Related Manuals for LG MH-704A
Summary of Contents for LG MH-704A
- Page 1 MICROWAVE/GRILL OVEN SERVICE MANUAL MODEL: MH-704A CAUTION BEFORE SERVICING THE UNIT, READ THE SAFETY PRECAUTIONS IN THIS MANUAL.
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Page 2: Specifications
SPECIFICATIONS ITEM DESCRIPTION MODEL MH-704A Power Requirement 220 Volts AC 50 Hz Single phase, 3 wire grounded Microwave 1,300W Grill 1,150W Combination 2,400W Power Output 900 Watts full microwave power (IEC705) Microwave Frequency 2,450 MHz Magnetron 2M214 - 39F Timer 99 min. -
Page 3: Control Panel
OPERATING INSTRUCTIONS FEATURES Oven Front Plate Window Door Screen Door Seal Display Window Control Panel Safety Door Lock System Grill Rack Glass Tray Rotating Ring CONTROL PANEL 1. INDICATORS 2. SET CLOCK: Used to set the time of day. 3. POWER: Used to select the desired power level for cooking. -
Page 4: Operating Sequence
OPERATING SEQUENCE The following is a description of component functions 6. GRILL COOKING during oven operation. Desired Stop Grill Start 1. SETTING THE CLOCK cooking time Set the Stop 7. COMBINATION COOKING clock clock correct time Desired NOTE: You can set 12 hour clock or 24 hour clock Desired Stop combi... -
Page 5: Schematic Diagram
SCHEMATIC DIAGRAM... -
Page 6: Circuit Description
CIRCUIT DESCRIPTION power of microwave oven as POWER LEVEL. GENERAL DETAILS (refer to page 1-1) • The low voltage transformer supplies the necessary • One complete cycle of relay 2 is 22 seconds. voltage to the micom controller when power cord is plugged in. - Page 7 MICROWAVE/GRILL OVEN SERVICE MANUAL MODEL: MH-704A CAUTION BEFORE SERVICING THE UNIT, READ THE SAFETY PRECAUTIONS IN THIS MANUAL.
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Page 8: Tools And Measuring Instruments
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 •... -
Page 9: Measurement With Outer Case Removed
MEASUREMENT WITH OUTER CASE NOTES WHEN MEASURING REMOVED • Do not exceed meter full scale deflection. • The test probe must be removed 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. -
Page 10: Measurement Of Microwave Power Output
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 4187 X (∆T) + 0.88 X (T ) X M a load of (1000±5) g of potable water. -
Page 11: Fan Motor Assembly Removal
D. DOOR GROSS ASSEMBLY REMOVAL E. HIGH VOLTAGE TRANSFORMER 1) Open the door. REMOVAL 2) Remove the choke cover cap very carefully with a 1) Discharge the high voltage capacitor. flat-blade screwdriver. 2) Disconnect the leadwire from magnetron, high voltage CAUTION : Be careful not to damage door seal plate transformer, and capacitor. -
Page 12: Magnetron Removal
H. AIR DUCT ASSEMBLY REMOVAL J. REMOVING THE TURNTABLE MOTOR 1) Remove the turntable. 1) Disconnect the leadwire from lamp and MGT 2) Remove the turntable shaft VERY CAREFULLY thermostat. with a slotted screwdriver. 2) Remove the mounting screw to the magnetron. 3) Lay the unit down on its back. -
Page 13: Pcb Assembly Removal
K. PCB ASSEMBLY REMOVAL L. INTERLOCK SYSTEM 1) Remove the control panel assembly from the 1) INTERLOCK MECHANISM cavity. (Refer to control panel assembly removal The door lock mechanism is a device which has on previous page.) been specially designed to eliminate completely 2) Remove screws which hold the PCB SUB ASS’Y to microwave activity when the door is opened during the control panel. -
Page 14: Interlock Continuity Test
INTERLOCK CONTINUITY TEST WARNING : FOR CONTINUED PROTECTION AGAINST EXCESSIVE RADIATION EMISSION, REPLACE ONLY WITH IDENTICAL REPLACEMENT PARTS. TYPE NO. SZM-V 16-FA-63 OR VP-533A-OF FOR PRIMARY SWITCH TYPE NO. SZM-V 16-FA-62 OR VP-532A-OF FOR MONITOR SWITCH TYPE NO. SZM-V 16-FA-63 OR VP-533A-OF FOR SECONDARY SWITCH B. -
Page 15: Component Test Procedure
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. -
Page 16: High Voltage Capacitor
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 then... - Page 17 COMPONENTS TEST PROCEDURE RESULTS FUSE Check for continuity of the fuse with an Normal Abnormal multi-meter. NOTE: If the fuse is blown, check the primary, the secondary, and 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.
- Page 18 COMPONENTS TEST PROCEDURE RESULTS Disconnect the 8 pin Cooking Start connector from P.C.B. (Refer to schemetic diagram on page 4-3) Cooking Start Relay 3 RELAY 2, RELAY 3 OF P.C.B. (Wire leads removed.) Note: Relay Relay 1: Fan motor Turntable motor Oven lamp Relay 2: Microwave Relay 2...
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Page 19: Troubleshooting
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. - Page 20 (TROUBLE 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.
- Page 21 (TROUBLE 2) Oven does not operate at all ; Display window does not display any figures and no input is accepted. CONDITION CHECK RESULT CAUSE REMEDY Replace primary Malfunction of the Check continuity 1. Fuse blows. Continuity. and monitor monitor switch. of monitor switches.
- Page 22 (TROUBLE 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 Defective Replace Check continuity 1.Setting time does No continuity. secondary switch. secondary switch.
- Page 23 (TROUBLE 5) No microwave oscillation even though oven lamp and fan motor run (Display operates properly) CONDITION CHECK RESULT CAUSE REMEDY No microwave Disconnect the Defective P.C.B Replace P.C.B No continuity. oscillation. wire leads from assembly assembly relay 2 and check continuity Continuity.
- Page 24 (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 Defective P.C.B. Replace P.C.B. Disconnect the Abnormal. you set lower assembly. assembly. wire leads from power level.
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Page 25: Exploded View
EXPLODED VIEW INTRODUCTION OVEN CAVITY PARTS INTERIOR PARTS BASE PLATE PARTS DOOR PARTS LATCH BOARD PARTS CONTROL PANEL PARTS... -
Page 26: Door Parts
DOOR PARTS 13581A 15006A 13536A 13552A 13213A 14890A 14026A 14970A 13720D 13806F... -
Page 27: Control Panel Parts
CONTROL PANEL PARTS 24781M 268711 23572A WTP018 26638A... -
Page 28: Oven Cavity Parts
OVEN CAVITY PARTS WTT021 33112U WTT021 35264A 348102 35301A 33550H WMT002 35300A 348101 33052M WTT010 35026G WTT011 33390G 34960A 34370T 34036W 35889A 36549S WTP013... -
Page 29: Latch Board Parts
LATCH BOARD PARTS WSZ085 466001 43501A 43500A 466003 44510A 466001... -
Page 30: Interior Parts
INTERIOR PARTS 568771 WSZ062 56411A WSZ112 54826A 56930V 56930G 948502 50FZZA WSZ002 WTT028 56549F 56201A WSZ002 55900A WTT037 54974S WTP004 56930M 56851D 56912B WSZ002 WSZ002 50CZZH 56851C 948501 55262A WTT028 54810C 56324A WSZ002... -
Page 31: Base Plate Parts
BASE PLATE PARTS 56170D 63302A 63303A 948503 647781 WTT021 WTT030 WSZ002 WSZ062...