Bad Transformer?

[sr1200]

I have 2 API clone units with the same power supply (whistle rock).  One is a 2 channel, the other a 4 channel.  The 2 channel, when racked, causes some crazy buzz on the unit right above it when powered on.  (coming from the power transformer) The 4 channel does not exhibit this behavior if they are swapped.  The buzz from the unit above can still be heard if i place the 2ch api 2 spaces away with another piece in between them.  I have some MU metal strips, dont know if thats the correct solution for this, but was more interested in WHY this is happening with one and not the other.  The only other difference i can spot is that I used a nylon standoff for the 2ch units power TX  and just a long metal screw for the 4 channel.  Could the TX be bad (even though its functioning electronically)? Thoughts?

 

[radardoug]

Nylon standoff causing lack of ground? Transformers come in all flavors from good to bad, expensive to cheap. Eventides always had cheap power trannys and hummed.

 

[sr1200]

im beginning to wonder if theres something wrong with the unit above the one I think has the issue.  Im using a trident transformer in the 4ch api unit.  I have a 4 ch. Neve clone above that the hum is heard through.  Might have to re-think some transformer placement in these guys.