The arcade game he got a hold of was "Two Crude," a JAMMA-based side-scrolling beat 'em up. (I have also seen it referred to as "Two Crude Dudes.") The power cord was missing from it, but we had no guarantees that the thing was going to work if it was replaced.
I have no idea what the thing was originally. It's a woodgrain cabinet - the monitor appeared to be in good condition, looking at it from behind (but it'll need a cap kit someday soon). The cab had a switching power supply. I tapped the new cord into it, but nothing happened. (I did unplug the PCB, just to be safe, initially.)
The interlock switch was fucked-up, and I assumed that I was going to have to bypass it. I had to do the same thing with my Mr. Do!, so no prob there.
However, the Milker dropped by after a bit, and jiggled the wire to the monitor. It was enough to get the thing to turn on. There was a loose wire that I later secured.
The buttons were quite sticky on the control panel - I think only two were actually functional. Milk threw some WD-40 into them, and that cleared them right up. We played a quick game and I adjusted the monitor - too much red, initially!
I also brought with me jrok's Multi-Williams board. Mostly because I wanted to be able to troubleshoot if the Two Crude PCB was bad, but also because if the cab DID work, I wanted to see the thing in action. (It's KILLING me that I don't have a horizontal JAMMA cab... Denver has to be the one place in the world with no horizontal JAMMA specimens. I haven't seen one on craigslist in almost a year.)
The Multi-Williams PCB is AWESOME. The guys at the haunt played some Robotron, Joust and Defender, and I was pretty psyched that the cab held up so well, after being discarded in storage for so long.

At any rate, I was pumped that the three years I've spent dorking around with these things paid off in a real way that helped somebody else.
Obviously, Two Crude is not the spookiest game in the world. It'd be ideal to have something like Ghosts n' Goblins in there... but Gn'G isn't JAMMA. Its sequel (Ghouls n' Ghosts) is, but that board was going for $250 if you could find it at all. There's gotta be a spookier JAMMA board that is affordably priced. We'll figure it out.