So here's the story.

Playing the game and suddenly lose the display. Open the backbox and find there is a loose screw between the two display PCBs - I am guessing this has shorted something? Check the fuse on the interboard and it is blown.

Now here's the dumb part..... I grab one of my fuse contraptions to test the display but I put in the 3A version. Just dumb I know.

Next thing - big sparks and I have blown a hole through 6184 at U4 - (replacement on order now)

My question is how do I troubleshoot this? I am guessing if I just replace the chip, it is likely to blow again. I have started testing resistors etc. but I am just fumbling in the dark here.

Any help much appreciated.

Followed the schematics and isolated the 1N4004 at D4 was bad. Replaced diode, transistor and correct fuse: solved.