8 Feb
2022
8 Feb
'22
1:04 p.m.
So it sermsdectape heads are special. I don?t think
Dec would have the desire to make them internally so they probably contractef with a
company already set up to do that. Who were the big tape head manufacturers at that time?
Does anyone know?
A photo of the back of a TU56 DECtape head can be seen at
https://www.pdp8online.com/tu56/pics/head_label.shtml?small .
The head has a label on it that reads:
Western Magnetics
Glendale Calif.
Record
7282
I've never seen a TU56 in person and have no idea if they have separate read, write,
and erase heads or some other combo. The "Record" notation on the above
head's label hints to me this might be a write head.
I found that and other DECtape photos at https://www.pdp8online.com/tu56/tu56.shtml .
-- Ron
8 Feb
8 Feb
1:18 p.m.
On 2/8/22 13:04, Ron Pool via cctech wrote:
Mine also says Western Magnetics, Glendale CA, but does not have a part
number.? Just serial numbers.? At least I assume they are serial numbers
"19984" and "19976".
I've seen evidence that a few souls in the 50s managed to make magnetic
heads from scratch (heck, Ivan Sutherland is claimed to have made a
functioning magnet drum storage device when he was in 12th grade,) so
give the modern world of CNC milling and availability of every manner of
sheet metal via Internet searchers, I figured their just *might* be a
possibility of growing one of these from scratch - tolerances (other
than head gap) appear pretty generous, but I just don't have enough info
to crack what the coil construction is to be.? There may be enough
information to do a stab at it, but I'm not sure I have the energy (or
even the skill) to give it a credible effort.
I've seen evidence of 'head repair' services, but I doubt they include
digging out the wires from solid epoxy.
Any information available would be appreciated.
-Gary
--
-Gary
So it
sermsdectape heads are special. I don?t think Dec would have the desire to make them
internally so they probably contractef with a company already set up to do that. Who were
the big tape head manufacturers at that time? Does anyone know?
A photo of the back
of a TU56 DECtape head can be seen at
https://www.pdp8online.com/tu56/pics/head_label.shtml?small .
The head has a label on it that reads:
Western Magnetics
Glendale Calif.
Record
7282
I've never seen a TU56 in person and have no idea if they have separate read, write,
and erase heads or some other combo. The "Record" notation on the above
head's label hints to me this might be a write head.
I found that and other DECtape photos at https://www.pdp8online.com/tu56/tu56.shtml .
-- Ron
1:19 p.m.
On 2/8/22 13:04, Ron Pool via cctech wrote:
Mine also says Western Magnetics, Glendale CA, but does not have a part
number.? Just serial numbers.? At least I assume they are serial numbers
"19984" and "19976".
I've seen evidence that a few souls in the 50s managed to make magnetic
heads from scratch (heck, Ivan Sutherland is claimed to have made a
functioning magnet drum storage device when he was in 12th grade,) so
give the modern world of CNC milling and availability of every manner of
sheet metal via Internet searchers, I figured their just *might* be a
possibility of growing one of these from scratch - tolerances (other
than head gap) appear pretty generous, but I just don't have enough info
to crack what the coil construction is to be.? There may be enough
information to do a stab at it, but I'm not sure I have the energy (or
even the skill) to give it a credible effort.
I've seen evidence of 'head repair' services, but I doubt they include
digging out the wires from solid epoxy.
Any information available would be appreciated.
-Gary
So it
sermsdectape heads are special. I don?t think Dec would have the desire to make them
internally so they probably contractef with a company already set up to do that. Who were
the big tape head manufacturers at that time? Does anyone know?
A photo of the back
of a TU56 DECtape head can be seen at
https://www.pdp8online.com/tu56/pics/head_label.shtml?small .
The head has a label on it that reads:
Western Magnetics
Glendale Calif.
Record
7282
I've never seen a TU56 in person and have no idea if they have separate read, write,
and erase heads or some other combo. The "Record" notation on the above
head's label hints to me this might be a write head.
