A few years ago I bought one of these off eBay. I dusted it off recently and noticed 4 of the circular knobs on the right were erratic - when moved would constantly fluctuate and not settle at one value. I could tell this because the led display which shows a value between 0 and 127 goes crazy when I move theses knobs from zero. To to use it I have to leave these knobs at zero and not use them at all. I was wondering if anyone with electronics knowledge out there would know how to go about fixing these four faulty knobs?