I think if this is bad, a switching power supply is used to replace the board. This what I did on my Robotron. The PS was about $40 or so. This is where I kinda screwed up a bit and removed the whole power supply. After hooking everything back up, I blew the monitor since I eliminated the isolation transformer.
I'll never do that again, so I can walk you through some of it if indeed its the problem.
I'm going to see a Pac-Man machine in a few days that is supposed to be non-working.. I'm getting kinda excited about a project.