Corotor II servo alignment

[pacificrim]

I just got a used Corotor II and hooked it up on the bench with my ASC 1. When turned to Horizontal it lines up to a probe support, but at Vertical it is off by about 10 degrees. When it stops a little short the servo motor continues for a brief moment even though the probe has stopped. That is probably the distance that is missing. I can then advance the probe with the ASC1 and it looks right at about 55 degrees.

I plan to replace the servo but want to make sure that there is nothing else to consider.

 

[Cham]

Make sure the probe is free to turn and not binding through about half a turn. Did you remove the servo and check it's operation when not turning the probe? Does sound like a bad servo though.

 

[pacificrim]

Thanks for the reply. I took the servo off it and the probe is free moving and the servo acts the same when removed from the Corotor where it stops and has a very brief rumble after. I guess when the new one comes that should fix it.

 

[Cham]

There's a potentiometer that controls the position of the unit, often these get worn and dirty, and the resistance becomes inconsistant throughout travel. This often causes the "rumble" as the stepper motor gets pulses from both directions and is hunting for a posotion that keeps changing. I've temporarily fixed them by taking the servo apart and blasting the potentiomenter with contact cleaner. It's only a stop-gap measure though that keeps the unit going until a new one arrives.

 

[pacificrim]

There's a potentiometer that controls the position of the unit, often these get worn and dirty, and the resistance becomes inconsistant throughout travel. This often causes the "rumble" as the stepper motor gets pulses from both directions and is hunting for a posotion that keeps changing. I've temporarily fixed them by taking the servo apart and blasting the potentiomenter with contact cleaner. It's only a stop-gap measure though that keeps the unit going until a new one arrives.

Thanks for the tip. I'll give it a try as the new one inches its way through the mail.