9 Feb
2009
9 Feb
'09
4:13 p.m.
I've been reading the now increasingly mistitled thread on alignment disks, and
it's gotten me thinking. What IS required to make alignment disks? I've always
aligned malfunctioning floppy drives "the wrong way", using a known good disk -
or an original software disk. On the Commodore 64 (and most systems, really), you can get
the drives working well enough like this, but as others have pointed out, it's not the
"right way". I just don't have any alignment disks. "Good enough"
is much better than "not at all", and I don't mess with the drive alignment
unless I have to. I'd love to be able to align drives properly though. And that
requires an alignment disk.
There are different kinds of alignment disks too - analog and digital, ones that are
intended to be used with a special program on a particular computer, and those intended to
be used with a scope.
With today's modern machining technology, it should definitely be possible to create a
system to write new alignment disks. Starting with a standard floppy drive, you could
replace the stepper drive with something more precise and controllable. Then, you have to
somehow accurately calibrate this whole thing. Is there a document out there that
describes the track layout of a standard (say, 5 1/4" 48tpi, 40 track) diskette?
There has to be a spec, one that describes exactly the distance between tracks, the width
of a track, and the distance from the center hub to the beginning of the first track. If
you had that information, and precision measurement tools, one could set up and calibrate
the drive to spec.
Then, of course, there needs to be a controller for the thing, a computer interface to
control the precise positioning of the head, as well as being able to read/write to the
disk.
It's possible. It's beyond the equipment and tools at my disposal, but it's
definitely doable for a hobbyist who has access to a machine shop and good tools.
Anyone out there a machinist? :)
-Ian
9 Feb
9 Feb
4:28 p.m.
That's part of my questions too,
as time goes on, these disks we have *will* eventually fail. the magnetic flux will waver,
and data will be lost,
they'll no longer be useful for alignment. and the longer time passes, the worse it
gets, same too with the drives.
that's part of what I was saying, for current conditions, "good enough"
might be all we have, it's better than nothing.
and as time goes on, we may be stuck with it.
I'm curious if anyone out there would spend the time/money/effort to recreate these
things properly, over time.
and then, what do you do in one generation? or two? one is bad enough, none of us are
getting any younger.
I'm reminded of that question someone posted, about putting a computer and software in
a time capsule, to be reopened in 50 years.
turned out to be totally impractical (as the components wouldn't last).
do we just preserve the software in some sort of digital format, and 'hope' that
someone carries it on?
at least in digital form, we can transfer it from media to media every few years and hope
to keep it viable.
that's one reason I'm digitizing all the software I have, I have rare stuff that
will cease to exist if I don't.
Dan.
Date: Mon, 9 Feb 2009 13:13:51 -0800
From: ian_primus at yahoo.com
To: cctalk at classiccmp.org
Subject: Alignment disks, and the creation thereof
I've been reading the now increasingly mistitled thread on alignment disks, and
it's gotten me thinking. What IS required to make alignment disks? I've always
aligned malfunctioning floppy drives "the wrong way", using a known good disk -
or an original software disk. On the Commodore 64 (and most systems, really), you can get
the drives working well enough like this, but as others have pointed out, it's not the
"right way". I just don't have any alignment disks. "Good enough"
is much better than "not at all", and I don't mess with the drive alignment
unless I have to. I'd love to be able to align drives properly though. And that
requires an alignment disk.
There are different kinds of alignment disks too - analog and digital, ones that are
intended to be used with a special program on a particular computer, and those intended to
be used with a scope.
With today's modern machining technology, it should definitely be possible to create
a system to write new alignment disks. Starting with a standard floppy drive, you could
replace the stepper drive with something more precise and controllable. Then, you have to
somehow accurately calibrate this whole thing. Is there a document out there that
describes the track layout of a standard (say, 5 1/4" 48tpi, 40 track) diskette?
There has to be a spec, one that describes exactly the distance between tracks, the width
of a track, and the distance from the center hub to the beginning of the first track. If
you had that information, and precision measurement tools, one could set up and calibrate
the drive to spec.
Then, of course, there needs to be a controller for the thing, a computer interface to
control the precise positioning of the head, as well as being able to read/write to the
disk.
It's possible. It's beyond the equipment and tools at my disposal, but it's
definitely doable for a hobbyist who has access to a machine shop and good tools.
Anyone out there a machinist? :)
-Ian
_________________________________________________________________
The new Windows Live Messenger. You don?t want to miss this.
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5:09 p.m.
On Tue, 10 Feb 2009, Tony Duell wrote:
print it out, and then OCR it?
that's one
reason I'm digitizing all the software I have=2C I have rare stu=
ff that will cease to exist if I don't.
I find that a very curious statement. Surely software is digital to begin
with, so how do you 'digitise' it? 
9 Feb
9 Feb
5:06 p.m.
