The standard Alembic pots are pretty premium stuff - sealed (although not totally) and self-cleaning. If the body of the pot is rectangular and blue or black in color, these are also high-precision pots with a plastic conductive element.
The way the pot works is that there's a metal arm (the wiper) connected mechanically to the shaft and electrically to the center terminal. The wiper sits on a conductive element who's ends are connected to the other two terminals on the pot. The greater the distance between the wiper and an end terminal, the greater the resistance. The conductive element is usually a molded piece of carbon. The fancy plastic conductor pots use a conductor made of special plastic which is trimmed with a laser beam so the resistance change is very precise.
When dust gets on the conductive element, you get dead spots, and scratchy noises. With regular pots, it's easy for dust to get in the case, although it's not usually like a dust storm flying around in your control panel. With the fancier pots, there's no openings in the case and the really fancy pots even are sealed around the shaft so you could use them underwater.
In the better pots, the wiper is shaped to push dirt off the track when you turn the pot a lot. Sometimes whatever got in there just won't come out.
The easiest fix is just to replace the pot. You probably want to contact Alembic for an exact replacement, even if it's kind of expensive. You could put in a regular old DiMarzio pot in a pinch, but it might not fit in the space of your OEM pot and you may have trouble fitting the knob on too.
I wouldn't blast contact cleaner in there if you have a rectangular pot. The oil in there might eat up the conductive element. You may find a blast of compressed air down the shaft (even from one of those air duster cans) might help, but if it doesn't work, just replace the pot.
David Fung
