Can anyone offer any tips on how to add a flux band to a transformer? Do I just wrap some copper, or does it need to be electrically connected in some specific way? I am getting a tiny tiny bit of induced hum from the PT to the OPT and am looking to try this as a way to quiet things. Also, is this better to do on power transformers, or outputs, or both?
the simple way is to turn the direction of both transformers, there will have a point of the best
Tony Ma
Tony Ma
Use a copper strip that almost completely covers the bobbin window oriented so that it parallels the windings, pass it over the outside of the core - not around the bobbin otherwise this will look like a shorted turn. Should be snug against the outside of the windings and the core - solder where the ends meet. Check primary excitation current (no secondary windings connected) before and after (if the band is acting like a shorted turn the current will be very high relative to before) check for excessive heating.
I would use it only on the power transformer.
FWIW I'm quite sure Doug has taken all of the usual precautions, hence his question about the flux band.
I would use it only on the power transformer.
FWIW I'm quite sure Doug has taken all of the usual precautions, hence his question about the flux band.
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Te flux cooper band? I try it on OPT. The first time not short the ends band and.... no noticiable changes.
My OPTs are very close to the main ones.They haven hum without the power triodes on sockets.They haven problems with direct electric induction from the main trafo.The solution is more space between them but my chasis is little and this is not possible.No solution.
Now I short the ends from the belly band and... the hum ( ohhhh!!!) is away.This shield works in the both ways: in and out.The shield also is connect to ground.
The sound is now better, in especial at the high frequencies (minor flux leakage or low intermodulatión from main?). I dont know.
Maybe is a subjetive appreciation.
Cheers
My OPTs are very close to the main ones.They haven hum without the power triodes on sockets.They haven problems with direct electric induction from the main trafo.The solution is more space between them but my chasis is little and this is not possible.No solution.
Now I short the ends from the belly band and... the hum ( ohhhh!!!) is away.This shield works in the both ways: in and out.The shield also is connect to ground.
The sound is now better, in especial at the high frequencies (minor flux leakage or low intermodulatión from main?). I dont know.
Maybe is a subjetive appreciation.
Cheers
Yes, the shield acts in both ways.
Yes, the shield reduces leakage magnetic field.
Did you try the shield on power transformers first?
Popilín, I did not on the main trafo. Is a few complicate to do.
... and you are right: the main trafo is the source of the disturbances.Better work on this point: the origin of the problem.
Thank´s Popilín.
... and you are right: the main trafo is the source of the disturbances.Better work on this point: the origin of the problem.
Thank´s Popilín.
You are welcome!
Yes, that is the idea, solving the problem on the source and you will prevent some other hum problem.
If you wrap the band so that the overlap is not lying against the winding or the core (i.e. not touching anything but air) then it's much easier to solder. Tack solder the edges then the seam. If you are careful all the solder will get sucked into the seam and the result will look nice.
BTW, never wrap a toroid with a band, even out of curiosity. Darn near melted a strip of copper playing around this way...
If the shield is made on the outer face of the toroid I do not see the problem.
Toroids have another issue, they are often fixed with a circular metal piece and a bolt to the chassis, if you put a grounded (chassis) wire in contact with the central bolt/metal piece it is formed a closed loop, i.e. a short circuit.
Toroids are treacherous... 😀
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