(Topic ID: 175434)

Sometimes a Coil Sleeve is Just a Coil Sleeve

By bdPinball

7 years ago


Topic Heartbeat

Topic Stats

  • 23 posts
  • 16 Pinsiders participating
  • Latest reply 11 months ago by alkregha
  • Topic is favorited by 1 Pinsider

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#1 7 years ago

Or is it? I got a batch of coil sleeves, and they seem like maybe they aren't exact?

First I want to ask if I'm the only one who just trims down a coil sleeve if is too long for the application? Is there any problem with doing this?

Last night I fought with some Coils in a target unit on my Flash, and as usual, I had the problem with the sleeve coming out, but then the new sleeve won't go in. I've ready other posts talking about how sleeves go in very hard on some williams flipper coils. This wasn't a flipper coil, or even one of those HUGE reset coils like they use on Bally games. To the eye all my coil sleeves appear to be the same, but I haven't taken a caliper or micrometer to them or anything. But after fighting with it all night, This morning I tried a new coil sleeve and it slipped together with no problems.

ALSO- Has anyone else found that hollowing out the inside of a coil just slightly, with a drill slightly smaller than the coil hole, and just make sure the walls a smooth? I've tried going the other direction and sanding down the Coil sleeve to it's smaller to fit in the hole but I can't seem to find anything to hold the coil sleeve, and then make it spin fast enough to use sandpaper to take off a little bit. When I was finally able to get something to work (not very well) it ended up roughing up the coil sleeve, sort of negatiting any benefit from change in size.

FInally, If you get a sleeve stuck inside of a coil, has anyone else taken to using a sabre saw to cut a slot, allowing the sleeve to come out, Or another way I found was to use the same drill that I used to hone out the inside of the coil. It seemed to get inside the coil sleeve and sort of rip it out of there.

Anyone have any better way of dealing with the sleeve-too-big / Coil ID too small problem? If so I'd love to hear them! Or ways you've found to make the process easier.

-Brian

#2 7 years ago

Coils swell when they overheat. When that happens, they need to be replaced.

I can't say I've had to make any adjustments to a sleeve unless I needed a specific length cut down in a pinch.

Where are you buying your sleeves from?

#3 7 years ago

I have had issues with new and used sys11 flipper coils being super tight. I use a rubber mallet to get the sleeves in.

#4 7 years ago

I have had occasions where one brand new sleeve would not fit into a coil, but an "identical" new sleeve would fit.
Seems odd, but it happens. Must be some variance in the manufacturing.

#5 7 years ago

Yes on all accounts to your questions.

I sometimes trim down sleeves to get them to the right length.

Some batches of sleeves I get seem tighter than others. Others will fit. It is probably due to tolerances of the sleeve itself and the coil's bobbin. A 1/2" spade bit can be used to shave down the inside of a coil bobbin to help get a sleeve to fit. I've done this on occasion.

A 1/2" spade bit will also let you easily get a stuck sleeve out of a coil. Just drill it out. The only thing you have to watch is if it gets away from you or you are too aggressive you can crack the coil's bobbin.

#6 7 years ago

If they get stuck you can remove them by tapping them out with a 5/16" nut driver.

#7 7 years ago
Quoted from jeffc:

If they get stuck you can remove them by tapping them out with a 5/16" nut driver.

This sometimes works, but I find they are often too stubborn for this. Try the nut driver first, but when that fails that's why I recommend the 1/2" spade bit.

#8 7 years ago

If you are having trouble inserting or extracting a coil sleeve, best to just replace the coil. It's got heat damage from age/overuse.

#9 7 years ago
Quoted from jeffc:

If they get stuck you can remove them by tapping them out with a 5/16" nut driver.

That is what I do. If the coil is still connected I have a helper hold the coil while I pound the 5/16" nutdriver in with a mallet. Usually this will get the old sleeve out. If the sleeve is still stubborn, then I unsolder the coil and bring it over to the vise. Now open the vise jaws just enough for the sleeve. Now go to it with the 5/16" nutdriver and mallet. That usually gets it out.

