(Topic ID: 229228)

Demagnetizing Armatures?


By pindude80

1 year ago



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  • 39 posts
  • 15 Pinsiders participating
  • Latest reply 1 year ago by zacaj
  • Topic is favorited by 1 Pinsider

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coil (resized).png
20181112_115237 (resized).jpg

#1 1 year ago

I was working on my 1976 Williams Blue Chip for the past 2 weeks. I had a couple problems that had myself and people trying to help me from the forum chasing our tails. I figured it out last night- the armature plates are magnetized and not releasing which was causing different intermittent problems. I put a piece of electrical tape on the armature plate and it fixed one of the problems, but the other one- ball count unit problem, sometimes works properly, sometimes on reset it cause that relay and others to "chatter" and not engage properly and then other times the armature sticks giving me my original problem.

Is there a way to demagnitize these, buy new ones, or use something other than electrical tape that I'm currently using?

#2 1 year ago

Are you sure they're magnetizing and not just getting stuck? I've had success using a flap wheel to sand both sides with a dremel.

#3 1 year ago

I'm not 100% sure they are magnetized, I just know they are sticking. Is there a way to tell if they are magnetized or not?

#4 1 year ago
Quoted from pindude80:

Is there a way to tell if they are magnetized or not?

Does a piece of steel stick to it? Nail, bobby pin, needle, something like that?

#5 1 year ago

I can test it tonight with some metallic like you mentioned.

#6 1 year ago

I recalled from years ago that heat can be used to remove magnetism from magnets. I wonder if the same concept would work with a metal pinball part that's been magnetized. Ie I wonder if you could put the part in the oven for a while and let it bake and then it's magnetism would be gone?

#7 1 year ago

It would probably melt the plastic piece the switch blades go in unless I drilled out the rivet and re-riveted it.

#8 1 year ago
Quoted from pindude80:

It would probably melt the plastic piece the switch blades go in unless I drilled out the rivet and re-riveted it.

Oh yeah, I meant you would need to drill it and rivet it. Just the metal parts

#9 1 year ago

soldering gun is a poormans degausing ring

#10 1 year ago
Quoted from pinhead52:

soldering gun is a poormans degausing ring

Cool! What is the soldering gun method?

#11 1 year ago

Actually its a lot easier.

Remove them and hit them with a hammer a few times. Done

The blow from the hammer actually reorients the dipoles to randmoize them and the magnetism goes away.

#12 1 year ago
Quoted from rufessor:

Actually its a lot easier.
Remove them and hit them with a hammer a few times. Done
The blow from the hammer actually reorients the dipoles to randmoize them and the magnetism goes away.

That makes sense. What is the best way to get them off, pull the switch stack?

#13 1 year ago
Quoted from pindude80:

Cool! What is the soldering gun method?

Would do this all the time in the field on Ms. Pac Man video monitors. People thought I was crazy until the ugly green corners became normal colors again.

Take soldering gun and hold sideways, body up to the glass over the screen. Turn on (So, plugged in with extension cord or in the service outlet of the pin next to the game) and rotate in small, circular motions around the outside edge of the monitor. About three cycles of this fixes all what ails the monitor.

#14 1 year ago
Quoted from rufessor:

Actually its a lot easier.
Remove them and hit them with a hammer a few times. Done
The blow from the hammer actually reorients the dipoles to randmoize them and the magnetism goes away.

You can take the coil stops and throw them hard onto a concrete surface with some results as well. Usually, the parts disappears though and you end up replacing it with a new, unmagnetized part.

#15 1 year ago

You need one of these.....I use them for tape machine heads, but have used it to degause and demag other things.

20181112_115237 (resized).jpg
#16 1 year ago
Quoted from foureyedcharlie:

You need one of these.....I use them for tape machine heads, but have used it to degause and demag other things.
[quoted image]

I still have one similar to that from Olson Electronics. Akron, Ohio.......

#17 1 year ago
Quoted from MrBally:

Usually, the parts disappears though and you end up replacing it with a new, unmagnetized part.

Hahaha- absolutely

#18 1 year ago

Put them in the freezer for a couple of days.
Also, be sure the brass insulating washer is installed between the coil and the frame.

#19 1 year ago

Put them in a brown paper bag, take them outside on a sunny day. Hold the bag over your head and run around in the street clucking like a chicken.

Done and done!

#20 1 year ago
Quoted from pindude80:

Cool! What is the soldering gun method?

soldering gun puts out a changing mag field, just bring it close to the object, passing up and down the object

#21 1 year ago
Quoted from pinhead52:

soldering gun puts out a changing mag field, just bring it close to the object, passing up and down the object

Ok, I was wondering how to do it and how it worked.

#22 1 year ago
Quoted from darcangeloel:

I recalled from years ago that heat can be used to remove magnetism from magnets.

The curie point of steel or iron is somewhere above 1,000 degrees Fahrenheit. So unless you've got an autoclave lying around, your oven isn't going to get hot enough.

