[R-390] Cleaning Potentiometers

[Tim Shoppa]

> What are you guys using to clean and take the noise out of carbon
> potentiometers?

A new pot.

Off the top of my head, there are only 5 pots in my R-390A (local
audio, line audio, limiter, carrier meter, if gain) and they're
all vanilla.  (OK, the limiter has a little-bit-funky switch on
the back, but if that's in fine condition, it can be transplanted
to a new pot maybe with a little drilling/milling).

When I do put new ones in, it's mil-spec cermet or plastic.  I'm
not going to claim that they'll never get noisy, but they've been
damn good so far.

Tim.