On Thu, 12 Apr 2007 17:49:49 +0000, SparkyGuy wrote:
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?

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/...ransformer.jpg

It acts as a shorted turn; it has something to do with "leakage inductance".

Cheers!
Rich