26 Oct
2020
26 Oct
'20
9:01 a.m.
http://mnembler.com/computers_mini_stories.html
"George Dragner always wore a belt with a metal dragon buckle. He was a colorful
character known for pissing off management. His most
famous act was tossing a chair through the window at a customer site. The customer refused
to believe that the lack of humidity in the room
was screwing up his magnetic tape media. As the tape heads depend on the moisture from
the air to prevent the magnetic oxide from being
torn off the media from the friction during a rewind. George broke the window to prove his
point. He was right ! "
There is a minimum RH specified for tape, but "tape heads depend on the moisture from
the air" ??
26 Oct
26 Oct
1:28 p.m.
Hello Al,
Am 26.10.2020 um 17:01 schrieb Al Kossow via cctalk <cctalk at classiccmp.org>:
There is a minimum RH specified for tape, but
"tape heads depend on the moisture from the air" ??
First of all, my experiences are from ancient audio reel-to-reel tape. So maybe I?m wrong.
Also add the fact that ?screwing up? is not a precise description of what actually
happened with the tapes?
I guess that not enough moisture can probably brittle the plastic film, the magnetic
coating has been applied to. Some plastic can absorb humidity. If you add this to the high
speed the tape reels were wound, I could imagine that a really dry environment can affect
tapes.
I can?t come up with an idea in which way the tape head could be adding to the
?screwing?.
:wq! PoC
6:30 p.m.
Thanks for that Al. Never thought about humidity and mag tapes as
only time I used to backup data to 9 track tapes was in Vancouver
where humidity always high. Also used Time Shoppa's and Kevin
McGuigan's drives to extract data from those tapes in
Vancouver. Doubt I'll be copying any more of my mag tapes but will
definitely keep that in mind in case I do that in Kamloops where RH
quite low in winter. Have a humidity sensor in my guitar case as
have to moisten a sponge every few weeks to go in guitar so wood
doesn't crack. Can detect shrinkage of wood by increase in resonant
frequency of strings increasing as wood shrinks. Also take extreme
care when touching any non-TTL IC during winter here.
http://mnembler.com/computers_mini_stories.html
"George Dragner always wore a belt with a metal dragon buckle. He
was a colorful character known for pissing off management. His most
famous act was tossing a chair through the window at a customer
site. The customer refused to believe that the lack of humidity in
the room was screwing up his magnetic tape media. As the tape heads
depend on the moisture from the air to prevent the magnetic oxide
from being torn off the media from the friction during a rewind.
George broke the window to prove his point. He was right ! "
There is a minimum RH specified for tape, but "tape heads depend on
the moisture from the air" ??
10:50 p.m.
Hi all,
Back in the early 70's I was an operator on an IBM 360/40 with 4
tapedrives. Nobody could understand that sometimes a tape transfer would
stop saying "end of tape", mainly around 3 PM, when not called for. It
was mainly one specific drive, but its two neighbours, one on each side,
could also behave like this. Tape drive specialists visitied us,
scratched their heads, and went off again. When the blinds were rolled
down, the error disappeared. The reason for the strange behaviour was
that the sun could shine into the machine room when it was in a specific
position, so it could send some light into the drive, where the tape
then reflected the light into the sensor, making it believe that it had
met the end-of-tape marker.
/Nico OZ 1 BMC
On 2020-10-26 17:01, Al Kossow via cctalk wrote:
http://mnembler.com/computers_mini_stories.html
"George Dragner always wore a belt with a metal dragon buckle.? He was
a colorful character known for pissing off management.? His most
famous act was tossing a chair through the window at a customer site.
The customer refused to believe that the lack of humidity in the room
was screwing up his magnetic tape media.? As the tape heads depend on
the moisture from the air to prevent the magnetic oxide from being
torn off the media from the friction during a rewind. George broke the
window to prove his point.? He was right ! "
There is a minimum RH specified for tape, but "tape heads depend on
the moisture from the air"? ??
11:24 p.m.
We had a similar problem when I was at IBM and we were developing a
follow on to the PC/AT (it never shipped). We had a bunch of
prototypes in the lab running tests with stepper HDDs (rather than
voice coils) We kept having disk errors (failure to find track 0) when
running tests.
It took us a while to figure several things out:
1) all of the machines were run with their covers off
2) all of the machines that failed were by the windows
3) the failures always happened at a particular time of day
After a bit of head scratching we discovered that the tack 0 sensor was
optical and at that particular time of day the sun at a particular
angle did not allow the sensor to register that the drive was at track
0.
TTFN - Guy
On Tue, 2020-10-27 at 06:50 +0100, nico de jong via cctalk wrote:
Hi all,
Back in the early 70's I was an operator on an IBM 360/40 with 4
tapedrives. Nobody could understand that sometimes a tape transfer
would
stop saying "end of tape", mainly around 3 PM, when not called for.
It
was mainly one specific drive, but its two neighbours, one on each
side,
could also behave like this. Tape drive specialists visitied us,
scratched their heads, and went off again. When the blinds were
rolled
down, the error disappeared. The reason for the strange behaviour
was
that the sun could shine into the machine room when it was in a
specific
position, so it could send some light into the drive, where the tape
then reflected the light into the sensor, making it believe that it
had
met the end-of-tape marker.
/Nico OZ 1 BMC
On 2020-10-26 17:01, Al Kossow via cctalk wrote:
>
> http://mnembler.com/computers_mini_stories.html
>
> "George Dragner always wore a belt with a metal dragon buckle. He
> was
> a colorful character known for pissing off management. His most
> famous act was tossing a chair through the window at a customer
> site.
