|
Home > Archive > Electrical Engineering > April 2007 > Where to scavenge mu-metal?
You are viewing an archived Text-only version of the thread.
To view this thread in it's original format and/or if you want to reply to
this thread please [click here]
| Author |
Where to scavenge mu-metal?
|
|
| SparkyGuy 2007-04-11, 5:25 pm |
| Is this stuff prolific in old CRT monitors, or TVs? Need about a square foot
or so...
Sparky
| |
|
| SparkyGuy wrote:
> Is this stuff prolific in old CRT monitors, or TVs? Need about a square foot
> or so...
>
Nope, only in higher-end legacy lab equipment. With legacy I mean >>25
years old.
--
Regards, Joerg
http://www.analogconsultants.com
| |
| Andrew Gabriel 2007-04-11, 5:25 pm |
| In article <0001HW.C2428AF804BED28AF01826C8@news.sf.sbcglobal.net>,
SparkyGuy <SparkyGuy@mumcrank.ck> writes:
> Is this stuff prolific in old CRT monitors, or TVs? Need about a square foot
> or so...
Wrapped around old oscilloscope tubes.
I don't think old TVs ever merited its use.
--
Andrew Gabriel
[email address is not usable -- followup in the newsgroup]
| |
| Barry Lennox 2007-04-11, 5:25 pm |
| On Wed, 11 Apr 2007 19:50:17 GMT, SparkyGuy <SparkyGuy@mumcrank.ck>
wrote:
>Is this stuff prolific in old CRT monitors, or TVs? Need about a square foot
>or so...
>
>Sparky
Old oscilloscopes or the like would be your best bet for this
Barry
| |
| Chris Jones 2007-04-11, 8:25 pm |
| SparkyGuy wrote:
> Is this stuff prolific in old CRT monitors, or TVs? Need about a square
> foot or so...
>
> Sparky
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
| |
| Bill Janssen 2007-04-11, 8:25 pm |
| SparkyGuy wrote:
> Is this stuff prolific in old CRT monitors, or TVs? Need about a square foot
> or so...
>
> Sparky
>
>
Look at old oscilloscopes.
Bill K7NOM
| |
| Phil Allison 2007-04-11, 8:25 pm |
|
"Joerg"
> SparkyGuy wrote:
>
>
> Nope, only in higher-end legacy lab equipment. With legacy I mean >>25
> years old.
** 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
| |
|
| Phil Allison wrote:
> "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.
>
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.
--
Regards, Joerg
http://www.analogconsultants.com
| |
| Arfa Daily 2007-04-11, 8:25 pm |
|
"Andrew Gabriel" <andrew@cucumber.demon.co.uk> wrote in message
news:461d3fec$0$759$5a6aecb4@news.aaisp.net.uk...
> In article <0001HW.C2428AF804BED28AF01826C8@news.sf.sbcglobal.net>,
> SparkyGuy <SparkyGuy@mumcrank.ck> writes:
>
> Wrapped around old oscilloscope tubes.
> I don't think old TVs ever merited its use.
>
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
| |
| Phil Allison 2007-04-11, 8:25 pm |
|
"Joerg"
>SparkyGuy wrote:
>
> On flat screen displays?
** I said **CRT ** - you FUCKING IDIOT !!!!
Try learning to read sometime !!!
> 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.
** Cheap Asian made scopes usually have no mu-metal at all, just a tin plate
ES shield around the neck - so they are highly subject to external AC
fields.
More expensive Asian scopes ( ie 60 MHz and up) usually have a mu-metal
shield on the CRT.
Examine almost any European, US or Australian made scope and you will find
it has a full size mu-metal shield -excepting scopes employing PDA (Post
Deflection Acceleration) where the mag shielding is not needed near the tube
face.
........ Phil
| |
| MassiveProng 2007-04-11, 8:25 pm |
| On Thu, 12 Apr 2007 00:29:38 GMT, Joerg
<notthisjoergsch@removethispacbell.net> Gave us:
>Phil Allison wrote:
>
>
>On flat screen displays? What for? Sorry, but that would be like
>applying sun screen under the swimsuit.
