4 Nov
2025
4 Nov
'25
7:53 a.m.
---------- Forwarded message ----------
From: Paul Koning <paulkoning(a)comcast.net>
To: "cctalk(a)classiccmp.org" <cctalk(a)classiccmp.org>
Cc:
Bcc:
Date: Sun, 2 Nov 2025 14:43:49 -0500
Subject: [cctalk] Re: How hard would it be to make new dec tape media?
10-20 years ago I had a good Point-of-Contact (POC) at 3M (before we both
retired). I asked him whether they still (at that time) made DECtape media
and was told that 3M had sold their magnetic media operations to another
company who also got out of the business before I contacted them. I also
asked my POC (and the contact at the other company) if any DECtape media
had been kept in a warehouse or similar -- he checked 3M's inventory system
and told me that they had no record of any remaining DECtape media. The
other company's contact had a similar "you've struck out" story.
Bob
P.S. I thought that I read here or in a PDP-8-specific forum/mail-list
that DECtape wasn't actually laminated on both sides, which apparently
explained the visible red oxide material removed from dirty DECtapes while
cleaning them (per whoever posted their observations)?
On Nov 2, 2025, at 10:46 AM, Jon Elson via cctalk
<cctalk(a)classiccmp.org>
wrote:
On 11/1/25 20:49, ben via cctalk wrote:
years ago, we made working replacements from 3/4" instrumentation tape, but
it was NOT laminated. It had a print-through issue where if left sitting
for a few months, it would start getting errors. I have no idea if there
is anywhere you can buy 3/4" instrumentation tape. Maybe you can get 3/4"
video tape.
Bitsavers has the 3M spec for 480 and 481 sandwich tape, I'm not sure
which of these two is what DEC used. It seems crazy, but it can't hurt to
ask 3M if they still make that stuff.
paul
How hard would it be to make new dec tape media?
60 year tape could use a replacement.
Ben.
DecTape is laminated, ie. it has Mylar on both sides of the oxide. 50
4 Nov
4 Nov
8:41 a.m.
New subject: How hard would it be to make new dec tape media?
Bob
P.S. I thought that I read here or in a PDP-8-specific forum/mail-list
that DECtape wasn't actually laminated on both sides, which apparently
explained the visible red oxide material removed from dirty DECtapes while
cleaning them (per whoever posted their observations)?
I wiped the recording side of a DECtape with alcohol and all of the oxide
came off. I don't remember if it was a DEC manufactured tape.
--
Michael Thompson
9:36 a.m.
New subject: How hard would it be to make new dec tape media?
On Nov 4, 2025, at 10:53 AM, Bob Vines via cctalk
<cctalk(a)classiccmp.org> wrote:
I know of oxide rubbing off, I cleaned it off DECtape drive heads and tape guides often
enough. But the spec is quite clear, the stuff is indeed laminated. The upper layer is
very thin, though; spec is 0.04 mil. So one would expect heavily-used tapes to have that
layer wear off at least in spots. I expect that's what we were seeing.
paul
...
P.S. I thought that I read here or in
a PDP-8-specific forum/mail-list
that DECtape wasn't actually laminated on both sides, which apparently
explained the visible red oxide material removed from dirty DECtapes while
cleaning them (per whoever posted their observations)? 
11:50 a.m.
New subject: How hard would it be to make new dec tape media?
On Tuesday (11/04/2025 at 10:53AM -0500), Bob Vines via cctalk wrote:
10-20 years ago I had a good Point-of-Contact (POC) at 3M (before we both
retired). I asked him whether they still (at that time) made DECtape media
and was told that 3M had sold their magnetic media operations to another
company who also got out of the business before I contacted them. I also
asked my POC (and the contact at the other company) if any DECtape media
had been kept in a warehouse or similar -- he checked 3M's inventory system
and told me that they had no record of any remaining DECtape media. The
other company's contact had a similar "you've struck out" story.
Surely the "other company" was Imation, which was spun off from 3M in
1996, taking all of the magnetic and optical media and many other similar
products and technologies.
https://en.wikipedia.org/wiki/Imation
Many family and friends here in MN, in the 3M sphere, suffered through
this, umm, disaster.
My dad started 3M's optical recording business-- spinning up production
for laser discs and CDs in the early 80s.
cje
--
Chris Elmquist
12:48 p.m.
New subject: How hard would it be to make new dec tape media?
From: Paul Koning <paulkoning(a)comcast.net>
...
Bitsavers has the 3M spec for 480 and 481 sandwich tape, I'm not sure
which of these two is what DEC used. It seems crazy, but it can't hurt to
ask 3M if they still make that stuff.
paul
The LINCtape pictures in Dave Gesswein's site make it clear that DECtape is 3M 481
tape, except really old ones which apparently are 489. I'd love to see a 489 spec
sheet. Assuming that "1.0 mil" refers to the substrate, 489 is a hair thicker
than 481 (which has an 0.92 mil substrate according to the data sheet).
paul
1:41 p.m.
New subject: How hard would it be to make new dec tape media?
On 11/4/2025 12:48 PM, Paul Koning via cctalk wrote:
This may be insanely naive on my part, but wouldn't it be possible to
use cut down tape from existing sources to use as a replacement?
Something like 9 track, or even VHS tape... DIYing a device to create
split tape wouldn't be that difficult.
g.
--
Proud owner of F-15C 80-0007
http://www.f15sim.com - The only one of its kind.
http://www.diy-cockpits.org/coll - Go Collimated or Go Home.
I'm not crazy, I'm plausibly off-nominal!
ScarletDME - The red hot Data Management Environment
A Multi-Value database for the masses, not the classes.
https://github.com/geneb/ScarletDME - Get it _today_!
From: Paul
Koning <paulkoning(a)comcast.net>
...
Bitsavers has the 3M spec for 480 and 481 sandwich tape, I'm not sure
which of these two is what DEC used. It seems crazy, but it can't hurt to
ask 3M if they still make that stuff.
paul
The LINCtape pictures in Dave Gesswein's site make it clear that
DECtape is 3M 481 tape, except really old ones which apparently are 489. I'd love to
see a 489 spec sheet. Assuming that "1.0 mil" refers to the substrate, 489 is a
hair thicker than 481 (which has an 0.92 mil substrate according to the data sheet).
paul
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days inactive
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5 comments
5 participants
participants (5)
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Bob Vines -
Chris Elmquist -
Gene Buckle -
Michael Thompson -
Paul Koning