Mr Ian Primus wrote:
With today's modern machining technology, it
should definitely be possible
to create a system to write new alignment disks.
The question that popped into my head was "how long will floppies last?" -
there's no point creating alignment disks if the existing media's all failed
and there's no new stock being produced. I'm not sure how much life floppies
have left in them - 10 years? 30? 100?
The time might be better spent producing drop-in replacements for entire
floppy disk units. It'll be sad when big ol' 8" and 5.25" drives truly
are
obsolete, but I suppose that day will come sooner or later.
I think I'll miss the death-rattle of encountering a bad disk block, or even
the grinding/squealing noise as the surface of a disk falls off and demolishes
the drive head. Any magical "solid state" replacement should really include
audio output and the ability to randomly lose bits of your data... :-)
5:22 p.m.
On Mon, 9 Feb 2009, Jules Richardson wrote:
The question that popped into my head was "how
long will floppies last?" -
there's no point creating alignment disks if the existing media's all failed
and there's no new stock being produced. I'm not sure how much life floppies
have left in them - 10 years? 30? 100?
Just so long as I have READ capability until the last media is dead and
gone.
I think I'll miss the death-rattle of encountering
a bad disk block, or even
the grinding/squealing noise as the surface of a disk falls off and demolishes
the drive head. Any magical "solid state" replacement should really include
audio output and the ability to randomly lose bits of your data... :-)
Ah HA!
THAT is what is missing from simulation!
5:34 p.m.
Fred Cisin wrote:
Well, the weight needs to be right too, so that it hurts appropriately
(according to drive size) when you drop it on your foot ;)
I think
I'll miss the death-rattle of encountering a bad disk block, or even
the grinding/squealing noise as the surface of a disk falls off and demolishes
the drive head. Any magical "solid state" replacement should really include
audio output and the ability to randomly lose bits of your data... :-)
Ah HA!
THAT is what is missing from simulation! 
6:11 p.m.
On Mon, Feb 9, 2009 at 5:34 PM, Jules Richardson
<jules.richardson99 at gmail.com> wrote:
Fortunately, I have yet to drop much of anything vintage on my foot
(but I've gotten plenty of nicks and pinches racking and unracking
disk drives).
For the record, I do *not* want to drop either of my largest two
drives on a foot (DEC RA81 and CDC 9766).
-ethan
Fred Cisin wrote:
>>
>> I think I'll miss the death-rattle of encountering a bad disk block, or
>> even the grinding/squealing noise as the surface of a disk falls off and
>> demolishes the drive head.
Heard that plenty of times. My first head crash was an RK05F. :-(
Ah HA!
THAT is what is missing from simulation!
Well, the weight needs to be right too, so that it hurts appropriately
(according to drive size) when you drop it on your foot ;) 
10 Feb
10 Feb
5:03 p.m.
Fred Cisin wrote:
Actually, WinUAE has a very convincing simulation of what Amiga floppy
drives sound like if you turn it on. It's really cool to hear the drive
noises as you run a game from a floppy disk file...
--
Jim Leonard (trixter at oldskool.org) http://www.oldskool.org/
Help our electronic games project: http://www.mobygames.com/
Or check out some trippy MindCandy at http://www.mindcandydvd.com/
A child borne of the home computer wars: http://trixter.wordpress.com/
I think
I'll miss the death-rattle of encountering a bad disk block, or even
the grinding/squealing noise as the surface of a disk falls off and demolishes
the drive head. Any magical "solid state" replacement should really include
audio output and the ability to randomly lose bits of your data... :-)
Ah HA!
THAT is what is missing from simulation! 
2:54 p.m.
The time might be better spent producing drop-in
replacements for entire
floppy disk units. It'll be sad when big ol' 8" and 5.25" drives truly
are
obsolete, but I suppose that day will come sooner or later.
I suspect that day will come (if ever) when the last floppy disk of that
size is no longer useable, and there is no way to make a replacement. The
drives themselves will be repairable (as I've said before, apart from the
heads, just about any other part can be made or repaired in a good home
workshop).
Aren't there strictly 2 prolems, though. The first is keeping machines
with flopyp drives running, assuming you have the software on something
that's still readable. And for that a solid-state replacement is one
possible answer. I seem to remember reading about some open-source floppy
emulator on the web, the prolem being it only had enough memory for a
single-sided (5.25" or 3.5") disk image. Which somewhat limits the
usefulness.
The second iproblem is that you find a floppy disk in good condition (not
shedding oxide, etc) and you need to read it. To do that you could use an
accurately aligned floppy drive, which means you need the alignment disk.
-tony
9 Feb
9 Feb
5:20 p.m.