Learn to read, dummy. It says RIGHT THERE 8 lines up... C R T s
>
>Note that he wrote he needs a square foot. I've only seen that much in
>really old scopes.
Old 20" CRTs for PCs as well as some TVs have it.
> 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.
Then he'll just have to cannibalize two. D'oh!
| |
| Rich Grise 2007-04-11, 8:25 pm |
| On Wed, 11 Apr 2007 19:50:17 +0000, SparkyGuy wrote:
> Is this stuff prolific in old CRT monitors, or TVs? Need about a square foot
> or so...
>
I was looking for some mu metal one day, and someone suggested CoNetic:
http://www.magnetic-shield.com/prod...netic-size.html
Hope This Helps!
Rich
| |
| aubrey.mcintosh@gmail.com 2007-04-12, 3:25 am |
| On Apr 11, 8:12 pm, Rich Grise <r...@example.net> wrote:
> On Wed, 11 Apr 2007 19:50:17 +0000, SparkyGuy wrote:
>
> I was looking for some mu metal one day, and someone suggested CoNetic:
>
> http://www.magnetic-shield.com/prod...netic-size.html
>
> Hope This Helps!
> Rich
Hmm. Its on topic and probably useful. Even addresses the annealing
question. Are you new to SED?
| |
| Michael A. Terrell 2007-04-12, 3:25 am |
| "aubrey.mcintosh@gmail.com" wrote:
>
> On Apr 11, 8:12 pm, Rich Grise <r...@example.net> wrote:
>
> Hmm. Its on topic and probably useful. Even addresses the annealing
> question. Are you new to SED?
No, he just can't figure out which of 20 names to use.
--
Service to my country? Been there, Done that, and I've got my DD214 to
prove it.
Member of DAV #85.
Michael A. Terrell
Central Florida
| |
| John Larkin 2007-04-12, 3:25 am |
| On Wed, 11 Apr 2007 19:50:17 GMT, SparkyGuy <SparkyGuy@mumcrank.ck>
wrote:
>Is this stuff prolific in old CRT monitors, or TVs? Need about a square foot
>or so...
>
>Sparky
Why?
John
| |
| **THE-RFI-EMI-GUY** 2007-04-12, 3:25 am |
| You might try your local recycling center to see where thay tear down
old CRT monitors and TV's. Maybe if they let you come by you can spot some.
SparkyGuy wrote:
>Is this stuff prolific in old CRT monitors, or TVs? Need about a square foot
>or so...
>
>Sparky
>
>
>
--
Joe Leikhim K4SAT
"The RFI-EMI-GUY"©
"Treason doth never prosper: what's the reason?
For if it prosper, none dare call it treason."
"Follow The Money" ;-P
| |
| **THE-RFI-EMI-GUY** 2007-04-12, 3:25 am |
| Isn't moo metal what they make cow magnets from!
SparkyGuy wrote:
>Is this stuff prolific in old CRT monitors, or TVs? Need about a square foot
>or so...
>
>Sparky
>
>
>
--
Joe Leikhim K4SAT
"The RFI-EMI-GUY"©
"Treason doth never prosper: what's the reason?
For if it prosper, none dare call it treason."
"Follow The Money" ;-P
| |
| Tim Williams 2007-04-12, 3:25 am |
| I used to think so, but when I went to college, I learned that it's made
from cats!
Tim
--
"Librarians are hiding something." - Steven Colbert
Website @ http://webpages.charter.net/dawill/tmoranwms
"**THE-RFI-EMI-GUY**" <rhyolite@nettally.com> wrote in message
news:461daa2b$0$19414$4c368faf@roadrunner.com...
