Does anyone know if by modding these units if they are no longer UL Listed?
I'm not changing the way they work, so they are more refurbished than modded, and I'm pretty much only replacing things that can wear out anyway. I don't think this would be any different than buying a reconditioned piece of vintage gear or having a tech re-cap an audio component. The Furutech or Schurter parts I use in them are UL listed, so I do not think this will affect the UL listing. UL listing is also not required for residential applications, there's tons of unlisted and dangerously built electronics on the market, this is not one them... it is well built to begin with and Made in the USA.