It has not been very easy but our Control surface "Control 24" has been repaired. The Technical Support from Digidesign has been very efficient and has changed the power supply for free even if we had no more warranty. It seems they have had tons of problems with these power supplies but Digidesign has been honest and has not tried to deny or to be of bad faith with us. So now the problem is over, and we can restart our recordings ! Greeeaaat !