I don't know much about this hardware group. Information would be appreciated. I know Mystic Marathon has a built in sound board, while Blaster has a separate sound board.
From Tim Lundquist:
There are manuals and schematics on Al Kossow's site that are a tremendous help (actually for Mystic Marathon, which is darned close to the rest). Those and a logic probe have been the keys to fixing all the ones I've encountered. Problems I've fixed have mostly been bad RAM, bad CPU's, broken traces, corroded traces, missing components, bad EPROMs... standard stuff. The hardware's self tests are excellent too, so once you get video showing, you're most of the way done.