I got a couple of used servos at an auction, IS there a good way to test the servos, and if so what to test for? I assume to plug it in, put some load on it and make sure it does not slip, make sure that it centers correctly all the time?

Thanks

Jon

That sounds pretty good to me

I always look to see if they come back to the same center from both directions

I also listen for humming noise

That they don't hunt for the position

That they move normally without jumping

http://www.york-electronics.com/ works well to exercise servos for testing. You'll want to see how well they center and check for damaged gears. These can usually be felt but opening it up is the best way to check gears.

One way to check your servos quickly is to place a resistive load on the control surface...

e.g. you push back with your hand... against the surface movement to a small degree while moving the surface.

As you move the surface while resisting it's motion, look for any movement which is dissimiliar or causes the surfaces to act in a racheting manner. This represents a broken or worn gear on the servo or a problem with the sensor.

It's not an all encompassing test, as the device which Bruce listed, but it sure beats not testing.