LG MB-314XB Service Manual Download Page 26 | Manualshive

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5-16

CONDITION

CHECK

RESULT

CAUSE

REMEDY

No microwave
oscillation.

No continuity.

Continuity.

Abnormal

Defective high
voltage
transformer.

Replace high
voltage
transformer.

Normal

Defective PCB
assembly.

Replace PCB
assembly.

Disconnect the
wire leads from
relay 2 and
check continuity
of relay 2.
(Operate the unit)

Check high vol-
tage transformer

Output is full power
when you set lower
power level.

Abnormal.

Defective PCB
assembly.

Replace PCB
assembly.

Disconnect the
wire leads from
relay 2 and check
continuity relay 2.
(Operate the unit)

Abnormal

Defective high
voltage capacitor.

Replace high
voltage capacitor.

Normal

Check high vol-
tage capacitor.

Abnormal

Defective high
voltage diode.

Replace high
voltage diode.

Normal

Check high vol-
tage diode.

Abnormal

Defective
magnetron.

Replace
magnetron.

Check
magnetron.

(TROUBLE 5) No microwave oscillation even though oven lamp and fan motor run.

(Display operates properly)

NOTE : • 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.
• When removing the magnetron, be sure to install the magnetron gasket in the correct position

and in good condition.

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Summary of Contents for MB-314XB

Page 1: ...CROWAVE OVEN SERVICE MANUAL MODEL MB 314XF MB 314XB CAUTION BEFORE SERVICING THE UNIT READ THESAFETY PRECAUTIONS IN THIS MANUAL P NO 3828W5S1803 March 2001 Printed in Korea Website http biz lgservice com ...

Page 2: ...tron 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 transmiss...

Page 3: ... CIRCUIT DESCRIPTION 4 4 SERVICE INFORMATION 5 1 TOOLS AND MEASURING INSTRUMENTS 5 1 MICROWAVE LEAKAGE TEST 5 1 MEASUREMENT OF MICROWAVE POWER OUTPUT 5 3 DISASSEMBLY AND ADJUSTMENT 5 3 INTERLOCK CONTINUITY TEST 5 7 COMPONENT TEST PROCEDURE 5 8 TROUBLE SHOOTING 5 12 EXPLODED VIEW 6 1 REPLACEMENT PARTS LIST 7 1 SCHEMATIC DIAGRAM OF P C B 8 1 PRINTED CIRCUIT BOARD 8 2 P C B PARTS LIST 9 1 CONTENTS ...

Page 4: ...tts Single phase 3 wire grounded 1 000 Watts full microwave power IEC60705 2 450 MHz 2M246 0 99 min 99 sec 530 W x 313 H x 394 D 348 W x 222 H x 365 D 16 3 kg approx 18 3 kg approx Touch Control System Clock 1 00 12 59 Microwave Power for Variable Cooking Power level HIGH Full power throughout the cooking time 9 Saute approx 90 of Full power 8 Reheat approx 80 7 Med High approx 70 6 Medium approx ...

Page 5: ... 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 2 1 CAUTIONS Unlike other appliances the microwave oven is high voltage and high current equipment Though it is free fro...

Page 6: ...ical parts of the unit Do not install the oven next to a conventional surface unit or above a conventional wall oven 5 Use microwave oven in an ambient temperature less than 104 F 40 C 6 Place the microwave oven on a sturdy and flat surface at least 10 cm 4 inches from the wall 7 Place the microwave oven as far away as possible from TV RADIO COMPUTER etc to prevent interference GROUNDING INSTRUCTI...

Page 7: ...el or defrost weight 10 START This feature allows oven to begin functioning 11 COMBI 12 AUTO REHEAT This menu has been preprogrammed to reheat food automatically by selecting menu 13 AUTO DEFROST This feature provides you with the best defrosting method for frozen foods 14 OPTION You can select sound ON OFF demo ON OFF and scroll speed 15 MICRO This feature is used for manual cooking or 2 stage co...

Page 8: ...O SET CHILD LOCK Touch the pad Touch and hold PARAR BORRAR pad BLOQUEADO appear on the display TO CANCEL CHILD LOCK Touch the pad Touch and hold PARAR BORRAR pad DESBLOQUEADO disappears 9 OPTION You can select ON OFF of beeper ON OFF of demo and scroll speed To select sound ON OFF To select scroll speed To select demo ON OFF PARAR BORRAR FRIJOLES PARAR BORRAR 30 MÁS PARAR BORRAR 1ST STAGE INICIO P...

Page 9: ...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 20A ...

Page 10: ...ately 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 aver...

Page 11: ...ich 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 5cm spacer supplied with the probe Operate the oven at its maximum output Measure the microwave radiation using and electromagnetic radi...

Page 12: ...on The test probe must be removed 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 with 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 horizontally al...

Page 13: ... The microwave power output P in watts is calculated from the following formula 4187 x T T is measured 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 Stirring devices and measuring instruments are selected in order t...

Page 14: ...he 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 ...

Page 15: ... to the magnetron To prevent microwave leakage tighten the mounting screws properly making sure there is no gap between the waveguide and the 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 is easily removed by pinching the eight parts with a wire cutting 4 Disconnect the l...

