F9
Bauknecht
High-Voltage System Fault (Transformer Models)
Microwave shows F9 and does not heat; sometimes accompanied by a humming noise.
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Safety Warning
This repair may involve working with high voltage components or water connections. Always unplug the appliance before removing any panels.
If you are not confident in your ability to perform this repair safely, we strongly recommend contacting a professional technician.
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Possible Causes
Shorted high-voltage diode, Failed high-voltage capacitor, Shorted magnetron, Faulty high-voltage transformer
How to Fix / Troubleshooting
Critical safety warning: The high-voltage section of a microwave is extremely dangerous. Do not attempt to test or replace HV components unless you are trained and equipped to safely discharge the capacitor.
- Step 1 – Stop using the appliance: If F9 appears with unusual noises or smells, unplug immediately.
- Step 2 – Visual inspection (external only): Check the power cord and plug for damage. Do not open the cabinet unless qualified.
- Step 3 – Professional service: A technician will test the HV diode, capacitor, transformer, and magnetron for shorts or opens and replace the defective component(s) with genuine Bauknecht parts.
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Repair Difficulty
Professional Required
5/5
Required Part
High-Voltage Diode or Capacitor
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