Help needed with Battlezone

[battlecrazy]

I am in dire need of some help with my Battlezone game! This is a game that I resurrected from the dead a few years ago and it has been working (for the most part, anyway) until just recently when I decided to try to sell it. Anyway, it powers up OK and the startup screen is good, but when I try to start a game, all it does is blanks out and starts over. I've reflowed all solder joints and connections and reseated socketed parts until I'm blue in the face. The self test mode shows a 6 and 8 code in the prom test area. What does this mean and more importantly, how can I fix this machine quickly?