GE LMAB1240ST User's Manual
Contents
1. CONDITION CHECK RESULT CAUSE REMEDY 1 Fuse blows Check continuity Continuity LO Malfunction of the Replace fuse of monitor monitor switch primary monitor switch with secondary door closed TE switches and No continuity RELAY RY2 of P C B Assembly Replace fuse Continuity gt Shorted contact at gt drin Hane switch with he primary swich secondary door opened I nur switches and No continuity RELAY RY2 of P C B Assembly Check continuity y Continuity gt Malfunction of Replace fuse of secondary secondary switch primary monitor switch with secondary door opened nur switches and No continuity RELAY RY2 of P C B Assembly Disconnect one Nona Defective high Replace high side of the wire voltage capacitor voltage capacitor gt lead connected from transformer placard Defective high volt Replace high volt to the high 9 age transformer age transformer voltage NOTE All these switches must be replaced at the same time capacitor and operate the unit Refer to page 5 7 5 8 2 Fuse does not blow cord Check continuity No continuity of thermostat gt2. CONDITION CHECK RESULT CAUSE REMEDY Check the Lower than 9096 of Decrease in power Suggest customer ow power source rating voltage source voltage contact local voltage with load electric power utility co or Normal qualified electrician Disconnect the Defective P C B Replace P C B y Wire leads from assembly assembly relay 2 and check on and off gt Normal time with multitester Measure the Abnormal Defective Replace output power i magnetron magnetron NOTE Simple test of power output conducted by heating one liter water for one min if available Minimum 8 5 C temperature rise is normal condition 5 14 TROUBLE 5 microwave oscillation even though oven lamp and fan motor run Display operates properly CONDITION CHECK RESULT CAUSE REMEDY No microwave Disconnect the No continuity Defective P C B Replace P C B oscillation wire leads from assembly assembly relay 2 and check continuity y Continuity of relay2 Operate the unit Check high vol Defective high Replace high gt L tage transformer e AROMA voltage voltage transformer transformer Normal high vol Abnormal Defective high Replace high tage capacitor voltage capacitor voltage capacitor Normal Check high vol Defective high Replace high tage diode Annormal voltage diode voltage diode Normal Che
3. 5 1 MICROWAVE LEAKAGE TEST tid tenta rinitis 5 1 MEASUREMENT OF MICROWAVE POWER OUTPUT m nnne 5 3 DISASSEMBLY AND ADJUSTMENT tantes tt 5 3 INTERLOCK CONTINUITY TEST ineat ten tente taste tate ret inniti datae 5 7 COMPONENT TEST PROCEDURE eniin 5 8 TROUBLE SHOOTING rnit 5 11 EXPLODED VIEW ee 6 1 REPLACEMENT PARTS LIST Ha aa nahe 7 1 SPECIFICATIONS ITEM DESCRIPTION MODEL LMAB1240ST Power Requiremen 120 Volts AC 60 Hz 13 3A 1500 Watts Single phase 3 wire grounded Power Output 1200 Watts full microwave power IEC60705 Microwave Frequency 2450 MHz Magnetron 2M246 050GF Timer 0 99 min 99 sec Outside Dimensions 203 19 x 1117 20 x 1621 46 Cavity Dimensions 1413 75 x 910 27 x 15 Net Weight 34 9 lbs Shipping weight 38 6 lbs Control Complement Touch Control System Clock 1 00 12 59 Microwave Power for Variable Cooking Power level Full power throughout the cooking time approx 90 of Full power 8 Reheat approx 80 approx 70 6 Medium approx 60 50 4 Defrost 40 30 2 Simmer 20 10 Rating Label Location a Back Side y Accessories Owner s m
4. 5 TEST PROCEDURE RESULTS Antenna Chassis Filament 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 CAPACITOR Measure the resistance Ohm meter scale Rx1000 Terminal to terminal Normal Momentarily indicates several ohms and then gradually returns to infinite Measure the resistance Ohm meter scale Rx1000 Terminal to case Normal Infinite HIGH VOLTAGE DIODE NOTE Some inexpensive meters may indicate infinite resistance in both direction Measure the continuity Forward Ohm meter scale Rx10000 Normal Continuity Abnormal Infinite Measure the continuity Reverse Ohm meter scale Rx10000 5 9 Normal Infinite Abnormal Continuity COMPONENTS TEST PROCEDURE RESULTS RELAY 2 Check for continuity of relay 2 with an POWER N ES ohm meter LEVEL Remove wire leads from relay 2 and operate the unit 4 sec 6 sec 8 sec 10 sec 12 sec 14 sec 16 sec 18 sec 20 sec 22 sec Relay 2 Measure resistance Normal Wire leads removed Ohm meter scale Rx 1 A Approx 85 100 ohm B Approx 10 25 ohm Abnormal Infinite or several ohm TURNTABLE Measure the resistance Normal Approx 100 150 ohm MOT
