Quoted from dhalem:
I haven't tried removing it for fear of rocking the boat. I can do so tonight. Assuming that is the case, what's the right way to track this down and fix it?
If the 5v isn't making it to the CPU board without that jumper, then the game won't boot. No harm in removing it from the jumper for a moment to test it out...just don't short it on something else. If it boots with the jumper there, the question is does it play okay without resetting...if yes....why was it there in the first place? If no, then......go from there. If it doesn't even boot without the jumper, then you know the 5v isn't getting to to the CPU board...or if it is, there's something borked on the CPU board itself, but it's a lot better starting point.