[R-390] OT: Humbug transformer

[2002tii]

Barry wrote:

>Is there any sage advice to cutting down on the hum?

If it hums, it's because something is moving -- laminations or coils 
(or both).  The only way to decrease it is to stop the movement.  You 
could try potting it in epoxy potting resin, but to have a reasonable 
assurance of success you'd need to do it under a pretty good vacuum 
to ensure that the epoxy penetrates everywhere it needs to go.  Aim 
for at least 1/2" of potting compound on all 6 sides of the xfmr.

Tape-wound toroids are generally better than EI- or C-core 
transformers in this regard, but many of them aren't silent, either.

Trying to damp the movement by mounting the xfmr solidly to something 
else won't help unless the something else is much heavier than the 
xfmr, and it can do nothing about parts of the xfmr itself vibrating.

Best regards,

Don