx1 Filament terminals 1 Ω Meter scale Rx1000 Filament to chassis Normal infinity ...

Page 90: ...90 LMVM2277ST Capacitor Test T 28 ...

Page 91: ...re leads They may be equipped with press tab releases Measure the resistance between the following points Meter scale Rx1000 Terminal to terminal Normally indicates several ohms then gradually drifts toward infinity Terminal to case Normal infinity ...

Page 92: ...92 LMVM2277ST Capacitor Test T 28 The capacitor can be serviced while the oven is still mounted Remove the door See page 22 ...

Page 93: ...93 LMVM2277ST Capacitor Test T 28 Remove a single screw and take off the cover that covers the capacitor ...

Page 94: ...94 LMVM2277ST Relay T 29 Test the relay by removing its connector and measuring the continuity between the terminals ...

Page 95: ...95 LMVM2277ST Fan Motor T 29 ...

Page 96: ...otor T 29 Unplug the fan connector and measure the resistance between the terminals Terminal A Red Terminal B Brown Terminal C Yellow A C 12 16 Ω A B 9 23 Ω Other readings or infinite resistance indicates a motor failure ...

Page 97: ...97 LMVM2277ST Low Voltage Transformer T 29 ...

Page 98: ...98 LMVM2277ST Low Voltage Transformer T 29 Unplug the transformer connector and measure the resistance between the terminals Terminal A Red Terminal B Black Terminal C White A C 18 30 Ω A B 18 30 Ω ...

Page 99: ...99 LMVM2277ST High Voltage Diode T 30 Measure the continuity in both directions using meter scale Rx1000 Forward Normal continuity Defective infinity Reverse Normal infinity Defective continuity ...

Page 100: ...100 LMVM2277ST High Voltage Diode T 30 ...

Page 101: ...101 LMVM2277ST High Voltage Diode T 30 This photo shows the diode connected with 9 VDC applied to the cathode The meter reads 0 00 VDC because the diode is blocking the flow ...

Page 102: ...102 LMVM2277ST High Voltage Diode T 30 This photo shows the diode s forward bias with 9 VDC connected to the anode ...

Page 103: ...103 LMVM2277ST Turntable Motor T 31 Remove the connector and measure the resistance across the terminals using meter scale Rx1000 Normal 2 3 3 5 kΩ Defective any other reading ...

Page 104: ...104 LMVM2277ST Ventilation Fan Motor T 31 ...

Page 105: ...n Motor T 31 Unplug the connector and read the resistance between the various terminals using meter scale Rx1 NORMAL TURBO Blue Black 4 20 Ω HIGH Blue White 19 35 Ω MEDIUM Blue Gray 26 42 Ω LOW Blue Brown 34 50 Ω DEFECTIVE Infinity ...

Page 106: ...106 LMVM2277ST Humidity Sensor T 31 ...

Page 107: ...three wire connector to the sensor at the circuit board end Set your ohm meter to Rx1000 The resistance should be as indicated on the table within 10 Infinite resistance or a dead short indicates a sensor failure 1 and 3 Black red 6 kΩ 2 and 3 Red white 3 kΩ 1 and 2 Black white 3 kΩ ...

Page 108: ...108 LMVM2277ST Stirrer Fan Motor T 32 ...

Page 109: ...109 LMVM2277ST Stirrer Fan Motor T 32 Remove the connector and measure the resistance across the terminals using meter scale Rx1000 Normal 120 135 Ω Defective any other reading See page 21 ...

Page 110: ...perational it should be checked for microwave leakage before servicing begins The standard for microwave emission is 5mW cm2 LG s voluntary standard is much lower at 1mW cm2 A microwave leakage test MUST be performed after the oven is serviced for any reason ...

Page 111: ...quipment microwave survey meter such as a Holaday HI 1500 or HI 1501 or a Narda 8100 or 8200 non conductive 600 cc beaker glass or plastic approximately 3 inches 900 mm in diameter glass thermometer 32 F to 212 F 0 C to 100 C in 1 graduations ...

Page 112: ...112 LMVM2277ST Microwave Leak Test T 33 Procedure Pour 275 15 cc of water into the beaker Verify the temperature to be 68 F 9 F 20 C 5 C Set the leakage meter to 2 450 MHz Use the 2 inch 5 cm spacer ...

Page 113: ...Leak Test T 33 Operate the oven at high maximum output Check for microwave emissions by holding the probe perpendicular a 90 angle to the surface and scanning less than 1 inch 2 5 cm per second in the area shown in the diagram ...

