22 Jun
2005
22 Jun
'05
1:09 a.m.
If you recall there was a discussion about tape catridges that could
not be read because their coating was falling off.
I was thinking, what if we reverse the tape, so that the magnetic
head come in contact with the plastic backing and not the oxide.
Would it be possible to read the data then?
Obviously I am talking about a one-off operation, just to get the
stuff off the tape.
**vp
22 Jun
22 Jun
6:01 a.m.
That's an interesting idea and certainly worth a try but I sort of doubt
you'd be able to read the magnetic bit pattern through the plastic tape.
But if you coud it would probably save a lot of data.
Joe
At 04:09 AM 6/22/05 -0400, you wrote:
If you recall there was a discussion about tape
catridges that could
not be read because their coating was falling off.
I was thinking, what if we reverse the tape, so that the magnetic
head come in contact with the plastic backing and not the oxide.
Would it be possible to read the data then?
Obviously I am talking about a one-off operation, just to get the
stuff off the tape.
**vp
8:12 a.m.
On Wed, 22 Jun 2005, Joe R. wrote:
That's an interesting idea and certainly worth a
try but I sort of doubt
you'd be able to read the magnetic bit pattern through the plastic tape.
But if you coud it would probably save a lot of data.
I have my doubts. I would think that if a tape is going to flake, it's
going to flake whether you are running the oxide side against the head or
not.
--
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12:41 p.m.
If you recall there was a discussion about tape catridges that could
not be read because their coating was falling off.
I was thinking, what if we reverse the tape, so that the magnetic
head come in contact with the plastic backing and not the oxide.
Would it be possible to read the data then?
I think you'd lose almost as much oside (rubbing on the other layers of
tape on the spool, on the tape guides, etc) and would be almost certain
not to get a useful signal off the tape.
Spacing the magnetic part (the oxide coating) away from the head (by the
thickness of the tape base) would kill off the HF response of the drive.
You'd almost certainly not be able to resolve individual bits.
-tony
2:37 p.m.
Tony wrote....
Spacing the magnetic part (the oxide coating) away
from the head (by the
thickness of the tape base) would kill off the HF response of the drive.
You'd almost certainly not be able to resolve individual bits.
Ok, use a magnetic fingerprinting powder on it ;) Actually, I've heard (and
seen) there IS a liquid solution that will let you visibly see the dots on
mag tape.
THEN... read the bits optically.
Jay
3:43 p.m.
Ok, use a magnetic fingerprinting powder on it ;)
Actually, I've heard (and
seen) there IS a liquid solution that will let you visibly see the dots on
mag tape.
There is. It generally goes under the name of 'Magnasee' and is a
colloidal suspension of iron oxide in some suitable volatile liquid. I
have no idea where you get it nowadays, though.
-tony
4:14 p.m.
At 11:43 PM 6/22/05 +0100, you wrote:
I still have a bottle of it but what good would it do to know the binary
pattern? You couldn't program a new tape with it.
Joe
> Ok, use a magnetic fingerprinting powder on it ;)
Actually, I've heard
(and
seen) there IS
a liquid solution that will let you visibly see the dots on
mag tape.
There is. It generally goes under the name of 'Magnasee' and is a
colloidal suspension of iron oxide in some suitable volatile liquid. I
have no idea where you get it nowadays, though.
6:34 p.m.
Joe wrote.....
I still have a bottle of it but what good would it
do to know the binary
pattern? You couldn't program a new tape with it.
Uh, yes you could. The bits revealed on the tape could be read optically.
Build something like an optical paper tape reader mechanism but with much
better optics. Then take the data to a system with mag tape and write a new
one.
Just a thought. Perhaps a stupid one, but a thought nontheless :>
Jay
23 Jun
23 Jun
11:19 a.m.
I still have a bottle of it but what good would it
do to know the binary
pattern? You couldn't program a new tape with it.
Maybe not with the standard HP controller , but you could, surely, send
pulses with the right spacing to a tape drive to recreate the pattern on
a new tape.
