Some progress...
Not smoke or bang.
P1 is showing roughly in the middle what looks to be a no. 6 (perhaps with a 1 locked on) and P3 is showing a 0.
Sounds good, I must go for today. Try swapping Player 1 and 3 displays and see what happens. Good visual way to tell if the processor is running is to see if the displays cycle from high score to date to last score played. If you leave it on should cycle ever 5 to 10 seconds or so.
We will get there in the end 
Thanks for the help thus far. Two steps forward....
Well at least I know now the CPU is not booting....
