I have seen, on this list and otherwise, comments about cards that
allow a VCR to be plugged in and data to be written to them. I was
wondering if
a) this is a good idea
b) why these things cost so much - shouldn't a simple D/A converter
and serial port do?
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On May 3, 23:30, Tony Duell wrote:
> On (almost) all hard disks, the head doesn't drag on the disk - it floats
> on a film of air. Even if the head crashes, the intertia of a stack of
> 14" aluminium platters is considerable, and the most likely result is
> that the head/mounting is ripped off the arm and flung into the HDA
> housing/across the room.
That's what happened to my Seagate, as far as I could see.
>
> > Can any of these stories happen to a modern drive?
>
> Unlikely. The platters are a lot smaller for one thing, so they can
> probably rotate faster without breaking up. And there's likely to be more
> complex speed control of the spindle motor, so it may not be able to
> overspeed significantly.
>
> I'm not worried about my PC drive suddenly spreading bits of platter
> through the front of the case.
No, but the load bang I described was from a 3.5" winnie.
--
Pete Peter Turnbull
Dept. of Computer Science
University of York
On May 3, 23:38, Tony Duell wrote:
> Tim wrote:
> > Same goes for the RL01/RL02 (which will spin about 3000 RPM instead
> > of nominal if you convince them to spin up without a pack).
>
> Yes, but with no pack there's no platter to break up :-)
>
> I'm not going to try it, but what does an RL0x do if you get it to
> overspeed with a pack in place, I wonder? Probably not a lot.
Not much, it just goes rather faster than normal. I've seen it happen when
a servo circuit failed (actually, a field servoid had removed a vital
component from a drive that he thought wouldn't be used again).
--
Pete Peter Turnbull
Dept. of Computer Science
University of York
On May 3, 23:23, Tony Duell wrote:
> Pete Turnbull wrote:
> > I have a couple of 14" Fujitsus (a massive 135MB apiece) similar to
that.
>
> Well, that Shugart I mentioned is either 12Mbytes or 24Mbytes depending
> on how many disks/heads were fitted at the factory.
>
> > They're the predecessors to the Eagles, which have heavy cast metal
HDA
> > enclosures. Much more fun to watch (and listen to).
>
> I remember the Eagle... I've got the service manual somewhere (given to
> me along with some other manuals) and I once had to repair a later drive
> (2361???) that was somewhat similar to the Eagle (maybe it was called a
> Double Eagle or something - I forget). The HDAs in those drives certainly
> look impressive.
Super Eagle. Impressive? Yes, those fins really are there to cool it.
--
Pete Peter Turnbull
Dept. of Computer Science
University of York
On May 3, 19:16, Allison J Parent wrote:
> Anyone have or know where I can find specs for TEAC FD55E drives?
>
> I know they are single sided half height but I suspect they are 96tpi
> 80track drives.
Easy way to find out is to try it :-)
There's a small amount of data on TEAC's web site,
http://www.teac.com/dsp/fd/fd_55.html
but that's really for the -R series which are newer. I've got jumper and
setting info for the GFR (similar to RX33) and a little info on the FD55-FB
and FD55-BVU (40 trk DS) and FD55-GFV-17 (HD 80 trk).
TEAC also have a faxback service, and there's a catalogue of the faxback
documents at
http://www.teac.com/dsp/catalog.html
You could try http://www.psyber.com/~tcj as well.
--
Pete Peter Turnbull
Dept. of Computer Science
University of York
<With all this talk of hard drives slicing themselves and adjacent
<walls to pieces, how is it that the motor can spin up to such a
<high speed when it's not supposed to, and why doesn't the head
<dragging on the disk surface cause it to stop?
Head draging...? only if it's crashed even then the motors on those old
drives were huge.
<Can any of these stories happen to a modern drive?
Less likely as smaller platters, less mass and more exotic speed control
servos. The big difference is that you would need som really amazing RPM
to make a 3.5" plater fracture and fail where a 14" platter has a far
higher speed at the perimeter at a lower RPM. Without running the numbers
a 14" platter goes transsonic at the perimeter at something like 14,000
RPM however before you get to that speed the forces working on the metal
are high enough that it will exceed the tensile strength. Also small
imbalances show up with increasing rotational speed and the platter start
to develop vibratory waves which if allow to go to destructive extremes
make for good stories.
