Demagnetizer Recommendations

[RCDesign]

@Endeavor: -Yes, but your version takes a bit of "skill" to get to work!

The versions with coils work with distance attenuation - the field gets weaker as you move the part/movement away from the coil.

The automatic ones often use current attenuation, the field gets weaker around the part/movement  so the part can be still.

 

 

(picture from: https://www.j-ndk.co.jp/en/product/index_datsuji.html)

 

In my version a capacitor is charged (takes abt .3s) and is then then is used in a parallel LC-circuit that takes abt. 50ms for the field to go  from fully charged to zero. (depending on capacitor values, voltage and size of coil).

The biggest plus is that you do not need to lift/move the movement in the coil/field and the results are equal time and time again! 

Edited October 11, 2018 by RCDesign

[Endeavor]

Thank you for the additional information

I now also understand again how the coil / capacitor circuitry works. Where I was initially a bit puzzled about was what kind of capacitor was used and therefor whether the AC was first converted to DC. Now knowing the L/C principle again, it may be wise to put up a schematic of your system with the details of the components. We don't want somebody to grab an electrolytic capacitor and "blows the place" or seriously harm himself....... The modern electrolytic capacitors do rupture, or have a relief-valve, but the old ones don't, and they take off like a rocket when connected to AC or hooked up wrongly to DC. (don't ask me how I know )

So if you have a simple schematic of your system with the components details, then at least that part is covered

Thanks again!

 

Edited October 11, 2018 by Endeavor

[JohnR725]

The other thing that is needed when playing with magnets and watches is a way of figuring out if your watch really is magnetized or not.

So there's the old-fashioned way with a compass image attached for how to do that. then a link to a free app for your phone from a company that wants to sell a really expensive demagnetizer.

https://www.lepsi.ch/watch-demagnetizer/

 

[jdrichard]

On 5/19/2016 at 7:17 AM, oldhippy said:

This is what you need. If you get anything that is to powerful it can distort the hairspring which is the main part that needs demagnetizing.

http://www.ebay.co.uk/itm/like/161822826949?limghlpsr=true&hlpv=2&ops=true&viphx=1&hlpht=true&lpid=122&chn=ps&googleloc=9045125&poi=&campaignid=207297426&device=c&adgroupid=13585920426&rlsatarget=aud-133395220866%3Apla-131843272146&adtype=pla&crdt=0&ff3=1&ff11=ICEP3.0.0-L&ff12=67&ff13=80&ff14=122&ff19=0

Link doesn’t work. Could you get a pic?

[maal]

I would like to share a simple modification of a cheap Chinese demagnetizer. I found the modification in this video: https://www.youtube.com/watch?v=AhTYBPdJG7A.
I applied this modification in a newly bought demagnetizer (from Aliexpress) and it works quite well.

[VWatchie]

Just noted that the links to my video review of the "Elma Antimag" demagnetizer no longer works so for anyone interested here's an update:

 

[Woolshire]

I have an old (1940?) demagnetizer. I’ve read about how some of these old ones are maybe too strong to put complete watches through, but never had an issue until yesterday: I put a complete cased watch in the hole, pushed the button and then slowly pulled it out, like I have 100’s of times. This time, the roller jewel actually got knocked out! When I took the back off the watch to see what happened I found it (luckily) on the ledge of the case! Looks like these strong demagnetizers can be too much sometimes?

I better buy a less aggressive one for complete watches. Anyone else ever see such a thing?

[jdm]

1 hour ago, Woolshire said:

I better buy a less aggressive one for complete watches. Anyone else ever see such a thing?

No need to buy another one, just start a bit more far away from the object. However it's also true some demagnatizers are made for mechanical shop use not watchmaking. 

[JohnR725]

4 hours ago, Woolshire said:

This time, the roller jewel actually got knocked out!

You didn't tell us what kind of a watch this is or how old it is? I think you'd find under normal circumstances it would take a heck of the impact to knock a roller jewel out. Very common on older watches that they become loose with time so anytime you're working on older watch your always supposed to check the roller jewel because quite a few times are on the verge of falling out anyway.

Watch companies are interesting for their recommendations. Omega is concerned of having too strong of a magnetic fields but then there are so looking at wristwatches. They don't have to deal with the things we deal with in the field that are often bigger than a wristwatch. Then there also looking for a tool that will tell you if the watches magnetized because compasses really aren't reliable.

