LG MC-804AR User Manual

MICROWAVE/GRILL
CONVECTION OVEN
SERVICE MANUAL
MODEL : MC-804AR
CAUTION
BEFORE SERVICING THE UNIT, READ THE
SAFETY PRECAUTIONS IN THIS MANUAL.

LG MC-804AR Specifications

General

Brand	LG
Model	MC-804AR
Category	Microwave Oven
Language	English

Summary

Microwave Oven Service Manual Introduction

Service Manual Safety Precautions

Read safety precautions before servicing the unit.

Appliance Specifications

Power Requirement and Output

Details electrical input requirements and power outputs for microwave, grill, and convection.

Key Component Specifications

Lists magnetron model, frequency, timer, dimensions, and weight.

Control Complement and Accessories

Details power levels and included accessories like trays and racks.

Operating Instructions and Control Panel

Control Panel Overview and Functions

Explains the functions of each button and display on the control panel.

Operating Sequences

Setting the Clock Sequence

Step-by-step guide for setting the oven's clock.

Cooking Mode Sequences

Procedures for microwave, grill, convection, and combination cooking.

Multi Stage and Auto Cooking Sequences

Steps for multi-stage cooking, auto cook, and auto defrost functions.

Quick Start and Adjustment Operations

Guide for using quick start, more/less adjustments, and child lock.

Schematic Diagram

Main Circuit Board Schematic

Detailed electrical schematic of the main control PCB.

Circuit Description and Operation

Monitor Switch and Door Operation

Explains monitor switch function and door interlock behavior during cooking.

Power Level and Time Setting Circuits

Describes circuit behavior when setting power and time for cooking.

Motor and Fan Operation

Details the operation of turntable, circulation, and fan motors.

Convection and Grill Cooking Circuits

Explains circuit behavior when starting convection or grill cooking.

Service Information and Tools

Necessary Tools for Servicing

Lists standard tools required for appliance repair.

Measuring Instruments for Testing

Lists specialized instruments for testing and measurement.

Microwave Leakage Test Procedure

Detailed steps for measuring microwave radiation leakage.

Equipment for Leakage Testing

Lists specific equipment needed for leakage testing.

Microwave Leakage Measurement Procedures

Leakage Measurement with Outer Case Removed

Procedure for measuring leakage with the oven casing off.

Measurement Guidelines and Notes

Important notes and tips for accurate leakage measurements.

Record Keeping and Notification

Requirements for documenting leakage test results.

Leakage Measurement with Assembled Oven

Procedure for measuring leakage with the oven fully assembled.

Microwave Power Output Measurement

Power Output Calculation Formula

Formula used to calculate microwave power output based on water temperature rise.

Disassembly and Adjustment Procedures

Out Case Removal Steps

Steps to remove the outer casing of the oven.

Power Supply Cord Removal

Procedure for disconnecting the power supply cord.

Control Panel and PCB Assembly Removal

Steps to remove the control panel and main circuit board.

Door Assembly Removal and Checks

Door Gross Assembly Removal Steps

Detailed instructions for removing the entire door assembly.

Post-Replacement Door Checks

Essential checks after door assembly replacement, including leakage.

Magnetron Removal and Replacement

Magnetron Removal Procedure

Steps to safely remove the magnetron assembly.

Magnetron Replacement Notes

Considerations for installing new magnetron, including gasket and leakage checks.

Component Removal Procedures

Noise Filter, HV Diode, Capacitor, Fan Motor Removal

Steps for removing filter, HV diode, capacitor, and fan motor.

Oven Lamp Removal

Procedure for replacing the internal oven lamp.

High Voltage Transformer Removal

Steps to safely remove the high voltage transformer.

Motor, Thermistor, Sheath Heater Removal

Procedures for removing circulation motor, thermistor, and heater components.

Turntable Motor Removal

Turntable Motor Disassembly Steps

Detailed instructions for removing the turntable motor assembly.

