Microwave produces loud buzzing, humming, or crackling noises during operation, sometimes accompanied by a burning smell.

Safety: If you smell burning or see sparks, stop the microwave immediately and unplug it.

• Inspect waveguide cover: With the unit unplugged, locate the mica or plastic waveguide cover on the side wall or ceiling. If it is burnt, bubbled, or has holes, it can cause arcing and noise.
• Clean cavity: Remove any carbonized food splatter near the waveguide area. Use a mild detergent and soft cloth; do not scrape the metal cavity.
• Do not operate with damaged cover: If the waveguide cover is damaged, do not use the microwave until it is replaced.

If noise continues after cleaning or cover replacement: The magnetron or other high-voltage components may be failing. These require professional diagnosis and replacement.