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LG MC2841SPS, Service Manual

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LG MC2841SPS Service Manual Download Page 18

5-8

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)

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 scale: Rx1000)
• Filament to chassis

Approx.: 2.0 ohm
Approx.: 150 ohm
Less than: 1 ohm

Normal: Infinite
Normal: Infinite

Normal: Less than 1 ohm

Normal: Infinite

FILAMENT 
WINDING
TERMINAL

PRIMARY  
TERMINAL

SECONDARY  
TERMINAL

COMPONENT TEST PROCEDURE

Summary of Contents for MC2841SPS

Page 1: ...MODEL MC2841SPS ...

Page 2: ...r 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...

Page 3: ...ATIC DIAGRAM 4 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 13 TROUBLE SHOOTING Display shows error mode 5 19 EXPLODED VIEW 6 1 REPLACEMENT PARTS LIST 7 1 CONTENTS ...

Page 4: ...MED HIGH 720W approx 80 of Full power MEDIUM 540W approx 60 of Full power DEFROST 360W approx 40 of Full power LOW WARM 180W approx 20 of Full power CONVECTION Max 230 C GRILL COMBINATION Owner s manual Cook book Glass turntable Rotating ring Rack High Low 1 1 ITEM MODEL Power Requirement Power Output Microwave Frequency Magnetron Timer Outside Dimensions Cavity Dimensions Net Weight Shipping weig...

Page 5: ...tron 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 from danger in ordinary use extreme care should be taken du...

Page 6: ...to prevent interference 8 Do not touch the front glass during or after cooking of the Grill and Combination mode This glass is very hot during heater operating 9 Do not operate the oven at microwave and combination mode with Grill rack placed in the cavity when the oven is empty EARTHING INSTRUCTIONS This microwave oven is designed to be used in a fully earthed condition It is imperative therefore...

Page 7: ... time of day 4 START Q START One tap allows oven to begin functioning 5 COOK TIME Used to select cook time 6 MICRO Used to select power level for cooking 7 GRILL Used to select the grill cooking 8 COMBI Used to select the combination cooking 9 CONVECTION Used to select the convection cooking 10 AUTO COOK Used to cook the foods listed by one touch Turntable Rotating Ring Oven Front Plate Window Doo...

Page 8: ...Dial Stop Clear Select Grill Desired cooking time Start Stop Clear Select Convection Desired convection temp 40 C 100 C 230 C Start Stop Clear Select Convection Desired convection temp 40 C 100 C 230 C Press Dial Stop Clear Select Grill combi Desired cookinglevel Desired cooking time Start Press Dial Stop Clear Select Conv combi Desired cookinglevel Press Dial DesiredConv temp 100 C 230 C Press Di...

Page 9: ...SCHEMATIC DIAGRAM 4 3 Conv therostat ...

Page 10: ... 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 are cut off primary winding voltage of the...

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: ...e 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 along t...

Page 13: ...mperature after heating T0 Temperature of bowl M Weight of bowl is measured while the microwave generator is operating at full power Magnetron filament heat up time is not included 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 to minimize addition or removal of heat ...

Page 14: ...e oven F AIR DUCT ASSEMBLY REMOVAL 1 Disconnect the leadwire from lamp 2 Remove the mounting screw to the cavity G MAGNETRON REMOVAL 1 Disconnect the leadwire from the high voltage transformer and high voltage capacitor 2 Carefully remove the mounting screws holding the magnetron and the waveguide 3 Remove the magnetron ASS Y until the tube is clear from the waveguide NOTE 1 When removing the magn...

Page 15: ...r 2 Disconnect the leadwire from magnetron high voltage transformer and capacitor 3 Remove the screw holding the high voltage transformer to the baseplate K THE TURNTABLE MOTOR REMOVAL 1 Remove the turntable 2 Remove the turntable shaft VERY CAREFULLY with a slotted screwdriver 3 Lay the unit down on its back 4 Remove the turntable motor cover The turntable base cover is easily removed by pinching...

Page 16: ...M 1 INTERLOCK 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 latc...

Page 17: ...d 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 closed m...

Page 18: ...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 scale Rx1000 F...

Page 19: ...inal 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 sure ...

Page 20: ...r switch operation replace the defective switch and the fuse at the same time Replace just the fuse if the switches operate normally NOTE Make sure heater is fully cooled when tested Measure the resistance Multi meter scale Rx1 Normal Grill heater Approx 42 ohm at 20 30o C Convection heater Approx 63 ohm at 20 30o C Normal more than 0 5 Mohm Normal Abnormal Measure the resistance with 500V 100M oh...

Page 21: ...lay 5 Convection FAN MOTOR Wire leads removed TURNTABLE MOTOR Wire leads removed Measure the resistance Ohm meter scale R x 1 Measure the resistance Ohm meter scale R x 1000 Check for P C B connector Normal Approx 300 500 ohm Abnormal Infinite or several ohm Normal Approx 10 20 kohm Abnormal Infinite or several ohm B Cooking Start OFF Relay 2 Relay 3 Relay 5 1 2 3 4 5 6 7 8 9 Cooking Start OFF ...

