Microwave makes loud buzzing or humming noise when running, and food may not heat properly.

Safety first: Unplug the microwave. Do not touch high-voltage components.

• Confirm noise source: Remove the outer cabinet and carefully run the unit for a few seconds with a cup of water inside (only if you can do so safely with all interlocks in place). Identify whether the noise comes from the transformer, magnetron, or another area.
• Tighten hardware: After unplugging again, tighten mounting screws on the transformer and magnetron if they are loose.
• Inspect for arcing: Look for burn marks or carbon tracking near high-voltage connections and the waveguide.
• Professional repair: If noise persists or heating is poor, have a technician test and replace the high-voltage transformer or magnetron as needed.