Vintage Synth Repair

Hola-
>I've come across a Prophet 5 rev 2 for servicing which has a Cooper MIDI interface.
>This appears to be a simple board that goes between the keyboard and the P5 front panel;  has MIDI In and  Through (no Out),
>and a channel select switch on the front panel.  The ROM on the board is labeled "JL Cooper MIDI Keyboard Matrix 1.0".
>
>Does anyone have any knowledge of / experience with these?  It looks like something they may have applied to other synths from that time as well.  Operating instructions, hidden functions, whatever?
>Thanks.
>
G.M. Montalbano
analogsynthservice.com