Where to scavenge mu-metal?

Is this stuff prolific in old CRT monitors, or TVs? Need about a square foot or so...
Sparky

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SparkyGuy wrote:

Nope, only in higher-end legacy lab equipment. With legacy I mean >>25 years old.
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Regards, Joerg

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"Joerg"

** Where does this jerk off get his weird ideas from ??
The laws of magnetics have not been repealed in the last 25 years.
ALL good quality scopes using CRTs have mu-metal shields.
Even ones made today.
........ Phil
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Phil Allison wrote:

On flat screen displays? What for? Sorry, but that would be like applying sun screen under the swimsuit.
Note that he wrote he needs a square foot. I've only seen that much in really old scopes. Newer CRT versions have a skinny shield right around the CRT and that ain't going to be enough to harvest a complete sqft from.
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Regards, Joerg

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On Thu, 12 Apr 2007 00:29:38 GMT, Joerg

Learn to read, dummy. It says RIGHT THERE 8 lines up... C R T s

Old 20" CRTs for PCs as well as some TVs have it.

Then he'll just have to cannibalize two. D'oh!
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Gave us:

Piss off.

You got that lawyer yet?

--
Posted via a free Usenet account from http://www.teranews.com


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Wrapped around old oscilloscope tubes. I don't think old TVs ever merited its use.
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Andrew Gabriel
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writes:

Back in the days of 90 degree delta-gun shadowmask tubes, an external magnetic shield most certainly was used around the bowl. The degaussing coils were usually fixed to it, and it mounted using the same four corner bolts as fixed the tube to the cabinet front. Many were my sliced fingers, from the razor-sharp edges of these shields, when I was an apprentice engaged in replacing these tubes ...
Arfa
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wrote:

Old oscilloscopes or the like would be your best bet for this
Barry
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SparkyGuy wrote:

I have vague memories of hearing that if you bend it (or straighten it) then it loses its special properties and needs to be re-annealed in some fancy vacuum furnace thing or something like that. If you found a weird-shaped piece of this stuff inside an old oscilloscope then I I'm not sure that you could use it unless you needed it in exactly the shape that you found it in.
There is a German place that sells little mu-metal boxes (cylindrical cans actually): http://www.buerklin.com/gruppen/KapH/H161260.asp and here is some self-adhesive mu-metal foil: http://www.buerklin.com/gruppen/KapL/L210600.asp
Actually I suppose the existence of the mu-metal foil product brings into question whether it really matters whether you bend the mu-metal. Perhaps someone else knows for certain.
Chris
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SparkyGuy wrote:

Look at old oscilloscopes.
Bill K7NOM
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wrote:

Why?
John
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On Wed, 11 Apr 2007 20:20:12 -0700, John Larkin

He wants to see if it works as well as tin foil for alien/government shield hat making.
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message

Wasn't there some of this stuff involved in a Lil' Abner episode?
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My bench power supply's transformer is coupling hum into my breadboard. Yes, I can move my circuit farther away, but I'd rather solve the problem (short of replacing an otherwise good supply) than the symptom.
It's a 70's vintage lam transformer with half a dozen secondary windings. I'd prefer a toroid, but it will be cheaper to simply shield this one.
--
Sparky


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wrote:

Mu-metal probably won't help. A copper shorting strap around the transformer would. You can make that out of sheet copper, or even bare wire and a lot of solder.
Or, um, move it farther away.
John
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John Larkin wrote:

Flashing material can be obtained at almost every major hardware store. But not the Al stuff, as that won't solder...
--
Regards, Joerg

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Can use Al if I don't need to solder? Or is it solder that makes it effective against the magnetic field?
Thanks,
--
Sparky


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SparkyGuy wrote:

Al won't be very good but to be of some help against EM fields it would at least need to be riveted. After a while it'll oxydize though.
Think of it this way: In order to muffle a magnetic field coming from the inside you need to short out any induced currents. A work of caution if you ever do that around toroid transformers: If there is a metallic stud that holds them in place never, never let a shield touch that. It might result in molten metal sparkling all around you.
--
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My understanding is that it should be high-nickel content metal, such as is mu, and that without that content magnetic fields aren't much effected by metals.

Or does solder serve as the poor-man's nickel?
Sounds like DIY mu-copper :-) You say "strap" which I interpret as not full-height of the transformer. Should it be less-than the height of the lams? Or is taller better?
Isn't that a lot of wire (a tertiary winding)?
Wrap the sheet around and bolt it under the feet of the xfmr? (Only need to shield in 1 direction, really: forward.)

Yeah, thanks for that, John... :-)
--
Sparky


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