RK06 alignment pack

[Writing alignment disks] I have an idea that some of these units used an optical interferometer to determine the head position They normally have eccentric tracks so that the signal amplitude varies as the disk turns. Look at that on a 'scope and adjust for the right bits being the same amplitude and you're on-track. While the servo surface can't be re-written in the field (that is what determines head positions, after all), I see no reason why the data surfaces can't be reformatted on a drive which has a separate servo surface like the RK06/07 On such drives 'head alignment' really means getting the data heads lined up with (or the right offset from) the servo head. Incidentally, I once saw a procedure (maybe HP) for rewriting the servo surface of a fixed/removeable drive in the field. It used special electronics, but not any special mechanics. It went like this : Mount a good removeable pack Use the servo surface of that to position the heads (all of them) Step a track at a time, maybe with deliberate offsets (can be done) and write to the servo surface in the fixed disk stack Now use the rewriten fixed servo surface to position the heads and reformat the fixed disk data surfaces. -tony Johnny