News:

"The phone is a remarkably complex, simple device,
and very rarely ever needs repairs, once you fix them." - Dan/Panther

Main Menu

Ringer Loses Magnetism When it is Disassembled

Started by Dennis Markham, March 29, 2009, 02:45:17 PM

Previous topic - Next topic

Nick in Manitou

As a nonscientific beginner...what does this mean to me?

At what point of dis-assembly does one run into this problem?

I assume that the ringer assembly can be removed from the base plate for cleaning?

Just make sure that you don't...what?

This problem would be the same for all the different ringer types we would run into on W.E.s, A.E.s, S-Cs, etc?

Thanks,
Nick

JorgeAmely

It means that if you remove the ringer coil, you lose some performance. This is well documented in the ITT publication.

If you remove the magnet, then it is highly unlikely that the ringer will operate like it left the factory unless the magnetic circuit itself is exposed to a high constant flux in order to recharge the magnet.
Jorge

Nick in Manitou

Thanks, Jorge,

So, the assembly can be removed from the base plate, but don't disassemble the ringer unit beyond that point?

HowardPgh

I wonder if the loss effect is instantanious. Like when you remove a bad coil from a C4 ringer and immediately replace it.  Involves removing the two screws that hold the core laminations, lift out, slide core out from old coil, slide into new coil and replace assembly.
Howard
Howard

Dan/Panther

I wonder if maybe it has something to do with how you handle the parts or if they touch etc. after being disassembled.
I recently worked on my Kellogg Banjo, that turned out to have a shorted ringer coil. I couldn't figure out why every time I plugged that particular phone in, every thing went dead, all my phone lines. It was the coil. I removed the ringer, and replaced the coil. The phone appears to work normally. However, even though the ringer is the same design as the WE500 ringer, it does sound slightly different when it rings, and I have no comparison, because I had never heard the phone ring before I replaced the coil.

D/P

The More People I meet, The More I Love, and MISS My Dog.  Dan Robinson

G-Man

Even with a shorted coil connecting it to your telephone line should not have caused "everything to go dead."

It would seem to indicate that either the capacitor was faulty or mis-wired in the circuit and when the coil was replaced it was correctly reconnected. A non-shorted coil would also sieze the line if the capacitor was not connected in series with it.

As far as the loss of magnetism in C-series ringers is concerned, this is well documented in BSP, and ITT manuals that reside in the TCI Library. IIRC the 1949 Bell Labs 500-set document (TCI Library) states that the magnet is charged once the ringer has been fully assembled.

JorgeAmely

Quote from: Nick in Manitou on January 11, 2013, 12:09:20 PM
Thanks, Jorge,

So, the assembly can be removed from the base plate, but don't disassemble the ringer unit beyond that point?

Sir, that is correct.
Jorge

JorgeAmely

Quote from: HowardPgh on January 11, 2013, 12:09:48 PM
I wonder if the loss effect is instantanious. Like when you remove a bad coil from a C4 ringer and immediately replace it.  Involves removing the two screws that hold the core laminations, lift out, slide core out from old coil, slide into new coil and replace assembly.
Howard

The ITT manual says that if the coil is shorted and replaced with a new coil, the ringer performance will be affected, but still work.
Jorge

TelePlay

Quote from: JorgeAmely on January 11, 2013, 11:33:11 AM
. . . unless the magnetic circuit itself is exposed to a high constant flux in order to recharge the magnet.

"1949 Bell Labs 500-set document (TCI Library) states that the magnet is charged once the ringer has been fully assembled."

What would you suggest (Vs/As/Seconds)?

Charles

I have had this problem. How do you "Charge" a magnet?

dsk

On really old magneto ignition systems for MC motors, it was done by putting it in a short (2sec? manual switch on-off) huge electromagnetic field.

I have never had a ringer with so bad magnet that it wont ring at all, but some older telephones has been quite weak, and they has been better and better when used.

dsk

Bill

#26
The guys who restore old engines - cars, tractors, motorcycles, or anything else with a magneto-based spark ignition, or anything with a generator - face this problem quite often. There are a number of articles in their newsgroups that describe magnet-rechargers. There are quite a few in Gas Engine Magazine. Here is one.

http://www.magnetoparts.com/inst_guides/charger/page1.htm  ( dead link 3/11/23 )

EDIT:  Similar link to the above dead link:

https://www.youtube.com/watch?v=m0EAooruji0

To me, the process looks just plain ugly.

As has been noted above, you have to immerse the weakened magnet in a very strong magnetic field. This usually involves a coil of heavy wire, a very large DC current through the coil, and specially-shaped pole pieces (iron cores) inside the coil, to funnel the magnetic field into the magnet. The one in the article above works with 40 amps through 500 turns (40 pounds) of #10 solid copper wire, gining a field strength 20,000 amp-turns. The pieces being magnetized in the article are roughly similar in size to the pieces in a ringer.

Some articles say that it helps to whack the magnet while the current flows. Some say not. Some say that using a magnetic field (coil or current or both) that is too small is worse than doing nothing. But they all say that after the magnet is charged, you have to put a "keeper" on it until you get it reinstalled in its original position. To me, that is the hard part. You put it in the charger, align it with the poles of the charger, turn on the current, whack it, and turn off the current. Now what? How do you get it from the charger back into the device (the ringer in our case) while never opening the magnetic circuit around the magnet (i.e., removing the keeper)? I'm sure the factory had some special tools - but for us, I don't know. But it is important - the magnet lost its charge in the first place when it was removed from the magnetic circuit.

I would love to hear the answer.

Bill

dsk

Quote from: Bill on January 30, 2013, 01:16:07 PM

1) Some say that using a magnetic field (coil or current or both) that is too small is worse than doing nothing.

2)I would love to hear the answer.

Bill

1) If small currents ruins it, then it should be bad to use it, because when its rings it is even used AC who demagnetizes it.  

2) Yes we would like to get the answer too.

It should be possible to switch out the existing coil with another, and give the magnet a pus in the ringer, or even just put on lots of dc pulses on the existing coil. How much DC voltage may it cope with if we just give it a 1 sec pulse, lets say 10 times within a minute.

Rectified 120V will give about 170V, will this fry the coil?
Rectified 240V will give about 340V, will this fry the coil?


Or just buying this one? http://www.magnetsource.com/Solutions_Pages/magnetizrsetc.html


dsk

poplar1

"4.02  If the 481A tool is used to remagnetize the
          ringer in a set equipped with an apparatus unit hav-
ing a condenser under the induction coil, it will be necessary
to remove the unit mounting screws and move the unit so
that the pole-pieces of the tool can engage the ringer magnet."

Bell System Practices
Station Installation and Maintenance
Section C31.123
Issue 1, 3-21-40
AT&T Standard

"1.01 This section covers the conversion of subscriber sets   
         from sidetone to anti-sidetone type at the station
(without removing the set from the wall) throught the in-
stallation of D-158395 Apparatus Units and also the mainte-
nance of these apparatus units."

(In other words, converting a 534A subset to a 634A.)

So what is a 481A tool and does anyone have one?

"C'est pas une restauration, c'est une rénovation."--François Martin.

TelePlay

Nine years later, new information that helps with the resolution of issues noted in this topic has been posted and can be found at this link.

http://www.classicrotaryphones.com/forum/index.php?topic=27312.0


This YouTube video shows how this is done on a magneto magnet, similar to magneto magnets in crank phones and magnetic pole receivers.

https://www.youtube.com/watch?v=m0EAooruji0


The form link above also has a post by the member who re-magnetized their magnetic pole receiver.

The following images show the YouTube magnet restoration device and other information about magnetic fields.