Larry, NoLand hasn't been using the so called
"potted-so-noone-can-ever-fix-it epoxy box" for years now. You must
have a fairly old unit. I suggest that you take another look at the
Noland Engineering products:

www.nolandengineering.com

I suspect that when that potted mux or yours was purchased, it was a
lot better and less expensive than anything else available at that
time. Of course, the obsolete potted configuration is not best now.
That's why it is obsolete and not sold anymore.

The current NoLand products work great and they're still priced right.