[sdiy] Source for center tapped pots? Anyone?

[fmg]

Hi Thomas and list

Sorry if this post is a bit late, I had to wait the weekend to
re-assemble the scanner (no digital cameras here)

This is a diy center tapped pot. There are hundred of pots in
shapes, colors and sizes, this is one of the oldest, most common
and easily workable.

Some photos (or scans):

http://www.geocities.com/eqys/var_tmp/pote1.jpg
A thin U bent pre-soldered wire enters in a 1 mm. hole made in
the pot substrate, very near the resistive pcb. Solder is aplied
on both sides and then slightly pressed with pliers to make a "rivet"

http://www.geocities.com/eqys/var_tmp/pote2.jpg
Conductive ink (silver based) makes the contact between the solder
and the resistive surface. Once ink dried contact area can be trimmed
with a needle.

http://www.geocities.com/eqys/var_tmp/pote3.jpg
To prevent failures due to stress the cable is fixed (glued).
For 100k and lower values I use (a local equivalent of) Locktite.
For higher values I prefer a fat drop of acrylic lacquer (takes
hours to dry)

http://www.geocities.com/eqys/var_tmp/pote4.jpg
This is 1M linear pot. I made the same mod to 8 of them. The signal
input is the wiper. It "routes" the buffered signal to the LP and HP
VCF inputs, both at the pot ends. The tap goes to the BP VCF input.
(...yes a Steiner VC filter).

This was a common practice decades ago. Then (in my region) was a
fever in the hobbyst to make "loudness control" (a bass enhance for
small signals) wich used log pots tapped at 1/4 of the travel.

Today this pot mod is a rare practice, but I can bet there are people
in this very list that have done it before.

If you experience troubles with comercially available ones, don't
make your project to vanish, keep in contact, may be we can find
a way to "make" the correct pot for your project.

Best regards

Fabio
.


-- 
Fabio Gonzalez
Posadas, Argentina