26 May
2012
26 May
'12
10:45 p.m.
Hey folks. I'm looking for a DEC H9281 backplane, the four-slot, dual
width one with screw terminals for power. Does anyone have one lying
around that they can part with?
-Dave
--
Dave McGuire, AK4HZ
New Kensington, PA
27 May
27 May
1:42 a.m.
On Sun, May 27, 2012 at 7:45 AM, Dave McGuire <mcguire at neurotica.com> wrote:
?Hey folks. ?I'm looking for a DEC H9281 backplane, the four-slot, dual
width one with screw terminals for power. ?Does anyone have one lying
around that they can part with?
Been watching eBay for it since I've known of its existence. Apart
from one from one of those pesky resellers, I
haven't seen any come to
pass...
re,
Sander
2:47 p.m.
On 05/27/2012 04:42 AM, Sander Reiche wrote:
:-(
--
Dave McGuire, AK4HZ
New Kensington, PA
Hey folks.
I'm looking for a DEC H9281 backplane, the four-slot, dual
width one with screw terminals for power. Does anyone have one lying
around that they can part with?
Been watching eBay for it since I've known of its existence. Apart
from one from one of those pesky resellers, I haven't seen any come to
pass... 
3:48 a.m.
New subject: Loose oxide issues
Hi all,
A friend of mine is having some issues with old disks (Apple II, from
the early 80s). He's finding that on trying to access them, the drive
becomes unresponsive and won't read even disks previously known to be
good. He says that they don't show signs of foreign matter/growth, so
I'm guessing they're losing oxide onto the head. He's sent me his drives
and I've sent him some of mine; his ones were fine after a head clean,
but definitely nonfunctional before that.
So, my question is: is there any way he can tell whether a particular
disk has this loose oxide problem, without running the disk in a drive?
The drives in question aren't very easy to open and clean manually
(later Unidisk plastic-case drives), and he has no cleaning disks
(though they are pretty rough on heads anyway, I hear). Perhaps gently
rubbing the disk with a cotton bud might reveal very loose oxide without
damaging the disk too much, but I doubt the disk would release enough to
discolour the bud.
I'm actually thinking about making a "safe" cleaning disk, perhaps with
smooth plastic on the unused side, and some sot of low-abrasive cloth on
the other. Even for me, that would be easier than pulling a drive to
bits every time the head gets dirty.
Thoughts, anyone?
Thanks,
Mike
5:11 p.m.
New subject: Loose oxide issues
On 27 May 2012 at 22:48, Mike van Bokhoven wrote:
So, my question is: is there any way he can tell
whether a particular
disk has this loose oxide problem, without running the disk in a
drive? The drives in question aren't very easy to open and clean
manually (later Unidisk plastic-case drives), and he has no cleaning
disks (though they are pretty rough on heads anyway, I hear). Perhaps
gently rubbing the disk with a cotton bud might reveal very loose
oxide without damaging the disk too much, but I doubt the disk would
release enough to discolour the bud.
A sure sign is a "squealing" or other noise when the drive is reading
a disk.
Absent that, I go by brands; I don't trust Control Data or Wabash
floppies. The budget Dysans (pink label, not purple) were terrible
also, but fortunately you don't see many of those survivng. Brown
Disk, some Radio Shack-branded disks (I suspect they were probably
from CDC) and a few others are equally bad. Read at
your own risk.
You can test a 5.25" disk for flaking by scratching the oxide near
the hub with an X-acto knife. Go easy--you can make any media flake,
but the bad stuff *really* flakes. It doesn't harm the data, since
you're completely outside of the storage area.
Beyond that, look to how the disks were stored. If they were stored
at 40C or above, expect trouble from any disk.
