Olin, I'm not sure you understand. I have it disconnected. The wiper is
bad and/or the carbon (or whatever they use today) trace is worn off
inside. I measured the total value at 5k. The wiper doesn't make
connection internally over much of the travel, at least not well or
randomly. If you're suggesting total resistance, I have that - not
difficult. If you're suggesting a way to profile what the values are at
various degrees of rotation, I'm not getting it...

I did like the idea of a parallel resistor Bob. Lots of ways to play
with that. Don't know why that didn't occur to me! That's the kind of
approach I usually take.=20

As far as taking it apart Joe, it's plastic welded together. If I break
it open, I may just see if cleaning and/or reworking fixes it, with some
lube to prevent future issues. I'll want to have a good plan for
re-assembly, because if I go to that length, it'll make sense to just
fix it if it's fixable. My experience in the past has been that the
track wears and creates 'dust', which causes intermittent connection or
resistance values. It's a lot easier when the thing is put together with
metal tabs or such. ;)

I did look at getting a 'factory' part. As you might guess, being near
the factory Carl, they don't sell internal components. They're happy to
sell you another one for a few Benjamin Franklin portraits... Their
'schematic' is nothing more than how the accessory parts go together. I
did find one shop that listed internal parts, although the model
matching wasn't perfect. Not sure how _they_ get supplied, since there
is no 'authorized' repair or parts depot. A pot listed as almost $30.
Minimum order was $40 I think. Plus shipping, etc. It's just a standard
motor with brushes, pot, switch, and an analog controller inside.
Sheesh! Pots are a buck. I do notice that the way it's made accommodates
different parts (long story) throughout, as if they buy in lots and cast
parts can accept different parts. That could mean different pots
physically, but the same controller board or same value pot, or perhaps
the pot is matched to the particular controller board inserted. No way
to know without talking to the factory and/or designer. The nice women
on their help lines may be good at recipes, but not manufacturing or
engineering I'd guess...

If it gets too deep, a $10 Harbor Freight motor controller and a little
'bypass' surgery inside the motor base might do it. Not pretty, but at
least there's a backup plan. ;)

-Skip


On Tue, 2011-02-22 at 07:35 -0500, Olin Lathrop wrote:=20
> IVP wrote:
> >> It seems to not be quite linear, but it jumps around so much and
> >> never does the same thing twice, so who knows
> >
> > Take it apart and measure directly on the track
>=20
> He shouldn't even need to disconnect it since one end is already not
> connected.  Crank the pot so that the wiper is at the connected end, then
> measure accross the ends.  The existing circuit will then be only connect=
ed
> to one end of the resistor, so you can measure the resistance without
> interference.
>=20
>=20
> ********************************************************************
> Embed Inc, Littleton Massachusetts, http://www.embedinc.com/products
> (978) 742-9014.  Gold level PIC consultants since 2000.

--=20
http://www.piclist.com PIC/SX FAQ & list archive
View/change your membership options at
http://mailman.mit.edu/mailman/listinfo/piclist
.