Dec RL01 drive problem

I have an RL01 drive which isn't working correctly. I've opened up the back end of the drive so I can see what is happening and what I see is this. 1. Drive starts to spin up, but it's obvious by looking at the spindle of the drive motor, that the motor never reaches full speed. 2. After about 5 seconds, the drive slows some, and the heads attempt to load. 3. The heads then chatter back and forth. They appear to move in about .25 inches and then retract. 4. This continues until I spin down the drive. If I pull the pack out, and hold the switches closed manually, the motor does reach full speed (although the heads never attempt to load). If anyone has any suggestions as to what might be the problem, I really apprecite some information. Thanks, Bill King