Well another year has passed and I've made space in the workshop to finally get this done, sold, and out of my life (hopefully!) Have made loads of progress the last couple of days on this, the most important part being it's now playing absolutely perfectly for the first time since owning it.
Our main issue was between the indicator unit (the arrow that spins) and the scan relay.
It's a very ingeniously designed circuit this, whenever the arrow is moved, the scanning relay pulses a wiper across a board until it finds the location where the arrow has moved to, awarding a mystery amount of points (either 50, 100 or 150) depending on how long the score motor has to run to find the new location of the indicator arrow. The issue here was that between the contacts of the indicator arrow unit was a little charred, enough to actually short across to the next number, this was the same on the scanning relay too so both units tended to get a bit confused as to what number they were on (causing the score motor to continually run and pulse the scanning relay)
I filled away the charred areas and cleaned it up as best I could but the pads were still arcing across, so my solution was to cut a small groove in-between each pad to create a nice air gap and remove the shorts. And then we had a beautifully perfect indicator unit.... Almost......
When the arrow moves it's supposed to knock out the light and collect the number it's landed on, this wasn't happening. I'll whittle down hours of searching and say it was a contact on the 1st ball relay not quite closing with enough force to enable the circuit (even though I had continuity through the entire circuit, which was baffling to say the least)
So the main feature of the machine is now fully working for the first time, which was exciting but after spending 8 hours on the thing I was pretty sick of the sight of it. A few other small issues cropped up while testing... The bumpers being the main thing, not staying lit when they should be and swapping over on their own, this was simply tensioning a few contacts in the 2 bumper relays (one for yellow, one for green) and that problem was sorted too.
None of the score reel lights were working so I saw to that and repaired the holders. And none of the blinker bulbs behind the machines name worked either, this was due to a naff contact in the game over relay, which makes sure the name of the game is only blinking during attract and not during gameplay, which I think is a nice touch as to not put off players