While most people use isoproanol to clean heads, I've found some
sticky oxide that won't come off using alcohol. For that, I
CAREFULLY use a swab moistened in perchloroethylene, being careful to
steer clear of any plastic surfaces. The old cleaning kits used
Freon TF, but unless you have an "in" with Special People, you can't
get it. Too bad, that--if commercial businesses hadn't slopped it
around by the tankerload, the "ozone hole" thing may never have
happened.
For what it's worth,
Chuck
8:23 p.m.
New subject: Loose oxide issues
On 28/05/2012 12:11 p.m., Chuck Guzis wrote:
A sure sign is a "squealing" or other noise
when the drive is reading
a disk.
Interesting - now I'm mentally comparing the disk to a violin string,
and the head to the bow/hair, though the roles are all swapped around;
grippiness perhaps provided more by the disk than the head, for
instance. I'm imagining the slightly sticky failing oxide causes the
gripping like rosin. Bit of a mad thought there...
Absent that, I go by brands; I don't trust Control
Data or Wabash
floppies.
Strangely enough, the first disk I ever bought (I'd guess in 1980 or so)
was Control Data, and it spent years being squashed and bent in my
school bag, but it still works OK to this day. One sample doesn't mean
much though!
The budget Dysans (pink label, not purple) were
terrible also, but
fortunately you don't see many of those survivng. Brown Disk, some
Radio Shack-branded disks (I suspect they were probably from CDC) and
a few others are equally bad. Read at your own risk.
A problem may be that we're in New Zealand - there is some commonality
in brands, but a lot of difference too. For instance, we'd see Dick
Smith disks in place of Radio Shack. Plenty of Dysans here though.
You can test a 5.25" disk for flaking by
scratching the oxide near the
hub with an X-acto knife. Go easy--you can make any media flake, but
the bad stuff *really* flakes. It doesn't harm the data, since you're
completely outside of the storage area.
Good idea, I'll mention that to my friend and see if he's willing to
give it a go.
Beyond that, look to how the disks were stored. If
they were stored at
40C or above, expect trouble from any disk. While most people use
isoproanol to clean heads, I've found some sticky oxide that won't
come off using alcohol. For that, I CAREFULLY use a swab moistened in
perchloroethylene, being careful to steer clear of any plastic surfaces.
Fortunately, in NZ we'd pretty much never see 40 degrees C, though in
roof spaces etc I'm sure it can reach and exceed that. I'll ask. In the
end, maybe figuring out an easy way to clean the heads is best. I've
considered making an easy-access drive, where the electronics and case
can be moved without needing to loosen any fasteners, meaning I can
easily clean the heads with a cotton bud or similar. When fiddling with
30 year old media, regular failures are to be expected!
Mike
9:03 p.m.
New subject: Loose oxide issues
Fortunately, in NZ we'd pretty much never see 40
degrees C, though in roof
spaces etc I'm sure it can reach and exceed that.
Yes, indeed it does. I had a stash of Dick Smith System 80 disks stored up
there (in a roof space under corragated iron) for a few years in the 1990s.
Bad idea. Almost every one was unusable due to media damage when I tested
them after moving house. I recall it did get pretty hot in that roof space.
Others stored in a cool dry place (my university office for example) were
fine.
Tez (also in New Zealand)
On Mon, May 28, 2012 at 3:23 PM, Mike van Bokhoven <mike at fenz.net> wrote:
On 28/05/2012 12:11 p.m., Chuck Guzis wrote:
A sure sign is a "squealing" or other
noise when the drive is reading a
disk.
Interesting - now I'm mentally comparing the disk to a violin string, and
the head to the bow/hair, though the roles are all swapped around;
grippiness perhaps provided more by the disk than the head, for instance.
I'm imagining the slightly sticky failing oxide causes the gripping like
rosin. Bit of a mad thought there...
Absent that, I go by brands; I don't trust Control Data or Wabash
floppies.
Strangely enough, the first disk I ever bought (I'd guess in 1980 or so)
was Control Data, and it spent years being squashed and bent in my school
bag, but it still works OK to this day. One sample doesn't mean much though!