On Mon, 9 Feb 2009, Mr Ian Primus wrote:
I've been reading the now increasingly mistitled
thread on alignment
disks, and it's gotten me thinking. What IS required to make alignment
disks? I've always aligned malfunctioning floppy drives "the wrong way",
using a known good disk - or an original software disk. On the Commodore
It may well be adequate for you.
But, . . . I PRODUCE "original software disks", although admittedly WAY
less than 20 years ago. If you end up "aligning" a drive for best
readability using one of MY distribution disks (or even one of
MICROS~1's), then we end up with a RESPONSIBILITY (could prob'ly get
sued!) to make sure that they are properly/well aligned, not merely "good
enough to work in a "known good" drive" (which might be FINE for your
use).
Yikes! People "aligning" drives to match MY drives??!?
With today's modern machining technology, it
should definitely be
possible to create a system to write new alignment disks. Starting with
a standard floppy drive, you could replace the stepper drive with
something more precise and controllable. Then, you have to somehow
accurately calibrate this whole thing. Is there a document out there
that describes the track layout of a standard (say, 5 1/4" 48tpi, 40
track) diskette? There has to be a spec, one that describes exactly the
distance between tracks, the width of a track, and the distance from the
center hub to the beginning of the first track. If you had that
information, and precision measurement tools, one could set up and
calibrate the drive to spec.
Yes, the specs are readily available.
It would not be a major feat of prototyping to build a drive that MAKES
alignment diskettes.
For RADIAL alignment, even I (grossly, totally incompetent as a machinist)
could create a CRUDE digital alignment disk with specs and Harbor Freight
tools!:
Take a drive with a narrow head (96TPI or 100TPI), (The Micropolis lead
screw, if not too worn (lash!), seems ideal),
align it, ACCURATELY!
add a dial indicator for more precision, maybe improve the clamping,
maybe change the tunnel erase?
record a few tracks at 48TPI,
Record a track very slightly further out than spec,
(you can manually rotate the lead screw a fixed amount)
record the next track very slightly further IN than spec,
record the next track further out from spec,
the next one further in than spec, etc.
Read some tracks.
Do you get more errors on odd numbered or even numbered tracks?
Then, of course, there needs to be a controller for
the thing, a
computer interface to control the precise positioning of the head, as
well as being able to read/write to the disk.
You can make a stand-alone controller for the task - called a "drive
exercisor" or "exOrcisor"
Or, use a PC. Trivial software to convert a PC into a drive exercisor.
It's possible. It's beyond the equipment and
tools at my disposal, but
it's definitely doable for a hobbyist who has access to a machine shop
and good tools.
It actually wouldn't take much (see above).
Anyone out there a machinist? :)
Although he
won't admit to it, Tony is a better machinist than some
professionals that I have dealt with (I ended up doing my own valve seat
grinding, but sent out flywheel resurfacing, crank balancing, etc.)
It might be worthwhile to give Tony a 100TPI drive, and get him to make
some alignment disks.
--
Grumpy Ol' Fred cisin at xenosoft.com
6:33 p.m.
cctalk-bounces at classiccmp.org wrote:
Take a drive with a narrow head (96TPI or 100TPI),
(The
Never having build a drive from rocks isn't going to stop me
from speculating.
Given that there must be engineering drawings around and so on
(and assuming that appropriate permissions - if any - are obtained
to replicate such drives), I assumed that a well equipped hobbyist
could put together the mechanical aspects of a drive. (Alternatively,
throw an appropriate sum towards a machine shop).
I'm also assuming that some parts are likely to still be available:
you don't need an original motor - just one with the right
characteristics (or which can be modified).
But what about specialist parts that are likely to be unique
to a drive? Once all the existing drive heads are dead, how
difficult would it be to produce a suitable head for a 8" drive
or a 5.25" drive or a 3.5" drive?
BTW: I'm also assuming that if you can get a working drive built
then you can also fairly easily modify it to write off-track
at will in a deterministic way ... just a simple matter of
tolerances, no?
Are there any other parts (other than the head) which would be
difficult to fabricate from scratch?
Antonio
7:25 p.m.
--- On Mon, 2/9/09, arcarlini at iee.org <arcarlini at iee.org> wrote:
But what about specialist parts that are likely to be
unique
to a drive? Once all the existing drive heads are dead, how
difficult would it be to produce a suitable head for a
8" drive
or a 5.25" drive or a 3.5" drive?
There's not much point in building a device to write alignment disks if all existing
disk drives (i.e. what we're going to be aligning) are gone.
I've heard this doom and gloom talk about "when all the drives are dead" and
"when nothing is left to read $MEDIA" - and while I admit that these things are
likely to happen eventually, I also don't believe it's a problem for any of us.
Working examples of common microcomputer hardware is everywhere. The trick is to maintain
it. I don't see any problem in keeping an Apple IIe in operational condition so that
it will still work in the year 2050.
