New to the forum semi new to pachislo machines. Picked this up for next to nothing because it wasn't working... needed tokens....wanted to see if anyone had any info on this model. It plays great but doesn't pay out nearly as much as others I have had. I have the odds set to 6.

There are 4 black plugs on the motherboard labeled a b c d . A is the only one plugged in and there is a sticker with the same and a is filled in. Anyone know what these are for?