Microwave makes loud buzzing or humming noise while running, louder than usual, with reduced or no heating.

Safety first: Unplug the microwave. Do not continue to operate it while it is making abnormal loud noises.

• 1. Compare with normal: If possible, recall how the unit sounded when new. A deep, very loud buzz often indicates HV issues.
• 2. Check for loose items: Ensure there are no metal utensils or foil in the cavity causing arcing. Remove any suspect items and test briefly.
• 3. Visual inspection (internal, for professionals): Remove the cover and inspect the transformer, magnetron, and HV wiring for burn marks or arcing traces.
• 4. Professional repair: Replacement of the transformer or magnetron requires high-voltage expertise and should be done by a technician.