5. Microwave oven plug is not inserted tightly Output power is too low Low AC input voltage Food temperature is too low REMEDY Avoid using other electrical appliances when you use the microwave oven Insert microwave oven plug securely Use the microwave oven at adequate line voltage Sparks occur This may not be a defect It is possible that the food should be cooked for a longer time period Using metallic ware and allowing it to touch the oven wall Do not use metallic ware for cooking except that noted in the cooking guide Ceramic ware trimmed in gold or silver powder is used Uneven cooking Inconsistent intensity of microwave by their characteristics 5 11 Do not use any type of cookware with metallic trimming 1 Use plastic wrap or 2 Stir once or twice while cooking soup cocoa milk etc PROBLEM 1 The following visual conditions indicate a probable defective control circuit Incomplete segments Segment missing Partial segment missing Digit flickering NOTE Slight flickering is normal mb Colon does not turn on or blink A distinct change in the brightness of one or more numbers in display One or more digits in the display are not lighting
6. CLOCK EZ ON 4 1 1 DISPLAY The display includes a clock and indicators that tell you the time of day cook time settings and cooking functions selected 2 AUTO TOUCH Touch this pad to cook without entering a cook time or power 3 AUTO DEFROST Touch this pad to defrost foods by entering weight 4 QUICK DEFROST Touch this pad to defrost foods quickly 5 NUMBER PADS Touch number pads to enter cook time power level quantities or weights 6 TIME Touch this pad to set a cook time 7 POWER Touch this pad to set a cook power 8 STOP CLEAR It used to stop oven and clear all entries except time day 9 Ez ON You can extend cooking time in multiples of 30 seconds by repeatedly touching this pad during cooking 10 START This feature allows oven to begin functioning 11 CLOCK Touch this pad to set time of day 12 TIMER Touch this pad to set timer OPERATING SEQUENCE The following is a description of component functions during oven operation 1 SETTING THE CLOCK STOP CLEAR 3 CLOCK gt NUMBER 3 CLOCK ex To set 4 30 touch number key 4 3 and 0 NOTE 1 This is a 12 hour clock 2 Clock will operate as long as power is applied to the oven 2 CANCEL FUNCTION Touch the STOP CLEAR pad whenever you need to cancel an entry or a function currently in use The display will either return to the last item entered or to the
7. Continuity Check continuity of power supply No continuity 5 13 Defective Replace thermostat thermostat Defective power Replace power supply cord supply cord PROBLEM 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 1 Setting time Check continuity No continuity Defective Replace does not count of secondary secondary switch secondary switch down when switch with touching START door closed L Continuity pad L Check the con gt Continuity y Defective P C B Replace P C B nection between assembly assembly CN1 connector m gt and P C B L No continuity Loose connection gt ides em assembly ignty Si Fan MOOGT Check fan motor H Abnormal 3 Defective fan motor Replace fan motor oven lamp do not turn on Check oven lamp Abnormal L Defective oven lamp Replace oven lamp Normal PROBLEM 4 Oven seems to be operating but little heat is produced in oven load
8. gt TH LG Website http us lgservice com Eletrodom sticos F rum Todo sobre Electrodom sticos www eletrodomesticosforum com MICROWAVE OVEN MODEL LMAB1240ST CAUTION BEFORE SERVICING THE UNIT READ THE SAFETY PRECAUTIONS IN THIS MANUAL December 2004 P NO 3828W5S5057 Printed in Korea 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 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 1 interlock operation 2 proper door closing 3 seal and sealing surfaces arcing wear and other damage 4 damage to or loosening of hinges and latches 5 evidence of dropping or abuse C Before turning on microwave power for any service test or inspection within the microwave generating compartments check the magnetron wave guide or transmission line and cavity for proper alignment integrity and connections D Any defective or misadjusted components in the interlock monitor door seal and microwave generatio
