Microwave display shows E004 and the unit will not start; sometimes accompanied by a faint burning smell previously.

Safety: Unplug the microwave. Inverter boards operate at high voltage and high frequency; servicing them requires specialist skills.

Basic checks:

• Ensure vents are clear and the appliance has adequate airflow.
• Perform a power reset by unplugging for 10 minutes and reconnecting.

Service-level actions:

• Remove the outer cabinet and locate the inverter power module (usually a separate PCB near the magnetron with large heat sinks).
• Inspect for obvious damage: burnt components, cracked solder joints, or bulging capacitors.
• Check the low-voltage connector from the main control board to the inverter for secure fit and no corrosion.
• If the inverter shows visible damage or tests faulty, replace the entire inverter module with the correct Neff spare part.

Because of the complexity and danger of inverter circuits, replacement should normally be done by a Neff-authorized technician.