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How to Test the Magnetrons Used in Commercial, Industrial, and Residential Microwave Ovens

© 1996-2013 by  J. Carlton Gallawa . All Rights Reserved Worldwide

(Czech is a West Slavic language with about 12 million native speakers; it is the majority language in the Czech Republic and spoken by Czechs worldwide. Alex Novak has kindly translated this page into the Czech language to share with his blog readers. The translated page is found here: Jak Test Magnetronsv Používaných v Mikrovlnných Troubách)

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THE MAGNETRON is the heart of a microwave oven. It is much like a radio transmitter in that it produces RF energy and radiates the energy into the cooking cavity where it is absorbed by the food. The magnetron uses permanent magnets and a half-wave voltage doubler circuit (the HV capacitor and HV diode) to oscillate and produce the 2450 Mhz cooking frequency, thus converting the 60 Hz supply voltage into microwave energy.

See Magnetron Structure and Operation for a detailed description of the magnetron tube
Click here for a comprehensive magnetron cross reference guide

Important Safety Information

The microwave oven is a very dangerous appliance to work on. For your personal safety, we respectfully ask that you read, fully understand and be prepared to follow carefully the list of very important safety precautions as well as the disclaimer at the bottom of this page BEFORE proceeding with any tests or troubleshooting.

Click HERE for a pictorial list of common types of magnetron failures that are clearly visible and require no testing.

The following resistance tests will conclusively reveal a magnetron that is shorted or one that has an open filament winding.

Test 1

  1. Unplug the oven (make sure the oven is completely disconnected from any power source)

  2. DISCHARGE ALL HIGH VOLTAGE CAPACITORS. Procedure

  3. Carefully remove all leads from the magnetron terminals. Proper wiring is important so make notes of the wire locations.

  4. Set the ohmmeter to its lowest resistance scale.

  5. Measure the resistance from one magnetron terminal to the other in either direction.

  6. The magnetron filament resistance should be less than one ohm.

Test 2

  1. With the meter set to the highest resistance scale, check from the magnetron terminals to the metal magnetron housing. (Be careful not to touch the meter leads as this will result in a false reading).

  2. The meter should read infinity (open circuit) regardless of meter polarity.

  3. Even a slight reading would indicate a defective magnetron.

Replacement Considerations

  1. Be careful not to strike or touch the antenna dome area.

  2. Do not set the magnetron near anything that is susceptible to magnetism, such as a computer hard drive, computer or TV monitor, any type of magnetic media, or certain types of watches..

  3. Be sure to transfer any add-on parts, such as an air duct or thermal fuse.

  4. Insure that the wire mesh RF gasket is intact and in place

  5. Examine the rim of the opening where the magnetron dome is to be inserted into the waveguide. Smooth out any irregularities, such as dents, pits, and burns. The rim surface should be bare metal, smooth to the touch. Use light-grade sandpaper - do not use steel wool.

  6. If possible, perform and RF leakage check around the magnetron.

  7. If there is evidence of poor terminal connections (i.e., discolored, burned, pitted connectors), repair or replace the slip-on connectors on the filament leads.

Comments and suggestions: mailto:john@microtechfactoryservice.com
The Complete Microwave Oven Service Handbook - Operation, Maintenance, Troubleshooting and Repair
The COMPLETE MICROWAVE OVEN SERVICE HANDBOOK
Operation, Maintenance, Troubleshooting and Repair

Copyright © 2013 by John C. Gallawa
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Copyright Information
Unless otherwise noted, all materials at this cite (including without limitation all text, html markup, graphics, and graphic elements) are copyrighted ©, 1989-2013 by J. Carlton Gallawa. The material available through this site may be freely used for attributed noncommercial educational purposes only. We ask that due credit and notification be given the author.

All materials appearing on this Web site may not be reproduced, stored in any retrieval system, or used in any way for commercial purposes without the express prior written permission of the copyright holder.

Disclaimer: The author assumes no liability for any incidental, consequential or other liability from the use of this information. All risks and damages, incidental or otherwise, arising from the use or misuse of the information contained herein are entirely the responsibility of the user. Although careful precaution has been taken in the preparation of this material, we assume no responsibility for omissions or errors.

Previous Page Home Page Important Safety Information Contact Us About the Author Free Case History Database Free Microwave Oven Troubleshooting Guide DOWNLOAD FREE SAMPLES FROM THE CD: The Complete Microwave Oven Service Handbook: Operation, Maintenance, Troubleshooting and Repair

Copyright © 1996-2013 by  J. Carlton Gallawa . All Rights Reserved Worldwide