Thank you for reopening this old post, and the following discussion. I have been chasing down a problem on my Space Mission as have had time, for a month or so and some of your discussion may give ideas on how to track my problem. Short description is most of the time, ball ends, new starts, everything fine. Part of the time, kicks out new ball, then keeps cycling kick out sequence including kick out coil fires, bonus unit fires to add the first bonus amount, match unit rotates, etc. This can be for just one additional kick out cycle, a few cycles, or endlessly until either turn off game, or lift pf and manually advance the bonus unit.

Will use your discussion and diagrams to work on figuring out my problem. Thanks again.

Thank you both. Hadn't yet reached the "I completely give up and will have to start a thread on Pinside" point yet, when I saw your discussion.

Rolf: Thanks for the suggestions. Will check out the test light, and zero position switch links when have a minute.

LeChuck: Bonus unit is stepping repeatedly, so either lift the pf, or during tests for this problem already had it lifted. If (wearing rubber gloves) I manually push the bonus unit step coil and arm while it is repeating, the repeating stops. Have checked the switches in this linkage multiple times and can't see what in this area would start, or why that would stop, the repeating.

Out hole switch was the first place I checked, and with pf lifted close this switch manually to simulate a ball return when troubleshooting this problem. I also have been trying through the schematic to track order of what happens, when, after a ball drain. But still have somewhat limited schematic reading / tracing skills.

And know the feeling of "fixing" something, only to have something seemingly unrelated rise up. Having that problem now on a Wms Twenty Grand. But that is a whole different story / thread.

Thank you both for the input, will keep "whacking away" at it and if truly reach a dead end will start a new thread.

First question, should I start a new thread? Was just at that point tonight when read your latest post. Followed the logic, and can't find any switches that seem out of place, or making or not making contact. But again, this is an intermittent problem. However, one "clue" maybe. When the game gets stuck in the ball return repeat loop, it doesn't advance the ball count unit. So somewhere, that step is being skipped as the reset routine repeats.

Also read the Monte Carlo link, good info, but maybe I am too tired tonight to really digest it and translate to the Space Mission problem.

Rolf, also read your Space Mission diagnosis link with Mfoam, and it helped with understanding of some of ball return / bonus unit / outhole logic. But didn't lead me to resolving my problem. But do want to let you know the bonus unit does reset properly from 0 to 1 and back. And switches in the proper locations and making good contact at 0 and 1.

One last note. After writing the above, and was giving up for the night. Ran the game through a couple of game cycles. At one point, on ball 4, started the repeating ball return cycle, turned it off and for first time when turned it back on and started a new game it started the repeat cycle at kick out of ball 1, through two on and off power / start game cycles. Then while repeating, lifted the play field, manually pushed up on the arm that is attached to the add bonus index coil, and repeat cycle stopped. Arrrgggghhh

Only had a few minutes this morning before work. But ran through 5 game cycles before 1 repeat incident. Then next 3 game cycles only repeated on 3 balls, then for only 2 to 4 repeat cycles each time before stopping on its own. But answered for certain:

Bonus unit does cycle between 0 and 1 on each repeat.

Bonus relay only fires one time, then doesn't fire again during repeat.

Also, was able to get it to repeat in no points scored just closing the outhole switch condition.

Have to get ready for work now, will try to look at it again tonight some time.

Thanks to both of you for your help. Been working on pins just short of 4 years now, and still run into these issues where just can't figure it out on my own. And let me know if and when you want me to start a new thread.

Update, through 6 more simulated games. Repeated 2 cycles twice, and 3 cycles twice, and definitely the bonus relay only fired one time. It did not fire on the repeats.

Second update. Isolated problem. It’s mechanical. Arms of bonus unit not always resetting properly.

Now just have to fix it.

Fixed (I I think) 6 games, no repeating. It wasn’t actually stepper arms, but related. When the arms engage on the stepper gear teeth to count down the bonus. There is a very slight double action in their making the gear move. The three switch contacts were adjusted to make or break contact on the second part of this slight double action.

By adjusting all three to make or break contact on the first part of the action of the gear / switch arm, it stopped the repeating. Hope this explanation makes sense.

nteresting, that's one that is pretty tough to troubleshoot systematically. The stepper units being mechanically erratic can cause anything. Did you happen to figure out how that correlated to your symptoms?

All the electrical testing and walking through the steps you provided kept pointing back to the bonus unit. But it seemed like there was nothing wrong until I took slow mo video on iPhone and noticed the two step motion. Then physically played with arms thinking they were the problem in that the two step motion was the fault.

Unscrewed stepper, and pushed coil plungers manually checking arm movement. Didn’t see a problem with the arms. But that was when I noticed the switches open / closed on the second part of the two step motion. Adjusted the switches to work on the first step on a hunch. And it seemed to work. So far.

I didn't think Pinside allowed video posts.

Not sure I did this correctly, first time trying. But below is link to slo mo video of bonus unit. I think.

Rolf, and all, video was before problem fixed. Have now played 11 games, no repeat problem. Switches / contacts were adjusted after this video, very slightly to the left as you look at the unit, so that they open or close on the first part of the two step motion.

Epilogue: after all that, appx game 15 problem came back. After more slow mo video, and with game off slowly going through mechanical action of bonus unit. Found what I think is the eos switch under the add bonus rocker arm was touching the bottom of the arm. By adjusting the switch so it only touched at the end of the stroke, now into 20 games with no problem. My takeaway, was a combination of slight switch maladjustments That needed correction.