I have also experienced problems with the long Williams flipper coil sleeves tolerance from sleeve to sleeve sometimes from the same batch! Some fit perfectly fine while others are super tight and you've got to beat the fuck out of it to get the sleeve in.

On normal coils, I've had a batch of 1-7/8 (or was it 1-3/4" ) that the entire batch (a bag of 100) had burrs on the end of them. I had to lightly sand them with sandpaper then they were fine. Seems to me that lately the tolerance and quality control for coil sleeves isn't what it should be. I *think* I got all of the problem sleeves from Pinball Life, but I also bought some from Marco and PBR.

#10 7 years ago
Quoted from CrazyLevi:

If you are having trouble inserting or extracting a coil sleeve, best to just replace the coil. It's got heat damage from age/overuse.

This is often and usually not true in my experience. It is due to variances in the sleeves and the coil bobbins. I'll have sleeves that won't fit right in many different coils, and they all weren't heat damaged, that's for sure.

#11 7 years ago
Quoted from bdPinball:

First I want to ask if I'm the only one who just trims down a coil sleeve if is too long for the application?

I got a good deal on a bunch of longer coil sleeves, so almost every one of mine I cut to size using a small pipe cutter and an old coil plunger.

#12 7 years ago
Quoted from RCA1:

I have had occasions where one brand new sleeve would not fit into a coil, but an "identical" new sleeve would fit.
Seems odd, but it happens. Must be some variance in the manufacturing.

This is exactly what I was talking about. I'm glad I'm got nuts!!!! Err, IM not nuts. Hahaha. The other one too.

-dp

5 years later
#13 1 year ago

Question...what happens if I run my machine without a coil sleeve? I replaced mine because it was sticking. Sticks with new ones as well. Without the coil sleeve it does not stick

#14 1 year ago
Quoted from MikeDiesel79:

Question...what happens if I run my machine without a coil sleeve? I replaced mine because it was sticking. Sticks with new ones as well. Without the coil sleeve it does not stick

The sleeve serves two functions. It prevents the plunger from wearing out the solenoid bobbin, and depending on the mech, it prevents the plunger from falling out of the coil or jamming.

If a sleeve will not fit, then the coil likely overheated and expanded at some point. You would need to replace the coil.

#15 1 year ago

How do you know that your coil needs to be replaced if it hasn't obviously caught on fire?

If you can't remove the coil sleeve, or you can't put a new coil sleeve in, THAT is when you replace what otherwise looks like a perfectly good coil.

I figure the failure of a coil sometimes goes like this:

The magnet wire has enamel on it to keep the windings from shorting to one another.

(EDIT: I had believed that there was movement of coil wires inherent within their operation, and had used an incorrect example of potted epoxy coils as an example... this wasn't correct, so I'm removing this paragraph... my apologies!)

So, when pinball coils are powered, with vibration and thermal expansion and contraction the magnet wires rub, very slightly against each other, and they can rub through the enamel coating, and short two windings of the coil together.

Now, if winding 2 shorts to winding 632, you've got pretty much a dead short. Fuses blow, driver transistors crack open, and the coil starts on fire. (Usually just gets a browned wrapper).

But suppose that winding 2 shorts to winding 30. You've bypassed some of the windings, but the coil mostly works, it just gets hotter, draws more power than it should. No external symptom... but the additional heat puts more thermal stress on the enamel coating of the other windings, and the coil is on a path to destruction.

Because the coil is hotter than it should be, the center bobbin and the coil sleeve get warmer than they should, and deform slightly.

So your indication that the coil is on a path to destruction is when the coil sleeve can't be removed, or a new coil sleeve can't be put in.

Running a coil that a sleeve won't fit in, just using the sides of the coil bobbin, can lead in the worst case to your coil starting on fire, filling your pinball and your house with stinky electronic smoke.

