15 May
2013
15 May
'13
4:09 p.m.
So I picked up a pair of Tek 4052, plenty of doc and spares, and some library tapes.
Sadly tapes were stored in less that ideal conditions.
So I have mouldy tapes, and lots of broken DC300 drive belts.
I am ready to ignore the mould, but what about the drivebelts ?
Any alternatives to pinching them from still functional cartridges ?
Jos
15 May
15 May
4:35 p.m.
Jos Dreesen wrote:
So I picked up a pair of Tek 4052, plenty of doc and
spares, and some
library
tapes.
Sadly tapes were stored in less that ideal conditions.
So I have mouldy tapes, and lots of broken DC300 drive belts.
I am ready to ignore the mould, but what about the drivebelts ?
Any alternatives to pinching them from still functional cartridges ?
Congratulations! The 4052 indeed a rare beast. Hopefully the ROMs in
the machines haven't gone south.
Earlier versions of the 4052 (and 4051) used a weird Motorola EPROM for
the firmware that has a tendency to forget. It is a weird pinout, and
isn't directly compatible with more standard EPROMs. I suggest that if
you have an operational machine that you pull the ROMs (carefully), and
read out their contents (assuming you have a way to read them) to
archive them in another form, should you need to make new ones someday.
There are quite a few different versions of the firmware, all with
particular little quirks that match up with hardware tweaks, so one
version of firmware may not run on certain boardsets.
As far as I've been able to find, there just doesn't seem to be a
suitable replacement for the drive bands. I've pillaged them from good
tapes to rescue tapes with important content. Thankfully, I have a
floppy system for my 405x machines, and I've copied most all of the
tapes to (8") floppies, and then made dupes of the floppies. I just
don't trust the tapes anymore. I wish that there was a way to image
these floppies by reading them with something else, but I just haven't
had the time to dig into it.
One thing to be aware of with the tapes is "stiction" of the tape if you
do replace the drive band. After stored for a long period of time
(especially if stored in higher temperatures, e.g., attic, metal shed,
etc.), the tape "sticks" to itself. If you just replace the drive band
without first winding the tape fully in both directions to break the
stiction, you may well break another drive band. You may find tapes
that are stuck together so badly that they can't be salvaged. I have
found more than a few like this.
Also, watch out for the capstan roller in the 4052 drive. It can turn
to goo, or end up with flat spots (especially if a tape was left in the
drive for a long time) that can really mess up a tape if you put it in.
If this happens, you have to figure out a way to rebuild the capstan so
that it drives the tapes properly. It's a pretty tight tolerance on the
size and material for the roller...too much pressure and the motor will
stall, and not enough, and the tape will slip.
Clean the tape head frequently, as old tapes tend to drop oxide pretty
bad. These drives are very sensitive to gunk on the heads.
The mold on the tape can cause the oxide to flake off, leaving bare
mylar base. This clearly makes the tapes unreadable, and makes a mess
of the tape head.
The tape drives used in the 405x machines were not so great at
interchange..if a tape was written on one machine, it more than likely
would have problems being read on another. There is an alignment
process that can help dial in the drive -- it is listed in the service
manual (hopefully you got one of those).'
Best of luck,
Rick Bensene
The Old Calculator Museum (and a few old computers, too)
http://oldcalculatormuseum.com
6:19 p.m.
Al K. wrote:
The 4709 manuals are about to be uploaded to bitsavers.
They are hard-sectored.
Isn't the model number for the floppy subsystem 4907?
I might be wrong, but that's what I recall.
They are hard-sectored floppies, definitely. I can't remember the
sector count, though.
Since the 4907 is GPIB-based, perhaps a PC with a GPIB card in it, and
some suitable code could prove successful at archiving the content of
the floppies in a form that is longer-lived. I doubt, though, that I'll
ever have the time to pursue it.
I inherited a bunch of Tektronix-branded floppies with one of the
systems (4051) that I got some time ago.
Don't know who the OEM was, but they are still good after all these
years.
The Tektronix-branded DC-300 tapes are really bad. The oxide comes off
very easily, and the tension bands are almost always broken. I got a
box of unopened NOS Tektronix-branded cartridges, and found that each
and every one, even though sealed in a plastic bag, had broken tension
bands, and oxide was separating from the tape.
The 3M-branded tapes definitely seem to hold up better -- I have a bunch
of old 3M DC-300A's as a set that were part of the UUNET Unix archive,
and they are still solid to this day. Anything Scotch-branded is
generally useless. Perhaps Tektronix OEM for the DC-300 tapes was
indeed Scotch.
In any case, Al -- Thanks for putting the docs online!
-Rick Bensene
6:49 p.m.
On 05/15/2013 03:19 PM, Rick Bensene wrote:
The 3M-branded tapes definitely seem to hold up better
-- I have a bunch
of old 3M DC-300A's as a set that were part of the UUNET Unix archive,
and they are still solid to this day. Anything Scotch-branded is
generally useless. Perhaps Tektronix OEM for the DC-300 tapes was
indeed Scotch.
"Scotch" is still 3M--just their budget brand. I recall having terrible
experiences with Scotch 777 back in the day. The 3M 700 "Black Watch"
tape was much superior.
--Chuck
17 May
17 May
9:51 p.m.
On 5/15/13 3:19 PM, Rick Bensene wrote:
Al K. wrote:
The 4709 manuals are about to be uploaded to bitsavers.