9. Display indicates a number different from one touched for example key in 5 and 3 appears in the display Specific numbers for example 7 or 9 will not display when key pad is touched Display does not count down with time blinking or up with clock operation Display obviously jumps in time while counting down Display counts down too fast while cooking Each indicator light does not turn on after setting cooking cycle Display time of day does not reappear when cooking is finished different from one touched 4 Random programming when touching other pads 5 Display is fixed at some figure and can not accept any input CONDITION CHECK RESULT CAUSE REMEDY 1 No input can be Check the conn confit Defective PCB Replace PCB programmed ection between y assembly assembly membrane key assembly and e Loose Connect them PCB assembly see connection tightly 2 Some inputs Replace key Everything works Defective key Replace key cannot be membrane as specified membrane membrane programmed assembly and assembly assembly check operation 3 Display shows a gt Still have trouble Defective PCB Replace PCB number figure assembly assembly 5 12 TROUBLE 2 Oven does not operate at all Display window does not display any figures and no input is accepted
10. Es zz e EB lt 2 L 34 EE Zo b x ns So E E O O 5 x E o E zm e 5 ES a g orm z gt CES TE Z E Lo een o lt amp gt m i i LO r lezlux 13 gt oO E E SO wl Sly n 2 lt 3 3 CN1 B 5 5 moon h adn h oo 5 1 0 0 1 1 9T9 no a ZIL g 13 XI lo P L jw 4 a a o 490 Lag ge fw ou sz 2 gt US Hose 00 gt 30 oat 0 Z cq IMPORTANT SAFETY NOTE THE SHADED AREAS ON THIS SCHEMATIC DIAGRAM INCORPORATE SPECIAL FEATURES IMPORTANT FOR PROTECTION FROM MICROWAVE RADIATION FIRE ELECTRICAL SHOCK AND HAZARDS WHEN SERVICING IT IS ESSENTIAL THAT ONLY MANUFACTURER 8 SPECIFIED PARTS BE USED FOR THE CRITICAL COMPONENTS IN THE SHADED AREAS OF THE SCHEMATIC DIAGRAM NOTICE SINCE THIS IS BASIC SCHEMATIC DIAGRAM THE VALUES OF COMPONENTS AND SOME PARTIAL CONNECTIONS ARE SUBJECT TO CHANGE FOR IMPROVEMENT 4 3 PRIMARY INTERLOCK SWITCH NOISE FILTER NO x a ES 87 e j 1 Se 00 a le 2 21 2 m gt S Sy m B ni so ES REA gt LO Zo Sur Li a I aw Sg 2 2 E 5 HO
11. The service personnel should inform the manufacture importer or assembler of any certified oven unit found to have a microwave emission level in excess of 5 mW cm and should repair any unit found to have excessive emission levels at no cost to the owner and should ascertain the cause of the excessive leakage The service personnel should instruct the owner not to use the unit until the oven has been brought into compliance If the oven operates with the door open the service personnel should Tell the user not to operate the oven Contact the manufacturer and CDRH Center for Devices and Radiological Health immediately NOTE Address on CDRH Office of Compliance HFZ 312 Center for Devices and Radiological Health 1390 Piccard Drive Rockville MD 20850 The service personnel should check all surface and vent openings for microwave leakage Check for microwave leakage after every servicing The power density of the microwave radiation leakage emitted by the microwave oven should not exceed 4 mW cm Always start measuring of an unknown field to assure safety for operating personnel from radiation leakage 5 1 NECESSARY MEASURING INSTRUMENTS TESTER VOLTS DC AC Ohmmeter Microwave survey meter Holaday HI 1500 HI 1501 Narda 8100 8200 Inch scale 600 cc non conductive material beaker glass or plastic inside diameter approx 8 5 cm 3 2 in Cylindrical and made of borosilicate glass vesse
12. a NOTE Leakage with the outer case removed less than pin in head 5 mW cm sq Leakage for a fully assembled oven Before the latch switch primary is interrupted with the door in a slightly opened position less than 2 mW cm sq 5 2 MEASUREMENT OF MICROWAVE POWER OUTPUT 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 The water is contained in a cylindrical borosilicate glass vessel having a maximum material thickness of 3 mm and an outside diameter of approximately 190mm The oven and the empty vessel are at ambient temperature prior to the start of the test The initial temperature T1 of the water is 10 2 C It is measured immediately before the water is added to the vessel After addition of the water to the vessel the load is immediately placed on the center of the turntable which is in the lowest position and the microwave power switched on The time T for the temperature of the water to rise by a value AT of 10 2 is measured where T is the time in seconds and AT 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 The microwave power output P in watts is calculated from the following formula 4187 x AT T P is measu