> Isn't moo metal what they make cow magnets from!
| |
| MassiveProng 2007-04-12, 3:25 am |
| On Wed, 11 Apr 2007 20:20:12 -0700, John Larkin
<jjlarkin@highNOTlandTHIStechnologyPART.com> Gave us:
>On Wed, 11 Apr 2007 19:50:17 GMT, SparkyGuy <SparkyGuy@mumcrank.ck>
>wrote:
>
>
>Why?
>
He wants to see if it works as well as tin foil for alien/government
shield hat making.
| |
| Long Ranger 2007-04-12, 3:25 am |
|
"MassiveProng" <MassiveProng@thebarattheendoftheuniverse.org> wrote in
message news:v6or139v5ns3gr6jndk3dj1fid5f65u914@4ax.com...
> On Wed, 11 Apr 2007 20:20:12 -0700, John Larkin
> <jjlarkin@highNOTlandTHIStechnologyPART.com> Gave us:
>
>
> He wants to see if it works as well as tin foil for alien/government
> shield hat making.
Wasn't there some of this stuff involved in a Lil' Abner episode?
| |
|
| MassiveProng <MassiveProng@thebarattheendoftheuniverse.org> wrote in
news:030r13lu1ra7p6bdu6qp5hf1c8uejk5q53@4ax.com:
> On Thu, 12 Apr 2007 00:29:38 GMT, Joerg
> <notthisjoergsch@removethispacbell.net> Gave us:
>
>
> Learn to read, dummy. It says RIGHT THERE 8 lines up... C R T s
Piss off.
>
> Old 20" CRTs for PCs as well as some TVs have it.
>
>
> Then he'll just have to cannibalize two. D'oh!
You got that lawyer yet?
>
--
Posted via a free Usenet account from http://www.teranews.com
| |
| SparkyGuy 2007-04-12, 1:25 pm |
| > Why?
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
| |
| John Larkin 2007-04-12, 1:25 pm |
| On Thu, 12 Apr 2007 16:08:23 GMT, SparkyGuy <SparkyGuy@mumcrank.ck>
wrote:
>
>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.
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
| |
|
| John Larkin wrote:
> On Thu, 12 Apr 2007 16:08:23 GMT, SparkyGuy <SparkyGuy@mumcrank.ck>
> 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.
>
Flashing material can be obtained at almost every major hardware store.
But not the Al stuff, as that won't solder...
--
Regards, Joerg
http://www.analogconsultants.com
| |
| SparkyGuy 2007-04-12, 1:25 pm |
| > Mu-metal probably won't help.
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.
> 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 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.)
> Or, um, move it farther away.
Yeah, thanks for that, John... :-)
--
Sparky
| |
| Rich Grise 2007-04-12, 1:25 pm |
| On Thu, 12 Apr 2007 02:29:41 +0000, Michael A. Terrell wrote:
> "aubrey.mcintosh@gmail.com" wrote:
>
> No, he just can't figure out which of 20 names to use.
Hey, Michael - just because _you_ can't figure out which name I'm using,
doesn't mean that _I_ can't. ;-)
I use the different names to distinguish between whether I'm being
technical or goofing around.
Some people don't afford such simple considerations. :-)
Thanks!
Rich
| |
| SparkyGuy 2007-04-12, 1:25 pm |
| > Flashing material can be obtained at almost every major hardware store.
> But not the Al stuff, as that won't solder...
Can use Al if I don't need to solder? Or is it solder that makes it effective
against the magnetic field?
Thanks,
--
Sparky
| |
| Don Lancaster 2007-04-12, 1:25 pm |
| SparkyGuy wrote:
> Is this stuff prolific in old CRT monitors, or TVs? Need about a square foot
> or so...
>
> Sparky
>
As soon as you cut it or otherwise stress it, mu metal becomes worthless.
--
Many thanks,
Don Lancaster voice phone: (928)428-4073
Synergetics 3860 West First Street Box 809 Thatcher, AZ 85552
rss: http://www.tinaja.com/whtnu.xml email: don@tinaja.com
Please visit my GURU's LAIR web site at http://www.tinaja.com
| |
|
| SparkyGuy wrote:
>
>
> Can use Al if I don't need to solder? Or is it solder that makes it effective
> against the magnetic field?
