Microwave shows E7 and will not start; sometimes accompanied by a loud humming noise before shutdown.

Safety Warning: Inverter-based microwaves operate at very high voltages and frequencies. Internal repairs should only be performed by qualified technicians with proper equipment.

User-level actions:

• 1. Unplug and reset: Disconnect power for 10 minutes, then reconnect and test. If E7 reappears immediately, internal power components are likely damaged.
• 2. Listen for abnormal sounds: If you hear loud buzzing or humming just before E7 appears, discontinue use immediately to avoid further damage.

Because E7 typically indicates a failure in the inverter or high-voltage power supply, do not attempt internal repairs yourself. Contact an authorized RCA service center for diagnosis and replacement of the inverter board or related components.