Thanks Retro. The fuse is definitely 3a but might be a fast blow and not a slow blow. I guess first step is to get slow blow fuses and see what happens. As a result of fuse blowing displays or game does not turn on. Does this sound correct?

No - this isnt right. Unless they did something quirky with Gen 1 which i doubt, after all Mr zaccaria was a clever fellow... anyone working on these boards will tell you that Zaccaria is a clever system.

You should be able to take out both under playfield fuses and have the game still boot... all the fuses do is feed power to the coils away from the boards.. there is no power from the coils to the boards. It all comes from the power board.

Your displays use 170V and 5.6V which is fed through the CPU.

Disconnect your boards and start by testing all voltages on the power board... sounds like there are more than 1 fault on your game