Thank you Gyula for the information. I didn't replace any components. I received this complete device with this plug included and without a diode D2. Ok, I'll desolder the connector and will solder the cables directly on the pads. As for the type of diode I found several topics here. Don't know which post to follow. Guess a standard Si diode like 1N4148 should work?
DL8AAP Carsten