Okay,

The game was having an issue where it would boot okay some times, and sometimes only the gi would come on. So I shotgun replaced the connectors on the PS board with trifurcon pins and connectors. When on my last connector (CN6) I was working to fast and accidently messed up the order of the wires. The four grey wires that are in the connector I accidently spaced down one extra space. Is supposed to be

empty hole
Grey - 5V
Grey - 5V
Grey - 5v
Grey/white - 12v
empty hole

What I put it as is
empty hole
empty hole
grey - 5v
grey - 5v
grey - 12v
grey white - 0

So I sent 12v to one of my 5 volt lines on the cpu. As soon as I turned the machine one, I heard a little pop noise (which I knew was bad) so I turned it off right away. The smell of burnt entered my nose and I knew I had screwed up. I relooked over my wiring and saw what I did and fixed it.

So now the MPU wont boot. The PIA and 5v line stay on constant. I do have the initial "Back to the future" sound line that plays when you power the machine up. I don't know this boot well enough to really even know where to start looking. I pulled the board and saw the 3 5v lines connect to a little round mini coil looking thing and a glass diode. Diode measures within spec so I didn't blow it.

You understood this perfectly and the illustration is spot on what I did. The power supply board is fine. Its putting out the proper voltages now after I fixed the wiring mistake. the MPU is now getting a solid 5v from the PS board, so I know the problem lies within the MPU board.

I have a DE simpsons which has the same MPU I believe, I guess I could pull that board and put them next to each other and start measuring components one by one.

Going through the schematic, I think I blew d23. It's giving me reading in both directions, which it should only read in one direction cause it's a diode.

Going to replace it then go from there.

This is officially fixed. I pulled the diode and it measured fine out of circuit so I put it back in. I started looking around the board, as the schematic does show it jumpers off to to much.

I was inspecting IC's when I came to the ram IC and noticed that lettering in the middle of the was brown while all the rest of the lettering on it was nice and white. It was a fresh NVram I had just tossed in the game too. I pulled it and set it aside and put the stock one back in. Game fired right up.