Looking to add “modern” nc to my old tape turn. It does not have any no on it now. The servos run by some hand dials that have either a tach or resolver on them that go back to the amplifiers. These dials also have motors on them that run by using the joystick. I want to replace the amps with ones that have step / direction input. The lathe also has resolvers / encoders that are gear driven off the lead screw pulleys. So the questions I have are:

1) what voltage would these servos run at? The nameplates are wore off so I can tell but suspect 90V or 110V maybe??? The amps run off of 110V

2) where to fit new encoders? It will be a lot easier to replace the resolvers that are driven by the lead screw pulley, but that gear seems to be about 3:2 ratio to the motor. Plus there is a bit of lash between the gears which I suspect would result in some jitter. The tach on the back of the motor doesn’t have a shaft sticking out that I can attach to. I suppose I could remove the tach brush holders and see about fixing an encoder in its place. Is it feasible to run the encoder on a driven gear rather than the motor shaft?