> From: sndgroom@...
>
> After a careful cleaning of all sliders, nothing changed.
> What is strange is that measuring their values with a tester
> they look like working fine as variable resistors. I'm
> thinking it might be the MUX and ordered some chips to check.

It's hard to see noisy pots with a meter. The best way to see if the sliders are dirty is to put a scope probe on the wiper as you move it up and down in normal operation, to see if the line on the screen remains clean as it rises and falls. If the slider is dirty, you'll see obvious discontinuities and erratic behavior. But obviously you can't do that unless you have access to a scope.

I'd need a more precise description of the behavior to guess what else might be wrong. Are you getting the same behavior from all sliders, or are some bad and others okay? Can you swap the 4051 muxes, and see if the bad behavior moves to different sliders? Do the levers work okay, or do you get erratic output from them too? (They go through the same mux.)

--

Ciao, Paul D. DeRocco
Paul mailto:pderocco@...