I know as I have an operating Morrow (thinkertoys) DISCUS with a 10mb
memorex(m101) 8" drive.
Allison
On May 3, 18:19, Tony Duell wrote:
> > Well, seen after the fact when I was called in to 'repair' it...
> >
> > Probably over 15 years ago, NorthStar offered a 14 inch hard drive in
an
> > external cabinet for use with the 'Horizon' microcomputers. It was
> > amusing to watch with the top of the enclosure off as the entire unit
> > was enclosed in a slightly smoked brown Plexiglass 'bubble'.
>
> That description matches a number of 14" hard disks available at that
> time. I still have a Shugart SA4000 (on a PERQ 1) which has a similar
> design of HDA. But that one uses a synchronous mains motor to turn the
> disks (and produces the write clock from a special head on one of the
> disks, thus synchronising the whole thing to the disk rotation).
I have a couple of 14" Fujitsus (a massive 135MB apiece) similar to that.
They're the predecessors to the Eagles, which have heavy cast metal HDA
enclosures. Much more fun to watch (and listen to).
--
Pete Peter Turnbull
Dept. of Computer Science
University of York
Truly incredible. The official explanation sounds like something
>from a book on Chernobyl. What the heck did the thing use for a
motor? Diesel or Gasoline?
>
>At 04:53 PM 5/2/98 -0400, you wrote:
>>
>>Anyone ever seen a worse failure?
>
>Well, seen after the fact when I was called in to 'repair' it... And
>actually, quite a good thing that no one was there to witness it! (you
>will see why in a moment)
>
>Probably over 15 years ago, NorthStar offered a 14 inch hard drive in
an
>external cabinet for use with the 'Horizon' microcomputers. It was
amusing
>to watch with the top of the enclosure off as the entire unit was
enclosed
>in a slightly smoked brown Plexiglass 'bubble'.
>
>The down side was that the sector wheel/transducer/tachometer assembly
was
>external to the sealed housing and frequently caused "sector not found"
>errors as dust collected on it. This required regular (monthly or so)
>cleaning which required removal of the HDA from the external enclosure
in
>order to access the bottom of the assembly. (quickly rectified by our
>staff after a couple of calls by using a 'nibbler' tool to add a 2"x3"
>opening on the bottom of the external enclosure that we could access
the
>assembly through)
>
>It was also noted in one of the service bulletins that since this
assembly
>also served as the tachometer for the spindle drive, that you could
tell if
>the wheel was becoming dirty by a "surging" sound coming from the unit
even
>if you did not experience sector errors. Little did we know...
>
>We had one customer who tended to keep his system up 24x7 since he had
an
>external sales staff that used the system to file orders and he liked
to
>work from home. (dial-in lines) He also liked to run the HD with the
upper
>part of the external enclosure removed so that he could show off to
>customers and clients just how advanced their operation was. (ignoring
our
>warnings that this would allow the unit to attract dust and dirt more
rapidly)
>
>Well... One Monday morning I get to the shop and we have a number of
>messages on the answering machine (in increasing levels of agitation).
He
>starts off by explaining that Friday evening he started getting
frequend
>'sector' errors reported from the system. Over the course of the day
>Saturday the errors increased and the system response degraded. Sunday
>morning the system would not answer a call at all. Sunday evening he
got a
>call from the Alarm Monitoring company that something had tripped the
>offive alarms. When he went in to check the building, he noted that
there
>"appeared to be a problem with the hard drive" and wanted us out there
>first thing to make sure he did not lose any data.
>
>So... a couple of us went out expecting to have to clean out the wheel
>assembly (yet again) and perhaps correct a couple of glitched
sectors...
>WRONG!
>
>When we entered the computer room, it was quite obvious that there was
a
>bit more than a "problem with the hard drive"!
>
>The room looked like someone had stood in the center of the room with
an
>M-16, and used it to try to cut the room in half. Clear around the
room at
>about table top level were pieces of plastic and metal stuck into the
wall
>boards. The plexiglas 'bubble' from the HDA was gone (obviously
shattered)
>and the platters had large chunks missing from them. No need to even
look
>for the head/arm assemblies.
>
>After an extended discussion with the customer, of which most of the
time
>was spent explaining that we would NOT be able to recover any data from
the
>drive, we set about collecting the wreckage and installing a new drive
and
>software.