And, it's not like this stuff goes away completely. Spring-driven phonographs are
still around. Wire recorders are still around. And floppy drives will still be around in
20 years. And yes, media will age - but a lot of it should still be readable, and Athana
still makes floppy disks to this day. You can get new media now. I have disks from the
70's that still work fine.
But, we're drifting off-topic again. The question is really "Can a hobbyist, with
modern technology, build a device to write new alignmnent disks?". I definitely think
so. Such a device would definitely be a mix of new and old parts. I mean, why reinvent the
disk drive? The basic disk motor, heads, frame, etc. should be fine.
The only thing I think that could use an upgrade would be the positioner. Voice coil
positioning isn't really what we want here. The only thing we care about is precision,
not speed. A stepper would work, just maybe one that's more precise than the one in
the drive - or perhaps one that's gear reduced. A leadscrew based drive might be a
good candidate, with some kind of precision servo on it. It doesn't matter how fast it
is, just as long as it's accurate. Who cares if it takes ten minutes to write an
alignment disk?
This old equipment can be kept functioning for a very long time - provided that it's
maintained. And part of maintaining it is keeping it in good alignment.
-Ian
7:40 p.m.
On Mon, 9 Feb 2009, Mr Ian Primus wrote:
But, we're drifting off-topic again. The question
is really "Can a
hobbyist, with modern technology, build a device to write new alignmnent
disks?". I definitely think so. Such a device would definitely be a mix
of new and old parts. I mean, why reinvent the disk drive? The basic
disk motor, heads, frame, etc. should be fine.
The only thing I think that could use an upgrade would be the
positioner. Voice coil positioning isn't really what we want here. The
only thing we care about is precision, not speed. A stepper would work,
just maybe one that's more precise than the one in the drive - or
perhaps one that's gear reduced. A leadscrew based drive might be a good
candidate, with some kind of precision servo on it. It doesn't matter
how fast it is, just as long as it's accurate. Who cares if it takes ten
minutes to write an alignment disk?
~30 years ago, I took an SA400, added an additional tiny pointer and made
labelled calibration marks alongside the spiral groove. It was CERTAINLY
useless for alignment, but it worked GREAT for introducing an OS class to
the basics of what a drive did. "watch as it goes to track 0 to read the
boot sector." "Notice the return to the directory track after it writes
the data." I had a few students who couldn't understand the fundamental
problems with SMARTDRV, including re-arranged write sequence, until I went
through the process a few times, and then said, "What happens if the power
goes away NOW?"
The drive is long gone, but I occsaionally [not recently] stumble across
some of my extra SA400 groove disks.
--
Grumpy Ol' Fred cisin at xenosoft.com
8:06 p.m.
Mr Ian Primus wrote:
I've heard this doom and gloom talk about
"when all the drives are dead"
and "when nothing is left to read $MEDIA" - and while I admit that these
things are likely to happen eventually, I also don't believe it's a problem
for any of us.
I admit I do tend to be interested in trying to preserve things for longer
than my own lifespan :-)
Working examples of common microcomputer hardware is
everywhere. The trick
is to maintain it. I don't see any problem in keeping an Apple IIe in
operational condition so that it will still work in the year 2050.
But how do you "maintain" floppy media?
Sure, the machines can be kept going - replacing a chip here and there, or
when supplies of those chips have gone, by simulating the device's function in
whatever logic is flavour of the period.
But it seems apparent that floppies fail - either through wear or natural
deterioration. You could simulate the drive and media (as I mentioned), but
then it's not "floppy disk" any more.
I don't think anyone's going to invest the time and money needed to truly
preserve floppies intact; that sounds like a lot of expensive analysis into
why binders fail, and a lot of expensive research to then fix the problem - a
problem that almost nobody in the commercial arena cares about.
I suppose someone might magic up a way of creating DIY floppies from scratch
in a home lab, but I'm not holding my breath.
And, it's not like this stuff goes away
completely. Spring-driven
phonographs are still around. Wire recorders are still around. And floppy
drives will still be around in 20 years. And yes, media will age - but a
lot of it should still be readable, and Athana still makes floppy disks to
this day. You can get new media now. I have disks from the 70's that still
work fine.
My *guess* would be that there'll still be a lot of floppies readable in 20
years - maybe somewhere around 50% or 60% of what we have now. But in 50 or
100 years? I think that one day they'll be gone. (note that I'm talking
*using* here - I don't doubt that someone will magic up a no-contact way of
reading floppy contents one day...)
But, we're drifting off-topic again.
We do that a lot :)
The question is really "Can a
hobbyist, with modern technology, build a device to write new alignmnent
disks?". I definitely think so. Such a device would definitely be a mix of
new and old parts. I mean, why reinvent the disk drive? The basic disk
motor, heads, frame, etc. should be fine.
