I have a problem with my Stern Nine Ball.

When I lock a ball in the left lock it drops all remaining drop targets on the left side one at a time and gives 3000 points as it is supposed to. But at random times when it is dropping the targets it will drop a target and at the same time fire the left slingshot or the outhole kicker.

It is quite random, never the same drop target , as in it doesn't always do it when say #2 drops or #5 drops. And never the same amount of targets, for instance never just after the second target drops or the third. It's always random, and sometimes it only fires the drops and not the left sling or outhole. And it always drops the targets properly.

Things that have been done or checked.

1: New Alltek Mpu was substituted, same problem.
2: New power board, same issue.
3: Re-pinned all connectors, and yes I mean all of them.
4: Tested the diode and cap on the slingshot and they are fine.
5: All switches checked multiple times in multiple ways, no switch problems at all. All gapped properly and all working properly.
6: All wiring checked and appears correct.
7: Running rom version 60
8: Pia's swapped with working ones from Meteor. Same problem.

Any ideas?

Thats the thing, it's completely random. Sometimes I can put the ball in the lock on the first ball and it drops all the targets and nothing else fires. Other times it drops 2 targets and on the third it pops the left sling at the same time as the third. Other times it drops one and fires the sling then 2 more drop fine then the next one drops and the sling fires again.

The outhole kicking out a second ball randomly happens also about every 10 tries. And it usually kicks it out right before the lock kicks out it's ball.

And this is with me re-setting the machine, starting a game and physically taking the ball and putting it in the lock and doing it again 4 times to see what happens. It is never the same.

On the solenoid test everything fires fine and nothing changes if I flex the board. Both of those connectors have also been repinned.

Here's a video of the problem.

https://drive.google.com/file/d/1_80psQAXqofHQP7esMXAONykoDifzbLE/view?usp=sharing

It's something in the switch matrix apparently. I can trigger the slingshot randomly when I drop the lit targets manually. Still no pattern at all.

Pulled every single switch diode. They were all good.

This one has me stumped

Disconnected every capacitor , no change.

Took the Meteor MPU-200 out and switched roms and put it in the Nine Ball. Same problem.

Geez , this sucks.

Got the slingshot problem fixed!

Drop target #6 had a failing diode apparently. Replaced it and no more slingshot problem!

Can't seem to fix the 2nd ball eject problem though

Here's whats happening. On the first ball when I lock the ball the targets all drop and the ball is ejected, then another ball is ejected into the shooter lane. It doesn't seem to do this on the next 3 lock balls. When on ball 2 and 3 it sometimes odes it and sometimes not.

If there is only one ball in the outholes it won't do it. If I force drop target 1 to not drop the second time after the drops reset, it won't do this.

I have replaced almost every diode on the machine now and still can't figure this one out.

So close yet so far away!

I wish. I can take all the balls out of the trough after I start a game , lock the ball and it never tries to eject the saucer. If there is a ball in the saucer the game almost always ejects a ball on the first ball lock.

Arrrggghhhh!

I've been through the switch test a hundred times. No switches are registering wrong.

If I unplug the coin door after I start a game the game goes into tilt and shuts off.

The weird thing is that when I duplicate this problem there are only 2 switches closed. The saucer and the lock. The drips all drop then reset so their switches are not closed. Then after it enacts the locked ball it enacts another ball sometimes. So not a while lot of switches that can be involved it seems.

Maybe it's not a switch problem? I mean what switch would trigger the outhole kicker to kick? Not the outhole switch. I think I'm looking in the wrong spot.

After the ball is locked the mpu has to tell the lock kicker to kick out the ball . Around that point it is also telling the outhole coil to kick out a ball. Now why would that happen? Bearing in mind it's not a Mpu problem, it does it with 3 different ones. It's not a driver board problem, it does it with 2 working boards.
Doesn't seem to be a pin problem as I have re-pinned the whole game now.
Soo where does that leave me?

But I have used 3 different Mpu's and 2 different driver boards. In every conceivable combination. They all act the exact same. Wouldn't that be a sign it's not on the Mpu or Driver board?

The knocker and the sling turned out to be a bad diode on the #6 switch.
Just the outhole problem now.

oh ok. Well I just went to the machine. Put the multimeter on each pin with an alligator clip and molex pin. They all had continuity even when wiggled and yanked on. The headers have all been re-soldered. Don't think that's the problem.

Well I finally tracked it down. Bad diode in the shooter lane switch. Farm sometimes thought a ball had never been ejected from the outhole. So after 8 seconds it would eject another one. Just the exact amount of time it takes to drop all 8 drop targets and eject the locked ball. Lol

Yep and almost 30 hours of troubleshooting.