Jump to content

Bergeon Demagnetiser Switch Replacement


JBerry

Recommended Posts

Hey folks,

I recently picked up this 2321 Bergeon Demagnetizer, the plastic ring that secures the momentary switch to the top of the wooden block had perished and snapped off, and no longer retains the button.

I'm fairly clueless when it comes to electronics. I picked up a new switch of the correct diameter, problem is I'm not sure if the switch is of the correct rating.

The switch is rated 3A 250V/AC, but I'm not sure about the amp rating of the demagnetizer. Anyone have any ideas?

dem 3.jpg

dem 2.jpg

dem 1.jpg

Link to comment
Share on other sites

If you have a multimeter you can find the resistance of the coil, then divide the wall voltage by that to get your amp draw.

Amps = volt/ohms

If they had listed the wattage, you could use amps= watts/volts. By the same formula if we imagine it draws 2 amps, you'd be at almost 500 watts which I'm pretty sure it doesn't use. I think you are safe with your 3 amp switch.

  • Like 1
  • Thanks 1
Link to comment
Share on other sites

5 hours ago, AndyHull said:

The only similar demagnetiser I could find on line states it is 80 Watts. That would be approximately 1/3 A at 240V or about 700 mA at 110V. A 2A or 3A switch should be fine.

Thanks for the advice Andy. I fit the switch and it's working well!

photo_2019-03-13_01-37-22.jpg

Link to comment
Share on other sites

19 hours ago, nickelsilver said:

If you have a multimeter you can find the resistance of the coil, then divide the wall voltage by that to get your amp draw.

hmmm careful, multimeters measure resistance and you can't figure current knowing resistance and volts if its an AC signal with a coil .  I agree, if the power is given, then yes Ohm's law works, but we're dealing with with AC so the ohms has to be impedance not resistance....and you can't measure impedance with a multimeter (they measure resistance only, whereas impedance is resistance, inductance and capacitance, you need a fancy LCR).  

Look at it this way, if you connected a wire between the legs of AC mains, bang you blow the breaker.  But if you coil that same wire, it now has inductance.  That's why say a transformer (which is a wire connecting the mains but in a coil) doesn't blow the breaker.

I think the right answer was given on the switch so all is good, just saying with coils and AC keep in mind inductance has to part of applying ohms law to get power

 

Good job on the repair, it looks very professional

 

Edited by measuretwice
  • Like 1
  • Thanks 1
Link to comment
Share on other sites

3 hours ago, measuretwice said:

hmmm careful, multimeters measure resistance and you can't figure current knowing resistance and volts if its an AC signal with a coil .  I agree, if the power is given, then yes Ohm's law works, but we're dealing with with AC so the ohms has to be impedance not resistance....and you can't measure impedance with a multimeter (they measure resistance only, whereas impedance is resistance, inductance and capacitance, you need a fancy LCR).  

Look at it this way, if you connected a wire between the legs of AC mains, bang you blow the breaker.  But if you coil that same wire, it now has inductance.  That's why say a transformer (which is a wire connecting the mains but in a coil) doesn't blow the breaker.

I think the right answer was given on the switch so all is good, just saying with coils and AC keep in mind inductance has to part of applying ohms law to get power

 

Good job on the repair, it looks very professional

 

A very valid point. Also in some cases the power goes through other components before it reaches the coil. There may be some form of inrush current limiting device , an NTC or something similar,  that will also mess up your calculations if you simply try to gauge the current by measuring coil DC resistance, especially if you simply measure across the mains plug.

You can use a clamp meter to measure current, but you then need to clamp it round only one of either the live or the neutral. Simply clamping it round the whole mains cable wont give you a valid answer either.... and then we come to what do you mean by AC power, are you talking about average AC voltage or true RMS...etc...  but that is a whole different story.

In some simple cases, you can get a rough estimate by measuring the coil resistance, but it will only give you a possible ballpark figure.

In this particular case, it is probably near enough for our purposes. Anything more complicated (motors, active electronics or whatever), and you could be miles out.

Edited by AndyHull
Link to comment
Share on other sites

All correct, and I admire your knowledge, but why make the matter over complicated?

Here we have a coil without iron core and a low frequency of 50 or 60 Hz. You will find no relevant difference between AC or DC resistance...

Frank 

Link to comment
Share on other sites

38 minutes ago, praezis said:

All correct, and I admire your knowledge, but why make the matter over complicated?

