degausser

[Brett]

I want to make a degaussing coil. I don't have a used one from from a
TV. Anyone have a good idea for materials? Thanks to all.

 

[Jerry G.]

This is something I would not suggest you make yourself. There are thousands
of scrap sets around, as long as you get one from the same size CRT, and the
mains voltage is the same as your set, then there should not be any problem.
Even buying one new, it is not very expensive.

Visit some of the local TV service shops, and see if they have one that they
can sell you.

--

Jerry G.
==========================


I want to make a degaussing coil. I don't have a used one from from a
TV. Anyone have a good idea for materials? Thanks to all.

 

[mike]

I want to make a degaussing coil. I don't have a used one from from a
TV. Anyone have a good idea for materials? Thanks to all.

Not at all clear what you want to do with it.
If you want to demagnatize a crt, you can make a quick and dirty
one with one big turn of #10 wire chucked in an old weller soldering gun.
mike

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[Brett]

Not at all clear what you want to do with it.
If you want to demagnatize a crt, you can make a quick and dirty
one with one big turn of #10 wire chucked in an old weller soldering gun.
mike

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Return address is VALID.
Wanted, 12.1" LCD for Gateway Solo 5300. Samsung LT121SU-121
Bunch of stuff For Sale and Wanted at the link below.
Compaq Aero floppy,ram,battery.
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Toshiba & Compaq LiIon Batteries, Test Equipment
30pS pulser, Tektronix Concept Books, spot welding head...
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Sorry, I do want de-magnetize a CRT. I am curious now how to make one.
I tried, but I'm not sure how much current flow is necessary to create
a decent magnetic field. I tried a 2 watt/12k ohm resistor in series
with the coil. Calculated current was extremely low, in the micro amp
range. I didn't use magnet wire for the coil, regular 14-16ga wire
wrapped around an iron ring 3 times. Needless to say, the electron
beam didn't flinch when rubbed all over the face of the CRT.

 

[Bob Shuman]

Brett,

I'm not a degaussing expert, but (unless you have lots of coils) think that
your calculated current sounds way too low. Keep in mind that the coil
itself will add inductance (LH @60 hertz?) which will limit the current and
reduce the need for a current limiting resistor.

Also, I do not think using a steel core is a good idea since the iron in the
steel will retain its magnetism defeating the purpose behind using
alternating current (and possibly doing more harm than good).

Bob

 

[BWL]

My old man (40 years+ TV servicer) always made his own by connecting several
coils from dead tv's together in series. I don't remember how many it took, but
the end result ended up weighing about 5 lbs after bing covered with plenty of
black tape. You couldn't leave it plugged in too long, or it would start
overheating; about 15-30 secs was all it took...

 

[Sam Goldwasser]

Sorry, I do want de-magnetize a CRT. I am curious now how to make one.
I tried, but I'm not sure how much current flow is necessary to create
a decent magnetic field. I tried a 2 watt/12k ohm resistor in series
with the coil. Calculated current was extremely low, in the micro amp
range. I didn't use magnet wire for the coil, regular 14-16ga wire
wrapped around an iron ring 3 times. Needless to say, the electron
beam didn't flinch when rubbed all over the face of the CRT.

Figure something like 200 Amp-turns, give or take a few. In other
words, 1 A through 200 turns of wire or 100 A with 2 turns. You can
make one that will work reasonably well with about 100-200 turns of #20 or
fatter wire in a 6 inch coil in series with a 300 W (115 VAC) light bulb.
I may be off by a factor of 2 one way or the other but this should get
you started.

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[Tim Perry]

Sorry, I do want de-magnetize a CRT. I am curious now how to make one.

a solder gun works fine for this. just pull the trigger and place the body
near the CRT and swish it around. then pull slowly away before releasing the
trigger.

bulk tape erasers work fine also.

 

[Brett]

Figure something like 200 Amp-turns, give or take a few. In other
words, 1 A through 200 turns of wire or 100 A with 2 turns. You can
make one that will work reasonably well with about 100-200 turns of #20 or
fatter wire in a 6 inch coil in series with a 300 W (115 VAC) light bulb.
I may be off by a factor of 2 one way or the other but this should get
you started.

--- sam | Sci.Electronics.Repair FAQ Home Page: http://www.repairfaq.org/
Repair | Main Table of Contents: http://www.repairfaq.org/REPAIR/
+Lasers | Sam's Laser FAQ: http://www.repairfaq.org/sam/lasersam.htm
| Mirror Site Info: http://www.repairfaq.org/REPAIR/F_mirror.html

Important: Anything sent to the email address in the message header is ignored.
To contact me, please use the feedback form on the S.E.R FAQ Web sites.

Thank you all for replies. I think the 100 watt light bulb connected
would work with what I have, but previous advice was to just buy one,
which I will. I don't have the patience for a couple hundred turns.
Last question though, I though an iron core in a coil aided the
magnetic field, opposed to an air coil. Any l;ast comments would be
appreciated. Thanks again to all.

 

[Bob Shuman]

Brett,

Yes, iron will most definitely increase the magnetic flux and the resulting
strength of the electromagnet, but iron also has a tendency to retain its
magnetism after the electrical field has been removed. If you want to
observe this phenomenon first hand, take a large steel nail and wind it with
enough wire to create decent electromagnet using a small DC voltage source
of your choice. Connect the source and then use the magnet to pick up some
small items (steel tacks or paperclips work well) and then remove the
voltage source while the items are still attached. You will notice that the
items are not released immediately, but instead stay attracted to the steel
nail/core for a brief instant after the voltage has been removed.

With a de-gaussing coil, you are using alternating current (60 hertz) to
change the orientation of the field 60 times a second. You are using this
alternation in the poles to de-magnetize the item you are de-gaussing. My
concern with using the iron core is that I'm not sure how quickly the magnet
will be able to switch orientation with the steel/iron core. Also, with the
iron core, you will get a short duration of a potentially high strength
"permanent" magnet from the last AC cycle seen prior to removing the voltage
source and if you are still close could leave the item being degaussed
magnetized (just like when you started).

Bob

 

[jakdedert]

Brett,

Yes, iron will most definitely increase the magnetic flux and the
resulting strength of the electromagnet, but iron also has a tendency
to retain its magnetism after the electrical field has been removed.
If you want to observe this phenomenon first hand, take a large steel
nail and wind it with enough wire to create decent electromagnet
using a small DC voltage source of your choice. Connect the source
and then use the magnet to pick up some small items (steel tacks or
paperclips work well) and then remove the voltage source while the
items are still attached. You will notice that the items are not
released immediately, but instead stay attracted to the steel
nail/core for a brief instant after the voltage has been removed.

With a de-gaussing coil, you are using alternating current (60 hertz)
to change the orientation of the field 60 times a second. You are
using this alternation in the poles to de-magnetize the item you are
de-gaussing. My concern with using the iron core is that I'm not
sure how quickly the magnet will be able to switch orientation with
the steel/iron core. Also, with the iron core, you will get a short
duration of a potentially high strength "permanent" magnet from the
last AC cycle seen prior to removing the voltage source and if you
are still close could leave the item being degaussed magnetized (just
like when you started).

Wouldn't the flux of the powerful alternating coil swamp out any residual
magnetism from the core? After all, if you're doing it 'by the book,'
you'll be far away from the crt before you cut the power.

jak