Proper adjustment of the wah pedal potentiometer

(C) Marc Ahlfs 2003

Overview: you want the widest possible sweep allowable by the foot treadle, but you also want to be sure you don't install the new pot in such a way that it gets pushed beyond its internal 'stopping' point. 

Remove the bottom cover and lay the pedal upside-down on its foot treadle.

Loosen the screw holding on the "P"-shaped, plastic rack-gear support, move the support to the side, and disengage the rack gear from the pot-shaft gear.

Since the rack gear travels upward (from this orientation) when the pedal is depressed, notice that this will rotate the potentiometer's shaft gear in a counter-clockwise direction. We're going to start from the fully-depressed position as our reference point, so rotate the pot's shaft gear counter clockwise all the way until it stops.

Now, squeeze the foot treadle in to its fully closed position, enough to compress the rubber spacers under the front edge of the pedal and click the on/off switch to its fully-depressed position. You know this is as far as the pedal and the rack gear are ever going to travel.

Now, rotate the pot shaft clockwise by about one gear-tooth (as a safety buffer zone) and then engage the rack gear into pot shaft gear. Keep pressing the rack gear into the shaft gear as you release the tension from the foot treadle, so you retain the alignment of the gears as the shaft rotates slightly to allow the footswitch to come to its resting position.

Now, re-install the rack-gear support and tighten the screw just until it is snug (don't strip it).

Following these instructions will give you the maximum available "treble" portion of your wah's sweep. If you would like a darker-sounding, bassier wah, you may back off the potentiometer a few more gear teeth (clockwise) before re-installing the rack gear support.

Illustrations and links to more information:

Wah pedal wiring diagrams available at FullTone.com

Schematics and analysis of the classic wah circuit at http://www.geofex.com/ (click on "Technology of the..." in the upper left and go to "Wah Pedals")

Hot Potz II Pinout Diagram
Common Potentiometer	Dunlop Hot Potz II