The budget Dysans (pink label, not purple) were terrible also, but
fortunately you don't see many of those
survivng. Brown Disk, some Radio
Shack-branded disks (I suspect they were probably from CDC) and a few
others are equally bad. Read at your own risk.
A problem may be that we're in New Zealand - there is some commonality in
brands, but a lot of difference too. For instance, we'd see Dick Smith
disks in place of Radio Shack. Plenty of Dysans here though.
You can test a 5.25" disk for flaking by scratching the oxide near the
hub with an X-acto knife. Go easy--you can make
any media flake, but the
bad stuff *really* flakes. It doesn't harm the data, since you're
completely outside of the storage area.
Good idea, I'll mention that to my friend and see if he's willing to give
it a go.
Beyond that, look to how the disks were stored. If they were stored at
40C or above, expect trouble from any disk. While
most people use
isoproanol to clean heads, I've found some sticky oxide that won't come off
using alcohol. For that, I CAREFULLY use a swab moistened in
perchloroethylene, being careful to steer clear of any plastic surfaces.
Fortunately, in NZ we'd pretty much never see 40 degrees C, though in roof
spaces etc I'm sure it can reach and exceed that. I'll ask. In the end,
maybe figuring out an easy way to clean the heads is best. I've considered
making an easy-access drive, where the electronics and case can be moved
without needing to loosen any fasteners, meaning I can easily clean the
heads with a cotton bud or similar. When fiddling with 30 year old media,
regular failures are to be expected!
Mike
28 May
28 May
9:59 a.m.
New subject: Loose oxide issues
On 28 May 2012 at 15:23, Mike van Bokhoven wrote:
Interesting - now I'm mentally comparing the disk
to a violin string,
and the head to the bow/hair, though the roles are all swapped around;
grippiness perhaps provided more by the disk than the head, for
instance. I'm imagining the slightly sticky failing oxide causes the
gripping like rosin. Bit of a mad thought there...
Well, not exactly. Much of the property of violin bow hair has to do
with the structure of the hair itself. Try bowing your violin with a
piece of rosined monofilament fishing line and you'll see what I
mean. Horsehair is used for a reason...
Strangely enough, the first disk I ever bought
(I'd guess in 1980 or
so) was Control Data, and it spent years being squashed and bent in my
school bag, but it still works OK to this day. One sample doesn't mean
much though!
According to Herb Johnson (or one of his sources), a large quantity
of CDC disks were stored in an overheated warehouse, causing the
binder to fail. CDC never admitted it nor made good on the bad
floppies.
Anyone remember Kodak's venture into floppies offered with a lifetime
guarantee? Not only that, but they would recover the data for you?
It didn't last long.
Fortunately, in NZ we'd pretty much never see 40
degrees C, though in
roof spaces etc I'm sure it can reach and exceed that.
The flip side of the overheating thing is fungus and mold, which is
just as bad.
Good luck,
--Chuck
10:38 a.m.
New subject: Loose oxide issues
From: cclist at sydex.com
On 28 May 2012 at 15:23, Mike van Bokhoven wrote:
The worst I had was a number of N* disk that had the adhesive
used to hold the liners leak through the liners and contaminate
the disk surfaces.
As I recall, I removed the disk from the envelopes and
carefully cleaned them with alcohol and swabs. It didn''t
disolve the goo but made the surface not stick toit any more.
I was able to recover all the data and tranfer it to linerless
disk.
Dwight
Interesting - now I'm mentally comparing the
disk to a violin string,
and the head to the bow/hair, though the roles are all swapped around;
grippiness perhaps provided more by the disk than the head, for
instance. I'm imagining the slightly sticky failing oxide causes the
gripping like rosin. Bit of a mad thought there...
Well, not exactly. Much of the property of violin bow hair has to do
with the structure of the hair itself. Try bowing your violin with a
piece of rosined monofilament fishing line and you'll see what I
mean. Horsehair is used for a reason...
