I'm working on a Skylab pin for a friend of mine. The last (known) problem I have is that the game awards a double bonus on every ball - not just the last ball. I can't figure out why.

The ball count unit seems to be working fine - as does the Spacelab advance / step down unit. I've examined every relay that appears to be relevant, and they all look OK. I can't see anything obviously wrong with the score motor. The timing of the switch stacks / cams appears to be right. And, if I look through the coin door during "game play", I can see that the double bonus relay only activates on the last ball (as it should). And yet, the game still awards a double bonus on every ball - not just the last ball. Any thoughts on why this might be?

Thanks in advance for any help

OK, thanks. I'll check those two things. Thanks again!

I actually can't see the bonus relay. There's too much in the way when I look through the coin door. The double bonus relay is not activated on the first two balls, and activated on the last ball. It seems to be doing what it's supposed to do.

Thanks for the info. The double bonus relay looks fine. The (two) normally open switches are open, and the one normally closed switch is closed. When the relay is energized, the opposite is true I'm in the process of checking the ball index relay.
The ball count unit seems to be working fine. the M/B switch on that unit seems ok, the ball count goes up / down smoothly. Thanks again!

Initially, I thought Skylab was pretty hokey. It's not a fantastic game, but it's not terrible either. If you can make the captive ball "horseshoe" a regular part of play, it gets more interesting - by way of extra balls, and 1000 points per loop

Once again, I appreciate all of the advice / suggestions.
There WAS an issue with score motor switches, but it was not 3C. It was the make / break switches at 6B. The make / break "condition" at game over (ball zero) was opposite what the schematic showed. I adjusted those switches, and that resolved the continual double bonus problem.
With that resolved, I noticed that I had the same problem as another Pinsider. Specifically, the game awarded the correct end of ball bonus for even numbered bonus values (and for all double bonus values). But, for all odd numbered bonus values, the game would award an extra 1,000 points. As indicated in another post, I adjusted the "end of stroke" switches on the advance unit (so they open sooner / more quickly), and that resolved the remaining issue. Looks like the game is fine now.

I've marked this thread as complete.