13. clock 3 EZ ON STOP CLEAR EZ ON 4 AUTO TOUCH STOP CLEAR 3 POPCORN NOTE Heat only 1 package at a time 5 TIME COOKING COOK TIME STOP CLEAR gt NUMBER POWER NUMBER 3 START 6 MULTI STAGE COOKING 1ST STAGE COOK STOP CLEAR TIME NUMBER POWER NUMBER 2ND STAGE COOK TIME NUMBER POWER NUMBER START 4 2 7 AUTO DEFROST COOKING AUTO DEFROST NUMBER OF STOP CLEAR gt WEIGHT o START 8 CHILD LOCK This oven has a CHILD LOCK feature TO SET CHILD LOCK e Touch the STOP CLEAR Touch and hold 0 display pad pad LOCK appear on the TO CANCEL CHILD LOCK Touch and hold 0 pad LOCK disappears SCH EMATIC DIAGRAM 1 Check the Rating Model No PRIMARY INTERLOCK SWITCH no FUSE ME a _ gt 5 re 4 28 amp gt m e Q x S gt 25 x y 2z 26 a aw S A z 5 hi O oF o 2 3 WO O x Sr z is Eds
14. the tube is clear from the waveguide NOTE 1 When removing the magnetron make sure its dome does not hit any adjacent parts or it may be damaged 2 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 3 After replacing the magnetron check for microwave leakage with a survey meter around the magnetron Microwave energy must be below the limit of 5 mW cm With a 275 ml water load Make sure that gasket 15 rigidly attached to the magnetron To prevent microwave leakage tighten the mounting screws properly making sure there is no gap between the waveguide and the magnetron Waveguide Dome Waveguide Bracket Magnetron Gasket Magnetron G REMOVING THE TURNTABLE MOTOR 1 Remove the turntable and rotating ring 2 Lay the unit down on its back 3 Remove the turntable motor cover The turntable base cover 15 easily removed by pinching the eight parts with a wire cutting 4 Disconnect the leadwire from the turntable motor terminals 5 Remove the screw securing the turntable motor to the oven cavity ASSEMBLY 6 After repairing the motor rotate the removed turntable motor cover 7 Fit the turntable motor cover s projecting part to the base plate slit NOTE 1 Remove the wire lead from the turntable motor VERY CAREFULLY 2 Be sure to grasp the connector not the wires when removing
15. 0 2 V m 6 gt Bs 2 6 m ES lt H V 55 CAPACITOR zm cx y 11 amp T 2 gt 8 Hz T U lt zx AT Da cz x z amp a lt 1 a a E y d h 85 O m s m m x aj a co x 5 1 9OTO Ix sl na EN 15 ET M 98 15 5757 gu Su zliixiololxlo z SY iS 5 1 MAIN PCB g 52 J IMPORTANT SAFETY NOTE THE SHADED AREAS ON THIS SCHEMATIC DIAGRAM INCORPORATE SPECIAL FEATURES IMPORTANT FOR PROTECTION FROM MICROWAVE RADIATION FIRE ELECTRICAL SHOCK AND HAZARDS WHEN SERVICING IT IS ESSENTIAL THAT ONLY MANUFACTURER S SPECIFIED PARTS BE USED FOR THE CRITICAL COMPONENTS IN THE SHADED AREAS OF THE SCHEMATIC DIAGRAM NOTICE SINCE THIS IS BASIC SCHEMATIC DIAGRAM THE VALUES OF COMPONENTS AND SOME PARTIAL CONNECTIONS ARE SUBJECT TO CHANGE FOR IMPROVEMENT SCHEMATIC DIAGRAM Il check the Rating Model No ADD Noise filter 4 4 CIRCUIT DESCRIPTION GENERAL DETAILS The low voltage transformer supplies the necessary voltage to the micom controller when power cord is plugged in When the door is closed the primary switch is ON the secondary switch is ON and the monitor switch opens contact COM and NO WHEN SELECTING COOKING POWER LEVEL AND TIME The micom controller memorizes the function y
16. CHES Wire leads removed Check for continuity of the switch with an Ohm meter Door open Primary Switch Monitor Switch Switch NOTE After checking for the continuity of switches make sure that they are connected correctly 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 SEE PAGE 2 1 2 ALL OPERATIONAL CHECKS WITH MICROWAVE ENERGY MUST BE DONE WITH A LOAD 1 LITER OF WATER IN CONTAINER IN THE OVEN COMPONENTS TEST PROCEDURE RESULTS HIGH VOLTAGE TRANSFORMER Wire leads removed PRIMARY TERMINAL 1 Measure the resistance Ohm meter scale Rx1 and Rx100 Primary winding Approx 0 2 0 4 ohm Secondary winding 60 90 ohm Filament winding Less than 1 ohm Measure the resistance Ohm meter scale Rx1000 Primary winding to ground Normal Infinite Filament winding to ground Normal Infinite MAGNETRON Wire leads removed Measure the resistance Ohm meter scale Rx1 Normal Less than 1 ohm Filament terminal Measure the resistance Ohm meter scale Rx1000 Normal Infinite Filament to chassis 5 8