>
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.
--
Regards, Joerg
http://www.analogconsultants.com
| |
| Rich Grise 2007-04-12, 5:25 pm |
| On Thu, 12 Apr 2007 17:49:49 +0000, SparkyGuy wrote:
>
> 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?
It goes right on the outside of the lams, and around the windings, in
the same direction as the windings, like this:
http://www.germes-online.com/direct...Transformer.jpg
It acts as a shorted turn; it has something to do with "leakage inductance".
Cheers!
Rich
| |
|
| Rich Grise wrote:
> On Thu, 12 Apr 2007 17:49:49 +0000, SparkyGuy wrote:
>
>
>
> It goes right on the outside of the lams, and around the windings, in
> the same direction as the windings, like this:
> http://www.germes-online.com/direct...Transformer.jpg
>
> It acts as a shorted turn; it has something to do with "leakage inductance".
>
Yep, that's it. Just dawned on me where to buy the sheet stock: Hobby
shops or arts and crafts suppliers. The ones that cater to artists who
build stuff like Tiffany lamps or do other stained glass work. That's
where you can also buy copper tape, brass sheets and all that.
--
Regards, Joerg
http://www.analogconsultants.com
| |
| SparkyGuy 2007-04-12, 5:25 pm |
| > It goes right on the outside of the lams, and around the windings, in
> the same direction as the windings, like this:
>
http://www.germes-
online.com/direct/dbimage/50068769/Power_Supply_Transformer.
> jpg
Not necessary to ground it?
Is wider (as wide as the windings) best? Dimension confusion...
Thanks,
--
Sparky
| |
| Beachcomber 2007-04-12, 8:25 pm |
| On Thu, 12 Apr 2007 11:04:17 -0700, Don Lancaster <don@tinaja.com>
wrote:
[color=darkred]
>SparkyGuy wrote:
High MU metal is not a particularly rare material. I assume you are
attempting to shield something from a low frequency magnetic field.
You may find the cast-iron door of an old stove or wood furnace will
be all you need.
| |
| Arfa Daily 2007-04-12, 8:25 pm |
|
"Rich Grise" <rich@example.net> wrote in message
news:pan.2007.04.12.19.35.22.683121@example.net...
> On Thu, 12 Apr 2007 17:49:49 +0000, SparkyGuy wrote:
>
> It goes right on the outside of the lams, and around the windings, in
> the same direction as the windings, like this:
> http://www.germes-online.com/direct...Transformer.jpg
>
> It acts as a shorted turn; it has something to do with "leakage
> inductance".
>
> Cheers!
> Rich
>
That transformer in the picture is a ferrite cored one from a switch-mode
power supply, and is designed to run at a frequency of around 100kHz. A
copper band around such a tranny, is a whole different kettle of fish to
putting one around a low frequency power transformer. Some such trannies
have a copper shield right around the windings, inside the lamination limbs,
but if I recall correctly, this is more for electrostatic shielding
purposes, than magnetic. The first thing I would try, before getting all
complicated with mumetal shields, is to rotate the tranny through 90 degrees
in the horizontal, and if that doesn't work, doing the same in the vertical,
or any combination. I've found that this will often reduce or even eliminate
stray field pickup by adjacent circuitry. The tranny mounting holes may even
still line up in the best case, but even worst case, it's only a case of
drill 4 more, or make up a right-angle bracket.
Arfa
| |
| John Larkin 2007-04-12, 9:25 pm |
| On Thu, 12 Apr 2007 19:33:09 GMT, SparkyGuy <SparkyGuy@mumcrank.ck>
wrote:
>http://www.germes-
>online.com/direct/dbimage/50068769/Power_Supply_Transformer.
>
>Not necessary to ground it?
Not if your problem is magnetic field leakage.
>
>Is wider (as wide as the windings) best? Dimension confusion...