They are hard-sectored.
Isn't the model number for the floppy subsystem 4907?
I might be wrong, but that's what I recall.
oops
They are hard-sectored floppies, definitely. I
can't remember the
sector count, though.
In any case, Al -- Thanks for putting the docs online!
Just finished uploading the service manual today. The rom board with the
patching scheme is a little weird.
15 May
15 May
4:36 p.m.
--- On Wed, 5/15/13, Jos Dreesen <jdr_use at bluewin.ch> wrote:
I am ready to ignore the mould, but what about the
drivebelts ?
Any alternatives to pinching them from still functional
cartridges ?
A while back, someone reported success using Baumgarten's PlastiBands
(polyurethane "rubber bands") as a replacement, but I don't have any
experience with this myself.
--Bill
5:31 p.m.
On 05/15/2013 01:36 PM, William Maddox wrote:
A while back, someone reported success using
Baumgarten's PlastiBands
(polyurethane "rubber bands") as a replacement, but I don't have any
experience with this myself.
The 4.5" ones are a little on the small side and very difficult to get
on (three hands and 35 fingers would help), but they're good for at
least a couple of run-throughs.
The 6" ones are harder to find, but might be easier to work with.
But take a good look at the tapes--since the DC carts spool with the
oxide surface facing out (unlike, say, 9-track tape), the oxide will
very often get peeled off where the tension band contacts it. Then
you've got problems.
"3M" branded tapes are better in this respect than "Scotch" ones of
the
same type.
FWIW,
Chuck
17 May
17 May
1:15 p.m.
On Wed, May 15, 2013 at 4:31 PM, Chuck Guzis <cclist at sydex.com> wrote:
On 05/15/2013 01:36 PM, William Maddox wrote:
A while back, someone reported success using Baumgarten's PlastiBands
(polyurethane "rubber bands") as a
replacement, but I don't have any
experience with this myself.
The 4.5" ones are a little on the small side and very difficult to get on
(three hands and 35 fingers would help), but they're good for at least a
couple of run-throughs.
The 6" ones are harder to find, but might be easier to work with.
But take a good look at the tapes--since the DC carts spool with the oxide
surface facing out (unlike, say, 9-track tape), the oxide will very often
get peeled off where the tension band contacts it. Then you've got
problems.
"3M" branded tapes are better in this respect than "Scotch" ones of
the
same type.
FWIW,
Chuck
1:19 p.m.
On Wed, May 15, 2013 at 4:31 PM, Chuck Guzis <cclist at sydex.com> wrote:
On 05/15/2013 01:36 PM, William Maddox wrote:
A while back, someone reported success using Baumgarten's PlastiBands
http://www.amazon.com/Polyurethane-Plastibands-Pack-50-BASF-6500/dp/B00BSGS…
$14.99 / 50 from Amazon US
-Jon
P.S. Sorry about the previous empty message.
(polyurethane "rubber bands") as a
replacement, but I don't have any
experience with this myself.
The 6" ones are harder to find, but might be easier to work with.
2:21 p.m.
On 05/17/2013 10:19 AM, auringer tds.net wrote:
http://www.amazon.com/Polyurethane-Plastibands-Pack-50-BASF-6500/dp/B00BSGS…
$14.99 / 50 from Amazon US
I see that they're also available from at least one Burmese vendor:
http://prubuy-myanmar.com/-brand/3-polyurethane-plastibands-6--spJGeMUy-ptE…
And you can get what amounts to a 3-packages-for-the-price-of-2 with
free shipping from an eBay seller:
http://www.ebay.com/itm/3-Polyurethane-Plastibands-6-Pack-50-BASF-6500-/350…
I find that these things are also useful for bundling up cables. Unlike
rubber bands, they don't deteriorate (as quickly, at least).
--Chuck
16 May
16 May
5:03 a.m.
On Wed, 15 May 2013, William Maddox wrote:
A while back, someone reported success using
Baumgarten's PlastiBands
(polyurethane "rubber bands") as a replacement, but I don't have any
experience with this myself.
Sadly, they are absolutely unavailable in Europe.
Christian
5 a.m.
On Wed, 15 May 2013, Jos Dreesen wrote:
So I picked up a pair of Tek 4052, plenty of doc and
spares, and some library
tapes.
I could need a scan of part 2 of the service manual.
So I have mouldy tapes, and lots of broken DC300 drive
belts.
I am ready to ignore the mould, but what about the drivebelts ?
Any alternatives to pinching them from still functional cartridges ?
1. Bake the tapes (without belt, of course). That does only good.
2. Just take a belt from another QIC cartridge. Since I have tons of NOS
DC600 cartridges I usually use these as belt donators. But DC6150 belts
work equally well.
3. IMPORTANT: Before putting in the new belt, put it in hot water or pour
hot water (at least 50?C) over it. After that long standby time, the
belts have usually strechted too much to give the desired tape
tension. Heating them will shrink them to their original size *and*
elasticity. That operation is repeatable.
Christian
4155
days inactive
4158
days old
12 comments
7 participants
participants (7)
-
aek＠bitsavers.org -
auringer＠tds.net -
cc＠informatik.uni-stuttgart.de -
cclist＠sydex.com -
jdr_use＠bluewin.ch -
rickb＠bensene.com -
wmaddox＠pacbell.net