Have you checked to see if one of the technician switches got turned off? I think there's one in the back of the cab and one in the front (open the coin door and look around) you can actually see them looking from the back of your cab.
The switch looks like a little white stick and they can be pressed in, or pulled out into a locked position. If I recall, I also believe that there's a door switch on the back of the cab, if the door is off, the game wont turn on. Hopefully it's just something simple like that? My centipede cab did the same thing as yours, but it was right after I took off the back door and put it back on that it wouldn't power up. Good luck!
Steve