Strangely enough, the first disk I ever bought
(I'd guess in 1980 or
so) was Control Data, and it spent years being squashed and bent in my
school bag, but it still works OK to this day. One sample doesn't mean
much though!
According to Herb Johnson (or one of his sources), a large quantity
of CDC disks were stored in an overheated warehouse, causing the
binder to fail. CDC never admitted it nor made good on the bad
floppies.
Anyone remember Kodak's venture into floppies offered with a lifetime
guarantee? Not only that, but they would recover the data for you?
It didn't last long.
Fortunately, in NZ we'd pretty much never see
40 degrees C, though in
roof spaces etc I'm sure it can reach and exceed that.
The flip side of the overheating thing is fungus and mold, which is
just as bad.
Good luck,
--Chuck
11:17 a.m.
New subject: Loose oxide issues
On 28 May 2012 at 10:38, dwight elvey wrote:
As I recall, I removed the disk from the envelopes
and
carefully cleaned them with alcohol and swabs. It didn''t
disolve the goo but made the surface not stick toit any more.
I was able to recover all the data and tranfer it to linerless
On the other hand, I've cleaned problem floppies with alcohol and had
the oxide wipe right off the substrate.
I've even tried low-temp "baking" as performed with problem magtapes.
It didn't help.
Soap and water is really the safest cleaning agent. If the disk is
going to flake, it's going to flake.
One of these days, I'm going to try wiping a water-based lacquer on
one of the flakes and see if I can get at least one good read out of
it.
Certainly the best way to recover is to use som sort of non-contact
reading. Maybe adapt an old Bernoulli mech?
--Chuck
11:37 a.m.
New subject: Loose oxide issues
If anyone's interested, a good summary of the "baking" process:
http://audio-restoration.com/baking.php
--Chuck
1:01 p.m.
New subject: Loose oxide issues
On Mon, 28 May 2012, Chuck Guzis wrote:
If anyone's interested, a good summary of the
"baking" process:
http://audio-restoration.com/baking.php
Does this also happen to 9-track tapes? Any particular vintage or
brands?
Mike Loewen mloewen at cpumagic.scol.pa.us
Old Technology http://sturgeon.css.psu.edu/~mloewen/Oldtech/
1:14 p.m.
New subject: Loose oxide issues
On 5/28/12 1:01 PM, Mike Loewen wrote:
Does this also happen to 9-track tapes? Any particular
vintage or brands?
Absolutely. I've dealt with thousands of them.
http://bitsavers.org/oven.jpg (on the right) was the oven setup
http://bitsavers.org/tapes.jpg was the reading station
until I lost my CHM lab space
Worst
80's Memorex
BASF
DEC-labeled
Sun-labeled
Better
IBM-labeled
Graham Magnetics
HP-labeled (may be Graham)
3M
Most tape (even the 3M) is now showing water absorbsion in the binder so
it's not really that safe to try any reading without evaluating how sticky it is.
1:56 p.m.
New subject: Loose oxide issues
On 05/28/2012 04:14 PM, Al Kossow wrote:
On 5/28/12 1:01 PM, Mike Loewen wrote:
The worst was 3M blackwatch, It was a dark black rather than the
brown-beige
of the more common binders and it was know 25 years ago for moisture
shedding.
the usual solution was to bake the tape carefully at about 120-130F for
days to
dry it out and do a one pass transcribe. Reason for one pass is that
was likely
all you'd get if lucky.
It was the bane of the audio recording industry for 8 track masters
going south.
That same binder was used for floppies, and other reel to reel tapes
with long term issues.
In that era there were only a few major makers of magnetic tape web
(unslit,
or unpunched sheets of prepared magnetic media). So it was common to see
the same problem in many paces or the lack of a given problem depending
on the main producers.
DEC used several vendors over the years, as did many other based on
availability
and the formulation needed.
