Here is the pedal before opening it up. Another thing that I like about this pedal is that the on/off switch is off to the side so you don't activate the device by pushing the pedal in the full toe position.
Flip the pedal over and undo the four screws holding the bottom plate. There are two screws on each side.
You might have to open up the battery compartment to give yourself something to grab onto while pulling off the bottom plate.
Instead of a potentiometer, the Morley's use an LED and an LDR (light dependant resistor). A tab allows more light to hit the LDR as the pedal is moved forward into the toe position.
Power up the pedal (I prefer a battery when I'm working on pedals). Keep it on its back while you hook up the pedal to a guitar and amp. You can still work the foot pedal while the device is on its back. GENTLY push down on the LED. Moving the LED down means that the pedal will have to be in more forward position to pass the light. Try working the pedal after each adjustment. This should help smooth out the sweep.
Overall, the sounds of this Morley Classic Wah are comparable to a Dunlop Crybaby. It's a straightforward wah sound, not too radical, and a bit noisy. The pedal is solid but not high-end. OK if you're on a tight budget.