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(Topic ID: 54951)

Sticking pop bumpers

By PhilGreg

7 years ago

Topic Stats

  • 35 posts
  • 16 Pinsiders participating
  • Latest reply 44 days ago by the9gman
  • Topic is favorited by 1 Pinsider


Linked Games

#1 7 years ago

pop bumpers that stick down seem to be an issue with my Surf Champ machine. I'm pretty sure I identified the left one as the culprit. After cleaning out the coil core and inner tube, I first tried putting a larger spring in there (cut up a launch plunger spring and enlarged it).
That did the trick, but the coil having a harder time pulling down, and not getting all the way down, makes the ball shoot off slower and not hitting the drop targets hard enough.

Now I think the metal rods also rub up a little against the playfield holes. I was wondering if there would be any downside to drilling them a little larger, since they're hidden by the plastic disc anyway.


#2 7 years ago

Just rebuild the entire thing with the proper parts. Do all the pops at once. Probably will cost $15.

Don't drill anything larger!

#3 7 years ago

Experiencing the same problem with one pop bumper on a Jet Spin. Both pops were rebuilt but the one continues to stick, even swapped parts from the good to the bad to eliminate variables. With the ring in the stuck position, I can move the pop bumper body (screws loosened), wafer, etc and it will remain stuck. Like you, I suspect something not quite right with the playfield holes and the under playfield metal bracket that butts up underneath the playfield with holes for the pop bumper ring to go through.

#4 7 years ago

Put some pictures up.

Some Gotliebs needed slightly longer ring & rod assemblies, but I don't remember if Jet Spin was one of them. Or did you possibly put a longer one in by accident?

#5 7 years ago

Typically, this is caused by magnetized coil stops/plungers.
If it "sticks", but you can make it unstick with light upward pressure...there is a good chance that something is magnetized.

Hold the coil bracket in one hand.
Strike it crisply with a glancing blow with something metallic like a steel rod.
This "knocks" the magnetism out of it. Sounds weird, I know...but it works.

You can do the same for the plunger, but be careful to not dent the part of it that pulls into the coil sleeve.
Chris Hibler - CARGPB #31 - The Place to go for Pinball Repair Info

#6 7 years ago

Nice. Great thread back there... I took those things apart a couple of times to put mylar and to clean them up, so I don't have anything against rebuilding.
It looks like the plunger has some scratches (not sure how that can happen within the sleeve), so I might as well replace it.

I'm still wondering, since the bracket cannot be adjusted wouldn't enlarging the holes a tad still make sense?


#7 7 years ago

Are you sure it isn't sticking electrically? I mean are you sure the solenoid is off when it sticks? I also wouldn't drill anything larger. It once worked properly.

#8 7 years ago

I would agree, do not drill larger holes. The original holes should not have changed or moved, the electrical mechanical part must have changed.

#9 7 years ago
Quoted from PhilGreg:

It looks like the plunger has some scratches (not sure how that can happen within the sleeve), so I might as well replace it.

It can become magnetized and metal filings can chew it up, or the coil bracket can get loose and rub, or the spring can break and enter between the sleeve and plunger.

#10 7 years ago

Are you sure it's not the pop bumper relay that's causing it. The armature might be magnetized. The pop bumper coil EOS switch should turn off the pop bumper relay. Check if it's mechanical or electrical first. Turn the game off and pull the coil plunger in manually on the offending pop bumper. Does it stick? Then test it with the game on. Does it stick, is the EOS switch making good contact and working. Is the pop bumper relay firing and turning back off when the EOS switch opens. If the relay doesn't go to off, whilst it's on, turn the game off, is it still stuck on. If it is, touch the armature, does it release. If it does, it's magnetized. Take it off, strike the metal with a hammer a few times to release the magnetism, re install it and test again.
The chances of it being holes in the playfield are nil, that game must have worked for years with the existing holes.

#11 7 years ago

Yes, you must identify if it's a purely mechanical issue of the rod/ring not sliding thru the field (very unlikely) or electrical issue. One other thing I would check as part of that rebuild process-make sure the spoon and the tip of the skirt must be clean and polished. Those two pieces also need to be perfectly aligned so that the ball will not force the skirt tip out of the cup. Some people lube that spoon cup, but I prefer to leave it dry, but polished with novus, etc.

