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LG MH-1357M - User Manual

LG MH-1357M
55 pages
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MICROWAVE OVEN
SERVICE MANUAL
MODEL: MH-1355M
MH-1356M
MH-1357M
CAUTION
BEFORE SERVICING THE UNIT, READ THE SAFETY PRECAUTIONS IN THIS MANUAL.
Website: http://biz.lgservice.com
P/NO : 3828W5S6174
July, 1998
Printed in Korea

Questions and Answers

  • J
    jessica26Aug 6, 2025
    Why is my LG MH-1357M sparking?
    • A
      Austin AndersonAug 6, 2025
      Sparks can occur in your LG Microwave Oven for several reasons: * Using metallic ware that touches the oven wall. Avoid metallic ware, unless specifically allowed in the cookbook. * Using ceramic ware with gold or silver powder trimming. Do not use cookware with metallic trimming. * Food does not turn during cooking. If food or cookware extends beyond the turntable edges, rearrange it to allow turning.
  • A
    Angela GrayAug 10, 2025
    Why is the temperature in my LG MH-1357M Microwave Oven lower or higher than preset?
    • S
      summer23Aug 11, 2025
      If the temperature in your LG Microwave Oven is not as expected, it could be due to: * A defective relay 4 or 2 of the P.C.B. * A defective convection heater element. * A defective thermistor. * A defective circulation motor. * A defective drive mechanism of the circulation fan. Check and repair the drive mechanism. * A defective Solenoid. * A defective air duct assembly. Check and repair the air duct assembly.
  • M
    Megan DavidsonAug 16, 2025
    Why won't the oven light turn on when I open the door of my LG MH-1357M Microwave Oven?
    • B
      burtonallisonAug 16, 2025
      If the light in your LG Microwave Oven doesn't turn on when you open the door: * There might be no power in your home. Check the wall outlet. * There could be an open wire in the power cord or wire harness. Replace or repair the wiring. * The oven lamp switch may be defective or out of adjustment. * The oven light itself might be defective and need replacement. * There might be an open or loose wire connection to the components. Check the wiring. * The fuse or oven light may be blown.
  • A
    Alan Velazquez Jr.Aug 21, 2025
    Why doesn't the oven light turn on during the cook cycle in my LG MH-1357M Microwave Oven?
    • D
      danny25Aug 21, 2025
      If the oven light doesn't turn on during the cook cycle in your LG Microwave Oven, it could be due to: * A defective relay 3 of the P.C.B.
  • G
    Gloria FloresAug 26, 2025
    Why does the turntable motor operate normally but circulation motor does not operate in my LG MH-1357M?
    • T
      Teresa LinAug 27, 2025
      If the turntable motor works but the circulation motor doesn't in your LG Microwave Oven: * Relay 4 of the P.C.B. may be defective. * The circulation motor itself could be defective. * There might be open or loose wiring to the circulation motor. Check and repair the wiring.
  • A
    Amanda MurphyAug 31, 2025
    What to do if ":0" does not appear in display window when power cord is first plugged into wall outlet of my LG MH-1357M?
    • A
      Anthony MillerAug 31, 2025
      If ":0" does not appear in the display when you first plug in your LG Microwave Oven: * Ensure the microwave oven plug is fully and securely inserted into the wall outlet.

Summary

Safety Precautions

Specifications

Installations

Earthing Instructions

Instructions for properly grounding the microwave oven before servicing.

Feature Diagram

Control Panel

Control Panel Overview

Details on indicator lights, display window, and button functions.

Digital Readout Display Information

Examples of time, temperature, cooking power, and error displays.

How the Microwave;Convection Oven Works

Microwave Cooking Principles

Explanation of how microwave energy cooks food evenly.

Convection and Combination Cooking

How hot air and combined modes cook food.

Operating Instructions

Setting Time and Timer

Procedure for setting the time of day and using the regular timer.

Microwave and Convection Cooking

Steps for operating microwave and convection cooking modes.

Combination, Defrost, and Reheat Modes

Instructions for combination, automatic defrost, and reheat functions.

Popcorn and Child Lock Functions

How to use popcorn feature and set/cancel child lock.

Schematic Diagram

Stand-by Condition Circuit

Circuit diagram for the oven in stand-by mode.

Microwave Cooking Condition Circuit

Circuit diagram for the oven during microwave cooking.

Convection Cooking Condition Circuit

Circuit diagram for the oven during convection cooking.

Circuit Description

Magnetron Tube

Magnetron Tube Function and Testing

Description of the magnetron's role and how to test it.

Description and Function of Components

Core Component Functions

Explains the purpose of oven lamp, turntable motor, thermostats, and door mechanism.

Safety Interlock Switch System

Details on primary, secondary, and monitor interlock switches.

Convection System Operation

How convection heating, chamber, and damper work.

Necessary Tools and Measuring Instruments

Necessary Tools for Servicing

List of standard tools required for TV servicing.

Measuring Instruments Required

List of specialized instruments for testing and measurement.

Installation and Adjustment of the Interlock System

Interlock Switch Installation

Procedure for installing the primary, secondary, monitor, and lamp switches.

Interlock Switch Adjustment

Steps to adjust interlock switches to prevent microwave leakage.

Interlock Continuity Test

Primary and Secondary Switch Tests

How to check continuity of primary and secondary interlock switches.

Monitor Switch Test

Procedure to test the monitor switch continuity.

Disassembly and Parts Replacement Procedure

Removing Outer Case and Door Assembly

Steps to remove the oven's outer case and door.

Removing Control Panel and PCB Assembly

Procedure for disassembling the control panel and PCB.

Removing Magnetron and Fan Motor

Steps to remove the magnetron and cooling fan motor.

Removing High Voltage Components

Procedure for removing high voltage diode and capacitor.

Removing Transformer and Turntable Motor

Steps for removing the high voltage transformer and turntable motor.

Removing Switches

How to remove primary, secondary, monitor, and lamp switches.

Troubleshooting

Component Test Procedure

High Voltage Transformer and Magnetron Testing

Procedures to test the resistance of HV transformer and magnetron.

Motor and Switch Testing

How to measure resistance for motors and check switch continuity.

PCB Relay Testing

Testing the continuity of PCB relays for cooking functions.

Procedure for Measuring Microwave Energy Leakage

Leakage Measurement Methods

Techniques for measuring microwave leakage with equipment.

Assembled Oven Leakage Test

How to test leakage on a fully assembled oven.

Exploded View and Parts List

Door Parts List

Illustrated list of all parts related to the oven door.

Control Panel Parts List

Illustrated list of components for the control panel.

Oven Cavity Parts List

Illustrated list of parts making up the oven cavity.

Oven Interior Parts List

Illustrated list of internal components within the oven.

Switches Parts List

Illustrated list of various switches used in the appliance.

Circuit Board Diagram

Diagram showing the layout of components on the circuit board.

Circuit Board Schematic Diagram

Detailed schematic showing the electrical connections of the circuit board.

LG MH-1357M Specifications

General IconGeneral
BrandLG
ModelMH-1357M
CategoryMicrowave Oven
LanguageEnglish

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