Microwave repeatedly blows the internal fuse or trips the household circuit breaker when starting a cooking cycle.

Critical safety warning: Repeated fuse blowing or breaker tripping indicates a serious electrical fault. Do not repeatedly replace fuses or reset breakers. High-voltage components inside a microwave can be lethal.

User-level actions:

• 1. Stop using the appliance: Unplug the microwave immediately and do not attempt further operation.
• 2. Check outlet and circuit: Confirm that the outlet and circuit are correctly rated for the microwave and not overloaded with other appliances. However, if the breaker trips only when the microwave starts, the fault is likely internal.

Technician-level diagnosis:

• 3. Inspect internal fuse: With the unit unplugged, check the internal line fuse. If blown, investigate the cause before replacing.
• 4. Test high-voltage components: Safely discharge the capacitor, then test the high-voltage capacitor, diode, and magnetron for shorts using appropriate methods.
• 5. Inspect mains filter and wiring: Look for burnt or pinched wires, especially near the door area and around the transformer.

Due to the danger of high voltage, internal repairs should only be performed by qualified technicians. Users should arrange professional service or replacement of the microwave.