Microwave oven magnetron with cooling fins and antenna dome

Generic photo: Raimond Spekking · CC BY-SA 4.0

Microwave high-voltage diode test

The HV diode works with the HV capacitor to double the transformer voltage for the magnetron. It is made of many junctions in series, so an ordinary meter only shows it is not shorted. A shorted diode is a classic cause of no heat with a loud hum.

Single source ~20 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

Unlock all 4 steps with expected values

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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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