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LG MB-392AA - User Manual

LG MB-392AA
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MICROWAVE OVEN
SERVICE MANUAL
MODEL : MB-392AA
CAUTION
BEFORE SERVICING THE UNIT, READ THE
SAFETY PRECAUTIONS IN THIS MANUAL.

Questions and Answers

  • A
    Adrian EvansAug 12, 2025
    What to do if my LG MB-392AA doesn't cook at all even though the turntable rotates?
    • T
      Timothy GomezAug 12, 2025
      If your LG Microwave Oven's turntable rotates but it doesn't cook, it could be due to a malfunction in the power control switch or a faulty magnetron. You can replace the power control switch and the magnetron. Also, check the power control switch, monitor resistor, AC relay, H.V. transformer, H.V. diode, H.V. capacitor and magnetron.
  • C
    carla57Aug 16, 2025
    Why is the output power too low in my LG MB-392AA Microwave Oven?
    • M
      Michael JosephAug 16, 2025
      If the output power of your LG Microwave Oven is too low, it might be due to low AC input voltage. Use the microwave oven at adequate line voltage.
  • A
    Amanda HarperAug 20, 2025
    What to do if the food temperature is too low in my LG MB-392AA Microwave Oven?
    • T
      tara78Aug 20, 2025
      This may not be a defect. If the food temperature is too low in your LG Microwave Oven, it is possible that the food should be cooked for a longer time period.
  • C
    Christopher BergAug 23, 2025
    Why is my LG MB-392AA Microwave Oven sparking?
    • J
      Jacqueline WareAug 25, 2025
      Sparks may occur in your LG Microwave Oven if you are using metallic ware that touches the oven wall. Avoid using metallic ware unless specifically mentioned in the cooking guide. Also, sparks can occur if you are using ceramic ware trimmed with gold or silver powder. Do not use any cookware with metallic trimming.
  • B
    Barbara AndradeAug 27, 2025
    What to do if my LG Microwave Oven doesn't start even though the timer is set?
    • K
      Kendra MillsAug 28, 2025
      If your LG Microwave Oven doesn't start, even with the timer set, there may be a malfunction in the primary, secondary, or timer switch, or a faulty thermostat. Check the continuity of the primary switch with the door closed, the secondary switch with the secondary switch pushed, and the timer switch contacts. Also, check the continuity of the thermostat.
  • A
    Aaron YorkAug 31, 2025
    Why is the output power of my LG MB-392AA Microwave Oven low?
    • S
      skinnerjacobAug 31, 2025
      Low output power in your LG Microwave Oven can be due to several reasons: a decrease in power source voltage with load, voltage less than 207V, or a faulty magnetron. Check the power source voltage with load. If the voltage is low, contact your local electric power utility company or a qualified electrician. Also, measure the magnetron’s output.
  • A
    Andrew SmithSep 4, 2025
    How to fix uneven cooking in my LG Microwave Oven?
    • E
      Emily BrownSep 4, 2025
      Uneven cooking in your LG Microwave Oven can occur due to inconsistent microwave intensity. To resolve this, wrap the thinner part of the food with aluminum foil. Also, use plastic wrap or a lid while cooking. For soups, cocoa, or milk, stir once or twice during cooking.
  • P
    Philip GoodmanSep 7, 2025
    What to do if the oven lamp does not turn on in my LG Microwave Oven?
    • L
      Laura StokesSep 7, 2025
      If the oven lamp in your LG Microwave Oven does not turn on when the timer knob is pushed with the door closed, it could be due to several reasons. The fuse may have blown, there may be a malfunction of monitor switch (with door closed) or shorted contact at the primary switch. Replace the fuse, primary, monitor and secondary switches. Replace high voltage capacitor. Check continuity of the primary switch (with door opened). Disconnect one side of the wire lead connected from transformer to the high voltage capacitor and operate the unit. Replace high voltage transformer.

Summary

SERVICE INFORMATION

MICROWAVE LEAKAGE TEST

MEASURING MICROWAVE ENERGY LEAKAGE

Procedure for measuring microwave energy leakage using water and a meter.

MEASUREMENT WITH OUTER CASE REMOVED

WARNING: HIGH VOLTAGE PARTS

Warning about high voltage components like magnetron, transformer, capacitor.

MEASUREMENT WITH A FULLY ASSEMBLED OVEN

MEASUREMENT OF MICROWAVE POWER OUTPUT

DISASSEMBLY AND ADJUSTMENT

DOOR GROSS ASSEMBLY REMOVAL

HIGH VOLTAGE TRANSFORMER REMOVAL

FAN MOTOR ASSEMBLY REMOVAL

HIGH VOLTAGE CAPACITOR AND DIODE REMOVAL

MAGNETRON REMOVAL

REMOVING THE TURNTABLE MOTOR

INTERLOCK SYSTEM

INSTALLATION AND ADJUSTMENT OF LATCH BOARD

Steps for installing and adjusting the latch board for proper door function.

INTERLOCK CONTINUITY TEST

PRIMARY INTERLOCK SWITCH TEST

Procedure to test the primary interlock switch continuity for safety.

SECONDARY INTERLOCK SWITCH TEST

Procedure to test the secondary interlock switch continuity for safety.

MONITOR SWITCH TEST

Procedure to test the monitor switch continuity for safety.

COMPONENT TEST PROCEDURE

MAGNETRON

Resistance test procedure and expected results for the magnetron.

COMPONENTS

TROUBLE SHOOTING

COMMON PROBLEMS AND REMEDIES

Table detailing common microwave oven problems, their causes, and remedies.

TROUBLESHOOTING OVEN LAMP

TROUBLESHOOTING OVEN START

TROUBLESHOOTING LOW OUTPUT POWER

TROUBLESHOOTING GRILL FUNCTION

TROUBLESHOOTING NO COOKING

CAUTIONS

MICROWAVE RADIATION SAFETY

Safety precautions regarding microwave radiation exposure during servicing.

INSTALLATIONS

LG MB-392AA Specifications

General IconGeneral
BrandLG
ModelMB-392AA
Cooking Levels5
ColorWhite
Turntable Diameter245 mm

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