Page 114: ...wer Traditional T 34 Magnetron output and microwave power tend to deteriorate with age To determine whether an oven s output is within specification use the following formula and procedure FORMULA P 4 187 Mw T2 T1 0 55 Mc T2 T0 t ...

Page 115: ...tput in watts Mw mass of the water in grams Mc mass of the container in grams T0 ambient temperature in C T1 initial temperature of the water in C T2 final temperature of the water in C t heating time in seconds excluding the magnetron filament warm up time ...

Page 116: ...LMVM2277ST Microwave Power T 34 After inspecting or servicing the magnetron ensure the gasket is properly installed around the dome of the tube Check for microwave leakage following the procedure on page 33 ...

Page 117: ...quirements Microwave Power Output testing requires the ability of the technician to measure water temperature in degrees Celsius ºC to have two 2 one 1 liter plastic measuring beakers and a voltmeter that is capable of measuring 120 VAC with 1 volt accuracy ...

Page 118: ...118 LMVM2277ST Microwave Power T 35 Equipment Celsius thermometer Two 1 Liter Plastic Beakers Plastic does not absorb heat energy like glass AC Voltmeter ...

Page 119: ...oth of the 1 liter beakers to the 1000 ml 1 Liter measuring line Stir the water and determine that the tap water is cooler than 25º C record the temperature If the temperatures differ added the 2 numbers and divide by 2 to get an average 1 2 3 ...

Page 120: ...t a level that will center the beakers in the oven cavity and place the beakers on the rack Set the microwave oven for HIGH highest or 100 power level and set the cook time for 2 minutes Press the START button and heat the water for 2 minutes After heating for 2 minutes immediately remove the beakers stir the water with the thermometer and record the water temperature of both beakers 2 4 5 6 ...

Page 121: ...o beakers must be determined because of possible uneven power distribution within the oven cavity This could affect the ending temperatures of both beakers water If the water temperature in the 2 beakers differs add the two Celsius numbers and divide by 2 to get the average ending temperature ...

Page 122: ...e 2 beakers 20º C Ending Temperature of the 1st beaker 36 5º C Ending Temperature of the 2nd beaker 32 5º C 1st Beaker 36 5 C 2nd Beaker 32 5 C Total 69 0 C Average the sum by dividing by 2 69 2 34 5 av temp Subtract the starting Temperature is 20 start temp temperature rise 14 5 ...

Page 123: ... The output power of a microwave oven is greatly affected by the voltage under load of the AC power supply Measure the voltage under load at the wall receptacle where the oven is powered and operating The following chart shows the percentages of full power that are within limits at voltages from 108 VAC to 132 VAC See chart next slide ...

Page 124: ...124 LMVM2277ST Microwave Power T 35 70 75 80 85 90 95 100 105 110 115 120 125 108 110 112 114 116 118 120 122 124 126 128 130 132 LOW LIMIT HIGH LIMIT NOMINAL SUPPLY VOLTAGE POWER OUTPUT ...

Page 125: ...be made on microwave ovens operating on less than 108 VAC Below this point the power output drops sharply in an unpredictable manner Likewise operating an oven at voltages greater than 132 VAC should be avoided as damage to components may occur due to excessive electrical pressure ...

Page 126: ...000 watt oven operated at 114 VAC would be within limits at any point between 85 and 112 of the rated power 85 of 1000 850 watts 112 of 1000 1120 watts Therefore the oven would be nominal normal if the output power was between 850 watts to 1120 watts ...

Page 127: ...er T 37 When the power output measured falls outside the nominal normal range on the chart take the following steps If no other parts are defective and line voltage under a load is within tolerance replace the magnetron and retest ...

Page 128: ...ower discharge the high voltage capacitor and check the high voltage transformer A layer short circuit of the high voltage transformer may cause a low power output If burned places are found in the high voltage transformer and a smell of burning insulation is sensed replace the high voltage transformer ...

Page 129: ...129 LMVM2277ST Checkout Procedures T 38 The following procedures are offered to the servicer in the interest of saving time and isolating a problem quickly to provide a fast repair ...

Page 130: ...mary and secondary interlock switches and or monitor switch Check and adjust as necessary Fuse blows immediately when door is opened Fuse blows immediately when START is pressed with door closed Malfunction of high voltage transformer circuit including transformer diode capacitor magnetron blower motor or main board ...

Page 131: ... board Input current of more than 20 amps If the input current is more than 20 amps check the magnetron and related wiring If the input current is less than 0 5 amps there is no input to the high voltage transformer START fails but high voltage interlock switches door sensing and relay check good 1 2 ...

