Audible Buzz from Lexicon: dimmers & microwave?

Greetings all, I've scoured through the forums here and other sites to try and find an answer to a perplexing buzz that's been coming from the chassis of my Lexicon LX-7. The buzzing does not come through my speakers--ever. The buzzing comes from the Lexicon.

I have done the following:
1) I have brought my Lexicon in to be serviced. It passed with flying colors and *no buzzing*
2) I have switched power cords three times (Shunyata, Transparent, stock)
3) I have disconnected all balanced cables and speaker interconnects from the Lexicon. It sill buzzes regardless of whether or not something is connected.
4) I have plugged my Lexicon into my Panamax power conditioner