I contacted AUDIO PRO HEILBRONN Elektroakustik GmbH in Germany. That is the German Distributor of Soundcraft! They were very helpful and offered a very nice solution of this problem. I recommend contacting your local Distributor or the Dealer, were you bought the desk from. Make sure, to have the Serial Number in sight when contacting them. The Serial number can be found at the backside of the desk.
It seems like, that a small quantity of units have a power supply failure. But shit happens. It can be solved and I am a happy user of that desk again.