You don't want that. Replace that coil!

#16 1 year ago
Quoted from PinRetail:

There was a time when electronic consumer goods were being made, and they thought it would be a good idea to 'pot' the circuit board and the components in epoxy resin. They found that the coils in those circuits were no longer doing their job... coils have to flex and move with magnetism.

PinRetail I never heard about this. Could you provide a link where this is described ?

#17 1 year ago
Quoted from Zigzagzag:

PinRetail I never heard about this. Could you provide a link where this is described ?

Well!

You think you know something, and then you do a little research, and find out you don't know anything!

Very early epoxy potting of complete circuit boards had problems, and now (according to what I find on Google!) the processes are mature, they use better epoxies, and in some case silicon coatings on the coil wires.

Of course there is a whole science here, and I spoke foolishly, based upon limited understanding and outdated partial knowledge.

My apologies.

That having been said, in pinballs, the coils do get a lot of vibration, they do expand and contract with heat, and do fail due to the enamel coatings between windings failing. The enamel coatings fail a lot more when the coils are poorly made (Pincoils, sold through Marco had a higher failure rate than expected!)

#18 1 year ago

In my over 40 years of pinball repair, I have never seen a coil get shorted because of vibration or any other unknown cause. More likely is that vibration causes thin wire at solder lug, or a diode to break. Coils are usually quite tight wound, so there is very little vibration between windings.

I have seen coils shorted by overheating, melting wire insulation, because the coil drive was stuck on (stuck switch, or later, shorted transistor). Especially on older games, major cause of flipper coil burnout was a broken EOS switch not opening. This is where the partial shorts occur, and they sure make the coil hotter, causing more and more insulation breaks, eventually shorting driver transistor or until hopefully its fuse opens.

It is true that a sticking coil sleeve is a sign of previous overheating, and the coil should be replaced. Checking if the coil has partial short is easy, just measure the coil resistance and compare against tables. There are plenty around... here's one from John's Jukes:
https://www.flippers.com/coil-resistance.html

As for the epoxy potting, most coils in mobile uses e.g. cars seem to be potted (starter solenoid, A/C clutch magnet, door lock solenoids etc.) Of course a car has much more vibration and temperature/humidity changes than a pinball machine so probably that's why they are using it.

Using a coil without sleeve is a bad idea because it might be partially shorted, and with no sleeve the plunger has slack in movement and makes the operation weaker.

#19 1 year ago
Quoted from Tuukka:

In my over 40 years of pinball repair, I have never seen a coil get shorted because of shorts due to vibration.

Thank you for pointing this out. I bow to your experience, and I've already been quite wrong in this thread.

Thanks!

#20 1 year ago

Not having seen or recognizing it does not mean it could not happen. But it is unusual at least. And maybe the coils today are made with less durable materials than those of last century.

2 months later
#21 1 year ago

I accidentally just bought 1 3/4" coil sleeves when I am supposed to be using 2 3/16" coil sleeves. How much will it matter if I just use these that I have, even though they are about a half an in shorter than the plunger/coil and everything else?

#22 1 year ago

The sleeve helps secure the coil in the mount and protects the plunger from rubbing on the bracket. The end opposite the stop usually slides through the bracket a couple of millimeters.

You are better off just cleaning your old sleeve than using one too short.

5 months later
#23 11 months ago

Replying because this post helped me sanity check myself. I bought some marco 03-7066 sleeves for some 1 3/4” long x 1/2” OD Williams replacements. I could not get them started going into the coil. Got out the calipers: existing sleeves were 0.499”, Marco sleeves were between 0.502 and 0.505”. Just that little difference was enough to make it a nightmare. So I took a drywall sanding sponge and wet it, and lightly sanded all around the outside of the sleeves. Once done, I cleaned them and re-measured as 0.499-0.501 and was able to put them in. Still a snug fit but not impossible.

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