On Thu, 3 Oct 2024, Jon Elson via cctalk wrote:
Yes, and in a pinch I have done that. What you want is to hack the format
program so you can write just ONE track. Bulk erase the floppy and then
format just one track. Put a scope on the analog read amp signal and see if
it looks good. Then, loosen the screws on the stepper motor and turn the
motor to maximize the signal. Other drives with square motors require some
tweaking of the coupling between motor and linear rollator.
Trivial enhancements:
"Teaching grandma to suck eggs":
use DOS, not Windows 11.
Do a very thorough bulk erase.
And then use a 96tpi drive to write to it,
even if the target drive to be aligned is 48tpi.
That will give you a narrower track, centered on where the wide track
would have been.
On a PC, rather than trying to make sense out of Microsoft's FORMAT
program to modify it, it is not hard to go to Int13h and give it a format
command. With NEC type of controller, you will need to set up a buffer
containing a list of the sector header contents that you want.
(with WD controllers, you create a track image and do a "WRITE TRACK")
If the target drive to be aligned is 48tpi, and you use a 96tpi drive to
make the test disk, use a "360K" or "720K 5.25" disk, NOT a "1.2M" drive,
and remember that if you are going to write sector headers, to double the
cylinder number.
If you use a "1.2M" drive, be sure to set the motor speed to 300RPM, not
360 RPM and write at 250K bits per second,
OR, with the motor speed at 360RPM, write at 300K bits per second.
With analog alignment disks, you want at least a 20MHz scope; my NLS 215
portable scope was not adequate.
--
Grumpy Ol' Fred ci...@xenosoft.com
