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Old 4th September 2012, 06:39 PM   #27261
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Quote:
Originally Posted by FrankWW View Post
aeronautical, take a look at what Lazy Cat and Joachim Gerhardt are doing

I will and thanks.

I think I have decided to build something I can buy boards for. I know there are several of those about. The store here has some, I saw a post where someone is building a Doug Self preamp that has boards available. Mr. Curl suggested I could buy boards from clone of one of his designs.

Do you have any thoughts of what you might buid if you didn't want to make boards and didn't want to point-to-point of breadboard either?
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Old 4th September 2012, 06:56 PM   #27262
gpapag is offline gpapag  Greece
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Quote:
Originally Posted by jneutron View Post
A ferromagnetic sheet won't have a linear BH curve. Whtn it is excited by a field on one side, the other side will see a permeability modulation. This can create harmonics which are a product of the two frequencies being shielded. jn
You at least try to provide some explanation.
Some others take it for granted.
I will ask. The BH curve nonlinearity and the permeability’s dependence on H field strength are phenomena known on x-former cores.
Assuming audio x-formers (input, coupling, output) have been used, studied and optimized for decades, where is the data quantifying the harmonic distortion generation due to these nonlinearities of ferromagnetic materials? (links, reference)

The shielding effect a metal provides on magnetic fields, is more or less achieved by the eddy currents generated within it.
Electrical conductivity and magnetic permeability play an equal importance on the eddy’s -counter -magnetic field strength.
Among different –ferrous and non ferrous- metals, electrical conductivity varies a hundred fold. Magnetic rel. permeability varies some ten thousand fold.
Therefore, for low freq. fields (50/60Hz and harmonics), substituting non ferrous for ferrous shields, one has to increase the shield thickness two to four orders of magnitude for to achieve equal shielding effects.

Rel. distance: By old ARRL handbooks, the distance of a metal shield from a HF coil had to be minimum 3 coil diameters for the Q of the coil to be affected by less than 10% (from memory).

Quote:
Originally Posted by jneutron View Post
Hey, maybe there's a 747 vertical stabilizer available out there on E bay. Maybe a group buy?? A sheet of aluminum foil over the uranium would stop the alpha particles.
Still, some may take it seriously.
Free trading and unregistered procurement is illegal (material controlled by the national AECs)

Even thick primer paint hinters alpha. You are left to deal with the gamma.
Some 15 years ago the old balance weights had to be progressively replaced with tungstenium ones. The problem with depl. Ur. weights was with inter-granular corrosion.
Where attacked, depl. Ur. turned into thin, gray dust.
Once inhaled, alpha was eating you from inside.

George
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Old 4th September 2012, 07:06 PM   #27263
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Tube equipment usually (in my experience anyways)
uses steel chassis. Is this because of tradition going
back to before the superiority of aluminum or tube
circuitry having differant needs or ???????
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Old 4th September 2012, 07:28 PM   #27264
bcarso is offline bcarso  United States
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Quote:
Originally Posted by hitsware View Post
Tube equipment usually (in my experience anyways)
uses steel chassis. Is this because of tradition going
back to before the superiority of aluminum or tube
circuitry having differant needs or ???????
Steel was way cheaper and stronger. And it was sometimes coated with Cadmium. Ooops. Another toxic metal that people managed to survive. It was interesting when it developed a whitish coating. The old JBL SA600 had cad-plated RCA connectors. When my father's developed loud hum, he was sure it was an electrolytic that had to "re-form", and would cycle the power, after which many times the hum was gone, or at least lower-level enough to be tolerable. When I inherited the piece I finally realized that the cycling just induced an oxide-penetrating transient that restored the RCA shell and/or tip connection.
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Old 4th September 2012, 07:37 PM   #27265
gpapag is offline gpapag  Greece
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Originally Posted by bcarso View Post
And it was sometimes coated with Cadmium
It was interesting when it developed a whitish coating.
Then is the danger for the population (users)
Sacrificial anodic coating turned into (toxic) sticky dusty oxide (Avoid "Scratch and smell").

George
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Old 4th September 2012, 09:23 PM   #27266
bcarso is offline bcarso  United States
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Originally Posted by gpapag View Post
Then is the danger for the population (users)
Sacrificial anodic coating turned into (toxic) sticky dusty oxide (Avoid "Scratch and smell").

George
It would be interesting, possibly horrifying, to be able to find out what happened to some of the people who worked soldering cad-plated chassis with lead-bearing solder for my father's companies over the years. He himself used to carry bits of Pb-Sn solder around in his pockets along with change and car keys.
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Old 4th September 2012, 09:56 PM   #27267
morinix is offline morinix  United States
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Originally Posted by bcarso View Post
It would be interesting, possibly horrifying, to be able to find out what happened to some of the people who worked soldering cad-plated chassis with lead-bearing solder for my father's companies over the years. He himself used to carry bits of Pb-Sn solder around in his pockets along with change and car keys.
Those were the days!
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Old 4th September 2012, 10:19 PM   #27268
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Quote:
Originally Posted by bcarso View Post
He himself used to carry bits of Pb-Sn solder around in his pockets along with change and car keys.
Like I did.

I got used to when something is picked up as being more dangeropus than lots of other more dangerous things that means somebody wants to benefit from it. Like, asbestos had been declared most harmful in the building industry when the source of it left in Soviet Union mostly.
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Old 4th September 2012, 10:38 PM   #27269
wayne is offline wayne  United States
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I suppose I should stop using my mouth as a third hand for solder. Probably explains a thing or two. Lead is all natural though just like Plutonium, Arsenic and hemlock.
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Old 4th September 2012, 11:24 PM   #27270
bcarso is offline bcarso  United States
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Originally Posted by wayne View Post
I suppose I should stop using my mouth as a third hand for solder. Probably explains a thing or two. Lead is all natural though just like Plutonium, Arsenic and hemlock.
When I used to work at the bench a lot my geochemist grad student friend, who was doing a study about lead pollution due to tetraethyl lead in motor fuel, saw the smoke from the rosin core solder coming off of my iron. He asked me for a sample of the solder, which was Ersin Multicore.

He called me with some excitement. Mass spectrometry revealed that the isotopic constituency of the solder allowed its mines of origin to be identified as ones in Australia, unlike the lead added to gasoline. He wondered if I could spare a blood sample?

If I'd realized how much blood was involved I'd probably have declined, but went through with it. He returned with an analysis: I was well below the levels considered to be dangerous, but about 1/4 of the lead in my blood was indeed from the solder. The rest was just what was expected from living in Los Angeles, and not particularly close to a freeway

I was a little more careful to have the fumes vented away after that.
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