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Floppy Drive Alignment disk info.. maybe this can become an FAQ on this subject.

I

inotarobot

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Hi all,

Just reading another post here on a user with a Hard Sectored Drive that he is not sure is faulty or if its the floppy medium he has available, I recalled I have both 8", 5 1/4" and I thing also 3.5" Alignment floppies by Dysan.

I can only ever recall using them on soft sectored drives so I stared to search. I found a few articles and some old VCFED post so though I capture them here.

And see what original posters can comment plus maybe other can add.

so onward
 
http://www.vcfed.org/forum/showthread.php?18361-Copy-or-Create-Dysan-224-2A-Alignment-Disc/page2

From Dwight Elvey's post 4th Dec 2009.

Hi
Making an alignment disk is tricky but not entirely rocket science. There are
basically two types of track aligners. One is difficult to make while the
other is a lot simpler.
One requires an exact frequncy source that can produce a 1 MHz and a
999995 MHz ( for 300 rpm ) signals. This is generally beyond most
peoples capabilities. Also, you need to disable the tunnel erase
going the the head during writes. The rest is straight forward similar
to the method below.
The other is to be able to create a burst of constant data ( all 0's are fine )
at a specific delay around the disk. A sector length is fine.
This is more within our abilities.
The next is the ability to see the data on a disk. I suspect the stuff
they use at machine shops would work that is used to detect cracks
with a process called magna flux.
This would allow one to measure the exact track center as written.
( You might need to toss the disk after each measurement but we
are mostly just getting the head location exact. After that, a micrometer
on the head is enough ).
The next step is to be able to write slightly offset tracks. A micrometer
dial connected to a SA400 frame would work well here.
The idea is to put burst of data sequentially at different radial distances.
Two sequentially inside, two on either side and two more squentially.
This is a more trivial method that works just as well and is within
a reasonable home done setup.
Dwight
 
http://www.vcfed.org/forum/showthread.php?18361-Copy-or-Create-Dysan-224-2A-Alignment-Disc/page2

CHUCK wrote

We wrote our own alignment diskettes using a floppy drive whose stepper motor was gutted and simply used as a bearing. A shaft coupler was attached to the end of the leadscrew (where the stepper innards were) and attached to a 100:1 precision reduction train. The result was driven with a regular stepper--100 steps to the track. We used a precision position encoder attached to the head carriage itself. The whole mess was mounted on a 3/4" thick slab of aluminum.

We checked out both leadscrew and taut-band positioner drives and found generally, that the leadscrew positioners had far better repeatability than the taut-band models.

I saw a similar setup at the Tandon R&D lab, except that their positioner was gas-driven (from a tank of nitrogen) and the encoder was a laser model and this was mounted on a granite surface plate. They used this setup to write servo tracks for some of their hard disks.

As far as viewing magnetic tracks, the old standard used to be Magnasee or Visomag, but the CFC ban knocked those out of the market. I still have most of a carton of KyRead but there are other brands available, apparently.
 
http://www.vcfed.org/forum/showthrea...ent-Disc/page2

Nige the hippy wrote

The other alternative is to microstep the stepper motor (once it's set to the correct position), and always drive it in one direction (to eliminate positioning errors) before writing the alignment bursts, it wouldn't be an impossible task to write a bit of PIC/AVR code to generate a burst of 1mhz set distances after the index hole, and move the head across the track.
I built some boards at the last place I worked, with a microstepping driver, an AVR microcontroller some spare I/O a keypad & display, I wonder if there's any still around.
"Don't it always seem to go

with
CHUCKS reply

I don't know if the mechanical characteristics of the old 5.25" and 8" drives would be amenable to effective microstepping. There's usually quite a bit of mass attached these old things with various variable frictional aspects (e.g. the head contacting a rotating disk) that could really foul things up.

I think it'd work okay with 3.5" drives, however.

But it might be worth a try.

I could probably write 5.25" alignment diskettes right now if I wanted to engage in some microcontroller programming. I've got a couple of old Drivetec/Kodak (2 and 5 MB) floppy drives. These used factory-formatted embedded servo floppies, but their positioners would be perfect--there's a "coarse" stepper and a "fine" stepper that works off a lever arm. And the thing is 192 tpi to boot, so it writes a very narrow track.

BTW, these were the drives used on the Kaypro "Robie". Perhaps someone with one of these and a bigger interest than I (I have alignment floppies) in creating alignment diskettes might want to investigate.
 
Looking more at that Dec 2009 post called Copy or Create Dysan 224/2a Alignment Disk

maybe I should have just posted to end of it, or at least created this post in that same Forum section.

Can a Moderator advise please ?

maybe even more this post to Forum-Tech Support- Vintage Computer Hardware
 
I'll add one more thing to this pile.

It's been my experience that if you're interested in reading old floppies that the best approach is to have several drives misaligned by a half-track's width. I still get a fair number of floppies in that can't be read in a perfectly-aligned drive, but read just fine in a mis-aligned drive.

Fortunately, the old digital alignment floppies could tell you how far you were off from track center.
 
Chuck(G) said:
I'll add one more thing to this pile.

It's been my experience that if you're interested in reading old floppies that the best approach is to have several drives misaligned by a half-track's width. I still get a fair number of floppies in that can't be read in a perfectly-aligned drive, but read just fine in a mis-aligned drive.

Fortunately, the old digital alignment floppies could tell you how far you were off from track center.
Click to expand...

Are those special alignment disks any more more reliable then a regular floppy? I've been in the middle of aligning a drive only to have the 'good formatted' disk start to fail (and not initially caught that it was a disk issue vs the drive) so i just wonder if we acquired or made alignment disks, if it's a losing proposition these days since we're at the very end of most of these floppy disk lifespans? (forgive my ignorance on the topic since i've never actually seen an official alignment disk)
 
Well, they're engineered to be measurable in the case of digital alignment disks and symmetrical in the case of analog ones. Usually, you can get to within a mil or less of spec on a typical 5.25" drive. I've honestly never tried using a regular floppy as a standard, but I suppose it could work.
 
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