I once transplanted the entire keyboard from an A500 to an A4000 keyboard case. The only thing from the A4000 keyboard (apart from the case) was the controller PCB. It worked fine for a year or so, but the A500 k/b was already on the way out when i swapped it (the 4K keyboard was worse, though, so it was still an improvement).
Now i've got a brand new one from Power Computing, and its lovely ;-)