Page 132: ... continuously with a normal relay Buzzer sounds continuously or fails to sound Segments of the LED display fail to light light continuously or light when they should not Incorrect numbers or letters appear in the display Clock fails to keep time accurately 7 6 3 5 4 ...

Page 133: ...133 LMVM2277ST Relay T 39 Fan turns on when door is closed but START is not pressed ...

Page 134: ...134 LMVM2277ST Relay T 39 Fan does not turn on when door is closed and START is pressed ...

Page 135: ...135 LMVM2277ST Relay T 40 Oven lamp turns on when door is closed without pressing START ...

Page 136: ...136 LMVM2277ST Relay T 40 Oven lamp does not turn on when door is closed and START is pressed ...

Page 137: ...lowcharts T 41 Before starting the troubleshooting charts check to see if the oven is operable For display problems use charts A B and C If the oven does not heat try charts D and E If the ventilation fan does not operate use chart F ...

Page 138: ...138 LMVM2277ST Chart A No Power T 41 Check connector CN1 on the main board Reading across pins 1 and 3 blue wire and white wire the voltage should be 120 VAC ...

Page 139: ...139 LMVM2277ST Chart B Power But Doesn t Run T 42 Check the continuity of connector CN3 between pins 1 PK pink and 3 BL black when the door is closed ...

Page 140: ...TART ENTER is pressed If the fan doesn t run check the resistance of the fan motor Pins A and C 16 Ω 2 Ω Pins A and B 11 Ω 2 Ω If the fan motor is defective it will also affect the stirrer fan motor because the center tap if the main fan motor provides the 21 VAC supply for the stirrer fan ...

Page 141: ...141 LMVM2277ST Chart C continued T 43 ...

Page 142: ...7ST Chart D Runs But No Heat T 44 Check the primary and secondary interlock switches Check both thermostats TCO for the oven cavity and the magnetron Either switch could render the oven inoperable Check the relay ...

Page 143: ...143 LMVM2277ST Chart D continued T 45 Check the resistance of the high voltage transformer See page T 27 Check the high voltage capacitor See page T 28 Check the high voltage diode See page T 30 ...

Page 144: ...144 LMVM2277ST Chart E Beeper Beepeth Not T 46 Check the PCB Printed Circuit Board and all connectors ...

Page 145: ...145 LMVM2277ST Chart F Power Supply T 47 Check the ventilation fan for proper operation ...

Page 146: ...146 LMVM2277ST Main Board T 48 Connectors labeled ...

Page 147: ...147 LMVM2277ST Exploded View T 49 54 ...

Page 148: ...7ST Parts List T 55 57 The parts list is provided for your convenience to ensure that the part you have in your hand or on the truck is indeed the correct part number Always order parts by MODEL and SERIAL NUMBER ...

Page 149: ...149 LMVM2277ST Serial Numbers T 55 Example 801KW3400251 8 0 1 K W 0 0 2 5 1 Production Number Internal code Manufactured January 2008 3 4 Made in Korea ...

Page 150: ...150 LMVM2277ST Serial Numbers T 55 Sequential number Internal code Model ID Production site 2 Letters 12345 KR 406 YP 000002 Options New Serial Code ETA Mid 2008 Year and month of production YMM ...

Page 151: ...ers 02 MFL06272504 Manual Service 04 MFL06208702 Manual Installation 05 MEZ37728002 Label Cooking Guide 06 1 4922W5A060A Card Template 06 2 MBM38968801 Card Template 10 MAY39948401 Box 13213A ADV32254902 Frame Assembly Door 13536A 3536W1A007G Tape Sealing 13550L MCK36295901 Cover LED ...

Page 152: ... Watts Volts Amperes Additional Information Ohm s Law T 60 P WATTS Watts Volts2 x Ohms Watts Amperes2 x Ohms Watts Volts x Amperes E VOLTS Volts Volts Watts Amperes Volts Amperes x Ohms R OHMS Ohms Volts Amperes Ohms Volts 2 Amperes Ohms Watts Amperes 2 ...

Page 153: ...153 LMVM2277ST Chart Ohm s Law T 60 ...

Page 154: ...154 LMVM2277ST Temperature Conversion T 16 F 9 5 C 32 C 5 9 x F 32 ...

Page 155: ...155 LMVM2277ST Schematic New and improved on a double sized page folded in the back of the training manual ...

Page 156: ...156 LMVM2277ST ...

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