I had a very similar issue with my Simpsons pinball party. I needed to install a new LED DMD and used the advice posted in this topic. My problem now is that the machine resets during gameplay.
I have removed the fuse from the F1 position and I have checked and re-seated all connectors on all boards. Does anyone have any advise as to what I could look for next?

Thanks.

I don't have any mods on the machine, it is factory.
I could add in a 5V supply (an arcade switcher), but it is a pain in the butt. I will need to run another cable from the mains for it ( I think). Are there any other solutions available?

Good idea about the bill acceptor, unfortunately, this is a UK machine and has no bill accepter. I will have a look at the wiring and see if there is a set of wires that would be attached to a bill accepter.