Old AM servos on new FM Radios
The old servos did center with a narrower pulse width. usually this is not a problem with using the 1.5 millisecond pulse width now used by most manufacturers. If it is it will be noticable at full travel in one direction or the other due to the internal pot hitting its end point. If you open up the servo, you can usually reposition the pot so that it accomodates the 1.5 millisecond pulse and has equal travel in both directions. I have never had to do this on any I converted but some were close to hitting the end points on the internal pots.