I think he was looking for the firewire board for the printer. Not one for a computer. They are known to eventually fail on JV3 machines. I have one off to Kent at MacMedia for repair myself right now....
If all else fails and you have the board that is no longer working send them and email to arrange for repair. They are the only place I know of that repairs those boards by installing a new chip and resistors. Not free but a heckuva lot less than buying a new board from Mimaki.