Potentiometers: what do you suggest??

Tom May ftom at netcom.com
Wed Jun 11 09:06:42 CEST 1997

Terry Bowman <terrymbowman at rica.net> writes:

> The "A" indicates that the pot is linear taper. "B" indicates audio taper.

My RS pots have "B50Kohm", "A10Kohm", etc. printed on the back, where
the A and B are like you say except maybe with the opposite taper.
But (and I'm sounding like a broken record here) they *also* have a
small "a" in a circle which is stamped or otherwise imprinted directly
in the metal on the back.  The 16mm pot I got from Mouser has both
B100K and the "a" on the back.

> Mouser and Radio Shack pots are definitely NOT the same unless RS changed
> manufacturers recently.

Remember I got these RS pots in 1984.  Maybe even 1983.  They sucked
immediately.  They sure seem to be the same manufacturer as the
current Mouser pots.  It's just interesting that anything from RS gets
called junk but what is very possibly the same pot, slightly updated,
purchased from Mouser is ok.  I'm just telling ya, I got some cheap
pots with the little "a" on the back and they suck and now I'm leary
of anything with the same little "a" on the back until they have
proven themselves.  I'm not trying to defend RS or dis Mouser.  In
fact based on people's experiences here I'll probably order a whole
pile of inexpensive Mouser pots for my ASM-1 and replace any that get
a lot of use and wear out (if any) with something (hopefully) more

> Furthermore, I've always heard that RS pots have a
> dead zone at the CCW end of travel; the resistance doesn't change at all
> for quite a few degrees. Mouser pots don't seem to have this problem.

I think that's a feature.  I tested a bunch of pots I've got sitting
around and the only one that didn't have a dead zone at both ends was
still reading resistances of 20 to 30 ohms between the wiper and the
ends at full rotation, i.e., it wouldn't turn all the way off.  In
most cases I would rather have a dead zone than not be able to turn a
pot all the way off.  The Clarostat 53C3 pots had by far the largest
dead zones.


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