I just joined this group, owning a Marion ProSynth and hoping to find more information. I have uploaded my own findings on how to build a replacement power supply, since it is a bit weird. Hopefully that helps.
And if anyone can point me to the Windows XP editor that originally came with the Marion ProSynth, I'd be very happy.
Cheers from Finland,
Alessio
https://www.facebook.com/leadingmotive