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Website: http://us.lgservice.com
MICROWAVE OVEN
SERVICE MANUAL
MODEL: LMAB1240ST
CAUTION
BEFORE SERVICING THE UNIT, READ THE SAFETY PRECAUTIONS IN THIS MANUAL.
December, 2004
P/NO : 3828W5S5057 Printed in Korea
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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
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CONTENTS (Page) SAFETY PRECAUTIONS --------------------------------------------------------------------- Inside front cover SPECIFICATIONS ----------------------------------------------------------------------------------------------------- 1-1 CAUTIONS -------------------------------------------------------------------------------------------------------------- 2-1 INSTALLATION -------------------------------------------------------------------------------------------------------- 3-1 OPERATIN
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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. 3 17 21 Outside Dimensions 20 /19" x 11 /20" x 16 /46" 13 10 Cavity Dimensions 14 /75" x 9 /27" x 15" 34.9 lbs Net Weight 38.6 lbs Shipping weight Control Complement Touch Control System Clock : 1:00 - 12:59 Microwave Power for Vari
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CAUTIONS Unlike other appliances, the microwave oven is MICROWAVE RADIATION high-voltage and high-current equipment. Personnel should not be exposed to the Though it is free from danger in ordinary use, microwave energy which may radiate from the extreme care should be taken during repair. magnetron or other microwave generating device if it is improperly used or connection. • DO NOT operate on a 2-wire extension cord during All input and output microwave connections, repair and use. waveguide,
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INSTALLATION BEFORE YOU BEGIN, READ THE FOLLOWING INSTRUCTIONS COMPLETELY AND CAREFULLY. INSTALLING GROUNDING INSTRUCTIONS 1. Empty the microwave oven and clean inside it with For personal safety, this appliance must be fully a soft, damp cloth. Check for damage such as grounded at all times. misaligned door, damage around the door or dents In the event of an electrical short circuit, grounding inside the cavity or on the exterior. reduces the risk of electrical shock. The plug must be plugged i
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OPERATING INSTRUCTIONS FEATURES Oven Front Plate Window Door Screen Door Seal Display Window Control Panel Safety Door Lock System Turntable Roller Rest CONTROL PANEL 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. 1 3. AUTO DEFROST: Touch this pad to defrost foods by entering weight. 2 4. QUICK DEFROST: Touch this pad to defros
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OPERATING SEQUENCE The following is a description of component functions 7. AUTO DEFROST COOKING during oven operation. AUTO NUMBER OF STOP/CLEAR START DEFROST WEIGHT 1. SETTING THE CLOCK STOP/CLEAR CLOCK NUMBER CLOCK 8. CHILD LOCK ex.) To set 4:30, touch number key [4],[3], and [0]. This oven has a CHILD LOCK feature TO SET CHILD LOCK NOTE: 1) This is a 12 hour clock. • Touch the STOP/CLEAR pad 2) Clock will operate as long as power is applied to the oven. • Touch and hold 0 pad
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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,
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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,
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CIRCUIT DESCRIPTION • A high voltage of approximately 2100 volts AC is GENERAL DETAILS generated in the secondary of the high voltage • The low voltage transformer supplies the necessary transformer which is increased by the action of the high voltage to the micom controller when power cord is voltage diode and charging of the high voltage plugged in. capacitor. • When the door is closed, the primary switch is ON, the • The negative 4,000 Volts DC is applied to the filament secondary switch is O
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SERVICE INFORMATION TOOLS AND MEASURING INSTRUMENTS NECESSARY TOOLS NECESSARY MEASURING INSTRUMENTS Tools normally used for TV servicing are sufficient. • TESTER (VOLTS-DC, AC, Ohmmeter) Standard tools are listed below. • Microwave survey meter • Diagonal pliers - Holaday HI-1500 • Long nose pliers HI-1501 • Phillips screwdriver - Narda 8100 • Flat blade screwdriver 8200 • Wrench (size 5mm) • Inch scale • Nutdriver (size 5mm) • 600 cc non conductive material beaker (glass or plastic), 1 • Adjust
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MEASUREMENT WITH OUTER CASE NOTES WHEN MEASURING REMOVED • Do not exceed meter full scale deflection. • The test probe must be moved no faster than • When you replace the magnetron, measure for 1 inch/sec (2.5 cm/sec) along the shaded area, microwave energy leakage before the outer case is otherwise a false reading may result. installed and after all necessary components are • The test probe must be held by the grip portion of the replaced or adjusted. handle. Special care should be taken in mea
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MEASUREMENT OF MICROWAVE POWER OUTPUT • Microwave power output measurement is made with • The microwave power output P in watts is calculated the microwave oven supplied at its rated voltage and from the following formula: operated at its maximum microwave power setting with a load of (1000 ± 5)g of potable water. 4187 x (∆ T) P = • The water is contained in a cylindrical borosilicate glass T vessel having a maximum material thickness of 3 mm and an outside diameter of approximately 190mm. is
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Remove choke cover 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 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 Key Membrance Remove door Release Lever Door seal plate Button Spring Door Open Button E. DOOR ASSEMBLY REMOVAL 1) Open the door. 2) Remove the choke cover
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F. MAGNETRON REMOVAL G. REMOVING THE TURNTABLE MOTOR 1) Disconnect the lead wire from the magnetron. 1) Remove the turntable and rotating ring. 2) Carefully remove the mounting screws holding the 2) Lay the unit down on its back. magnetron and the waveguide. 3) Remove the turntable motor cover. 3) Remove the magnetron ASSEMBLY until the tube The turntable base cover is easily removed by is clear from the waveguide. pinching the eight parts with a wire cutting. 4) Disconnect the leadwire from the
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H. HIGH VOLTAGE TRANSFORMER K. IINTERLOCK SYSTEM 1) INTERLOCK MECHANISM REMOVAL The door lock mechanism is a device which has 1) Discharge the high voltage capacitor. been specially designed to eliminate completely 2) Disconnect the lead wire from magnetron, high microwave activity when the door is opened during voltage transformer, and capacitor. cooking and thus to prevent the danger resulting 3) Remove the screw holding the high voltage microwave leakage. transformer to the baseplate. 2) MOUN
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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 A. PRIMARY INTERLOCK SWITCH TEST B. SECONDARY INTERLOCK SWITCH TEST When the door is opened slowly, an audibl
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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 remo
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COMPONENTS TEST PROCEDURE RESULTS Antenna Gasket 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 Measure the resistance. Normal: Momentarily indicates CAPACITOR (Ohm-meter scale: Rx1000) several ohms, and • Terminal to terminal. then gradually returns to infinite. Normal: Infinite. Measure the resistance. (Ohm-meter scale: Rx1000) • Terminal to case. HIGH VOLTAGE Meas
