I called IBM support and the next day I've got a new keyboard, FRU 39T0982 which to my pleasant surprise is a NMB
I installed the new keyboard, which was easy using the included instructions. The new keyboard is a little "firmer" and no more weird sounds and two stops travel. I've asked a US layout, but I was told that I must purchase it and wait for it, because they don't have it in stock, so I stayed with the original layout.
It's a nice feeling to know that the good reliability and built quality of these machines is backed by good support.
Regards,
v.






