Ok, I figured this Bill Validator problem out and now I'm able to pump all of my hard earned money into my UMK3 machine.
This is for ARDAC UpStackers, in case anyone picks one up and needs help with it. I got mine off of ebay for $30. There are 8 wires coming off of the Bill Acceptor, here's the breakdown...
(top row)
Black (hot)
White (neutral)
Yellow (N/A)
Blue (+ for the coin slot)
(bottom row)
Brown (- for the coin slot)
Yellow (N/A)
White w/ yellow stripe (neutral)
White /w blue stripe (hot)
I cut an extension cord and used it for power, Bill Acceptors need regular old 110v juice. Wire the slim blade of the extension cord to the Black wire and the White /blue stripe. Wire the fat blade to the White wire and the White w/ yellow stripe. That'll give juice to the motor and the stacker. Then wire the solid Blue and the solid Brown to a coin slot. It doesn't matter which is which, they're interchangable. I had to adjust the coin multiplier in the game's settings, otherwise you only get one credit per dollar.
I hope this helps somebody.