Page 22: ...ROWAVE ENERGY LEAKAGE TEST MUST ALWAYS BE PERFORMED WHEN THE UNIT IS SERVICED FOR ANY REASON MAKE SURE THE WIRE LEADS ARE CORRECT POSITION WHEN REMOVING THE WIRE LEAD FROM THE PARTS BE SURE TO GRASP THE CONNECTOR NOT THE WIRES Normal COM 230V Approx 160 Ω Abnormal Infinite or several ohm ...

Page 23: ...el to discharge any static charge built up in your body CONDITION Microwave oven does not work Inserting many plug into one plug outlet and using them at the same time causes overloading 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 occurring Inconsistent intensi...

Page 24: ... Display counts down too fast while cooking 10 Each indicator light does not turn on after setting cooking cycle 11 Display time of day does not reappear when cooking is finished 12 Beep sound is not heard when correct key is touched 5 14 TROUBLE 1 The following visual conditions indicate a probable defective control circuit CONDITION CHECK RESULT CAUSE REMEDY Everything works as specified Still h...

Page 25: ...or closed Check continuity 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 TROUBLE 2 Oven does not operate at all Display window does not display any figures and no input is accepted NOTE All these switches must be replaced at the same time Refer to page 5 6 5 7 2 Fuse does not blow N...

Page 26: ...with door closed Check fan motor Check oven lamp Abnormal Abnormal Normal Defective fan motor Defective oven lamp Replace fan motor Replace oven lamp Loose connection Connection then tightly CONDITION CHECK RESULT CAUSE REMEDY Output is low Lower than 90 of rating voltage Normal Normal Abnormal Abnormal Measure the output power Disconnect the wire leads from relay 2 and check on and off time with ...

Page 27: ... Defective high voltage transformer Replace high voltage transformer Check H V transformer normal normal Abnormal Defective high voltage Diode Replace high voltage Diode Check H V diode Abnormal Defective high voltage capacitor Replace high voltage capacitor Check H V capacitor Abnormal Defective magnetron Replace magnetron Check Magnetron TROUBLE 5 No microwave oscillation even though oven lamp a...

Page 28: ...function the heater Replace Replace TROUBLE 6 Oven does not cook properly when programmed for the set power level Operates properly on HIGH CONDITION CHECK RESULT CAUSE REMEDY Output is full when you set lower power level Abnormal Disconnect the wire leads from relay 2 and check continuity relay 2 Operate the unit Defective P C B assembly Replace P C B assembly NOTE Make sure the wire leads correc...

Page 29: ...lay shows F01 No continuity Continuity Normal Abnormal Check the thermistor Defective thermistor Thermistor opened Replace the thermistor Loose connection Connect them tightly Check the connnection between Thermistor and P C B assembly Normal Abnormal Check the heater Defective heater Heater opened Replace the heater Defective P C B Assembly Replace the P C B Assembly TROUBLE 9 Oven seems to be in...

Page 30: ... 6 1 EXPLODED VIEW INTRODUCTION INTERIOR PARTS OVEN CAVITY PARTS LATCH BOARD PARTS CONTROL PANEL PARTS BASE PLATE PARTS ...

Page 31: ... 6 2 DOOR P ARTS 13581A ...

Page 32: ... 6 3 CONTROL PANEL PARTS 268711 23572A 23506A ...

Page 33: ... 6 4 OVEN CAVITY PARTS 33052M 36549S 33390G 34370T 35889A 33390M 33112U 372901 35300A 33390L 33390H ...

Page 34: ... 6 5 LATCH BOARD PARTS 33052N 466001 466003 466001 43500A ...

Page 35: ... 6 6 INTERIOR PARTS 50FZZA 50CZZH 56324A 56912B 56930G 56851D 56411A 56322A 56411B 36549T 36549U 365501 56411C 34810H 56930A 56411D 535041 535042 55900A 56201A 56892 365901 35300B 54974S ...

Page 36: ... 6 7 BASE PLATE PARTS 56170D ...

Page 37: ......

Page 38: ...Fuse Holder 1 R EA 1 21 35300B 5300W1A002F Heater Miraclon 1 R EA 2 22 56892 ACQ88369901 Cover Assembly Rear 1 R EA 1 23 33052M 3052W1M023A Cover Insulator 1 R EA 1 24 56170D EBJ61671001 Transformer high voltage 1 R EA 1 25 56324A 6324W1A001L Magnetron 1 R EA 1 26 35300A 5300W1A003L Heater Miraclon 1 R EA 1 27 372901 MEA62172901 Guide Air 1 R EA 1 28 56912B 6912W3B002Z Lamp Incandescent 1 R EA 1 2...

Page 39: ......

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