You are experiencing electrical noise from the motor affecting your servo. It IS NOT the servo gears.
Check the pcb as Barnyard says, also clean the contacts on the pcb and to it with some motor cleaner on a cotton bud, skim and re-brush the motor, also clean out the slots between the comm segments.
The motor brush shunts carry some current, but not all of it, some is conducted through the brush holder (tube) directly to the brush.
The snapped (or partially snapped) brush shunt has not sent electricity through the chassis to the servo.
It's a dirty motor causing this, nothing else. As long as there is copper left on the comm it is fixable and not bin fodder.
G
|