[sdiy] Endless Rotary Potentiometers

Richie Burnett rburnett at richieburnett.co.uk
Tue May 6 23:25:35 CEST 2014

I think these "dual wiper" endless pots are used in the Alesis Ion too. So might be worth looking for Alesis spares. I heard of Alesis sticking a replacement pot in the post after someone I know managed to shear the pot shaft clean off moving their Ion at a gig.

As far as I know the two wipers are 180 degrees apart physically, and some clever software makes sure the signal is taken from one wiper when the other wiper leaves the end of the track and jumps back to the start. Essentially, each wiper is used to cover up the discontinuity when the other wiper crosses the dead spot on the track. 

Hope this info helps, 


Sent from my Xperia SP on O2

---- Nathanael King wrote ----

>Hi List,
>I'm having trouble finding proper search terms. I just purchased a
>bunk mpd24. Seller said "Values are jumping all over the place". I
>found 3 problematic pots. I would have thought they would be simple
>encoders - silly me. My reading suggests Akai used potentiometers that
>rotate a full 360 degrees. They are a 9mm size and standard footprint.
>Metal shaft, threaded bushing. There are 4 pins - one for each end and
>!2! wipers. People that sell them linked below.
>I'm not interested in paying over $20 for 3 pots (call me crazy).
>Anyway, I thought I'd probe the list on the perchance someone has run
>across this before and has inside information. They are Alpha brand. I
>couldn't find a datasheet for these in the places I looked. Of course,
>Alpha will make anything you want in the right quantity, so I don't
>really expect much help from them.
>I have used de-oxit and come close to full functionality on some of
>the jumpy pots, but one isn't playing nice at all. So, yes, I'm trying
>to just clean it in the meantime. It appears someone spilled a sticky
>substance (beer) on the unit.
>Paper Products Music
>Synth-diy mailing list
>Synth-diy at dropmix.xs4all.nl

More information about the Synth-diy mailing list