Unhappy with the 120 degree range of movement for this digital servo motor [Malte] set out to expand its flexibility. He settled upon a hack that alters the feedback potentiometer in order to give the motor a wider range (translated).
The test video (embedded after the break) shows tick marks for before and after his alterations. You can see that the wider tick marks get much closer to the 180 degree range he’s interested in. The control method is no different than it was before, the internal circuitry is still listening for a control signal with pulses between 1 and 2ms to establish the position of the servo horn. [Malte] added resistors on the two outside legs of the feedback potentiometer. This is what that control circuit measures in order to judge the position of the servo horn. He’s using 1.6k Ohm resistors in this demonstration. But he didn’t just drop them in willy-nilly. His writeup discusses the calculations he used to determine the target voltage for the motor position he wants.