I found that and other DECtape photos at https://www.pdp8online.com/tu56/tu56.shtml .
-- Ron
1:49 p.m.
On Feb 8, 2022, at 4:04 PM, Ron Pool via cctech
<cctech at classiccmp.org> wrote:
This picture https://www.pdp8online.com/tu56/pics/TU56_front.shtml?large shows the tape
path clearly. There is just one head assembly that performs reading as well as writing.
I don't know what "Record" refers to; the numbers near it look vaguely like
a date code though not the usual year and week number.
The maintenance manual (on Bitsavers) speaks of a "read/write head" and has an
illustration that shows one of the head elements with a "read/write coil". So
the implication is that (a) there isn't an erase head, and (b) the same head serves
for read or write according to whether the coil is being driven or sensed. Come to think
of it, I think erase heads are an aspect of audio tapes, not relevant to computer tapes.
paul
So it sermsdectape heads are special. I don?t
think Dec would have the desire to make them internally so they probably contractef with a
company already set up to do that. Who were the big tape head manufacturers at that time?
Does anyone know?
A photo of the back of a TU56 DECtape head can be seen at
https://www.pdp8online.com/tu56/pics/head_label.shtml?small .
The head has a label on it that reads:
Western Magnetics
Glendale Calif.
Record
7282
I've never seen a TU56 in person and have no idea if they have separate read, write,
and erase heads or some other combo. The "Record" notation on the above
head's label hints to me this might be a write head.
I found that and other DECtape photos at https://www.pdp8online.com/tu56/tu56.shtml .
9 Feb
9 Feb
7:20 a.m.
On 2/8/22 15:49, Paul Koning via cctalk wrote:
> The maintenance manual (on Bitsavers) speaks of a "read/write head" and has
an illustration that shows one of the head elements with a "read/write coil".
So the implication is that (a) there isn't an erase head, and (b) the same head serves
for read or write according to whether the coil is being driven or sensed.
Yes, that
is right.
> Come to think of it, I think erase heads are an
aspect of audio tapes, not relevant to computer tapes.
No, all 9-track drives that I know of have erase heads that
erase the tape to a no-transitions state before it is
written on.? This allows you to obliterate old data when
writing a new record, and leave gaps between records.? Since
DecTape was synchronized by clock and mark tracks, that was
not needed.
Jon
8:11 a.m.
New subject: DEC Tape TU56 head pictures
I am in the process or restoring a TU56 so it's in pieces.? Pictures of
the head were requested so here they are.
These were taken with my phone so the quality is only mediocre.
This, like the rest of the drive, is in the process of being restored.
I'm still not sure how to clean the front of the head where the tape
touches the head.? Any ideas?
The pics are big so here is a link to the pic:
https://drive.google.com/drive/folders/1jwG4EZPd1bvNZLNWQ99ZDS42twq6Cf-a?us…
9:23 a.m.
New subject: DEC Tape TU56 head pictures
On Feb 9, 2022, at 11:11 AM, Mike Katz via cctalk
<cctalk at classiccmp.org> wrote:
I am in the process or restoring a TU56 so it's in pieces. Pictures of the head were
requested so here they are.
These were taken with my phone so the quality is only mediocre.
This, like the rest of the drive, is in the process of being restored.
I'm still not sure how to clean the front of the head where the tape touches the
head. Any ideas?
We always used isopropyl alcohol (91% or better).
paul
9:35 a.m.
New subject: DEC Tape TU56 head pictures
What about corrosion or calcification or whatever that crusty stuff is
on the heads.
I used 3M Scotchbrite to clean the sides.
On 2/9/2022 11:23 AM, Paul Koning wrote:
On Feb 9, 2022, at 11:11 AM, Mike Katz via cctalk
<cctalk at classiccmp.org> wrote:
I am in the process or restoring a TU56 so it's in pieces. Pictures of the head were
requested so here they are.
