mystic line extra ball design flaw - timing cams
A couple years ago I was going through a Safari and thought the extra balls were a little scarce. I went through and checked the switches, which looked ok. The I went to the trouble of fiddling with the mixers and spotting disc wipers to get 50V passed through and verified everything operated as it should.
The one thing I never checked was the cams themselves, which is what ernie did. What he found is shown in the picture below.
The top section of the picture shows the timing diagram and a picture of the cams. When life was good, cam 8 lifted its switch stack during the time that the cam 6 switches were lifted. Since 6A/6B and 8A were closed at the same time, a pulse could be generated to single step the extra ball unit.
Somewere along the way, bally changed cams 6 and 8. Cam 8 was probably due to some extra switches mounted in front of the control unit shaft. They shifted the lobe on cam 8 back, and didn't lengthen cam 6 lobe enough to compensate. As shown in the lower part of the picture, it is physically impossible for switch 8A to be closed when switch 6A/6B is, thus the single step circuit could never work.
So far we have verified the following games have the problem:
What about machine xxxx
To see if your game has the problem, you'll need to pull the backglass and lower the panel behind it. Then look at cams 6 and 8. If necessary, you can release the timer cams and turn them to see how the switches behave. If you don't have a manual, you won't know which cams are which. Send me a comment and I'll look it up. However, it's pretty much the case that cam 6 is the one with only one or two switches on it roughly in the middle of the timer cam switches. Cam 8 is two cams further away from the motor end.
If your game single steps to "extra" only ("extra" will light without "ball" lighting at the same time), then your game doesn't have the problem, or someone fixed it.
If you do check the cams, send me a comment and let me know
the game and whether it has the bug.