On Sun, 11 Aug 2013 09:03:05 -0700, dave
wrote:

I don't remember ever seeing a pot that flat "wore out".

Try taking apart the pots in a joystick. They get far more use than
any front panel control pot. I've seen them with grooves worn into
the carbon that match the individual fingers of the slider. I've also
seen the same thing in volume control knobs on 2way radios that
require turning the volume control to power on/off the radio. If you
leave such a worn grooved pot in place for a long time, the
lubricating grease will "migrate" into the grooves. When that
happens, the individual fingers will float on top of the grease, and
not make contact with the carbon, resulting in an intermittent. With
flat carbon, the fingers will push the grease out of the way. With a
grove in the carbon, the fingers will push the grease into the
grooves.

This also has caused me some grief in the distant past, where I would
"lube" a pot to break loose the shaft, and get the radio back with an
intermittent volume control a few months later. However, all this is
for high use 2way radio controls. I doubt that any hi-fi or even
commodity radio control would see sufficient use (or abuse) to put
grooves in the carbon.

--
Jeff Liebermann
150 Felker St #D http://www.LearnByDestroying.com
Santa Cruz CA 95060 http://802.11junk.com
Skype: JeffLiebermann AE6KS 831-336-2558