Pedal / pot trouble

[Minwah]

I have a set of analog Happ pedals hooked up to an AKI USB interface.  Since I got my cabinet running again the pedals don't work too well, especially the throttle pedal.

Trouble is essentially that releasing the pedal does not neccessarily return the pedal to 'not pressed'.  I have checked that the pot gear is not slipping on the pot shaft, or grinding over the toothed pedal cam thing...it seems to be turning fine.  I have calibrated the pedal in Windows, although this clearly shows the problem I have - the 'raw value' when pedal released often returns to a number greater than zero.

I am probably going to try replacing the pots as I think these are quite old.  Will this likely fix the problem?

Also worth noting is that these pedals do not turn the pots very much, but I would think calibration should take care of that.

http://www.happcontrols.com/driving/50806001.htm

http://dave.bit2000.com/aki.html

[Xiaou2]

Yes, if gears are not worn,  and shaft pin is tight,  then the only thing left is the
Pots.

 They do go bad in time.   Only thing is I cant recall which pot type goes into
them... Linear, or Audio Taper.   IE:  1,2,3,4,5   vs  1,2,5,8,15    I believe its
the first =  Linear.

[Minwah]

They do go bad in time.   Only thing is I cant recall which pot type goes into
them... Linear, or Audio Taper.   IE:  1,2,3,4,5   vs  1,2,5,8,15    I believe its
the first =  Linear.

Thanks, and I believe you are right, they are linear pots.

[surface tension]

If it's not written on the pot itself (linear or logarithmic), the easiest way to find out is to check the voltage on the wiper (centre pin - usually) when pressed half-way down, is half of the supply voltage. Sorry if I'm teaching you to suck eggs here.

You said that "the 'raw value' when pedal released often returns to a number greater than zero" suggesting that it has a dirty track. The lower end of the pot is going to be the area that gets the most use on a pedal too. Jittery control pedal would be a sure sign that the pot is dirty or worn.

[Minwah]

If it's not written on the pot itself (linear or logarithmic), the easiest way to find out is to check the voltage on the wiper (centre pin - usually) when pressed half-way down, is half of the supply voltage. Sorry if I'm teaching you to suck eggs here.

No you're not, thank you for the tip!

You said that "the 'raw value' when pedal released often returns to a number greater than zero" suggesting that it has a dirty track. The lower end of the pot is going to be the area that gets the most use on a pedal too. Jittery control pedal would be a sure sign that the pot is dirty or worn.

Again, thank you.  That confirms it for me