Similar issue, but I know its the actual control slider that is faulty, I tried a replacement second hand one but that had the same problem. Have rigged it up now so it runs off a switch at %50 all the time, was thinking of just wiring in a seperate resistor slider (potentiometer basically) on the control wire, however Im not sure what resistance range it should be, 10kohm, 50kohm? Any ideas? Can get them on ebay for about a fiver
Andrew, February 2013