Thought I would follow up with where I got to with this. I was basically getting nowhere with solving it so I ended up getting a mate around who used to service pinnys and arcades for a living years ago. All I had to do was supply the Karaken spiced rum for him.
After a few hours working on it without luck we basically decided to cut a wire that had been added to the coin door. It appeared the wire was there so that it would register a credit irrespective of which coin chute the coin was put in. As soon as we cut it, the game booted up and the "credit, tilt, slam" garbage disappeared.
However, we still had the locked on coil message. Some coils would work but we eventually worked out that everytime one of the pop bumpers was activated it blew the 5 amp fuse. We eventually discovered that the wires onto the coil lugs had been put on backwards (incorrect side) on each pop bumper.
Well in my defence I went back and looked at the photos I took before disassembly and I simply reattached them as they were originally attached when I got the game. So it was a previous owner at some point that put them on incorrectly. As the game was in pieces when I got it, I incorrectly assumed they were correct and copied it.
I have now spent most of today just tweaking little things to make sure everything plays nicely. Pretty much everything works now except for the 2 star rollovers that refuse to register plus a few inserts that seems to be intermittent, particularly with the vari-target. But getting very close now to being finished