Page 16: ...K MECHANISM The door lock mechanism is a device which has been specially designed to eliminate completely microwave activity when the door is opened during cooking and thus to prevent the danger resulting from the microwave leakage 2 MOUNTING OF THE PRIMARY MONITOR SECONDARY SWITCHES TO THE LATCH BOARD 3 INSTALLATION AND ADJUSTMENT OF THE LATCH BOARD TO THE OVEN ASSEMBLY Mount the latch board to t...

Page 17: ... an closed circuit 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...

Page 18: ... PROCEDURE RESULTS HIGH VOLTAGE TRANSFORMER Wire leads removed MAGNETRON Wire leads removed 1 Measure the resistance Ohm meter scale Rx1 and Rx100 Primary winding Secondary winding Filament winding 2 Measure the resistance Ohm meter scale Rx1000 Primary winding to ground Filament winding to ground 1 Measure the resistance Ohm meter scale Rx1 Filament terminal 2 Measure the resistance Ohm meter sca...

Page 19: ... Terminal to case Measure the continuity Forward Ohm meter scale Rx10000 Measure the continuity Reverse Ohm meter scale Rx10000 Normal Momentarily indicates several ohms and then gradually returns to infinite Normal Infinite Normal Continuity Abnormal Infinite Normal Infinite Abnormal Continuity NOTE When testing the magnetron be sure to install the magnetron gasket in the correct position and be ...

Page 20: ...ith an Multi meter Normal Gill heater Approx 15 at 20 30ûC Normal more than 1 0M NOTE Make sure heater is fully cooled when tested NOTE If the fuse is blown check primary the secondary the monitor switches H V D and H V C before replacing the fuse If the fuse is blown by improper switch operation replace the defective switch and the fuse at the same time Replace just the fuse if the switches opera...

Page 21: ...ec 2 6 sec 16 sec 3 8 sec 14 sec 4 10 sec 12 sec 5 12 sec 10 sec 6 14 sec 8 sec 7 16 sec 6 sec 8 18 sec 4 sec 9 20 sec 2 sec 10 22 sec 0 sec Normal A Approx 85 100 ohm B Approx 10 25 ohm Abnormal Infinite or several ohms Normal Approx 100 150 ohm Abnormal Infinite or several ohm NOTE A MICROWAVE LEAKAGE TEST MUST ALWAYS BE PERFORMED WHEN THE UNIT IS SERVICED FOR ANY REASON MAKE SURE THE WIRE LEADS...

Page 22: ... 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 Microwave oven 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 occur Inco...

Page 23: ... does not turn on after setting cooking cycle 11 Display time of day does not reappear when cooking is finished 5 13 TROUBLE 1 The following visual conditions indicate a probable defective control circuit CONDITION CHECK RESULT CAUSE REMEDY 1 No input can be programmed Continuity No continuity Defective PCB assembly Loose connection Replace PCB assembly Connect them tightly Check the conn ection b...

Page 24: ...of primary switch with door opened Disconnect one side of the wire lead connected from transformer to the high voltage capacitor and operate the unit Replace fuse Continuity Malfunction of secondary switch Replace fuse primary monitor secondary switches and RELAY RY2 of P C B Assembly No continuity Check continuity of secondary switch with door opened 2 Fuse does not blow No continuity Continuity ...

Page 25: ... all figures set but oven does not start cooking while desired program times are set and START pad is touched TROUBLE 4 Oven seems to be operating but little heat is produced in oven load 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 CONDITION CHECK RESULT CAUSE REMEDY Output is low Lower than 90 of...

Page 26: ... 2 and check continuity relay 2 Operate the unit Abnormal Defective high voltage capacitor Replace high voltage capacitor Normal Check high vol tage capacitor Abnormal Defective high voltage diode Replace high voltage diode Normal Check high vol tage diode Abnormal Defective magnetron Replace magnetron Check magnetron TROUBLE 5 No microwave oscillation even though oven lamp and fan motor run Displ...

Page 27: ...DOOR PARTS LATCH BOARD PARTS CONTROL PANEL PARTS INTERIOR PARTS BASE PLATE PARTS OVEN CAVITY PARTS 6 1 EXPLODED VIEW INTRODUCTION Model MB 314XF MB 314XB EV ...

Page 28: ...6 2 13213A 13552A 13536A 14026A 14970A 13581A 15006A 14890A 13720D DOOR PARTS EV ...

Page 29: ...6 3 23506A 268711 WTT028 24781M 24510L 250201 23572A 24970A CONTROLLER PARTS EV ...

Page 30: ...6 4 OVEN CAVITY PARTS EV 33052M 33112U WTT021 36549S WTP013 WNZ015 WTT010 WSZ184 340511 33390G 35300S 35026G 35889A ...

Page 31: ...6 5 LATCH BOARD PARTS EV WSZ085 466001 466003 466001 43500A 43501A ...

Page 32: ...RTS EV WTT037 WSZ002 WSZ002 WTT028 WSZ002 WSZ002 WSZ002 55900A 54810C 56324A 56912B 948501 35012A 55262A 56851D 50CZZH WTT028 WTP002 568771 56930V 56930V 34930W 56930G 54810A WSZ062 56411A 50FZZA 55006F 56549F 54974S ...

Page 33: ...6 7 BASE PLATE PARTS EV WTT WTT028 021 63302L 63303L 56170D WSZ002 948502 647781 63303R 63302R ...

Page 34: ...8 1 SCHEMATIC DIAGRAM OF P C B ...

Page 35: ...8 2 PRINTED CIRCUIT BOARD ...

Page 36: ......

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