Commercial Chef Noisy High Voltage Transformer or Magnetron

Microwave makes loud buzzing or humming noise while running, louder than normal, sometimes with reduced heating.

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Safety Warning

This repair may involve working with high voltage components or water connections. Always unplug the appliance before removing any panels.

If you are not confident in your ability to perform this repair safely, we strongly recommend contacting a professional technician.

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Possible Causes

Failing high-voltage transformer, partially shorted magnetron, loose mounting hardware causing vibration, high-voltage diode arcing

How to Fix / Troubleshooting

Safety: Unplug the microwave before any internal inspection. High-voltage components are dangerous.

User checks:

  • Verify that the noise is not caused by cookware (e.g., metal trim, utensils) by testing with only a cup of water.
  • If the noise persists and is a deep, loud buzz, discontinue use.

Technician checks:

  • Remove the cabinet and inspect the transformer and magnetron mounting bolts; tighten if loose.
  • If noise continues, test the magnetron, transformer, and diode. Replace any noisy or failing component.

Because of the risks, this repair is best left to professionals.

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Repair Difficulty

Professional Required 5/5

Required Part

High-Voltage Transformer
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