Microwave shows E5 and stops heating; fan and light may still operate.

Critical safety warning: High-voltage components (transformer, capacitor, diode, magnetron) can store and deliver lethal energy. Do not touch or test these parts unless you are trained and can safely discharge the capacitor.

• Step 1 – External checks: Confirm the outlet is good and the microwave is on a dedicated circuit. If the unit trips the breaker when starting, stop using it immediately.
• Step 2 – Access internal fuses: Unplug the unit and remove the outer cabinet. Locate the line fuse and, if present, the high-voltage fuse (often in a plastic holder near the transformer). Test fuses for continuity with a multimeter. Replace only with identical ratings.
• Step 3 – Visual inspection: Look for burn marks on the transformer, capacitor, and wiring. A burnt smell or melted insulation indicates a serious HV fault.
• Step 4 – Professional diagnosis: Testing the transformer, capacitor, diode, and magnetron requires specialized procedures. If any fuse is blown or E5 persists, have a professional Bomann technician test and replace the faulty HV component.