[Going back to ModWright]

A little De-Oxit will take care of the volume pot - it is just from lack of use. That may even be the case for the switches too. I would try that first . In fact, De-Oxit all the connections too. If that doesn't work for the switches then check/replace the tubes. There really isn't much that can go wrong other than the tubes.  If that doesn't work, then send it to Dan. 

HTH

[Aragon Aurum Preamp for sale]

Asking price?

How'd you end up with two?

TIA.