Core Power Technologies

Many transformers will hum under certain conditions.  Really good quality ones, produced under high levels of QC, usually don't.  A lot is in the QC.  If the winding is a little "off", an individual example of a brand with a generally good reputation may still hum.  I think that's why they thought they could solve the problem by sending you a replacement--if only they had.

Or a transformer might hum if it's being starved for current. you could measure your incoming voltage and if it's high that I could be part of the problem. 

@twoleftears I recall Mark selling off some B stock 1800’s having newly installed transformers. So there could be some truth to the transformer QC. 

I was speaking with Mark via phone about my 1800 and the additional power cables I ordered. In that conversation he apologized and said he was having health issues and had been in the hospital having testing done and was hoping it wasn’t cancer, but followed up by saying there was a history of cancer in the family. 

Next thing I know the communication completely dropped out, and then I hear the company is being sold. 

I truley hope he just decided it was it was time to call it quits and isn’t fighting a major health issue.