Please no concerns James.
The conrtoller was maybe damaged by a
high voltage spike from a bad power tube.
We have different controllers:
Till 2005 we had the AT89S8252.
Then the maufacture stopped production
and released the AT89S5253.
Please let me know which type is inside.
The difference is that the old one has
two 33pF caps located on the oscillator quartz
and the new one is running with 2 x 4,7pF caps.
I easily can send You the controller, new caps and/or a
complete midi board.
Cheers,
Peter