Microwave makes loud buzzing or humming noise while running, louder than normal, sometimes with a burning smell.

Safety: Unplug the microwave. Burning smells or unusual noises can indicate imminent failure or fire risk.

Steps:

• 1. Identify noise source: Run the microwave briefly with a cup of water and listen carefully (from a safe distance). Noise from the bottom often indicates turntable motor; from the side or rear, transformer or fan.
• 2. Check turntable system: Remove tray and roller ring and run again. If noise disappears, the issue is with the tray, ring, or coupler.
• 3. Inspect fan: With the cabinet removed (if you are competent), check that the cooling fan blades are not rubbing against shrouds or wiring. Adjust or secure as needed.
• 4. HV components: Loud, deep buzzing often points to a failing transformer or magnetron. These should be diagnosed and replaced by a technician.