Im trying to keep this simple here.

We HAVE to assume that the wiring is all OK until we have eliminated all other possibilities.

Im clinging to the time when you opened up the "A" player leaf switch. This allowed game to bust at 30 NOT 20 as it should... so with this switch open - logic is good.

There is NO path to ground on 20 points... not one that would fire the bust relay anyway.

So im thinking that at 20 points there is a short on a wiring or the stepper that is linking the 20 and the 30 together.

IF this is the case, then ground is given a path directly to BUST... we dont need 8 Re or 9 RE or even RO RE... it goes straight to bust relay and coil. And if im reading correct - you have verified the correct operation of 8,9 and RO

Make sure your wiper is not touching both contacts.. im assuming front and back are active on this.

Also lift the contact arm and test between increment 2 and 3... should be open.
Drop contact arm and test again - should still be open.


If the above tests OK, then its getting hard as 20 points is completely isolated from BUST



Also.... the game does start at zero yes?? It doesnt give 10 points at start up does it?

Welcome to my nightmare Gav . This is a bitch of a fault . I have already checked there is no continuity between 2 and 3 position on both 10's card reels (with and without the wiper installed).

Yes, i have verified correct operation and adjustment of switches on 8, 9 and rollover relays .

I too am clinging to the fact that opening the "A" player switch confirmed the 10's card reels (and that part of the cct) is working correctly. This test also verified that there is no active ground path via 8's 9's and rollover relay when there shouldn't be.
This test also isolated (in my mind) the cause to something on the side of the 1's card reels but I have just double checked them both again and can't find any short .
 Also, FYI, there is a seperate gorund wire connected to each of the 1's card reels that is not shown on the schematic. This is how they get fed a ground source.

I was also thinking about a false earth from the number match stepper, but it is isolated by a N.O switch on the dealer relay which is definietly open .

I'm starting to think I might have to try some creative rewiring ?