Microwave oven magnetron with cooling fins and antenna dome
Generic photo: Raimond Spekking · CC BY-SA 4.0

Microwave high-voltage transformer windings

The HV transformer has a primary, a high-voltage secondary and a low-voltage filament winding. Resistance checks find opens and shorts to the core; turn-to-turn shorts may still need a known-good comparison.

Cross-checked ~30 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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