> The customer refused to believe that the lack of humidity in the
> room
> was screwing up his magnetic tape media. As the tape heads depend
> on
> the moisture from the air to prevent the magnetic oxide from being
> torn off the media from the friction during a rewind. George broke
> the
> window to prove his point. He was right ! "
>
> There is a minimum RH specified for tape, but "tape heads depend
> on
> the moisture from the air" ??
>
27 Oct
27 Oct
1:51 a.m.
On 10/26/2020 11:24 PM, Guy Sotomayor via cctalk wrote:
It took us a while to figure several things out:
1) all of the machines were run with their covers off
I asked one of the mechanical
/ packaging guys at Microdata one time
what the hardest part
of making the cabinets and mechanical systems.
His response:? Making it still run with the cover on.? Mostly heat
problems and how to get it
out w/o too much noise (in some cases), and cost.
Thanks
Jim
1 Nov
1 Nov
3:19 p.m.
Guy Sotomayor says:
We had a similar problem when I was at IBM and we were
developing a
follow on to the PC/AT (it never shipped).
Was this the "PC II" (a "true" sequel to the PC) that magazines
constantly talked about IBM working on, until the PS/2 disappointed everyone?
--
geo:37.783333,-122.416667
27 Oct
27 Oct
1:48 a.m.
On 10/26/2020 10:50 PM, nico de jong via cctalk wrote:
IBM 360/40 with 4 tapedrives.
the 3420 drives
and I suspect their predecessors which were more common
on the 360s used
one light bulb to run the light from one bulb all over the drive.
The 3420's we had had a big box of spaghetti tubing which were the light
pipes to service our
?drives.? I had the box somewhere when we shut down.? The 3420s and
3803 went one way,
the most of the service spares were abandoned.
There were a lot of weird problems with light sensors on those drives.?
We had some on our
360/50 at UMR as well, but the 2314 disk drives were more entertaining
with hydraulic failures.
thanks
Jim
PS: when googling ran across this site using an interesting graphic with
interesting peripherals.
https://serverpartswarehouse.com/100-oem-ibm-9348-001-magnetic-tape-unit/
PPS:? 2420 drive reference page for that half inch drive.
https://www.ibm.com/ibm/history/exhibits/storage/storage_2420.html
7:50 a.m.
On 10/27/2020 12:50 AM, nico de jong via cctalk wrote:
Hi all,
Back in the early 70's I was an operator on an IBM 360/40
with 4 tapedrives. Nobody could understand that sometimes
a tape transfer would stop saying "end of tape", mainly
around 3 PM,
It was also well-known that you should not allow flash
pictures to be taken in the machine room, as ALL the tape
drives would unload simultaneously when the flash went off.
Jon
8:08 a.m.
-----Original Message-----
From: cctalk <cctalk-bounces at classiccmp.org> On Behalf Of Jon Elson via
cctalk
Sent: 27 October 2020 14:51
To: nico de jong <nico at farumdata.dk>; General at ezwind.net;
Discussion at ezwind.net:On-Topic and Off-Topic Posts
<cctalk at classiccmp.org>
Subject: Re: Strange magtape anecdote
On 10/27/2020 12:50 AM, nico de jong via cctalk wrote:
I remember when doing standby power generator tests we had to remember to off-line all the
drives at end of job, other wise they all tried to rewind at the same time....
.. and the generator could comfortably do two, stuttered a bit with three, but on the
first test as the fourth flicked in there was a big "bang" and lots of flapping
of tape, plus lots of cursing from our Site Engineer.,,,,
Dave
Hi all,
Back in the early 70's I was an operator on an IBM 360/40 with 4
tapedrives. Nobody could understand that sometimes a tape transfer
would stop saying "end of tape", mainly around 3 PM,
It was also
well-known that you should not allow flash pictures to be taken in
the machine room, as ALL the tape drives would unload simultaneously when
the flash went off.
Jon 
9:33 a.m.
On Oct 27, 2020, at 11:08 AM, Dave Wade G4UGM via
cctalk <cctalk at classiccmp.org> wrote:
...
I remember when doing standby power generator tests we had to remember to off-line all
the drives at end of job, other wise they all tried to rewind at the same time....
.. and the generator could comfortably do two, stuttered a bit with three, but on the
first test as the fourth flicked in there was a big "bang" and lots of flapping
of tape, plus lots of cursing from our Site Engineer.,,,,
A similar issue shows up with large collections of disk drives. That includes modern
small HDDs. The motor start surge current is a lot higher than the steady state current,
so starting a row of drives all at once -- or a box full of 3.5 inch HDDs in a modern
storage array -- can cause an overload.
In storage array firmware that's dealt with by spinning up the drives a couple at a
time, fewer at a time if one of the power supplies has failed.
paul
10:01 a.m.
Hello Paul,
Am 27.10.2020 um 17:33 schrieb Paul Koning via cctalk <cctalk at classiccmp.org>:
The motor start surge current is a lot higher than the
steady state current
I fondly remember my Seagate Elite 9GB (5.25? double height), nominal 5400 RPM. Power
applied, it slowly spins until a certain speed and then switches to ?second gear? to push
it to final speed. I measured 40W while doing that.
:wq! PoC
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aek＠bitsavers.org -
boris＠summitclinic.com -
dave.g4ugm＠gmail.com -
elson＠pico-systems.com -
ggs＠shiresoft.com -
jwsmail＠jwsss.com -
nico＠farumdata.dk -
paulkoning＠comcast.net -
poc＠pocnet.net -
ylee＠columbia.edu