Microwave makes loud buzzing, humming, or crackling noises during operation.

Safety: Unplug the microwave if you hear loud or unusual noises, especially if accompanied by burning smell or visible sparks.

User-level checks:

• Inspect waveguide cover: Look at the mica or plastic cover on the side wall (waveguide cover). If it is burned, cracked, or has food splatter, it can cause arcing and noise.
• Clean interior: Remove any food debris or metal fragments from the cavity.
• Turntable system: Remove the glass tray and roller ring, then run the microwave briefly with a cup of water (if safe to do so). If the noise disappears, the noise source may be the roller ring or tray.

Technician-level checks:

• Inspect and replace a damaged waveguide cover.
• Check the magnetron and HV transformer for mechanical noise or arcing.
• Test the turntable motor for grinding or excessive noise.