[sdiy] Scratchiness in TB-303 resonance pots

[Robin Whittle]

I have updated my page:

  http://www.firstpr.com.au/rwi/dfish/pot-wear/

to convey my new understanding of the cause of scratchiness in the
replacement pots from chipforbrains (TechnologyTransplant).

Previously I thought the problem was an alcohol soluble contaminant
- and that may well be a cause of trouble.

Now I believe that in some cases at least, there is a problem with
the inner 4 wipers (resistive track) of the outer pot not being bent
towards the track enough.  Since they are not completely
independently sprung from the 2 outer wipers (outer conductive
track) then the 2 outer wipers can push the whole thing down and
reduce the pressure of the 4 inner wipers.

I wrote to chipforbrains about the trouble when I discovered it
early this year and will convey this new information too.  Hopefully
it will help the manufacturers improve the next batch.

  - Robin