Yep, it could be done. But how rare are alignment disks? I was forever finding
5.25" ones, so there never seemed any particular shortage to me (I gave up
stockpiling, and just kept a couple of them). Other sizes might be different,
but I suspect there are a good number of 8" ones around amongst collectors who
have significant quantities of 8" hardware. Not so sure about 3.5", 3" etc.
though.
8:25 p.m.
Jules Richardson wrote:
But how do you "maintain" floppy media?
Sure, the machines can be kept going - replacing a chip here and
there, or when supplies of those chips have gone, by simulating the
device's function in whatever logic is flavour of the period.
But it seems apparent that floppies fail - either through wear or
natural deterioration. You could simulate the drive and media (as I
mentioned), but then it's not "floppy disk" any more.
I don't think anyone's going to invest the time and money needed to
truly preserve floppies intact; that sounds like a lot of expensive
analysis into why binders fail, and a lot of expensive research to
then fix the problem - a problem that almost nobody in the commercial
arena cares about.
That is already being done for the Commodore 64 with the .G64 file
format which is a GCR encoded 1541 disk image. This copies everything
including the protection. See http://c64preservation.com/ .
Cheers,
Bryan
I suppose someone might magic up a way of creating DIY
floppies from
scratch in a home lab, but I'm not holding my breath.
8:10 p.m.
Back in the day, I had a couple of friends who landed jobs at Jugi
Tandon's little "R&D" operation on Coleman Rd. near the San Jose
Airport. Most of what they did was come in after 10 AM and leave
before 4 PM (with the exception of the receptionist), but there were
one or two interesting things there.
One was some sort of servo writer/calibration rig for hard drives.
Basically a pneumatic piston (powered by a tank of nitrogen) rigged
up with a laser interferometer, all mounted on a 4" thick slab of
granite. I never did get the scoop on what was going on exactly, as
we left for a beer-filled afternoon and the subject never came up.
But heck, an enterprising hobbyist could create his own calibration
writer by salvaging the positioner out of a CD-ROM drive or perhaps
the head and positioner both out of a 5.25" hard drive. Floppy
drives aren't rocket science.
But it's the media that I'm most concerned about. Anyone know where
to get floptical media for my 20 MB Insite drive? Or some 6MB
formatted blanks for my Drivetec? Or some 3.25" media for my Dysan
drives?
Cheers,
Chuck
10 Feb
10 Feb
1:08 a.m.
Mr Ian Primus wrote:
I've heard this doom and gloom talk about
"when all the drives are dead" and "when nothing is left to read
$MEDIA" - and while I admit that these things are likely to happen eventually, I also
don't believe it's a problem for any of us.
Your are wrong. It might be true for the common formats, but there are drives out there
were the number of functioning units is approaching zero.
Try finding an Honeywell-Bull D100 "Cynthia" series cartridge drive or media
for instance...
Jos
6:16 a.m.
Mr Ian Primus wrote:
I've heard this doom and gloom talk about
"when all the drives
are dead" and "when nothing is left to read $MEDIA" - and while I
admit that these things are likely to happen eventually, I also
don't believe it's a problem for any of us.
Agreed. A little care in storage can go a long way as well. I have
original Ohio Scientific 5 1/4" floppies that are now 30 years old
(produced in 1979). They still read just fine. No indication of
oxide loss, binder loss or signal loss. I've owned them since
they were new and they have always been in a moderate to low
humidity, 65-75 degree environment. It won't surprise me to be
able to read them 30 years from now... if I last that long.
9 Feb
9 Feb
9:45 p.m.
On Mon, 9 Feb 2009 arcarlini at iee.org wrote:
Never having build a drive from rocks isn't going
to stop me
from speculating.
old drives are usually cheaper than rocks, and sometimes they don't
require as much machining
Are there any other parts (other than the head) which
would be
difficult to fabricate from scratch?
I have a hard enough time with door pins on TM100 drives. But, it would
seem that the media and heads would be the only part that couldn't be done
in a reasonably well equipped garage.
10 Feb
10 Feb
1:18 a.m.
Hi
I'd say that one should be able to create an alignment
disk. There are twobasic types I've seen. One should be
relatively easy the other is a little tougher.
The tougher one is the analog one where two signals
are recorded right next to each other and one is
1 cycle per revolution different than the other.
This generates the cats eye. The problem making this
type is creating the track width data that over laps.
Most head also have an erase field that would need
to be turned off. This is used to clear any noise
from older misaligned heads.
The next is getting
the overwriting just right
so the center of the signal is exactly on the
alignment track.
The next type is realively easy to create since
it requires little modification other than a method
of moving the head by small amounts.
One records small burst of signal with different
radial distance around the disk. The trick is here
that when looking at the output of the amplifier,
one sees steps up and down if it is aligned well
and just steps up or just down if off. This just
reqires a fine adjustement of the head possition
and a timed control of the write signal. A micrometer
should be enough to measure the position.
