(Topic ID: 105996)

Stern star trek pro-weak ball launch and top flipper getting stuck

By TronGuy

5 years ago

Topic Stats

  • 25 posts
  • 13 Pinsiders participating
  • Latest reply 5 years ago by Duex
  • Topic is favorited by 1 Pinsider


Linked Games

#1 5 years ago

So I've had this pin for 10 months, no real issues before that I couldn't fix.

Now the ball launch to start a game or multiball is very weak. Sometimes it fires good other times not. Typically it is strong to start a game and goes down from there. Occasionally my upper warp ramp flipper is sticking as well. All coils check out in test mode, but that doesn't measure strength does it? Just functionality.

Where should I start? Connections look good.

#2 5 years ago

How much play has it had. I noticed that my ST LE gets dirty than anything else I have.

Check to make sure that the prongs on the auto launcher line up with the ball. Then move the auto laucher plunger with your fingers to see if it moves smooth and free.

For the upper left flipper i would check them same thing. Move the actual bat and see if its smooth and free. I have noticed that I had to replace all three coil stops in my game as the brass rings shattered and bits were in the sleeve.

#3 5 years ago

I have way over 1000 games on it, maybe 2000. Both coil arms move freely and smoothly. The prongs not lining up is something I will check now. Thanks for the reply.

#4 5 years ago

what exflexer said about the flipper coil stops. seems like alot of these recently have been coming apart.

Saw a thread recently on the autofire for ACDC where the plunger was too high up in the coil and that was fixed by placing a little bit of rubber or bumper in between where the autolauncher bracket rests against the bottom of the playfield. Also might check the little blue plastic link to see if it's breaking.

#5 5 years ago

had the same problem on my ac/dc pro, couldn't find the problem, checked everything, driving me nuts.

then i realized i changed the shooter rod few days earlier, the rubber tip of the shooter rod was rubbing against the ball launch assembly, moved the shooter rod assembly to the right as much as i could.

problem fixed.

for your upper flipper, check the flipper assembly, everything, it's gotta be that, i hope.

Post edited by beatmaster: more infos

#6 5 years ago

Same thing happened to my upper right flipper. I replaced the coil stop and sleeve and it hasn't gotten stuck since. Probably your best bet.

I also have a problem with plunging ball now after 10 months. Turns out if I twist the plunger rod, it is shoots well in some positions and others it won't even get the ball to the lanes. Not sure what is going on there but try twisting (turning) yours and see if it makes it better. Mine doesn't appear warped or bent so not sure what's going on.

#7 5 years ago

I have been having the exact same two problems on my Pro. I've only had it about a month or so now and it was working fine when I got it. I'm afraid that I've done something to mess it up while in the process of installing several mods, without knowing it.

I've done all the checks above and near as I can tell it looks in order. I'm not exactly sure what I should be looking for with regards to the stop and all. It definitely seems mechanical because when I turn off the pin while it is stuck, it does not drop.

#8 5 years ago

Coil stops 100% the problem.

#9 5 years ago
Quoted from erak:

Coil stops 100% the problem.

This is my only pin and I am not afraid to work on it, but I don't know where to order these parts. I work on all of my video games so I am at least competent.

I would love a recommendation on what/where to order.

thanks for the input guys

#10 5 years ago

Coil stops for flippers


While you are in there, it would be a good idea to replace the sleeves. Get some extras as shipping kills the one and two purchases. Nice to have some on hand when needed too.


With that many plays it's a good time to do some flipper maintenance. Give the other parts a good cleaning and all should be good as new when finished.

#11 5 years ago

I like to replace these as well -

and these -

Not necessary but I like to use fresh stuff when putting flippers back together.

#12 5 years ago

I am ordering it all. Thanks for the links.

#13 5 years ago

That flipper link is not easily replaced. Unless you have a vice and correct size punch I would just order this instead. They are only like $4/each.


#14 5 years ago

What exactly goes bad with the coil stop? Is this something I could identify by inspecting it? Just not sure what I should be looking for. I can't really tell why mine is sticking. It doesn't happen all the time either. It's somewhat random.

#15 5 years ago

Normally, a coil stop will look like it's been hit with a hammer about 400,000 times. You will see and feel that the top is not flat anymore. But what we've been seeing lately is early failure of the coil stop from Stern. The stop itself will be loose in the bracket, or even fall off. It happened on my Tron in the first 350 games. Look for lots of metal shavings in the bottom of the cabinet, directly underneath the flipper.

#16 5 years ago

The auto plunger is designed with two pieces of medal that are split like two fingers throwing a ball. After many uses they will tend to separate. Fortunately the fix is easy - just squeeze the two pieces of metal closer together.