Door Interlock System

Interlock Mechanism and Switch Mounting

Description of door lock mechanism and how to mount safety switches.

Interlock Switch Continuity Testing

Primary Interlock Switch Test

Procedure to test the primary safety interlock switch continuity.

Secondary Interlock Switch Test

Procedure to test the secondary safety interlock switch continuity.

Monitor Switch Test

Procedure to test the monitor safety interlock switch continuity.

Component Electrical Testing

High Voltage Transformer Resistance Test

Measuring resistance of transformer windings and to ground.

Magnetron Resistance Test

Measuring resistance of magnetron filament terminals and to chassis.

Capacitor and Diode Testing

High Voltage Capacitor Test

Resistance and continuity tests for the high voltage capacitor.

High Voltage Diode Test

Forward and reverse continuity tests for the high voltage diode.

Fuse, Heater, and Thermostat Testing

Fuse Continuity Test

Procedure to check fuse continuity.

Heater Element Resistance Test

Measuring resistance of the grill heater element.

Thermostat Temperature Test

Testing oven and magnetron thermostat operation at different temperatures.

Motor, Heater, and Solenoid Testing

Circulation Motor Resistance Test

Measuring resistance of the circulation motor windings.

Grill Heater Resistance Test

Measuring resistance of the grill heater element.

Solenoid Resistance Test

Measuring resistance of the solenoid coil.

Rectifier Assembly Test

Testing the rectifier assembly for the solenoid.

PCB Relay and Keypad Testing

PCB Relay Continuity Test

Testing continuity of relays RY2, RY3, RY4 during operation.

Membrane Keypad Continuity Test

Checking continuity of membrane keypad switches.

Troubleshooting Guide

General Troubleshooting Cautions

Important safety and procedural warnings before troubleshooting.

Trouble 1: Oven Does Not Operate All

Diagnosing and resolving issues when the oven is completely inoperative.

Troubleshooting: Input and Programming Issues

Trouble 2: Input or Programming Errors

Diagnosing issues with input not being programmed or accepted.

Trouble: Display and Time Setting Issues

Resolving display freezes, input errors, or time countdown problems.

Troubleshooting: Microwave Cooking Problems

Trouble: Microwave Cooking Cycle Initiation

Diagnosing why the oven won't start a cooking cycle.

Trouble: Microwave Power Output Issues

Resolving low/high power and uneven cooking results.

Trouble: Microwave Oscillation Failure

Troubleshooting lack of microwave generation.

Trouble: Sparking and Metallic Ware Use

Identifying causes and solutions for sparking and improper metallic ware use.

Troubleshooting: Convection Cooking Failures

Trouble: Convection Cycle Start Failure

Diagnosing why convection indicator lights but cycle won't start.

Trouble: Incorrect Cavity Temperature

Resolving issues with oven cavity temperature being too low or too high.

Trouble: Convection Heater or Motor Issues

Diagnosing problems with convection heater, grill heater, or circulation motor.

Troubleshooting: Grill Cooking Failures

Trouble: Grill Cycle Start Failure

Diagnosing why grill indicator lights but cycle won't start.

Trouble: Incorrect Cavity Temperature

Resolving issues with oven cavity temperature being too low or too high during grill cooking.

Exploded View of Components

Door Parts Diagram

Exploded view of the oven door assembly components.

Control Panel Parts Diagram

Exploded view of the control panel assembly components.

Oven Cavity Parts Diagram

Exploded view of internal oven cavity components.

Latch Board Parts Diagram

Exploded view of the door latch board assembly components.

Interior Parts Diagram

Exploded view of internal components within the oven cavity.

Base Plate Parts Diagram

Exploded view of components on the oven's base plate.

PCB Schematic Diagram

Main Control Board Schematic

Detailed circuit diagram of the main printed circuit board.

Printed Circuit Board Layout

PCB Component Placement Diagram

Visual layout showing component placement on the PCB.