Quote Originally Posted by Marm View Post
First time the video worked for me. Sounds like you have the wrong number of steps per revolution set in the code. Find the manufacturer's datasheet on the exact motor you have, and then enter the the number of steps into the appropriate place in the code. I've had similar problems when working with Arduino and other steppers. If you need help locating the commands, Try the RAMPS site (or maybe some one here would know), or goto arduino.cc and check their examples. I can't imagine they'd be using an exotic stepper library to control the motor, so the exact how to on how to operate the motor's can be found there. I'm also assuming you have access to the source code and the Arduino IDE. If you don't, I'd imagine it'd be a very good idea to get it (it's free).

EDIT, Reread the OP. Probably not the steps per, as it worked before. I'd pull the motor out of the enclosure, and try to get it to run on it's on. Again, if you have an extra arduino board (why mess with the Mega in the printer, any arduino will work), Use one of the example steppers sketches and try to get it to turn on it's on, without anything on the axle. If it works, slowly add parts to it till if fails. You could have a bad bearing or something in the system.
Yes, there are some pins for plugging jumper caps under stepper driver on mainboard. Did plug the jumper caps correctly according to the building instruction?