Here we have a coil without iron core and a low frequency of 50 or 60 Hz. You will find no relevant difference between AC or DC resistance...

Frank 

It may seem that we are being pedantic, but it is more a case of highlighting and understanding the limitations of this technique, after all, for small values of flat, the earth is flat.

Link to comment
Share on other sites

11 hours ago, praezis said:

All correct, and I admire your knowledge, but why make the matter over complicated?

Here we have a coil without iron core and a low frequency of 50 or 60 Hz. You will find no relevant difference between AC or DC resistance...

 

good point, without the iron core they will be very close.   No interest in over complicating things, I overlooked lack of the iron core.  Point about caution on doing AC/coil/current calcs based on resistance stands as so often inductance is most of impedance

Edited by measuretwice
Link to comment
Share on other sites

Join the conversation

You can post now and register later. If you have an account, sign in now to post with your account.
Note: Your post will require moderator approval before it will be visible.

Guest
Reply to this topic...

×   Pasted as rich text.   Restore formatting

  Only 75 emoji are allowed.

×   Your link has been automatically embedded.   Display as a link instead

×   Your previous content has been restored.   Clear editor

×   You cannot paste images directly. Upload or insert images from URL.



  • Recently Browsing

    • No registered users viewing this page.
  • Topics

  • Posts

    • I've remained silent on this thread, and at the risk of upsetting everyone, the thing that worries me the most the the apparent absence of Mark. The moderators do a great job and the members also pitch in, and the site seems to run itself, but it is a concern for the future of this forum when the owner is absent for all intents and purposes. Like many of the comments above I would hate to log in one day and things be closed down as I rely on this site for ideas and knowledge and also cheer me up. maybe the Moderators could reach out to him, assuming he does not read this thread, and express our concerns and let us know the plans going forward? some kind of WRT ark
    • That was the exact reason for me starting this thread watchie. Still we haven't worked out how the regulars are going to hook up if it goes tits up. I honestly think something should be arranged to stay in contact, we all help each other so much. 
    • Yeah ive watched that a few times before,  i couldnt find my old school dividers to scribe it up 😅 Yep thats the guy i bought a roll from . Thanks Nicklesilver that answers that perfectly and more or less what i thought an experiment over time would prove . The jumper arm is quite thick along its length, i left it that way intentionally, i thought the original was probably very thin, i didnt see that it was already missing. Setting isn't particularly stiff as such just positive, i still need to take it out and polish where it mates with the stem release. 
    • Yes, "Sold out" is difficult to understand. There doesn't seem to be a lot going on. It's been nine months since any new video was published on the Watch Repair Channel. The Level 4 course on watchfix.com has been in progress for what feels like forever (several years!?). Maybe Mark's enterprises aren't doing well or perhaps already so profitable there's nothing much to motivate him for more material. Or, perhaps these days he's more into crochet. The real reason is probably something entirely different but it would be nice/interesting to know. I don't mean to sound gloomy or pessimistic, but I wouldn't be surprised to be met by an HTTP 404. Every day feels like a gift. Speaking of watchfix.com I've been postponing the "Level 5: Servicing Chronograph Watches" course for a very, very long time. Anyway, I just enrolled on it so it's going to be very interesting to see the videos. I must say, IMO there's nothing really that can compete with Mark's courses when it comes to presentation and video quality. It's simply world-class and makes me associate with some really expensive BBC productions.
    • Steel has some funny properties, or at least counterintuitive. The modulus of elasticity is effectively (not exactly, but close enough) the same for steel that is annealed and hardened. What changes is the point of plastic deformation* . If the movement of your spring doesn't pass that, it should work fine. It looks a little thick, I would thin it a bit maybe from the main body out about halfway, maybe 10-20% thinner (not in thickness, along its form). But if it works it works!   *So- if you have two bars of the same steel, one annealed, one at 600 Vickers (general hardness watch arbors might be), clamp them to a table so the same length is hanging out, and put a weight on the ends, they will bend the same amount. But if you continue to add weight, then remove it, at a point the annealed bar won't return to its original straightness. That's the point of plastic deformation. But up to that point, as springs, they are the same. However- their wear characteristics will be very very different. And getting the hardened bar past its point of plastic deformation takes a lot more effort.
×
×
  • Create New...