The trick is to know when the head is exactly aligned.
I suspect that the best way here is to write a signal
and then use some of the magnetic fluid to locate
the track written. Once the head location is calibrated,
one can use a uP to create the burst.
I'm sure I could create this at home.
Dwight
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1:49 a.m.
dwight elvey wrote:
Hi
I'd say that one should be able to create an alignment
disk. There are twobasic types I've seen. One should be
relatively easy the other is a little tougher.
I'd argue that it is far easier to build a drum data storage device, yet
nobody has done it. "It doesn't seem too hard..." is easy to say until
you try it.
Sure, it is possible, but it is moot if nobody is motivated enough to
actually do it.
3:04 p.m.
Yes, the specs are readily available.
It would not be a major feat of prototyping to build a drive that MAKES
alignment diskettes.
I've though of doing it. Maybe taking a 'spare' 8" drive and replacing
the postiioner with a manually-operated micrometer hrad (it doesn't
matter if I have to position the head by hand for each track, I don;t
need to prodcue alignment disks quickly!).
I am curious as to what the 'real' alignment signals look like. One
reference seemed to impley they were circular tracks not concentric with
the spidnle. Making those would be 'fun'...
You can make a stand-alone controller for the task -
called a "drive
exercisor" or "exOrcisor"
I was given a drive exerciser (darn useful it is too...). It's a simple
microcontrtoller application and a bit of TTL to generate f and 2f write
waveforms (there's no read electornics in the excerciser, you use a
'scope for that).
Alternitvely, some floppy drive service manuals include the schematics
for the manufactuer's exerciser and a suprising number of those are just
TTL chips (nothing programmable/programmed), so something similar could
easily be made.
Or, use a PC. Trivial software to convert a PC into a
drive exercisor.
Sure, ut a lot more bulky (which is an issue when I've got most of a
classic ocmputer all over my workbench!).
It's possible. It's beyond the equipment
and tools at my disposal, but
it's definitely doable for a hobbyist who has access to a machine shop
and good tools.
It actually wouldn't take much (see above).
Anyone out there a machinist? :)
Although
he won't admit to it, Tony is a better machinist than some professionals that I have dealt with (I ended up doing
my own valve seat
That alas, does not suprise me. I really do wish we could get away from
this idea that 'professional' is necessarily better than 'amateur'.
'Professional' means you're paid fro it , 'Amateur' means you do it
because you love it. And the second may well involve more care, more
attention to detail, and a better understanding of the subject than the
former. (Hint : How many computer 'professionals' these days would even
know what an alignment disk was, let alone be considering how to make one)?
-tony
6:10 p.m.
On Tue, 10 Feb 2009, Tony Duell wrote:
You don't also have a few PC's on your bench already?
--
Grumpy Ol' Fred cisin at xenosoft.com
I am curious as to what the 'real' alignment
signals look like. One
reference seemed to impley they were circular tracks not concentric with
the spidnle. Making those would be 'fun'...
The radial alignment tracks on the Dysan digital (according to what
Dysan said when they released it) ARE concentric, but with
individual sectors being out of spec on radius.
For non-concentric circular, couldn't you modify the disk clamping
mechanism to be slightly off of the spindle axis?
Or, use a PC.
Trivial software to convert a PC into a drive exercisor.
Sure, ut a lot more bulky
(which is an issue when I've got most of a
classic ocmputer all over my workbench!).
11 Feb
11 Feb
2:59 p.m.
On Tue, 10 Feb 2009, Tony Duell wrote:
Sure. But I am much more interested in the traditional analogue alignment
disks.
I am curious as to what the 'real'
alignment signals look like. One
reference seemed to impley they were circular tracks not concentric with
the spidnle. Making those would be 'fun'...
The radial alignment tracks on the Dysan digital (according to what
Dysan said when they released it) ARE concentric, but with
individual sectors being out of spec on radius.
For non-concentric circular, couldn't you modify the disk clamping
mechanism to be slightly off of the spindle axis?
The disk clamp isn't the problem, it generally 'floats' in an oversized
hole anyway. You;'d need to make a replacement spindle with the necessary
offset. Not too hard, but not tribial. The problem comes if you want 2
offset tracks say 180 drgrees out of phase (so one is at its innerpost
point when the other is at the outermost point). Aligning the media to
the offset hub accurately to do that would be 'interesting'.
Or, use a
PC. Trivial software to convert a PC into a drive exercisor.
Sure, ut a lot more
bulky (which is an issue when I've got most of a
classic ocmputer all over my workbench!). 
6:27 p.m.
The problem comes if you want 2 offset tracks say 180
drgrees out of phase
(so one is at its innerpost point when the other is at the outermost point).
Aligning the media to the offset hub accurately to do that would
be 'interesting'.
