Quoted from PinballGlory:
I notice that in the schematics there were a relay called YY but I dont see it in my relayboard so i suspect that this i the relay thats missing.
I think you may be looking too closely ... stand way back and look at the relay right above the adjust plug
given the location of those wires, I'd guess there was an adjust plug there and someone needed it.
look on the supplemental schem for more adjust plugs and if there are more, see what wire colors went to it/them.