Allison
Does this also happen to 9-track tapes? Any
particular vintage or
brands?
Absolutely. I've dealt with thousands of them.
http://bitsavers.org/oven.jpg (on the right) was the oven setup
http://bitsavers.org/tapes.jpg was the reading station
until I lost my CHM lab space
Worst
80's Memorex
BASF
DEC-labeled
Sun-labeled
Better
IBM-labeled
Graham Magnetics
HP-labeled (may be Graham)
3M
Most tape (even the 3M) is now showing water absorbsion in the binder so
it's not really that safe to try any reading without evaluating how
sticky it is.
1:25 p.m.
New subject: Loose oxide issues
On 28 May 2012 at 16:01, Mike Loewen wrote:
Does this also happen to 9-track tapes? Any
particular vintage or
brands?
Yes, mostly 70s vintage. 3M tapes are the worst in my experience,
although there are certainly other brands.
For a better overview, search for "Sticky Shed" on WikiP.
--Chuck
1:46 p.m.
New subject: Loose oxide issues
On 5/28/12 1:25 PM, Chuck Guzis wrote:
For a better overview, search for "Sticky
Shed" on WikiP.
Large quantities of air are absolutely critical for the process to work
well, along with rotating the reels and obviously having them vertical
in the airflow. If you look at the oven picture, you'll see nine fans
at the bottom, there are another 9 at the top, with a regulated heat
source below the bottom set.
I guess I can be happy that I don't have to deal with tape that hasn't
been saturation recorded. If you can keep the tape moving and it reads
at all, it will generally read all the way through.
1:22 p.m.
New subject: Loose oxide issues
On 05/28/2012 02:17 PM, Chuck Guzis wrote:
Certainly the best way to recover is to use som sort
of non-contact
reading. Maybe adapt an old Bernoulli mech?
Don't Bernoulli drives physically deform (though very slightly) the
disk underneath the head? If so, that sounds like bad news for worn-out
oxide binders.
-Dave
--
Dave McGuire, AK4HZ
New Kensington, PA
2:23 p.m.
New subject: Loose oxide issues
On 28 May 2012 at 16:22, Dave McGuire wrote:
On 05/28/2012 02:17 PM, Chuck Guzis wrote:
Yeah, maybe the ultimate answer is some sort of optical setup. Coat
or spray the disk with colloidal iron, then read it out using an
optical pickup of some sort. You wouldn't even have to spin the
disk.
--Chuck
Certainly the best way to recover is to use som
sort of non-contact
reading. Maybe adapt an old Bernoulli mech?
Don't Bernoulli drives physically deform (though very slightly) the
disk underneath the head? If so, that sounds like bad news for
worn-out oxide binders.
1:30 p.m.
New subject: Loose oxide issues
On 5/28/12 11:17 AM, Chuck Guzis wrote:
Certainly the best way to recover is to use som sort
of non-contact
reading.
Or a much more sensitive transducer (probably based on a more modern
magneto-restrictive read head).
One thing I noticed in a recent adventure in double-sided 8" floppy reading
was the recovery rate on the top head has been MUCH worse than the bottom.
I was running the drive vertically, so gravity shouldn't have been a factor.
1:55 p.m.
New subject: Loose oxide issues
On 05/28/2012 04:30 PM, Al Kossow wrote:
Isn't there some sort of magnetic imaging technology, by which
magnetic domains can be scanned via an imaging technique? I seem to
recall having read something about that in the scientific community
several years ago.
Certainly the
best way to recover is to use som sort of non-contact
reading.
Or a much more sensitive transducer (probably based on a more modern
magneto-restrictive read head). One thing I noticed in a recent adventure in
double-sided 8" floppy reading
was the recovery rate on the top head has been MUCH worse than the bottom.
Wow...what could have caused that, any theories or suspicions?
I was running the drive vertically, so gravity
shouldn't have been a
factor.
Very interesting indeed.
