I finally found the problem: connectivity in the wiring of the keyboard.
Thank you every body for your advices. It helped me concentrating on the source of the problem. I could have waste lots of time searching around in the fog. I thought at first it was a compatibility problem, because the work have been done very nicely, all solders are very clean (not done by me ...
).
I am hurry now to post the result with the instrument interface wich will be done soon (a double harp).
Wonderfull day to every one.