Hi, i recently got back with my 80s apple iie. It has a duodisk drive that i cleaned and speed calibrated and it works with most disks. I also had an empty NOS box of 2HD diskettes. I notice that they dont format. I read in here that HD disks are unreliable. Should they not work at all? as that is the case on my duodisk. Or is there something else calibration wise that should be done to the duo disk? I wanted to know if this HD issue is as binary as i see it on my unit. thanks
Perhaps someone here understands the entire physics behind this, but what I do know if that the HD disks have a thinner magnetic coating and smaller particle size so they are much better for higher density recording. Unfortunatly, these factors also make for a lower read signal and that coupled with a lower write current on the older 2D drives can cause inconsistencies in reading and writing HD disks in 2D hardware. So if you are trying to use HD disks with 2D hardware, you will always have issues. If you are using 2D disks in HD hardware, most disk drives can read/write the lower density media. HD disks are no more unreliable than 2D disks. It all has to do with the quality of the coating used when this disk was made.
Like I said others can probobly speak more to the actual physics of the media. For exmaple how many Oersteds/unit of measure etc..
ok, so this is expected behavior...i get the unreliable piece. But is it a full "don't work at all" or is it just for my drive that don't work at all?
Also does anyone knows where to get replacement belts for the duodisk?
Double Density floppy disks ALWAYS have a hub ring, giving it a slightly thicker hub, High Density floppy disks NEVER have a hub ring, zero, zip, nada, yielding a much thinner hub the same thickness as the rest of the disk. Because of this, the Apple Disk ][ or DuoDisk drive hubs cannot hold on to the HD disks as well to spin them properly.
That explains speed changes during the calibration process when you have a DD vs an HD disk inserted
Don't use 5.25" HD unless you can be very tolerant of failure. I had some on hand and thought, why not give it a try. My experience was the HD diskettes fail quickly and often with read failures. The same diskettes were reliable in a DOS PC.
Surely someone can figure out a quick-fix for "adding" a thin annular hub ring to HD diskettes akin to the DD disk hubs so they don't "slip" while spinning causing those errors.
The DD hub ring thickness measures .0085". Couldn't find my HD diskettes to measure their hub thickness.
But you know, DOS 3.2 had distribution disks with no hubs (or at least I have some for some reason that worked in Disk ][ drives maybe).
Don't bother with the 2HD disks. The magnetic coercivity is different from regular DS/DD & SS/DD. 2HD requires a more focused and more intense write signal.
Thanks Keatah - That's what I was trying to explain in my post above. Even if you affix a hub ring to the disk, the magnetic properties are such that it will be unreliable. This is the same if you have a 360K only 5.25" floppy in a PC and try to use an HD disk in it. It may work, it may not work, or it will not work for long. Just not good practice. The 3.5" diskettes are a little different and the magnetic properties between the 1.0MB and 2.0MB diskettes are much more tollerant. (You still need to poke an extra hole in the 1.0mb disks to make them 2.0mb. You can still get DSDD diskettes on ebay that are new in box. Not to say they haven't degraded, but if you pick a good brand like 3M or Sony I have had pretty good luck with them.
If you are looking for replacement belts, the duo uses Alps drive chassis. Even though This belt is labeled as for commodore 1541s, as far as I can tell from looking at my 1541 and my Apple drives with Alps mechanisms, they are the same as far as the motor and spindle go. So this belt should work. But I've never tried or measured one to confirm.
Thanks, for the link, i also found on the same site this rubber version of it which is $4.95 vs $12.95 for the fabric reinforced version. Not to be cheap :) but any thoughts on that?
The rubber degrades faster, even without use, stretches faster with use and varies more in temperature variations. For only $8 difference, I'd go with fabric and be done forever.