[sdiy] Fixing humming transformers in 1u rack units

[Ingo Debus]

Am 20.02.2010 um 14:38 schrieb Altitude:

> Some quick research
> revealed that this is caused by magnetic flux from the transformer  
> vibrating
> the top of the case and the general solution I could find was a  
> vague "cover
> it with something". So finally got around to looking at this on my  
> TX and
> per the Tx-81z service notes which has a diagram of the fix, all  
> that needs
> to happen is a metal shield needs to be clamped on top of the  
> transformer. I
> used 0.016" thick cold rolled steel which is nice and formable but  
> rigid
> enough to hold its shape so just bending the flanges in is enough  
> for it to
> clamp on to the transformer.

This is interesting, I once had the same problem. It wasn't the  
transformer itself humming, it was the steel case cover that was very  
close to the transformer (took me a while to find that out). My  
solution was to increase the distance between transformer and case  
cover :-) A few millimeters more were enough.

Did you check if your added metal shield gets hot, or if the  
transformer gets warmer than without shield? Somewhere the energy  
that used to vibrate the case cover must go. Some really nasty things  
can happen when a toroidal transformer is improperly shielded.  
Probably not an issue at all in your case, but I'd check nevertheless.


>   Not sure if aluminum would work or not,

I don't think it would.

Ingo