>
>Once back at the shop, a call to NorthStar brought a visit a few days
later
>from one of their technical support staff as well as an engineer from
the
>manufacturer of the HDA (Micropolis if I recall correctly).
>
>The "official" explaination went something like this:
>
>Due to the design of the (rather basic) tachometer circuit in this
unit, a
>missing sector pulse was intrepreted by the tach as a loss of spindle
>speed. (start-up mode mentality, if you are starting the drive and
don't
>see a pulse, speed up (or start-up) the motor until the required pulse
rate
>is achieved) This was the cause of the "surging" sound noted in
previous
>service bulletins.
>
>In "theory" (now apparently proven) if the sector/tach wheel became
>sufficiently dirty the tachometer circuit could attempt to keep
increasing
>spindle speed up to such a point where a failure of the unit might be
>induced either by overload failure of the spindle motor or by excess
>vibration caused by excess rotational speed.
>
>Apparently, no one ever considered a 'fail-safe' for the tachometer
circuit...
>
>While they never did detail just exactly what failed first, whatever it
was
>apparently caused a head crash severe enough to fracture one or more of
the
>platters, and from that point it was all downhill...
>
>Without the cover of the external enclosure to contain it, (a metal
>enclosure by the way) when things started to come apart there was
nothing
>to stop it! And the results were indeed quite spectacular.
>
>Made everyone a good deal more serious about keeping those sensor
wheels
>clean... (and the covers on!)
>
>BTW: NorthStar did replace the drive for us...
>
>-jim
>
>---
>jimw(a)agora.rdrop.com
>The Computer Garage - http://www.rdrop.com/~jimw
>Computer Garage Fax - (503) 646-0174
>
>
>
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Yes, you read correctly. One of the local thrift stores turned up a Xerox
'MemoryWriter 630' for all of $8.00. Since I was in the market for
something to fill out forms with, and curious about the MW series in any
case, I picked it up (with a grunt -- these are not light!).
It's built very robustly inside, and appears to be based heavily on the
8085 chip. The design and layout resemble (no surprise) the Diablo 630
series daisywheel terminals. A good vacuuming and a little oiling later and
it works just great. Original manufacture date is around 1984 (based on the
date codes I found on the components).
No CRT on this one, though I understand that was one option. If anyone
happens to have a user's guide, accessories, options, or diskettes for this
beast, please let me know.
Thanks in advance.
-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-
Bruce Lane, Sysop, The Dragon's Cave BBS (Fidonet 1:343/272)
(Hamateur: WD6EOS) (E-mail: kyrrin(a)jps.net)
"Our science can only describe an object, event, or living thing in our own
human terms. It cannot, in any way, define any of them..."
<To my knowledge no flavor of unix runs on anything less than a 32-bit
<processor. There's a unix-workalike for the C-64/128, but that's not
Your knowledge is limited. Unix was started and lived for years on
PDP-11s (a 16 bit machine) in the form of V5, V6, V7 and 2.9BSD and
2.11BSD. I may add it was on other machines like the Interdatas.
<quite the same thing. Anyway, it's called Lunix. I haven't tried it yet,
There is also ELKS embedded kernal linux aimed at XT class(16bit) and
other small machines.
<but it's possible that Lunix could become fairly popular amongst the
<8-bitters. The point I was trying to make about running Minix (since you
Linux is is one form of popular free unix and was launched on PC hardware
that happens to be 32bit(386 and later).
Fitting unix on most 8bitter means a minikernal and swapping as most
8bitters have only a 64k address space unless some banking logic was
added or the CPU is only of the later z80 varients with MMU(z180 1mb, z280
16mb).
<generally run that on a PC anyway) is that it just simply makes more
<sense to run Linux or FreeBSD or some other supported operating system.
Minix is supported exactly the same way LINUX is.
<It's possible to run those operating systems with 8MB comfortably
<(provided you're not running XFree86)...all the text-based stuff runs
<just fine. Besides 8MB RAM doesn't exactly break the bank nowadays. :)
Well, my 386 is running it in 8mb with xfree86 and while not blindingly
fast it does run well. Not everyone has bundles of cash for their
computer.
I find the idea of not less than 32bits, 200mhz cpus and large memory
being a must to be patently retrorevisionist to the history of what was
done before those things were available.
Allison