I snipped out an image of unacceptable tools strangely enough they don't show ever using the Elma Antimag? Then another image of the important points kinda hinting at the magnetic field for removing magnetism has to somehow be really special and multi-directions. Which is interesting if you look at the instruction sheet for the Horotec Magtest What they show looks exactly like the same kind a magnetic field should get from the Elma Antimag .

https://www.witschi.com/en/products/teslascope-2/

http://horotec.ch/news/MSA19.910/102/lang/2

 

[AndyShap]

Hi All,

I own an old Bulk audio tape eraser. It works perfectly.  I use it all the time to demagnetize my tools.  Is there any reason i can't use this as a demagnetizer for watches?

[ifibrin]

On 1/29/2022 at 6:28 AM, JohnR725 said:

You didn't tell us what kind of a watch this is or how old it is? I think you'd find under normal circumstances it would take a heck of the impact to knock a roller jewel out. Very common on older watches that they become loose with time so anytime you're working on older watch your always supposed to check the roller jewel because quite a few times are on the verge of falling out anyway.

Watch companies are interesting for their recommendations. Omega is concerned of having too strong of a magnetic fields but then there are so looking at wristwatches. They don't have to deal with the things we deal with in the field that are often bigger than a wristwatch. Then there also looking for a tool that will tell you if the watches magnetized because compasses really aren't reliable.

I snipped out an image of unacceptable tools strangely enough they don't show ever using the Elma Antimag? Then another image of the important points kinda hinting at the magnetic field for removing magnetism has to somehow be really special and multi-directions. Which is interesting if you look at the instruction sheet for the Horotec Magtest What they show looks exactly like the same kind a magnetic field should get from the Elma Antimag .

https://www.witschi.com/en/products/teslascope-2/

http://horotec.ch/news/MSA19.910/102/lang/2

 

That’s interesting… Which demagnetizer does Omega recommend then?

I’ve read elsewhere that the Greiner is supposed to be strong enough to demagnetize a cased watch, but wouldn’t have thought it could be too strong…

In your opinion is Omega being overly cautious? Most demagnetizers don’t exactly quantify exactly how powerful they are, so we would have no way of knowing either…

[JohnR725]

4 hours ago, ifibrin said:

Which demagnetizer does Omega recommend then?

If you look at the section you quoted there are two links those go to what they recommend. We do get in the image I snipped out hinting remarks of yes it could be too strong for and they don't specify this some watches. I've occasionally see on some wristwatches when they hairspring is jumping around wallets being demagnetized will have it looping part of it over the regulator pins in the F they go in fix that or just do it again that usually sometimes fixes itself. Then I don't know about the silicon hairsprings whether that is a possibility of damaging blows because I have a suspicion that silicon might be brittle even if it is a spring.

That of course there's the other little problem Omega's not dealing with really large watches like pocket watches.

Plus of course they have really deep pockets and they can recommend whatever they feel like because well I can. But I do like the idea of the solid-state detectors at these things have that tell you whether you have a magnetic field are not as I don't think the compass method is really reliable even though it's been around for very long time.

 

[valleyguy]

On 5/7/2018 at 2:04 AM, JohnR725 said:

So I have links to commercial and unfortunately expensive ones. Then if you want to make your own third link.

http://www.greinervibrograf.com/?pageID=12&lng=en

https://www.elma-ultrasonic.com/en/products/watch-testing-and-service-equipment/antimag/

http://www.instructables.com/id/Demagnetizer-From-a-Microwave-Transformer/

I was looking to get a demagnetizer so read all the posts in the demagnetizer section, i followed your link to the homemade demagnetizer using the microwave transformer, it seems to be the same type of circuit used in the elma demagnetizer, so thought i'd give the homemade one ago.

I already had a couple of old microwave transformers along with the other bits needed, diode, resistor, switches, i orderd a motor run start capacitor that came yesterday, i assembled it into a plastic biscuit box, it's a simple straight forward build, it works really well, i've never had a demagnetizer but seems better than the type you have to withdraw the watch away from slowly that i've seen discussed online.

I've ordered a new box to remount it into rather than a biscuit box to make it look a bit more professional, once it comes i will post some photos of the finished demagnetizer.

Thanks johnR725 for the link, that was a good find.

 

[valleyguy]

I got round to boxing the homemade demanetizer up last night, i moved it from the biscuit box, so now looks a bit more sturdy, it's easy and cheap to build and perfoms as well as the branded demagnetizer costing hundreds of pounds. I printed a crosshairs onto a self adhesive postal label to stick on the box a the centre of demagnetization area.

The only variation i made from the parts list was i used a 1N4007 diode instead of the 1N4004 listed as i have plenty of these, they are booth a 1 amp diode, i will change this diode to a 1N5408 diode as these are rated 3 amps.

