SMEG
High-Voltage Component Noise / Partial Short
Microwave makes loud buzzing or humming noise during operation, louder than usual; may or may not heat properly.
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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 magnetron, Saturating high-voltage transformer, Shorted high-voltage diode, Loose or vibrating transformer mounting
How to Fix / Troubleshooting
Safety: Unplug the microwave immediately if the noise is accompanied by a burning smell, smoke, or visible arcing.
User checks:
- Confirm that the noise is not caused by cookware (e.g., metal trim, loose covers) vibrating. Try heating a cup of water with different cookware.
- Ensure the microwave is placed on a stable, level surface to reduce resonance.
If the loud buzzing persists:
- Stop using the microwave. The noise often indicates a failing HV component that can fail catastrophically.
- Contact a technician to inspect the magnetron, transformer, and HV diode/capacitor.
Do not open the cabinet yourself; HV components can retain lethal charge.
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Repair Difficulty
Professional Required
5/5
Required Part
High-Voltage Diode
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