Didn't the Lisa have floppy drives with heads on opposite sides of the
spindle? :-)
--
Member of the toughest, meanest, deadliest, most unrelenting -- and
ablest -- form of life in this section of space, a critter that can
be killed but can't be tamed. --Robert A. Heinlein, "The Puppet Masters"
-
Information is more dangerous than cannon to a society ruled by lies. --James
M Dakin
8:13 p.m.
> The problem comes if you want 2 offset tracks say
180 drgrees out of phase
> (so one is at its innerpost point when the other is at the outermost point).
> Aligning the media to the offset hub accurately to do that would
> be 'interesting'.
On Wed, 11 Feb 2009, Roy J. Tellason wrote:
Didn't the Lisa have floppy drives with heads on
opposite sides of the
spindle? :-)
the "twiggy" drive. Apparently, not all 5.25" diskettes had thumbprints
on the media, so they added an extra access slot where your thumb would go
600 Oerstedt media, 96TPI???
There are 8 possible ways to put a 5.25" diskette into the drive, without
damaging it. Did the Lisa have two sets of heads, or was the extra access
slot there just to double the odds that the position in which it was
inserted would work?
12 Feb
12 Feb
10:59 a.m.
On Wednesday 11 February 2009 08:13:15 pm Fred Cisin wrote:
It's been a while, but my recollection is that they had two heads and each
had a pressure pad on the other side of the disk...
--
Member of the toughest, meanest, deadliest, most unrelenting -- and
ablest -- form of life in this section of space, a critter that can
be killed but can't be tamed. --Robert A. Heinlein, "The Puppet Masters"
-
Information is more dangerous than cannon to a society ruled by lies. --James
M Dakin
> The
problem comes if you want 2 offset tracks say 180 drgrees out of
> phase (so one is at its innerpost point when the other is at the
> outermost point). Aligning the media to the offset hub accurately to do
> that would be 'interesting'.
On Wed, 11 Feb 2009, Roy J. Tellason wrote:
Didn't the Lisa have floppy drives with heads
on opposite sides of the
spindle? :-)
the "twiggy" drive. Apparently, not all 5.25" diskettes had thumbprints
on the media, so they added an extra access slot where your thumb would go
600 Oerstedt media, 96TPI???
There are 8 possible ways to put a 5.25" diskette into the drive, without
damaging it. Did the Lisa have two sets of heads, or was the extra access
slot there just to double the odds that the position in which it was
inserted would work?
3:04 p.m.
The problem comes if you want 2 offset tracks say
180 drgrees out of phase
(so one is at its innerpost point when the other is at the outermost point).
Aligning the media to the offset hub accurately to do that would
be 'interesting'.
Didn't the Lisa have floppy drives with heads on opposite sides of the
spindle? :-)
11:43 p.m.
----------------------------------------
From: ard at p850ug1.demon.co.uk
To: cctalk at classiccmp.org
Date: Thu, 12 Feb 2009 20:04:31 +0000
Subject: Re: Alignment disks, and the creation thereof
YEs, but that wouldn't help. What you need to vary is the angular
position between the media and the offset spindle. Having a second head
180 degrees from the normal one has the same effect as rotating the
spindle _and media toghether_ throuhg 180 degrees.
-tony
Hi
Might it be easier to just turn the hub down by half a track.
When you mount the disk just make sure it is touching the hub.
Dwight
_________________________________________________________________
Windows Live?: Keep your life in sync.
http://windowslive.com/howitworks?ocid=TXT_TAGLM_WL_t1_allup_howitworks_022…
The problem comes if you want 2 offset tracks say
180 drgrees out of phase
(so one is at its innerpost point when the other is at the outermost point).
Aligning the media to the offset hub accurately to do that would
be 'interesting'.
Didn't the Lisa have floppy drives with heads on opposite sides of the
spindle? :-)
11 Feb
11 Feb
1:43 a.m.
You can make a
stand-alone controller for the task - called a "drive
exercisor" or "exOrcisor"
I was given a drive exerciser (darn useful it is too...). It's a simple
microcontrtoller application and a bit of TTL to generate f and 2f write
waveforms (there's no read electornics in the excerciser, you use a
'scope for that).
Alternitvely, some floppy drive service manuals include the schematics
for the manufactuer's exerciser and a suprising number of those are just
TTL chips (nothing programmable/programmed), so something similar could
easily be made. 
9 Feb
9 Feb
6:09 p.m.
Mr Ian Primus wrote:
With today's modern machining technology, it
should definitely be possible
to create a system to write new alignment disks. Starting with a standard
floppy drive, you could replace the stepper drive with something more
precise and controllable.
Like?
A voice-coil actuator /might/ be more accurate than a stepper, but you still
need a servo system to align it. Ladies and gentlemen, meet catch-22: you want
to write the servo tracks, but you need the servo tracks to write the servo
tracks...