These were taken with my phone so the quality is only mediocre.
This, like the rest of the drive, is in the process of being restored.
I'm still not sure how to clean the front of the head where the tape touches the
head. Any ideas?
We always used isopropyl alcohol (91% or better).
paul
12:44 p.m.
New subject: DEC Tape TU56 head pictures
On Wed, Feb 9, 2022 at 10:11 AM Mike Katz via cctalk
<cctalk at classiccmp.org> wrote:
I'm still not sure how to clean the front of the
head where the tape
touches the head. Any ideas?
Back in the day there was "Tape Head Cleaner" Which was a little tin
of trichlorotrifluoroethane (a.k.a. Freon 113) where you screwed the
cap off and it had a rod with a fluffy ball on the end inside, and you
would slather that all over the heads of 9-track tape drives etc. It
evaporated almost instantly. Of course after evaporating it floated up
and destroyed the ozone layer, so probably not super obtainable these
days.
A search for "Tape Head Cleaner" suggests there are similar modern
formulations used for HiFi equipment etc. that might be applicable.
1:46 p.m.
New subject: DEC Tape TU56 head pictures
On 2/9/22 12:44, Gavin Scott via cctalk wrote:
On Wed, Feb 9, 2022 at 10:11 AM Mike Katz via cctalk
<cctalk at classiccmp.org> wrote:
I find that perchloroethylene works to get stubborn tape-head deposits
cleaned up. Can be found in some formulations of brake cleaner as well
as the usual dry-cleaning solvent. Nonflammable, but somewhat toxic,
so use in a well-ventilated area. Not really plastic-safe, so use
sparingly. Also makes a great solder flux remover from PCBs.
--Chuck
I'm still not sure how to clean the front of
the head where the tape
touches the head. Any ideas?
Back in the day there was "Tape Head Cleaner" Which was a little tin
of trichlorotrifluoroethane (a.k.a. Freon 113) where you screwed the
cap off and it had a rod with a fluffy ball on the end inside, and you
would slather that all over the heads of 9-track tape drives etc. It
evaporated almost instantly. Of course after evaporating it floated up
and destroyed the ozone layer, so probably not super obtainable these
days.
A search for "Tape Head Cleaner" suggests there are similar modern
formulations used for HiFi equipment etc. that might be applicable.
2:11 p.m.
New subject: DEC Tape TU56 head pictures
Thank you.
On 2/9/2022 3:46 PM, Chuck Guzis via cctalk wrote:
On 2/9/22 12:44, Gavin Scott via cctalk wrote:
On Wed, Feb 9, 2022 at 10:11 AM Mike Katz via
cctalk
<cctalk at classiccmp.org> wrote:
I find that
perchloroethylene works to get stubborn tape-head deposits
cleaned up. Can be found in some formulations of brake cleaner as well
as the usual dry-cleaning solvent. Nonflammable, but somewhat toxic,
so use in a well-ventilated area. Not really plastic-safe, so use
sparingly. Also makes a great solder flux remover from PCBs.
--Chuck I'm still not sure how to clean the front of
the head where the tape
touches the head. Any ideas?
Back in the day there was "Tape Head
Cleaner" Which was a little tin
of trichlorotrifluoroethane (a.k.a. Freon 113) where you screwed the
cap off and it had a rod with a fluffy ball on the end inside, and you
would slather that all over the heads of 9-track tape drives etc. It
evaporated almost instantly. Of course after evaporating it floated up
and destroyed the ozone layer, so probably not super obtainable these
days.
A search for "Tape Head Cleaner" suggests there are similar modern
formulations used for HiFi equipment etc. that might be applicable.
818
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819
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10 comments
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amp1ron＠gmail.com -
bitwiz＠12bitsbest.com -
cclist＠sydex.com -
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go＠aerodesic.com -
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paulkoning＠comcast.net