-Dave
--
Dave McGuire, AK4HZ
New Kensington, PA
2:01 p.m.
New subject: Loose oxide issues
> One thing I noticed in a recent adventure in
double-sided 8" floppy reading
> was the recovery rate on the top head has been MUCH worse than the bottom.
> I was running the drive vertically, so gravity shouldn't have been a
> factor.
Maybe gravity is a factor, in that the mechanism has deteriorated
through age and that the gravity of being run horizontally may help?
(just a random thought.)
1:59 p.m.
New subject: Loose oxide issues
On 5/28/12 11:17 AM, Chuck Guzis wrote:
Certainly the best way to recover is to use som sort
of non-contact
reading.
Are any of the "developing fluids" for optical viewing of magnetic media
(used to be used for precise alignment in splicing helical-scan videotape)
of sufficient "reolution" to permit viewing a disk track? and then
recreating the pit pattern??
(quite a bit more extreme (and needed) than OCR'ing punch tape)
7:55 p.m.
New subject: Loose oxide issues
From: cclist at sydex.com
On 28 May 2012 at 10:38, dwight elvey wrote:
Hi
I'd not have done it without checking a safe spot first to
make sure I wasn't removing media.
I've seen pictures of using material like used for magnaflux
testing and then reading the disk optically.
With todays technics, I would think it could be easily
automated.
Dwight
As I recall, I removed the disk from the
envelopes and
carefully cleaned them with alcohol and swabs. It didn''t
disolve the goo but made the surface not stick toit any more.
I was able to recover all the data and tranfer it to linerless
On the other hand, I've cleaned problem floppies with alcohol and had
the oxide wipe right off the substrate.
2:46 p.m.
New subject: Loose oxide issues
On 29/05/2012 4:59 a.m., Chuck Guzis wrote:
Well, not exactly. Much of the property of violin bow
hair has to do
with the structure of the hair itself. Try bowing your violin with a
piece of rosined monofilament fishing line and you'll see what I mean.
Horsehair is used for a reason...
Ah well, it was really more of an interesting comparison than anything
precise - the gripping/shuddering type behaviour seemed similar. Next
thing, I was wondering if it might be possible to vary the tone somehow
and make a musical instrument out of a floppy drive with a sticky disk
in it, but then I realised that that was really going a bit mad. How
could you vary the resonant frequency of the disk? Not possible, I'd say!
The flip side of the overheating thing is fungus and
mold, which is
just as bad.
Oh yes, that's very common here. Fortunately, that doesn't seem to be as
problematic. I was experimenting with a box of unused disks that had
visible fungus patterns on them, and they actually read and wrote fine
for extended periods, and didn't seem to be leaving any residue on the
heads. Though I have had similar disks fail, and gum up heads too, so it
certainly is a problem, I wouldn't recommend using even those disks I
tested for anything important.
Mike
27 May
27 May
8:18 a.m.
On May 27, 2012, at 1:45, Dave McGuire <mcguire at neurotica.com> wrote:
Hey folks. I'm looking for a DEC H9281 backplane, the four-slot, dual
width one with screw terminals for power. Does anyone have one lying
around that they can part with?
I'm pretty sure that's the one I have that I'm looking to trade up (I've
wire-wrapped it to Q22, which can be undone if you want). I'll check when I get home
(tomorrowish) but I'll gladly trade for something if I have what you're looking
for. :-)
- Dave
4373
days inactive
4375
days old
25 comments
12 participants
participants (12)
-
aek＠bitsavers.org -
ajp166＠verizon.net -
cclist＠sydex.com -
cisin＠xenosoft.com -
dkelvey＠hotmail.com -
fraveydank＠gmail.com -
jon＠jonworld.com -
mcguire＠neurotica.com -
mike＠fenz.net -
mloewen＠cpumagic.scol.pa.us -
sander.reiche＠gmail.com -
terry＠webweavers.co.nz