Safety first: Stop the microwave and unplug it if you hear loud or unusual noises.

Check inside cavity: Remove the glass tray and roller ring. Inspect the waveguide cover (usually a mica or plastic panel on the side wall) for burns, cracks, or food splatter.
Clean thoroughly: Food residue on or near the waveguide cover can cause arcing. Clean the cavity with mild detergent, avoiding soaking the waveguide cover.
Inspect turntable parts: Ensure the tray is not rubbing against the cavity walls and that the roller ring is correctly positioned.
Test briefly: After cleaning and reassembly, run the microwave with a cup of water. If loud buzzing or crackling persists, unplug and arrange professional service.
Professional diagnosis: A technician should inspect the transformer, magnetron, and waveguide for damage and replace any faulty parts.

Warning: Do not operate the microwave if arcing (visible sparks) is observed.

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

Possible Causes