17. H BOARD TO THE OVEN ASSEMBLY Mount the latch board to the oven assembly Adjust the latch board so that oven door will not have any play in it when the door is closed Tighten the mounting screw Check for play in the door by pushing the door release button Door movement should be less than 0 5 mm 1 64 inch Don t push the door release button while making this adjustment Make sure that the latch moves smoothly after adjustment is completed and that the screws are tight Make sure the primary monitor and secondary switches operate properly by following the continuity test procedure ADJUSTMENT O DIRECTION SECONDARY SWITCH MONITOR SWITCH PRIMARY SWITCH INTERLOCK CONTINUITY TEST WARNING FOR CONTINUED PROTECTION AGAINST EXCESSIVE RADIATION EMISSION REPLACE ONLY WITH IDENTICAL REPLACEMENT PARTS ALL THESE SWITCHES MUST BE REPLACED AT THE SAME TIME TYPE NO SZM V 16 FA 63 OR VP 533A OF OR V 5230Q FOR PRIMARY SWITCH TYPE NO SZM V 16 FA 62 VP 532A OF OR V 5220Q FOR MONITOR SWITCH TYPE NO SZM V 15 FA 63 VP 533A OFF OR SECONDARY SWITCH PRIMARY INTERLOCK SWITCH TEST When the door is opened slowly an audible click should be heard at the same time or successively at intervals and the latches should activate the switches with an audible click If the latches do not activate the switches when the door is closed the switches should be adjusted in accordance with the ad
18. OR Ohm meter scale Rx 1 Abnormal Infinite or several Wire leads removed ohm NOTE AMICROWAVE LEAKAGE TEST MUST ALWAYS PERFORMED WHEN THE UNIT IS SERVICED FOR ANY REASON 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 10 TROUBLE SHOOTING WHEN YOU 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 panel 1 Check grounding before checking for trouble 2 Be careful of the high voltage circuit 3 Discharge the high voltage capacitor See page 2 1 4 When checking the continuity of the switches or of the high voltage transformer disconnect one lead wire from these parts and then check continuity with the AC plug removed do otherwise may result in a false reading or damage to your meter 5 Do not touch any part of the circuit on the PCB since static electric discharge may damage this control Always touch yourself to ground while working on this panel to discharge any static charge built up in your body Micom model only CONDITION CAUSE Microwave oven does not work Inserting many plugs into one outlet and using them at the same time blown fuse or breaker
19. PCB SUB ASSEMBLY to the control panel 3 Disconnect the flat cable from the PCB SUB ASSEMBLY and take off the PCB SUB ASSEMBLY Control Panel PCB Sub Asm Release le L Button Spring UM E DOOR ASSEMBLY REMOVAL 1 Open the door 2 Remove the choke cover very carefully with a flat blade screwdriver CAUTION Be careful not to damage door seal plate by screwdriver 3 Lift up and push the door NOTE 1 After replacing the door be sure to check that the primary switch monitor switch and secondary switch operate normally 2 After replacing the door check for microwave energy leakage with a survey meter Microwave energy must be below the limit of 4 mW cm with a 275 ml water load 3 When mounting the door assembly to the oven assembly be sure to adjust the door assembly parallel to the chassis Also adjust so the door has no play between the inner door surface and oven frame assembly If the door assembly is not mounted properly microwaves may leak from the clearance between the door and the oven 5 4 Remove choke cover Remove door Door seal plate ir ue gt a al F MAGNETRON REMOVAL 1 Disconnect the lead wire from the magnetron 2 Carefully remove the mounting screws holding the magnetron and the waveguide 3 Remove the magnetron ASSEMBLY until
20. Turntable Motor Wire Leads HIGH VOLTAGE TRANSFORMER REMOVAL 1 Discharge the high voltage capacitor 2 Disconnect the lead wire from magnetron high voltage transformer and capacitor 3 Remove the screw holding the high voltage transformer to the baseplate I FAN MOTOR ASSEMBLY REMOVAL 1 Discharge the high voltage capacitor 2 Disconnect the lead wire from fan motor and high voltage capacitor 3 Remove the screws holding the the suction guide ASSEMBLY to the oven cavity 4 Remove the two screws holding the fan motor ASSEMBLY to the suction guide ASSEMBLY J HIGH VOLTAGE CAPACITOR AND DIODE REMOVAL 1 Discharge the high voltage capacitor 2 Disconnect the lead wire from fan motor and high voltage capacitor 3 Remove the screw holding the suction guide ASSEMBLY to the oven cavity 4 Remove the screw holding the high voltage capacitor bracket and remove the high voltage diode earth Screw 2 Fan Motor Noise Filter ASSY H V Diode 2 K INTERLOCK SYSTEM 1 INTERLOCK MECHANISM The door lock mechanism 15 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 microwave leakage 2 MOUNTING OF THE PRIMARY MONITOR SECONDARY SWITCHES TO THE LATCH BOARD 3 INSTALLATION AND ADJUSTMENT OF THE LATC
