Website: http://us.lgservice.com Eletrodomésticos Fórum Todo sobre Electrodomésticos www.eletrodomesticosforum.com MICROWAVE OVEN SERVICE MANUAL MODEL: LMAB1240ST CAUTION BEFORE SERVICING THE UNIT, READ THE SAFETY PRECAUTIONS IN THIS MANUAL.
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.
CONTENTS (Page) SAFETY PRECAUTIONS - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - Inside front cover SPECIFICATIONS - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - 1-1 CAUTIONS - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
SPECIFICATIONS ITEM MODEL DESCRIPTION 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.
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 during repair. 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 connection. All input and output microwave connections, waveguide, flange, and gasket must be secure.
INSTALLATION BEFORE YOU BEGIN, READ THE FOLLOWING INSTRUCTIONS COMPLETELY AND CAREFULLY. INSTALLING GROUNDING INSTRUCTIONS 1. 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. 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.
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. 3. AUTO DEFROST: Touch this pad to defrost foods by entering weight. 4. QUICK DEFROST: Touch this pad to defrost foods quickly.
OPERATING SEQUENCE 7. AUTO DEFROST COOKING The following is a description of component functions during oven operation. STOP/CLEAR 1. SETTING THE CLOCK STOP/CLEAR CLOCK NUMBER AUTO DEFROST NUMBER OF WEIGHT START 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 • Touch the STOP/CLEAR pad • Touch and hold 0 pad LOCK appear on the display. NOTE: 1) This is a 12 hour clock.
SCHEMATIC DIAGRAM (I) *Check the Rating Model No. 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.
SCHEMATIC DIAGRAM (II) *Check the Rating Model No. (ADD Noise filter) 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.
CIRCUIT DESCRIPTION • 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. GENERAL DETAILS • The low voltage transformer supplies the necessary voltage to the micom controller when power cord is plugged in.
SERVICE INFORMATION TOOLS AND MEASURING INSTRUMENTS NECESSARY TOOLS NECESSARY MEASURING INSTRUMENTS Tools normally used for TV servicing are sufficient. Standard tools are listed below.
MEASUREMENT WITH OUTER CASE REMOVED NOTES WHEN MEASURING • 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.
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.
D. PCB ASSEMBLY REMOVAL Remove choke cover 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.
F. MAGNETRON REMOVAL G. REMOVING THE TURNTABLE MOTOR 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 the tube is clear from the waveguide. 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.
H. HIGH VOLTAGE TRANSFORMER REMOVAL K. IINTERLOCK SYSTEM 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 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 the oven assembly.
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.
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 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 CAPACITOR HIGH VOLTAGE DIODE NOTE : Some inexpensive meters may indicate infinite resistance in both direction. Measure the resistance. (Ohm-meter scale: Rx1000) • Terminal to terminal. Normal: Momentarily indicates several ohms, and then gradually returns to infinite.
COMPONENTS RELAY 2 TEST PROCEDURE RESULTS POWER LEVEL Check for continuity of relay 2 with an ohm-meter. (Remove wire leads from relay 2 and operate the unit.) 1 2 3 4 5 6 7 8 9 10 Relay 2 FAN MOTOR (Wire leads removed) Measure the resistance. (Ohm-meter scale: R x 1) 4 sec 6 sec 8 sec 10 sec 12 sec 14 sec 16 sec 18 sec 20 sec 22 sec 18 sec 16 sec 14 sec 12 sec 10 sec 8 sec 6 sec 4 sec 2 sec 0 sec Normal: A:Approx. 85 ~ 100 ohm. B:Approx. 10 ~ 25 ohm. B Abnormal: Infinite or several ohm.
TROUBLE SHOOTING WHEN YOU GET 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 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.
(PROBLEM 1) The following visual conditions indicate a probable defective control circuit. 1. Incomplete segments. • Segment missing. • Partial segment missing. • Digit flickering (NOTE: Slight flickering is normal.) 2. Colon does not turn on or blink. 3. A distinct change in the brightness of one or more numbers in display. 4. One or more digits in the display are not lighting. 5. Display indicates a number different from one touched, for example, key in 5 and 3 appears in the display. 6.
(TROUBLE 2) Oven does not operate at all, Display window does not display any figures, and no input is accepted. CONDITION 1. Fuse blows. CHECK Check continuity of monitor switch (with door closed). RESULT Continuity. CAUSE REMEDY Malfunction of the monitor switch. Replace fuse, primary, monitor, secondary switches, and RELAY(RY2) of P.C.B Assembly. No continuity. Replace fuse Check continuity of primary switch (with door opened). Continuity.
(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 1.Setting time does not count down when touching START pad. Check continuity of secondary switch (with door closed). No continuity. Check the connection between CN1 connector and P.C.B assembly. 2. Fan motor or oven lamp do not turn on. RESULT CAUSE REMEDY Defective secondary switch. Replace secondary switch. Continuity Defective P.C.B assembly.
(TROUBLE 5) No microwave oscillation even though oven lamp and fan motor run (Display operates properly) CONDITION No microwave oscillation. CHECK Disconnect the wire leads from relay 2 and check continuity of relay2. (Operate the unit) Check high voltage transformer RESULT No continuity. CAUSE REMEDY Defective P.C.B assembly Replace P.C.B assembly Defective high voltage transformer. Replace high voltage transformer. Defective high voltage capacitor. Replace high voltage capacitor.
#EV# EXPLODED VIEW INTRODUCTION OVEN CAVITY PARTS INTERIOR PARTS BASE PLATE PARTS DOOR PARTS LATCH BOARD PARTS CONTROL PANEL PARTS 6-1
#EV# DOOR PARTS 13581A 15006A 13552A 13536A 13213A 13551A 13352A 14026A 14970A 6-2
#EV# CONTROL PANEL PARTS 24781M 24930D 23551A 268711 23550D WTP018 24510L 24970A 23551B 6-3
#EV# OVEN CAVITY PARTS 33112U WSZ185 33052A WTT010 33390G 35889A 36549S WTP013 6-4
#EV# LARCH BOARD PARTS WSZ085 466001 43500A 466003 466001 6-5
#EV# INTERIOT PARTS (I) Check the rating label of Model and order SVC parts according to the Model No. Model: LMAB1240ST * Check the Rating Model No. WSZ002 * Check the Rating Model No. 56411A 568771 50FZZA * Check the Rating Model No. 56930V 55006F 34930W 56549F WTT028 WSZ002 55900A WTT037 * Check the Rating Model No.
INTERIOT PARTS (II) Check the rating label of Model and order SVC parts according to the Model No. Model: LMAB1240ST / 01 * Check the Rating Model No. * Check the Rating Model No. WSZ002 56411A 568771 50FZZA * Check the Rating Model No. 56930V 56201A 34930W 56549F WTT028 WEB001 55900A WTT037 * Check the Rating Model No.
#EV# BASE PLATE PARTS 56170D 63302A 63303A 948502 WTT021 647781 WTT028 WSZ002 6-8