LG MS-199H - User Manual

Questions and Answers

A
Anthony CrossAug 11, 2025
How to fix LG Microwave Oven that is operating but produces little heat?
- M
  Mrs. Janice MurphyAug 11, 2025
  If your LG Microwave Oven seems to be running but produces little heat, it could be due to a decrease in power source voltage or a defective PCB assembly or magnetron. It is suggested to contact your local electric power utility company or a qualified electrician. Alternatively, the PCB assembly or the magnetron may need replacement.
M
Mark GilmoreAug 16, 2025
What to do if my LG MS-199H Microwave Oven doesn't operate and the display window doesn't display any figures?
- E
  emilyholmesAug 16, 2025
  If your LG Microwave Oven doesn't operate, and the display window shows no figures, it could be due to a blown fuse, a malfunction of the monitor switch, or a defective high voltage capacitor. Try replacing the fuse, monitor switch, or high voltage capacitor.
M
markallenAug 23, 2025
What to do if my LG Microwave Oven sparks?
- S
  Susan WatsonAug 23, 2025
  If you observe sparks in your LG Microwave Oven, it could be due to using metallic ware that touches the oven wall. Avoid using metallic ware unless the cooking guide specifies otherwise. Another cause could be using ceramic ware trimmed with gold or silver powder. Refrain from using cookware with metallic trimming.
K
kelly36Aug 28, 2025
What to do if my LG MS-199H Microwave Oven display shows all figures set, but oven does not start cooking?
- P
  Patricia GrantAug 28, 2025
  If the display of your LG Microwave Oven shows all figures but the oven doesn't start, it could be due to a defective secondary switch, loose connection, defective PCB assembly, defective fan motor, or defective oven lamp. In such cases replace the defective part: secondary switch, PCB assembly, fan motor, or oven lamp. Also ensure all connections are tightly connected.
L
lisa38Sep 4, 2025
What to do if my LG MS-199H Microwave Oven has no microwave oscillation, but the oven lamp and fan motor run?
- I
  isabellasavageSep 4, 2025
  If your LG Microwave Oven has no microwave oscillation, even though the oven lamp and fan motor are running, it could be due to a defective PCB assembly, magnetron, circuit protector, high voltage transformer, high voltage capacitor, or high voltage diode. Consider replacing the defective component: PCB assembly, magnetron, circuit protector, high voltage transformer, high voltage capacitor, or high voltage diode.

This document is a service manual for the LG Microwave Oven models MS-198H and MS-199H, providing detailed information for servicing, maintenance, and troubleshooting.

Function Description

The LG Microwave Oven is a kitchen appliance designed for heating and cooking food using microwave energy. It operates by generating microwaves that cause water molecules in food to vibrate, producing heat. The manual covers the necessary procedures for disassembling, testing components, and troubleshooting common issues to ensure the oven functions correctly and safely. Key functions include various power levels for cooking, a turntable for even heating, and a control panel for setting cooking times and modes.

Important Technical Specifications

Microwave Frequency: The energy leakage monitor should be set to 2,450 MHz for accurate measurements.
Microwave Leakage Limits:
- Prior to servicing (if operative): Not to exceed 5 mW/cm².
- After servicing (fully assembled): Not to exceed 5 mW/cm².
- With outer case removed: Less than 5 mW/cm².
- With door slightly opened (before latch switch primary is interrupted): Less than 2 mW/cm².
Water Load for Testing: 275±15 cc of 20±5°C (68±9°F) water, contained in a 600 cc borosilicate glass beaker (inside diameter approx. 8.5 cm, max thickness 3 mm, outside diameter approx. 190mm, height approx. 90mm).
Temperature Rise for Power Output Measurement: A temperature rise (ΔT) of 10±2°K is used, with initial water temperature (T1) of 10±2°C. The maximum difference between final water temperature and ambient temperature should be 5°K.
Power Output Formula: P = 4187 x (ΔT) / T (where P is power in watts, ΔT is temperature rise, and T is time in seconds).
Interlock Switch Types:
- Primary Switch: SZM-V 16-FA-63 or VP-533A-OF.
- Monitor Switch: SZM-V 16-FA-62 or VP-532A-OF.
- Secondary Switch: SZM-V 16-FA-63 or VP-533A-OF.
Component Resistance Values (Approximate):
- High Voltage Transformer: Primary winding ~2.5 Ω, Secondary winding ~110 Ω, Filament winding <0.4 Ω.
- Magnetron: Between Filament terminal <1 Ω.
- Fan Motor: A~B 30~50 Ω, A~C 300~500 Ω.
- Turntable Motor: Approx. 100~200 Ω.
Door Movement Play: Should be less than 0.5 mm (1/64 inch) when pushing the door release button.

Usage Features

While primarily a service manual, it implicitly highlights user-relevant features through troubleshooting and safety guidelines:

Even Cooking: The turntable ensures even heating. Troubleshooting suggests stirring food, using plastic wrap/lids, and wrapping thinner parts with aluminum foil for better results.
Safety Interlocks: The door lock mechanism is designed to completely eliminate microwave activity when the door is open during cooking, preventing microwave leakage.
Control Panel: The control panel allows users to program cooking times and power levels. The manual details how to troubleshoot issues with input, display, and indicator lights.
Power Levels: The oven supports various power levels, which are checked during relay continuity tests (e.g., 20% power for 6 seconds, 100% power for 22 seconds).

Maintenance Features

The manual is a comprehensive guide for professional maintenance, covering:

Tools and Measuring Instruments: Lists essential tools like diagonal pliers, screwdrivers, wrenches, soldering iron, and specialized equipment such as a microwave survey meter (Holaday HI-1500/HI-1501, Narda 8100/8200) and an inch scale.
Safety Precautions: Emphasizes disconnecting power, discharging the high voltage capacitor, and reading safety precautions before servicing. It warns against contacting high voltage parts (Magnetron, H.V. Transformer, H.V. Capacitor, H.V. Cable Ass'y, H.V. Fuse).
Microwave Leakage Test: Detailed procedure for measuring microwave energy leakage using a water load and a survey meter. This test is crucial after any servicing and before returning the unit to the owner.
Disassembly and Adjustment: Step-by-step instructions for removing the outer case, power supply cord, control panel assembly, door, high voltage transformer, fan motor, high voltage capacitor and diode, air duct assembly, magnetron, and turntable motor.
Interlock System Maintenance: Detailed explanation of the interlock mechanism, mounting of switches to the latch board, and installation/adjustment of the latch board to the oven assembly. It includes a continuity test procedure for primary, secondary, and monitor switches.
Component Test Procedure: Provides methods for testing key components like the high voltage transformer, magnetron, high voltage capacitor, high voltage diode, relays, fan motor, and turntable motor using an ohmmeter, including expected resistance and continuity results.
Troubleshooting Guide: Flowcharts for diagnosing common issues such as the oven not working, low output power, sparks, uneven cooking, display problems, fuse blows, and no microwave oscillation. It suggests causes and remedies for each problem.
Record Keeping: Mandates recording measured values after adjustments/repairs and entering information on the service invoice. It also recommends annual calibration checks for the electromagnetic energy leakage monitor.
Genuine Replacement Parts: Stresses the importance of using genuine replacement parts listed in the manual to ensure safety and proper functioning.
Magnetron Gasket: Highlights the importance of installing the magnetron gasket correctly and ensuring it is in good condition to prevent microwave leakage.