#23 1 year ago
Quoted from mbaumle:

The curie point of steel or iron is somewhere above 1,000 degrees Fahrenheit. So unless you've got an autoclave lying around, your oven isn't going to get hot enough.

Ah got ya. Yeah I can't imagine most people would have access to anything that hot.

#24 1 year ago

Hot or cold works. In the freezer for a few days will do it. I don't think I've ever come across one that was magnetized though. They usually stick when the coil is not magnetically insulated from it's frame.

#25 1 year ago
Quoted from jrpinball:

Hot or cold works. In the freezer for a few days will do it. I don't think I've ever come across one that was magnetized though. They usually stick when the coil is not magnetically insulated from it's frame.

I can check this, how are they supposed to be magnetically insulated from the frame?

#26 1 year ago
Quoted from pindude80:

I can check this, how are they supposed to be magnetically insulated from the frame?

That's what the brass parts around the coil stop do. They break the magnetic path.

#27 1 year ago
Quoted from pindude80:

I can check this, how are they supposed to be magnetically insulated from the frame?

There's usually a brass washer between the coil's core and the frame. Later Gottlieb's had plastic molded around the end of the core so that a washer was not needed. I'm not sure how it's done on "Blue Chip". I owned one once, but sold it. As "homepin" states above, there's brass in the coil stops, and the coil stop itself has a nylon bushing and a nylon insert nut to keep it insulated. That's on coils with plungers such as steppers, pop bumpers, flippers, etc.

#28 1 year ago
Quoted from jrpinball:

As "homepin" states above, there's brass in the coil stops, and the coil stop itself has a nylon bushing and a nylon insert nut to keep it insulated. That's on coils with plungers such as steppers, pop bumpers, flippers, etc.

What did I need to look for on a relay setup since there is no coil stop?

#29 1 year ago
Quoted from pindude80:

What did I need to look for on a relay setup since there is no coil stop?

Again, there should probably be a brass washer between the core of the relay coil (hole where the screw goes in) and the relay frame. The screw that holds the coil in the frame should be brass as well.

#30 1 year ago
Quoted from mbaumle:

The curie point of steel or iron is somewhere above 1,000 degrees Fahrenheit. So unless you've got an autoclave lying around, your oven isn't going to get hot enough.

I've removed hard drive magnets from their backing using a 650 heat gun to soften the glue. The magnet was significantly weaker when I was done. So the oven may indeed work. It's free to try.

#31 1 year ago

A propane torch would surely be hot enough, but I think something else is the issue here.

#32 1 year ago

Just to clear up what may be a confusion point here...

The soldering gun method being talked about here (move in corcular motions close to the magnetized element) has nothing whatsoever to do with the temp of the element. It works because the soldering gun is plugged into an AC voltage and the tip basically forms an electromagnetic field that oscillates and scrambles the aligned field in the metal.

Dont try to heat you pieces with the element- its not hot enough to do anything by heat transfer- but you will very efficiently melt all the plastics near it.

#33 1 year ago
Quoted from jrpinball:

Again, there should probably be a brass washer between the core of the relay coil (hole where the screw goes in) and the relay frame. The screw that holds the coil in the frame should be brass as well.

Check some of the other relays that aren't sticking to see if they have a brass screw and a brass washer. The washer does not go under the screw head, but it goes between the end of the coil where the screw goes in, and the steel relay frame.

#34 1 year ago
Quoted from jrpinball:

Check some of the other relays that aren't sticking to see if they have a brass screw and a brass washer. The washer does not go under the screw head, but it goes between the end of the coil where the screw goes in, and the steel relay frame.

Ok, will do.

#35 1 year ago

You can see this coil has a copper piece on the end of the steel pole piece. This is acting to break the magnetic field in this particular design.

There are many variations and methods of doing this.
coil (resized).png

#36 1 year ago

Any chance you are confusing a lock-on or a weak lock-on for a magnetized armature? When it is "stuck" on, does turning the game off release it? Or can you get it "stuck" with the power off?

#37 1 year ago

I had that happen only one time, I think I just put one or two snips of electrical tape on the coil side of the armature, but it wasn't one of those 'always on' coils like a hold relay that get hotter than hell or it would probably end up melting it. I always look for the easy way... if it works.

#38 1 year ago

I had a similar issue once. I took the plate and sanded it smooth to be sure there was no mechanical binding. Then beat it with a hammer for a while. Then used a torch and heated it a couple times. After that my problem went away

#39 1 year ago
Quoted from frenchmarky:

I had that happen only one time, I think I just put one or two snips of electrical tape on the coil side of the armature, but it wasn't one of those 'always on' coils like a hold relay that get hotter than hell or it would probably end up melting it. I always look for the easy way... if it works.

I wouldn't recommend the tape technique. I tried this on a Grand Prix I had on location (so it got a lot of play). At first the tape fixed the issue, but eventually the tape molded to the shape of the coil head and actually made the sticking worse.

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