Microwave trips the household circuit breaker or blows a fuse when starting a cook cycle.

Critical safety warning: Repeatedly resetting a breaker on a shorted microwave can be dangerous. High-voltage components inside can be lethal. Do not continue to use the unit until the cause is found.

• Outlet test: Plug the microwave into a different properly rated outlet on a separate circuit, if available, to rule out a weak breaker. Do not use extension cords.
• Observe when it trips: If the breaker trips immediately when START is pressed, a high-voltage component is likely shorted. If it trips when the door is opened or closed, a door switch or wiring may be shorting.
• Do not open HV section: Internal diagnosis of the capacitor, diode, and magnetron should be done only by a trained technician.
• Next step: Discontinue use and contact a qualified service technician. Continued operation can damage your home's wiring and pose a fire risk.