[1] Although I think you could with an HP9877 or a 9825 running special
software, since those controllers are very dumb devices, they don't even
do any form of serial-parallel conversion. I am not so sure about the
9845 controller, it's got an HP custom bybrid in the middle with 64 pins.
Many of them go straight to the I/O bus, the rest go to the tape drive,
amplified read signal, etc. All the interesting stuff is inside that
hybrid...
-tony
22 Jun
22 Jun
4:45 p.m.
On Wed, 22 Jun 2005, Tony Duell wrote:
It USETA be readily available from professional video places for lining up
reel to reel tape and splicing it without losing synch.
A friend made some out of rust.
We used it to show students the tracks on some floppies.
On Wed, 22 Jun 2005, Joe R. wrote:
Ok, use a
magnetic fingerprinting powder on it ;) Actually, I've heard (and
seen) there IS a liquid solution that will let you visibly see the dots on
mag tape.
There is. It generally goes under the name of 'Magnasee' and is a
colloidal suspension of iron oxide in some suitable volatile liquid. I
have no idea where you get it nowadays, though. I still have a bottle of it but what good would it
do to know the
binary
pattern? You couldn't program a new tape with it.
... but with sufficient time and effort, you could MANUALLY
read the tape :-)
How long would an entire tape take?
--
Grumpy Ol' Fred cisin at xenosoft.com
10:15 p.m.
On Wed, 22 Jun 2005, Fred Cisin wrote:
More seriously, how about a semi-automated process to read the
data *optically* from severely damaged tapes?
Drag the tape slowly, oxide up, coat with colloidal FeO, run it
past a camera. Post-processed video data could be 'decoded', bad
spots stopped at, manually interpolated/ repaired (human visual
acuity is pretty damn good).
It USETA be readily available from professional video
places for lining up
reel to reel tape and splicing it without losing synch.
HEY HEY HEY we have standards here! THat's spelled YOUSTA. Get
with duh program.
pattern? You
couldn't program a new tape with it.
... but with sufficient time and effort, you could MANUALLY
read the tape :-)
How long would an entire tape take? 
23 Jun
23 Jun
6:59 a.m.
New subject: unreadable HP cartridges [now Magnasee]
At 12:15 AM 6/23/2005, Tom Jennings wrote:
Drag the tape slowly, oxide up, coat with colloidal
FeO, run it
past a camera. Post-processed video data could be 'decoded', bad
spots stopped at, manually interpolated/ repaired (human visual
acuity is pretty damn good).
I think the magnetic approach will win because that's what you
want to recover. In a race between a tape head and a relatively
coarse layer of Mangasee, I think the tape head wins.
You haven't established whether indefinite supplies of Magnasee
are available. One google-bit yesterday suggested that the
solvent was carbon tet. If someone still had a NOS case of it
you might be in luck.
Where the GNU Radio project wants to build a software radio, I think
we also need a mostly-software VCR: something with a tape transport
mechanism and a scanning digitizing head plus software to un-vertical,
un-bit, un-helix, un-whatever the data plus signal analysis to
bring it back to life.
When you finish this project, please call - I have some old 8mm
videotapes of the kids that went out of whack when the circa '92
Sony camcorder's surface-mount caps went south. Something's recorded
on the tapes, the camcorder was able to play it back after it
was recorded, but something else was drifting over time and
later the tape wouldn't play.
- John
12:02 a.m.
I was thinking, what if we reverse the tape, so that
the magnetic
head come in contact with the plastic backing and not the oxide.
Would it be possible to read the data then?
Nice idea, but, signal strength at the head varies with the square
of the distance between oxide and head, hence the need for
contact. If it were readily possible it would have been done from
the start -- it would eliminate contact wear. Finally, it's tape
flexing that knocks the oxide off, and spooling the tape
*probably* does most of the damage, thoguh not scraping it across
a head probably *would* help.
7123
days inactive
7124
days old
12 comments
8 participants
participants (8)
-
ard＠p850ug1.demon.co.uk -
cisin＠xenosoft.com -
jfoust＠threedee.com -
jwest＠classiccmp.org -
rigdonj＠cfl.rr.com -
tomj＠wps.com -
vcf＠siconic.com -
vp＠cs.drexel.edu