Think of it as a single, shorted secondary turn but *outside* the
laminations. Any field that leaks out of the transformer induces a
current into the strap, and it in turn generates a field that fights
the excitation. It should be thick, wide, and well-shorted, which
means well soldered. Copper is best.
John
| |
| MassiveProng 2007-04-13, 3:25 am |
| On Thu, 12 Apr 2007 16:08:23 GMT, SparkyGuy <SparkyGuy@mumcrank.ck>
Gave us:
>
>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.
Make sure you simply twist your output lines from the banana jacks,
right up to the circuit under test. Your noise figure should drop a
lot on that act alone. A couple turns per inch... not too damn loose
or it does no good.
| |
| MassiveProng 2007-04-13, 3:25 am |
| On Thu, 12 Apr 2007 17:50:43 GMT, Rich Grise <rich@example.net> Gave
us:
>Hey, Michael - just because _you_ can't figure out which name I'm using,
>doesn't mean that _I_ can't. ;-)
Boolshit. Have another drink, you alcoholic retard.
>
>I use the different names to distinguish between whether I'm being
>technical or goofing around.
More boolshit. You use them because secretly you want us all to know
just how retarded you really are.
>Some people don't afford such simple considerations. :-)
You're an idiot.
| |
| Brisclecone 2007-04-13, 9:25 am |
| MassiveProng <MassiveProng@thebarattheendoftheuniverse.org> wrote in
news:beut13h66o0e5452porsgrgpiqa17ncs8f@4ax.com:
> On Thu, 12 Apr 2007 17:50:43 GMT, Rich Grise <rich@example.net> Gave
> us:
>
>
> Boolshit. Have another drink, you alcoholic retard.
>
> More boolshit. You use them because secretly you want us all to know
> just how retarded you really are.
>
>
> You're an idiot.
>
Wanna play?
| |
|
|
"Rich Grise" <rich@example.net> wrote in message
news:pan.2007.04.12.18.51.15.376273@example.net...
> On Thu, 12 Apr 2007 02:29:41 +0000, Michael A. Terrell wrote:
>
> Hey, Michael - just because _you_ can't figure out which name I'm using,
> doesn't mean that _I_ can't. ;-)
>
> I use the different names to distinguish between whether I'm being
> technical or goofing around.
>
> Some people don't afford such simple considerations. :-)
>
> Thanks!
> Rich
>
Are you a solipsist, Rich?
Regards
Ian
;-)
| |
| SparkyGuy 2007-04-13, 1:25 pm |
| > You may find the cast-iron door of an old stove or wood furnace will
> be all you need.
Now *there's* a mental picture that deserves framing!
--
Sparky
| |
| SparkyGuy 2007-04-13, 1:25 pm |
| > Think of it as a single, shorted secondary turn but *outside* the
> laminations. Any field that leaks out of the transformer induces a
> current into the strap, and it in turn generates a field that fights
> the excitation. It should be thick, wide, and well-shorted, which
> means well soldered. Copper is best.
>
> John
No need to ground, I presume...
| |
| MassiveProng 2007-04-13, 1:25 pm |
| On Fri, 13 Apr 2007 09:01:56 -0700, SparkyGuy <SparkyGuy@mumcrank.ck>
Gave us:
>
>No need to ground, I presume...
Have you formed the leads going to your project into twisted pair
yet? I guarantee that will reduce injected noise a LOT.
| |
| joseph2k 2007-04-15, 9:25 am |
| Don Lancaster wrote:
> SparkyGuy wrote:
> As soon as you cut it or otherwise stress it, mu metal becomes worthless.
>
>
That is a completely garbage overstatement. Just the same, any tight bend
(bending r less than 10 thicknesses) will require annealing in a reducing
atmosphere.
It is really quite intolerant of cold working if you wish to maintain the
magnetic properties. Do not even flex it unnecessarily.
--
JosephKK
Gegen dummheit kampfen die Gotter Selbst, vergebens.Â_Â_
--Schiller
|
|
|
|
|