<"But 3.5" diskette drives are too difficult to modify. We've had good <read and write results by passing the index signal through a 1-shot <carefully adjusted to trigger slightly ahead of the actual index <position. But this is a very touchy arrangement, though it does work. < <I know that I have experienced the problem of the first paragraph on more <than the C10 disks. < - don Some formats produced with 1771 or 179x can be nasty. The fix is to delay the index using two oneshots one set long (95% or a rotation) and the second long enough to provide a recognizable pulse. This trick can permit you to "move" the index sensor as needed electronically. Allison