#12 7 years ago

In my case, I know the solenoid is off. I will have to try the demagnetize trick, when I get a chance, to see if that helps.

#13 7 years ago

I'll pile on - don't drill larger holes.

In addition to all that's been mentioned above (ensuring it's not due to the coil still being energized for various reasons), it is possible for the shafts of the bumper ring to rub against the wood of the playfield. This is caused by the shafts having become bent inwards a bit (like squeezed), which makes a tight fit.

This can be checked manually though, with the game off. The bumper ring should be able to be pulled down by hand, and have it spring back up, with no resistance. It should move freely, and even have a bit of play in it. If it does not, then the ring needs to be removed and the shafts checked for alignment. If it does move freely though, then that's not the issue (which would imply more of an electrical cause).

When gently bending the shafts back straight, it needs to be done carefully so the welds not break at the ring. It doesn't take much to get them straight though. Or new bumper rings are an option too.

#14 7 years ago

Good info from Pbr >
Also the parts for them are here >

On an Outer Space my brother had a sticking pop bumper rod/ring which was happening so after ordering a set of return springs and skirt springs it worked perfectly after a change out.
If the ring rods are bent then at $3.60 each is a bargain. From Pbr> 2 sizes
Used on Gottlieb® games starting with Surf Champ(1976) A16634 = GTB-A16634+

Substitute for early Gottlieb® games before Surf Champ(1976) A1316 = WLL-A4754

#15 7 years ago

Thanks everyone,
I'll have to double check all that stuff tonight.

I did notice that when prying the coil a little bit to one side, the ring was popping back up way more easily which is why I was thinking about that solution, but it may be something else causing it.

I'll get back after I check it out.

Thank you.

#16 7 years ago

Check the rods for straighness or breaks. I had one sticky pop on my Black Hole that had a perfectly clean break on the rod on one side. The break was almost imperceptible when it was fully up, but often the bumper would bind coming up because of the asymmetrical force on it. New ring and rod assembly fixed it. However, that fix required disassembling the whole pop bumper, so I ended up rebuilding the whole pop in the process.

#17 7 years ago

Finally, had a chance to look into sticking pop on my Jet Spin tonight. Everything on the pop was replaced but the bracket, plunger and coil stop which looked fine after a wipe down. Friend helped me look at it the previous night and he agreed that it appeared to be a magnetic type hold because you could move the body (screws loosened), wafer, etc and it wasn't releasing as if it was binding. He suspected the coil stops if it was anything magnetic. Replaced the coil stops tonight and everything seems normal for the test games I played. Add coil stops to the things to check on a sticking pop?

#18 7 years ago

Sometimes you just see flipper/pop components get magnetized and lots of little iron filings stick to it, binding it up; or in the worst case, simply sticking to the coil stop.

Now that you have experienced the magnet's holding power, you will be an expert in it's detection in the future.

Congrats on the fix!

#19 7 years ago

Well wouldn't you know it, you guys are right.

It is indeed magnetic sticking. And it's not the coil pulling in, looks like it's magnetized components. I tried doing the demagnetizing trick to no avail...

Oh well... might as well rebuild them.

Thanks for your help guys.

#20 7 years ago

You can also buy a little magnetizer/demagnetizer, a plastic unit with holes for mag/demag of tools etc. Handy for magnetizing screwdrivers too! Something like this one: link »

And even an old plug-in degausser unit might be good for demagnetizing parts. They used to sell them to bulk-erase tapes.

#21 7 years ago

I've got one of those red cube magnetizers, and it only can magnetize enough for the smallest screws you would ever use. It can't even make a #2 screwdriver magnetic enough to hold a screw.

I'm not sure it could ever do something as large as a plunger or coil stop.

#22 7 years ago

This is something which puzzles me with these games. I had also recently solved a magnetically sticking match relay.

The reason I'm puzzled is because if you want to demagnetize something you put it in an alternating magnetic field. If you want to magnetize something you put it in a pulsing non alternating magnetic field. Yet I had the relay sticking problem.

Is the pop bumper a DC coil? That might explain why it developed a sticking issue. I'd bet the plunger stop has some kind of non-magnetic alloy that is either missing or wore out. I'd replace that stop.

