I was expecting mumetal to be the best but looks like not !
youtu.be/oxg_hCvXSrw
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Klaas Robers wrote:Yes, but that works only for AC magnetic fields. The copper winding is shorted, the beginning is firmly connected to the end by soldering. Then you have a short circuited winding around the transformer as a whole. This induces a magnetic field opposing the magnetic stay field of the transformer.
Sometimes you also see a not too thin copper foil wrapped around the transformer, comparably to my winding. That copper foil is also soldered to form a short circuited single windinding. I had no foil, but I had yellow plastic insulated wire. However the insulation serves no goal at all. I could also have used uninsulated copper wire, but had that not laying around.
Klaas Robers wrote:The trick is that a magnetic field perfectly aligned with the centre of the CRT does almost no harm. So if you can place the transformer by rotating such that the external magnetic (stray) field of it is coinciding with the direction of the electron beam, you don't see the disturbances. And because you don't know how those stray fields are exactly directed, it is wise to rotate the transformer experimentally. I also have read in the past that initially the transformer is connected with long leads and you move the transformer by hand such that the picture is best. And then try to fix it in that position. Some compromises are in most cases unavoidable.
In general placing the transformer directly behind the CRT is a good plan. But then your cabinet is going to be even deeper than the CRT on its own needs. I also have seen two transformers with the CRT between them. This assumes that the transformers give equal magnetic stray fields.....
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