21. air flow The oven should not be installed in any area where heat and steam are generated because they may damage the electronic or mechanical parts of the unit Do not install the oven next to a conventional surface unit or above a conventional wall oven Use microwave oven in an ambient temperature less than 104 F 40 C Place the microwave oven on a sturdy and flat surface at least 10 cm 4 inches from the wall Place the microwave oven as far away as possible from TV RADIO COMPUTER etc to prevent interference 10cm 3 1 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 WARNING Improper use of the grounding plug can result in a risk of electric shock Do not under any circumstances cut or remove the third ground prong from the power cord plug PROPERL Y POLARIZED AND GROUNDED OUTLET Three Pronged Grounding plug OPERATING INSTRUCTIONS FEATURES Window Door Screen Oven Front Plate Display Window Control Panel Safety Door Lock System Turntable Roller Rest CONTROL PANEL Auto Touch POPCORN POTATO RESH FOOD FROZEN VEGETABLE PLATE ENTREE 1 BEVERAGE DEFROST DEFROST CLEAR
22. anual 8 cooking guide Glass turntable Roller Rest This microwave oven is designed for household use only It is not recommended for commercial purposes 1 1 CAUTIONS Unlike other appliances the microwave 15 high voltage and high current equipment Though it is free from danger in ordinary use extreme care should be taken during repair DO NOT operate on a 2 wire extension cord during repair and use NEVER TOUCH any oven components or wiring during operation BEFORE TOUCHING any parts of the oven always remove the power plug from the outlet For about 30 seconds after the oven stops an electric charge remains in the high voltage capacitor When replacing or checking you must discharge the high voltage capacitor by shorting across the two terminals with an insulated screwdriver Remove your watch 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 on the magnetron NEVER put anything into the latch hole and the interlock switches area 2 1 MICROWAVE RADIATION Personnel should not be exposed to the microwave energy which may radiate from the magnetron or other microwave generating device if it is improperly used or connectio
23. ating Model No Rating Model No 6 6 sr Check the Rating Model No gt OSS Check the Rating Model No INTERIOT PA RTS 11 Check the rating label of Model and order SVC parts according to the Model No Model LMAB1240ST 01 Check the Check the Rating Model No 152002 Rating Model 568771 2 Check the Rating Model No Check the Rating Model No 6 7 EV BASE PLATE PARTS 6 8 LG
24. ck Defective Replace magnetron abhormel magnetron magnetron NOTE Make sure the wire leads correct position When Removing the wire leads from the parts be sure to grasp the connector not the wires When removing the magnetron be sure to install the magnetron gasket in the correct position and in good condition Output is full power when you set lower power level Disconnect the wire leads from relay 2 and check continuity relay 2 Operate the unit Abnormal Defective P C B assembly Replace P C B assembly 5 15 EXPLODED VIEW INTRODUCTION OVEN CAVITY PARTS INTERIOR PARTS BASE PLATE PARTS DOOR PARTS LATCH BOARD PARTS CONTROL PANEL PARTS EV DOOR PARTS 6 2 CONTROL PANEL PARTS EV OVEN CAVITY PARTS 6 4 EV LARCH BOARD PARTS 6 5 EV INTERIOT PARTS 1 Model LMAB1240ST Check the Check the rating label of Model and order SVC parts according to the Model Check the R
25. justment procedure Disconnect the wire lead from the primary switch Connect the ohmmeter leads to the common COM and normally open NO terminal of the switch The meter should indicate an open circuit in the door open condition When the door is closed the meter should indicate a closed circuit When the primary switch operation is abnormal make the necessary adjustment or replace the switch with the same type of switch COMPONENTS TEST PROCEDURE B SECONDARY INTERLOCK SWITCH TEST Disconnect the wire lead from the secondary switch Connect the ohmmeter leads to the common COM and normally open NO terminals of the switch The meter should indicate an open circuit in the door open condition When the door is closed the meter should indicate a closed circuit When the secondary switch operation is abnormal make the necessary adjustment or replace the switch 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 the meter should indicate an open circuit When the monitor switch operation is abnormal replace with the same type of switch NOTE After repairing the door or the interlock system it is necessary to do this continuity test before operating the oven RESULTS SWIT