1 week later
#23 7 years ago

Sorry it took me so long to get back, but I work pretty slow on these things in between too much other stuff.
Has anyone had any luck with that demagnetizer cube? I just tried running each piece through there multiple times, but no luck.

I guess I'll have to do the rebuild, after all... Learning the hard way's the best way to remember

#24 7 years ago
Quoted from PhilGreg:

I guess I'll have to do the rebuild, after all... Learning the hard way's the best way to remember

You are going to be SO happy you decided to rebuild.

Rebuild them both and you will love them having full power.

#25 7 years ago

I guess so...
it just stumps me that all those unworn pieces cannot be brought back. That demagnetizer gizmo looked promising.

#26 7 years ago

You might try swapping the coil stops with the ones from the flippers and see if the problem follows or goes away. If the problem persists with the pop bumpers, then it's something else.

If they are magnetized though, whacking them with a hammer, or squeezing in a vice sometimes is enough to disrupt it. (Yeah, I know that sounds weird, but it does seem to help).

Coil stops are a bit pricey (relative to other EM parts), so salvaging them is worth a few more attempts.

#27 7 years ago

Well I think I spoke too fast... I played a couple games (the machine is Surf Champ), and the pop bumper I processed through the demagnetizer is definitely less sticky than the other one. I think it stayed momentarily stuck only once in 3 games.

I'll redo it and process the other one as well, get a couple dozen games in and get back to this thread.

In the meantime I've ordered stuff to rebuild it, might come in handy anyway.

#28 7 years ago

So I did both bumpers. I still have a bit of sticking from one of them, maybe I'll go through it again.
So from my perspective, if you have a nice game you don't mind spending a couple bucks on, by all means to the rebuild.
But... the demagnetizer is a cheaper alternative that will do a big difference, although may not perfectly solve the problem. It's not much simpler to do however, as you still have to pull apart most pieces.

#29 7 years ago

Maybe you stretch the plunger spring a bit to provide a bit more lift.

6 years later
#30 5 months ago

MUAHAHAH I have this SAME problem on my Gottlieb Pinball Pool. It is so frustrating to find the issue.
First when I was playing, the left pop was doing this. The ring would stick down, and turning the game off, it stayed down. If the pf was raised or you pulled the ring, it would come up, but it seemed/felt like it was magnetized plunger to coil stop.

I ended up ordering all new parts for that pop and in the mean time, swapped parts between the two and then when I put them back, the right pop started to have the issue. I have rebuilt the left and that seems to work 99%. The right is now acting magnetized and I just now, pulled it apart, hit the parts with a hammer, left in some water for a bit and hit with a hammer again. I'll rebuild when try and try again. Otherwise, i'll need another order....

#31 5 months ago

I had to order new coil stop and plunger. Hitting with a hammer, the small red dema/mag didn’t work. I’ll update when the parts come. I’ve never had or seen this issue before so it took me a while to figure out

#32 5 months ago


Can confirm the new parts fixed the magnetizing/sticking. I also put new springs in.

3 months later
#33 44 days ago
Quoted from northvibe:

Can confirm the new parts fixed the magnetizing/sticking. I also put new springs in.

good deal man. Im about to order parts to do the flippers and pop bumpers on my firepower. One pop bumper plunger feels gunky and is stuck down. Physically hard to move.

Then the right flipper sticks after a few games, but will go down if the ball hits it. I believe it’s that same thing you guys are describing. Biggest challenge now is knowing exactly what parts I need to buy.

#34 44 days ago
Quoted from Teamhex:

good deal man. Im about to order parts to do the flippers and pop bumpers on my firepower. One pop bumper plunger feels gunky and is stuck down. Physically hard to move.
Then the right flipper sticks after a few games, but will go down if the ball hits it. I believe it’s that same thing you guys are describing. Biggest challenge now is knowing exactly what parts I need to buy.

yeah, it really makes you feel like it is binding...but man it was just like....a WTF. Once rebuilt...bam, super smooth. If you play with it, you'll see and feel the magnetized parts but imo, just worth rebuilding and not even worrying.

#35 44 days ago

I had the same problem with my solar city ...tried everything ...buffed all the parts checked everything and it still stuck finally got fed up and switched the feed wires and for some reason that worked. Note: you can get away with this on old EM's because they are AC there is no diode or cap on a SS DC machine you would have to change the direction of the diode

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