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Diagnosing and Repairing Loose Magnetron Filament Connectors

© 1989-2013 J. Carlton Gallawa All Rights Reserved Worldwide

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.


When the following problem occurs, it can result in an unusually POWERFUL ELECTRIC CHARGE stored in the high-voltage capacitor, even after the oven is unplugged, making it particularly DANGEROUS if the HV capacitor is not properly and completely discharged.

If the connectors that slip onto the magnetron filament terminals become loose or are improperly crimped, it causes a buildup of resistive heat. As this occurs the connection further deteriorates resulting in low power output, eventually the magnetron either functions intermittently or not at all, giving the appearance of a defective magnetron. However, do not replace the magnetron until the integrity of the terminal connections are verified as described below:
  • Discoloration of the connector(s) or plastic insulator(s)
  • Small blackened pits in the magnetron terminal(s)
  • Melted, and decayed appearance
  • Also, as noted above, an unusually fearsome spark is produced when discharging the capacitor.

Solution: Repair defective terminals as follows:
Either (1) Clean the burned/pitted magnetron terminals and replace the slip-on connectors, making sure they fit tightly on the terminals; or (2) Cut away burned wire and connector(s). (Make sure there is enough remaining wire to reach with some slack) Clean terminals to prepare for soldering. Solder the filament leads directly to the magnetron. Be careful not to apply soldering heat any longer than necessary.

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