Can this linear servo operate connected directly into the RoboRio, or do we need a servo controller for it? I ask because we don’t have a servo controller, and the actuator has never worked. I posted my code here multiple times and no one found an issue with it, so I’m trying to figure out what else the problem could be.
You probably need something like the Rev Servo Power Module to source enough current for it.
The maximum power output of this device is 50N at 16mm/s, which works out to 800mW.
The maximum current provided by the 6V rail on the RIO is 2.2A, which is 13.2W.
Unless the efficiency is really bad or you have several servos running simultaneously, you should have enough power from the RIO, and definitely should be able to operate it in no-load conditions. However, I would still prefer to use a Rev power module as @solomondg suggests, especially as the 6V servo power rail is the first thing to drop in brownout conditions.
Have you checked that you actually have 6V on the center pin of your PWMs with a voltmeter? Not having this would not affect motor controller operation, only servos. If this is your problem, using the Rev module would be a valid workaround until you can get the RIO repaired.
Also, make sure you look at the documentation for those servos. They have a large deadband you need to set the bounds for, and for java and c++ they respond properly to the setSpeed method, not the regular set method for some reason.