> OK, so my mistake was to call the common feedback rail pin
> "ground". This is what I was connecting to the other pins to try
> to generate a MIDI note, as described in the manual, not to an
> arbitrary ground.
>
> Sorry for my initial inaccurate explanation.
>
> Sean

If it's nothing obvious (like a loose connection of the common feedback
line) the CTM64 has to be repaired. You may order a new PIC as a spare part
but from the distance I cannot guarantee that this will solve the problem.

Best wishes
Dieter Doepfer