EX2000 Floppy Drive Tester

On 8/12/2006 at 5:07 PM Dave Dunfield wrote: find Doing a good job on drive alignment generally requires an alignment diskette and a 'scope. However, there were alignment diskettes produced with tracks that were skewed across the width of a track. The idea being that you listed the sectors that could be read and that would tell you approximately how far off alignment you were. Back in the belt-drive DC motor days, things like Instantaneous Speed Variation were important, but you don't see that being tested on the direct-drive models now. Just a simple averaged speed check is adequate on modern drives. Leadscrew positioners (or even the cam-and-follower type in the SA400) sometimes display backlash, which can be checked with an alignment diskette by approaching the same track from the inside and the outside tracks. Taut-band positioners generally don't show much backlash. But in the bad old days, recovery from a data error could took the form of: 1. Re-read in place 3 trimes 2. Recalibrate (seek to track zero), seek to track and re-read 3. Recalibrate, seek past the track and then step backwards and re-read 4. Recalibrate, single-step to the track and re-read. What the first accomplishes is pretty obvious. The second attempts to make sure that the head position hasn't drifted and also tries to knock any schmutz loose from the head. The third attempts to compensate for backlash in the positioner. The fourth tries to anticipate a slugglish positioner mechanism. Cheers, Chuck