Having just adapted a PC power supply to run my Apple, I decided to play Moon Patrol. I had inadvertently let one of my drives fall about 3 cm, but I thought that wasn't enough to ruin my drive. Apparently it was, because it cannot now read disks. Sometimes, the stepper motor doesn't even step. In such cases, it will only move at all in phase 2; when the phase 2 signal is removed, the motor just returns to its previous position.