26. l max thickness 3 mm outside diameter approx 190mm height approx 90mm e Glass thermometer 100 C or 212 1 deg scale MEASURING MICROWAVE ENERGY LEAKAGE Pour 275 15 of 20 5 C 68 9 F water in a beaker which is graduated to 600 cc and place the beaker on the center of the turntable Set the energy leakage monitor to 2 450 MHz and use it following the manufacturer s recommended test procedure to assure correct result When measuring the leakage always use the 2 inch bcm spacer supplied with the probe Operate the oven at its maximum output Measure the microwave radiation using and electromagnetic radiation monitor by holding the probe perpendicular to the surface being measured Move probe along shaded area MIB 4 C P P 4 4 4 Probe scanning speed Less than 2 5 cm sec 1 in sec MEASUREMENT WITH OUTER CASE NOTES WHEN MEASURING REMOVED Do not exceed meter full scale deflection The test probe must be moved no faster than 1 inch sec 2 5 cm sec along the shaded area otherwise a false reading may result The test probe must be held by the grip portion of the handle A false reading may result if the operator s hand is between the handle and the probe When testing near a corner of the door keep the probe perpendicular to the surface making sure the probe When you replace the magnetron measure for microwave energy leakage before the outer case is ins
27. n All input and output microwave connections waveguide flange and gasket must be secure Never operate the device without a microwave energy absorbing load attached Never look into an open waveguide or antenna while the device is energized Proper operation of the microwave oven requires that the magnetron be assembled to the waveguide and cavity Never operate the magnetron unless it is properly installed Be sure that the magnetron gasket is properly installed around the dome of the tube whenever installing the magnetron ANTENNA Gasket COOLING FIN FILAMENT TERMINALS MAGNETRON CHASSIS GROUND MAGNETRON THE OVEN IS TO BE SERVICED ONLY BY PROPERLY QUALIFIED SERVICE PERSONNEL INSTALLATION BEFORE YOU BEGIN READ THE FOLLOWING INSTRUCTIONS COMPLETELY AND CAREFULLY INSTALLING 4 Empty the microwave oven and clean inside it with a soft damp cloth Check for damage such as misaligned door damage around the door or dents inside the cavity or on the exterior Put the oven on a counter table or shelf that is strong enough to hold the oven and the food and utensils you put in it The control panel side of the oven is the heavy side Use care when handling Do not block the vent and the air intake openings Blocking vent or air intake openings can cause damage to the oven and poor cooking results Make sure the microwave oven legs are in place to ensure proper
28. n 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 each oven prior to release to the owner CAUTION MICROWAVE RADIATION DO NOT BECOME EXPOSED TO RADIATION FROM THE MICROWAVE GENERATOR OR OTHER PARTS CONDUCTING MICROWAVE ENERGY CONTENTS Page SAFETY PRECAUTIONS Inside front cover SPECIFICATIONS ssicesissotsesseatseussectersssectspecsactsecarrctenescpeatyossbenerenspensbarcbarssceabersrornners 1 1 CAUTIONS O C M 2 1 INSTALLATION m el nee 3 1 OPERATING INSTRUCTIONS 4 1 FEATURES ME 4 1 CONTROL PANEL inacci n carac 4 1 OPERATING SEQUENCE 4 2 SCHEMATIC DIAGRAM I 15er tantae nnne rte sanar ntcnr cin drn cines arrancar arcano 4 3 SCHEMATIC DIAGRAM Il 4 4 CIRCUIT DESCRIPTION acertada andan tna nero 4 5 SERVICE INFORMATION sc een EFE 5 1 TOOLS AND MEASURING INSTRUMENTS
29. ou set The time you set appears in the display window Each indicator light turns on to indicate that the stage has been set WHEN TOUCHING THE START PAD The coil of the relay is energized by the micom controller Power input is supplied to the high voltage transformer through the fuse to the primary switch and relay 2 Turntable rotates 7 MONITOR SWITCH O PRIMARY SECONDARY SWITCH RELAY2 T SWITCH MICOM CONTROLLER A high voltage of approximately 2100 volts AC is generated in the secondary of the high voltage transformer which is increased by the action of the high voltage diode and charging of the high voltage capacitor The negative 4 000 Volts DC is applied to the filament of the magnetron WHEN THE OVEN IS SET AT ANY LEVEL EXCEPT MAXIMUM The micom controller controls the ON OFF time of relay 2 by the applied signal to vary the average output power of microwave oven as POWER LEVEL refer to page 1 1 One complete cycle of relay 2 is 22 seconds WHEN THE DOOR IS OPENED DURING COOKING Both the primary switch and relay 2 cut off the primary winding voltage of the high voltage transformer ON OFF of relay 2 is coupled electrically with opening and closing of the secondary switch When the door is opened the secondary switch is opened and when the door is closed the secondary switch is closed The cooking