Is there a document out there that describes the
track
layout of a standard (say, 5 1/4" 48tpi, 40 track) diskette? There has to
be a spec, one that describes exactly the distance between tracks, the
width of a track, and the distance from the center hub to the beginning of
the first track. If you had that information, and precision measurement
tools, one could set up and calibrate the drive to spec.
<VBG>
8-inch formats: ECMA-58, 59 and 69
5.25-inch formats: ECMA-66, 70, 78 and 99
3.5-inch formats: ECMA-100, 125 and
The FAT filesystem is also standardised -- ECMA-107
All of these wonderful documents are downloadable completely free of charge
from <http://www.ecma-international.org/>
Then, of course, there needs to be a controller for
the thing, a computer
interface to control the precise positioning of the head, as well as being
able to read/write to the disk.
I forget, are we fans of open-source hardware here? As in, circuit diagrams,
firmware, microcode, and operating software / APIs?
My USB disc analyser is "on the bench" and the prototype is talking to the PC
quite happily. Still working on getting the PIC and FPGA to talk, though. The
readback HDL code and RAM interface are proven working and pass the timing
simulations and testbench, but there's a slight difference between "works in
the simulator" and "works on the PCB".
The plan (at the moment) is to release the design, firmware and microcode some
time in July or August. This is slightly complicated by the fact that my
final-year BSc project just happens to be... "A hardware and software solution
for recovering data from obsolete flexible disk formats"
The software is "interesting". I've got a soft-PLL which seems to work quite
nicely (it tracks the drive speed on a bit-by-bit basis, and stores the
decoded bit *and* the deviation from normal).
Of course, I may well need a drive that's having speed regulation issues in
order to prove that it can track the speed correctly...
--
Phil.
classiccmp at philpem.me.uk
http://www.philpem.me.uk/
7:02 p.m.
On Mon, 9 Feb 2009, Philip Pemberton wrote:
Of course, I may well need a drive that's having speed regulation issues in
order to prove that it can track the speed correctly...
That's easy enough to do, just pinch the disk sleeve while the drive is
running. The more pressure you apply, the slower it goes. :)
g.
--
Proud owner of F-15C 80-0007
http://www.f15sim.com - The only one of its kind.
10 Feb
10 Feb
6:20 a.m.
Fred Cisin wrote:
On Mon, 9 Feb 2009, Philip Pemberton wrote:
MPI drives have a nice little trim pot on the top that adjusts the
RPMs.
Of course, I may well need a drive that's
having speed
regulation issues in
order to prove that it can track the speed
correctly...
On the Tandon TM100 series, the motor speed control is usually very
accessible on the back of the drive
3:41 p.m.
Of course, I may well need a drive that's having
speed regulation issues in
order to prove that it can track the speed correctly...
That shoukld be easy enough.. Many of the full-height 5.25" drives used a
combined motor and tachogenerator with a belt drive to the spindle. Teh
control circuit was often based round an LM2917 chip with a twiddlepot to
set the speed.
Eitehr turn the pot by hand to get the thing off-speed., or find some way
to inject a very slow analogue signal into the circuit to cause the speed
to vary a bit over time.
-tony
5:44 p.m.
On Tue, 2009-02-10 at 20:41 +0000, Tony Duell wrote:
If you were being excessively clever, you'd measure the speed of the
disc with the tachogenerator and apply some modulation to the twiddlepot
to let you choose any speed, right or wrong, and stick to it! If you
used a little microcontroller you could program in various test patterns
of wobbly speed, too.
Gordon
Of course, I
may well need a drive that's having speed regulation issues in
order to prove that it can track the speed correctly...
That shoukld be easy enough.. Many of the full-height 5.25" drives used a
combined motor and tachogenerator with a belt drive to the spindle. Teh
control circuit was often based round an LM2917 chip with a twiddlepot to
set the speed.
Eitehr turn the pot by hand to get the thing off-speed., or find some way
to inject a very slow analogue signal into the circuit to cause the speed
to vary a bit over time. 
5:51 p.m.
Philip Pemberton wrote:
A voice-coil actuator /might/ be more accurate than a
stepper, but you
still need a servo system to align it. Ladies and gentlemen, meet
catch-22: you want to write the servo tracks, but you need the servo
tracks to write the servo tracks...
I've seen photos of a gadget that was built to re-write servo tracks
on hard drives. It was set up in a clean room (of course) in the
early 1990s, with interchangeable modules for different makes/models
of drive. They were real, non-digital photos on 10x8 glossy paper!
Will ask about them again, and see if they can be scanned. The guy
who built it was an ex-UK101 user who I met at the local Linux
User Group.
--
John Honniball
coredump at gifford.co.uk
5633
days inactive
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days old
37 comments
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