Microwave oven magnetron with cooling fins and antenna dome

Generic photo: Raimond Spekking · CC BY-SA 4.0

Magnetron: filament and filament-to-case tests (microwave)

The magnetron turns high voltage into microwave energy. An ohmmeter can catch an open filament or a filament shorted to the case, but it cannot prove the tube makes full power. Rule out the HV diode, capacitor and transformer before ordering a magnetron.

Cross-checked ~40 min advancedBrands: All

Before you start

DANGER: the microwave high-voltage capacitor can hold a lethal charge after the cord is unplugged
Trained technicians only. Unplug, wait, discharge the HV capacitor with an insulated discharge tool and confirm 0 V with a meter before touching anything inside
Never operate the oven with the outer cabinet off or with door interlocks bypassed
Inexperienced users and handymen without HV training should refer the job

Diagnostic steps

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OnCall Tech is a reference tool for trained technicians and can make mistakes. Always disconnect power and confirm with the manufacturer's documentation before you work.

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