I have a Bally Air Aces which behaves erratic regarding assigning an extra ball to a player.
Often when the ball has drained and the bonus is being added to the player' score, the extra ball light lights up and the player is assigned an extra ball.
Sometimes it also happen during a game, while a player is nowhere near the kickout-hole which is supposed to activate the reward.

There's no pattern in the mis-attributuion: it can happen during any ball for any player at any score.

Attached is the relevant part of the schematic; full schematic here: https://www.ipdb.org/files/28/Bally_1975_Air_Aces_Schematic_Diagram_continuous.pdf

I don't really understand what actually activates the coil, even in a normal scenario (when the feature light is enabed and the player plays the ball in the 'enabled' kick-off hole.

To me it seems like a dirty contact problem.
Any ideas?

reset (resized).png

Well.. after cleaning the extra ball relay contacts, thinking it was a "break" contact opening because of vibrations or dirt on the contacts, the problem still persisting...

All of a sudden it hit my mind that it was not happening randomly... but always when crossing the 25000 points mark.

I checked the "bonus adjustment" feature and yeah indeed; that was what's being dictated..

So all in all, everything works fine, just a minor case of PEBKAC.