 

https://www.instructables.com/Demagnetizer-From-a-Microwave-Transformer/

 

 

 

 

[HectorLooi]

1 hour ago, valleyguy said:

I got round to boxing the homemade demanetizer up last night, i moved it from the biscuit box, so now looks a bit more sturdy, it's easy and cheap to build and perfoms as well as the branded demagnetizer costing hundreds of pounds. I printed a crosshairs onto a self adhesive postal label to stick on the box a the centre of demagnetization area.

The only variation i made from the parts list was i used a 1N4007 diode instead of the 1N4004 listed as i have plenty of these, they are booth a 1 amp diode, i will change this diode to a 1N5408 diode as these are rated 3 amps.

The microwave transformer looks like an overkill. Do you think a smaller, say a 25VA transformer, will work?

[valleyguy]

Yes a 25VA transformer will work as the current is very small, 25VA is more than adequate.

I agree the microwave tranformer is overkill, i only used it as i  already add a couple of them.

[Michael1962]

Hey everyone. A question that I am not aware of the answer to. 

Do you need to have a demagnetiser for working on clocks?

 

[JohnR725]

8 minutes ago, Michael1962 said:

Do you need to have a demagnetiser for working on clocks?

typically are only worrying about balance wheels with their hair Springs. As hairsprings do not like to be around magnets or influenced by being magnetized. So yes some clocks would but only for the balance wheel assembly or the platform escapement

[gbyleveldt]

3 hours ago, valleyguy said:

The only variation i made from the parts list was i used a 1N4007 diode instead of the 1N4004 listed as i have plenty of these, they are booth a 1 amp diode, i will change this diode to a 1N5408 diode as these are rated 3 amps.

Nice!

You should be ok with a 1N4007 diode. The 20 Ohm resistor would limit a lot of the inrush current into the capacitor, which is a pretty low value anyway.

[Michael1962]

Thanks @JohnR725  

[Kalanag]

I would like to remind of this video where a cheap Chinese demagnetizer was equipped just with a PTC to get an automatically fading magnetic field.

https://youtu.be/AhTYBPdJG7A

I followed this tutorial with perfect results.

Edited June 30, 2022 by Kalanag

[Endeavor]

On 6/30/2022 at 11:45 AM, HectorLooi said:

The microwave transformer looks like an overkill. Do you think a smaller, say a 25VA transformer, will work?

If you have one of these cheap "dumpsters" kicking around in your garage, they have a "midsize" transformer, see my DIY "Zapper" below ....

On 6/30/2022 at 1:53 PM, gbyleveldt said:

You should be ok with a 1N4007 diode. The 20 Ohm resistor would limit a lot of the inrush current into the capacitor, which is a pretty low value anyway.

With regards to the inrush current, my first resistors blew / burned out after repetitive used within a short period of time. I ended up with with these 6Ω 50watt resistors, three of them in series and as it happened, with the diode in between. Also the diode and the momentary switch have to be of ample capacity. I can't see the diode number which I used, but it's a beefy one. The momentary push button has a 15Amp rating. I do admit that I got "slightly" carried away with the capacitor; 45 µF

My "Zapper" zaps very well and doesn't overheat after repetitive use

 

Edited July 4, 2022 by Endeavor

[gbyleveldt]

10 minutes ago, Endeavor said:

With regards to the inrush current, my first resistors blew / burned out after repetitive used over a short period. I ended up with with these 6Ω 50watt resistors, three of them in series and as it happened, with the diode in between. Also the diode and the momentary switch have to be of ample capacity. I can't see the diode number which I used, but it's a beefy one. The momentary push button has a 15Amp rating. I do admit that I got "slightly" carried away with the capacitor; 45 µF

Heh, 45uF is a looot of capacitor for that circuit and would have substantial amount of inrush. Just eyeballing the size of your transformer, I’d hazard a guess you’d get away with a cap 5 times smaller and still generate enough of a discharge into the transformer without saturating its core like is likely happening now. When you saturate the core, it doesn’t make a larger magnetic field, it just converts that energy to some heat.

Edited July 4, 2022 by gbyleveldt

[Endeavor]

Yes, the capacitor which I had on hand is overrated, by how much I can't say. But the Zapper works really well and I'm not going to change it.

[Neverenoughwatches]

1 hour ago, gbyleveldt said:

When you saturate the core, it doesn’t make a larger magnetic field, it just converts that energy to some heat.

The cheap Chinese blue ones get bloody hot after a couple of repeat uses.