#17 5 years ago

I got under the hood again and took another look at my stuck flipper.

I noticed that the back of the coil stop(brass rivet/bushing on the outer side of the stop plate?) was loose by at least a few millimeters. It definitely had some visible play whereas the two main flipper stops were solid.

I tried removing the stop but there wasn't really anything I could do with it so put it back on. I also noticed a sort of washer around the stop that was slightly bent, I'm assuming as a sort of shock absorber, and normal. Flipper is still getting stuck though. It seems like it gets stuck magnetically. Manually the assembly seems fine and it springs back on its own when the coil isn't energized. I can get the flipper to drop back the majority of the time by pressing the flipper button halfway so as to only engage the main right flipper. I'm not sure of the correlation.

I took a look at the contacts for the flipper button assembly and the spacing seems fine to me, and it is visibly separating contact at the second stage when releasing the button.

I will try replacing the stop and while I'm at it, the plunger/link assembly and nylon tube too. Hopefully that will fix it as the game is pretty much unplayable right now.

#18 5 years ago
Quoted from PWhiz:

I can get the flipper to drop back the majority of the time by pressing the flipper button halfway so as to only engage the main right flipper. I'm not sure of the correlation.

Congrats, you just learned how to "stage" a flipper That's actually a tech used when you have a ball cradled and you need to shoot the ball past where the upper flipper is blocking. This happens as there are actually two switches in the stack that activates the side with two flippers. First leaf does the bottom and second does the top. By pressing the flipper to where only the first leaf is activated allows the lower flipper to go up and the top to stay down. Takes practice to be usable but is a good tech to learn.

The coil stop shouldn't have any play at all so it needs replacements. I'm not as confident as others that this will fix the problem but basically doing a rebuild (the parts linked) should solve the binding issue.

#19 5 years ago

Yeah, that was something that I picked up here before. It's good to reiterate it as it seems it is commonly unknown. I told my friend, who got me into pinball and owns a Tron, about this and watched his mind explode.

The reason I brought it up was because I thought there might have been some kind of bad contacting going on with the second leaf, and that it perhaps wasn't separating again when releasing the button(which it seems to do fine). But I'm still not getting the logic behind why, when the upper flipper gets stuck and pressing the button to only engage the first leaf, does it cause the upper flipper to drop. In my mind, it shouldn't be effecting the upper coil at all.

#20 5 years ago

vibration from the lower flipper mech most likely. Does it drop when you press the other flipper button?

#21 5 years ago


#22 5 years ago

Flipper fixed with just a new coil sleeve. The coil stop was in pefect condition when taking apart thw assembly. Didnt look into the auto plunger yet.

#23 5 years ago

The parts I ordered from PinballLife.com came in today. I replaced the two easiest things first, coil stop and sleave. BAM! That did the trick! It's rock solid now. So happy! Even the issue I had with mission selecting prematurely selecting missions went away(Which now I know was related).

I was also able to fix my "weak" auto plunger problem. I had followed Drainman's advice and used a pair of needle nose pliers to squeeze the two metal arms together a bit. It seemed to work for a short while but then got worse and the majority of the time it couldn't even successfully launch a ball all the way. So I tried the opposite and straightened them out completely. That did the trick. I'm thinking that wear and tear had cause them to slightly bend inward a bit. Now I know how to fix it if it ever gets weak again. And thanks Drainman for the tip cause it got me on the right track. If they had been spread apart then squeezing them together would have been the right choice.

Man, as a newb to pinball, being able to fix all this stuff on my own feels really good. Of course, I couldn't have done it without the help from you guys! Big thanks to all!

2 months later
#24 5 years ago

Has anyone found other solutions to this problem? I have a ST Pro that I got just about a month ago and the auto launch as lost most of its steam. It does come and go but doesn't seem to stay "strong" for very long. Everything is correct on the machine. No mods, (yet) and it is perfectly level. Its really frustrating when trying to hit skill shots and during multi balls. Rather than launching it all the way around the playfield and feeding it to the flippers, it doesn't even have the juice so it barley makes it to the poppers. This eats up valuable time you need to hit certain targets.

Any new ideas I can try?

#25 5 years ago

For me cleaning the balls helped a lot.
Additionally I played around a little bit with the mechanics (tightening the screw) and also used some WD40 on the mechanics.

Promoted items from the Pinside Marketplace
From: $ 5,599.00
Pinball Machine
Great American Pinball
4,800 (OBO)
Machine - For Sale
Richmond, VA

Hey there! Got a moment?

Great to see you're enjoying Pinside! Did you know Pinside is able to run thanks to donations from our visitors? Please donate to Pinside, support the site and get anext to your username to show for it! Donate to Pinside