The 6529B is the keyboard buffer chip in a Commodore 16 or plus/4. If your machine doesn't respond to any key-presses at all - even the function keys - this is probably to blame. The same fault can be caused by a TED failure but this is more unusual than the 6529B failure.

Our 6529B chips are tested in our own Commodore plus/4 to make sure the keyboard is fully working with this chip.