I worked on a 490 that had a seized-up gripper trunnion assembly. It put the motor into a bind which eventually took out the regulator transistor bolted to the side of the power supply box (mounted in a heat sink). Once I freed up the gripper linkage and oiled the heck out of it with 20 weight motor oil, the mechanism worked smoothly. Of course I ended up replacing the regulator transistor twice though. The first regulator transistor, an NTE replacement, turned out to be bad right out of the package. I bought an original numbered replacement instead and it worked fine.