30. red while the microwave generator is operating at full power Magnetron filament heat up time is not included about 3 sec The water is stirred to equalize temperature throughout the vessel prior to measuring the final water temperature e Stirring devices and measuring instruments are selected in order to minimize addition or removal of heat WATER LOAD SZ TURNTABLE DISASSEMBLY AND ADJUSTMENT A OUTER CASE REMOVAL 1 Disconnect the power supply cord from the outlet 2 Remove the screws from the rear of the case The outer case must be moved backward to be lifted off B POWER SUPPLY CORD 1 Remove the outer case 2 Disconnect two terminals and remove one screw of the ground terminal C CONTROL PANEL ASSEMBLY 1 Open the door 2 Disconnect the lead wire from RELAY RY2 of the PCB SUB ASSEMBLY 3 Disconnect the leadwire from connector CN1 of the PCB SUB ASSEMBLY 4 Remove screw which hold the controller assembly to the cavity 5 Lift up and pull out control panel assembly carefully from the cavity CAUTION DISCHARGE THE HIGH VOLTAGE CAPACITOR BEFORE SERVICING refer to page 2 1 5 3 Remove the screw Sg ground screw Lift up and pull out control panel UB D PCB ASSEMBLY REMOVAL 1 Remove the control panel assembly from the cavity Refer to control panel assembly removal on previous page 2 Remove screws which hold the
31. talled and after all necessary components are replaced or adjusted Special care should be taken in measuring the following parts Circled area of Fig below Around the magnetron The waveguide horizontally along the oven surface Hold vertically WARNING AVOID CONTACTING ANY when testing the top and bottom and horizontally HIGH VOLTAGE PARTS along RECORD KEEPING AND NOTIFICATION AFTER MEASUREMENT After adjustment and repair of any microwave energy interruption or microwave energy blocking device record the measured values for future reference Also enter the information on the service invoice The microwave energy leakage should not be more than 4 mW cm sq after determining that all parts are in good condition functioning properly and genuine replacement parts which are listed in this manual have been used At least once a year have the electromagnetic energy leakage monitor checked for calibration by its manufacturer SPECIAL TIP This oven used the button head screws MEASUREMENT WITH A FULLY z z AS ASSEMBLED OVEN After all components including the outer case are fully Ik assembled measure for microwave energy leakage Button Head around the door viewing window the exhaust opening Torx style 2 and air inlet openings Microwave energy leakage must not exceed the values prescribed below When you remove the screws use the tamper resistant Torx driver having
32. time stops counting down Relay stops functioning As the door is opened if the contact of primary switch and relay 2 and or secondary switch fail to open the fuse opens due to the large current surge caused by the monitor switch activation which in turn stops magnetron oscillation The fan motor rotates and cools the magnetron by blowing the air coming from the intake on the baseplate The air is also directed into the oven to exhaust the vapor in the oven through the upper plate Cooking time starts counting down 3 8 volts AC is generated from the filament winding of the high voltage transformer This 3 3 volts is applied to the magnetron to heat the magnetron filament through two noise preventing choke coils 4 5 J 7 MONITOR Y spa SWITCH O PRIMARY SECONDARY SWITCH RELAY2 SWITCH oc MICOM CONTROLLER SERVICE INFORMATION TOOLS AND MEASURING INSTRUMENTS NECESSARY TOOLS Tools normally used for TV servicing are sufficient Standard tools are listed below Diagonal pliers Long nose pliers Phillips screwdriver Flat blade screwdriver Wrench size 5mm Nutdriver size 5mm Adjustable wrench Soldering iron Solder Vinyl insulation tape Polishing cloth MICROWAVE LEAKAGE TEST CAUTIONS Be sure to check microwave leakage prior to servicing the oven if the oven is operative prior to servicing
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