I have a Fanuc P-50iA robot that J4 will not respond.
When you jog J4 in joint, J5 moves. All axis move correctly except J4. J5 moves correctly jogged in joint. We unmounted the J4 motor to see if it would turn, ruling out a gearing issue, it does not respond during the joint jog. Like it's not being called for. We get 65v on the servo board J4 connector when jogged but J5 still moves. Any ideas would be appreciated.
Note: As a check, we installed a new servo amplifier assembly and had the same result.