** 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The laws of magnetics have not been repealed in the last 25 years.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.
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 ...
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
There is a German place that sells little mu-metal boxes (cylindrical cans
and here is some self-adhesive mu-metal foil:
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.
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.
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.
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
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.)
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