George Gibson

ALMOST EVERY RC FLIER knows what a feedback pot is. Some of you may have learned about it the hard way when it was the culprit behind a crash that the best of piloting skills couldn't have prevented. It causes more trouble than any other part of the servo and is one of those supposed necessary evils we'd like to be able to do without. It's that little carbon-coated variable resistor in your servo that has to be taken apart, cleaned, and lubricated every so often. If the maintenance isn't done, the servo arm will eventually become erratic-jiggling, jumping, or trying to run continuously. When that happens you can generally kiss the model good-bye. The feedback potentiometer is used as a continuously-variable voltage divider. A fixed, regulated voltage is applied across the pot, and a wiper is rotated by the servo motor through the reduction gearing. The voltage is divided continuously as the wiper moves, and its amplitude is completely dependent upon the position of the wiper and, therefore, on the position of the output arm.