>From: "Jim Battle" <frustum(a)pacbell.net>
>At 06:09 PM 10/28/02 -0800, dwight elvey wrote:
>>Hi
>> Actually, I was bummed. ...
>> I had a Poly-88 setup but I think only one in 10 noticed
>>and even then, I think only 2 in those ten knew what it was.
>
>I spotted it, and I knew what it was. But how could you tell
>that? Probably other people were the same.
>
>> Of course, my display was all about tape recovery and not
>>the Poly-88. I don't think, maybe, 5 people all together
>>realized that.
>
>That, I didn't spot. I noticed the waveforms on the wall, but amidst the
>din (auditory and visual) it didn't register. I wish I had noticed,
>though, since it is an area I want to spend some time working on one of
>these years. Rather than letting it be lost to the moment, is there any
>chance of you writing up your work and putting it online somewhere (even
>posting it to this list and letting it get archived would work).
>
>I've read a half dozen very terse summaries of emulators and such that do
>this, but most work only on really clean tapes. They simply do some DC
>correction, perhaps a bit of filtering, and then time zero crossings and
>decode from there. Have you done something more sophisticated than
>this? Some of the Sol tapes I've looked at are way too corrupted for such
>a simple technique to work.
>
>There are a lot of communication theory ideas that could be applied to the
>problem directly; in addition, the file format is going to have some known
>structure that could be used to help train the receiver and disambiguate
>some cases.
>
>I'd be interested to hear more.
>-----
>Jim Battle == frustum(a)pacbell.net
>
>
Hi Jim
I will try to put something together. I did have an outline
posted at the exhibit but hoped many would ask questions
( quite a few did but only about 1/3 of those knew what
a Poly-88 was ). First, I didn't use any of the high tech
methods. I know a reasonable amount about DSP, having taken
a couple of courses and tinkered some as well. There is
little in DSP that will fix a dropout caused by folded tapes.
DSP can be used for such problems as high frequency rolloff
or print-thru. These problems are often over stated and
are not the most common problems.
Understanding how the data is recorded and how your machine
reads these back can be a large help. One also needs an alternate
method of reading the tape because the canned software usually
won't continue after an error. You also need to know the
method used to validate the replay. If you are lucky, they
used a CRC or ECC. In most cases, it was a simple check sum.
Recovery is more about bringing all the known stuff together
and recreating the missing parts. As long as the recorded
data is something like a program or text the problem can
often be solved. If it is something like raw data, ( strings
of meaningless numbers ) the chances are poor.
One of the first things to look for is duplicate tapes. Not
all errors happen at the same place and same time.
Like solving a mystery, it is all about putting all of the
pieces together and not just a single part. It is easier then
one would think but does take some time to develop the
tools needed to get all the information.
I don't have a web site to publish such information but
I suspect someone will provide it.
Anyway, I apologize for not having a bigger title. Even though
Sellam gave us plenty of extra time, I was still doing a lot
of last minute preparations.
Dwight
Hi Ross,
Do you have the Source of your "KIM-1" clock for me.
You told me about your clock, here:
http://www.learnmicros.com . I have a KIM-1, but I'm
afraid to connect it with power. I only can test it on
emulators, so maybe you have it for me...
Greetz,
Richard, The Netherlands.
__________________________________________________
Do You Yahoo!?
Everything you'll ever need on one web page
>from News and Sport to Email and Music Charts
http://uk.my.yahoo.com
Connecticut sounds good to me too. I am around Hartford and I presume David A. Woyciesjes who is often on this list is around New Haven. If someone wants advice on venues ask me by direct e-mail.
> From: Fred Cisin (XenoSoft) <cisin(a)xenosoft.com>
> IIRC, #26-1401 It is basically straight through, and can be made by
> crimping a card-edge connector on one end of ribbon cable, and a
> "centronics" amphenol connector on the other. Sorry, but I don't
remember
> which direction to offset the cable (for the 34 v 36)
Thanks, Fred. The docs give the pinouts on the card-edge, so a cable
should be no problem.
> The other 34 pin is for external floppies. It should be possible to
> identify which 34 is which by proximity to the disk controller.
Piece of cake -- thanks again.
> "expansion bus" On the model 1 it was 40 pin. Did they change to 50 on
> the 3?
I don't know -- I wonder why this is not shown in the docs?
Later --
Glen
0/0
> From: DAVID L. ORMAND <dlormand(a)aztec.asu.edu>
> I'm trying to help some guys outfit TI-99/4As with 360K
> drives. A year or so ago, they were still available from
> some of the surplus dealers I know about, but they seem
> to have disappeared.
>
> Does anyone have a line on supplies of 360K drives? The
> only ones I find via web search are $25, which seems a
> bit much for a once-ubiquitous drive that is now a little
> obsolete.
I've been picking them up on eBay, often in never-been-used condition, for
$10 - $12 including shipping. I've also found some in junk systems at
thrift stores. They are not as easy to find (at least in my neck of the
woods) as they were a couple of years ago, but the high-density "1.2 MB"
drives seem to be everywhere (including my shop -- I've got almost 50 of
them here!).
Glen
0/0
On Oct 30, 16:38, Patrick Finnegan wrote:
> I've got a 35mW HeNe Laser + Power supply that I picked up today for next
> to nothing. It seems to be having some problems - the laser (somtimes)
> blinks a few times when I first turn it on, and then stops.
As a few others have said, most common cause of an HeNe laser failing to
"lase" is loss of the helium. I, too, found that out the hard way.
Interestingly, the more it's used, the less likely that is to happen in a
given time (at least, so said the notes with the last HeNe tube I bought).
> Now, I've never really worked on a HV power supply before, and I'm trying
> to be careful when I play with things. First off, does anyone have a
> general idea of what sized dummy load ("resisitor") I should try haning
> off of the HV output to properly load it? I noticed that the laser tube
> has 3x27kohm resistors in series, would a couple watt approx 81kohm
> resistor be a good idea?
Probably not. Although not always obvious from the specs, most resistors
are only rated to some hundreds of volts, maybe a thousand or two. That's
why your laser has three in series instead of one bigger one.
> Also, does anyone have an idea for a failure mode to look for? I've got
> an O'scope, dmm, and various other tools at my disposal, but no
> 'authentic' HV test/mesurement gear.
You want a proper insulated HV probe for a start... you need to be able to
measure kilovolts if you want to check the power supply.
Check out Sam's laser FAQ at www.repairfaq.org
--
Pete Peter Turnbull
Network Manager
University of York
Hi -- does anyone have any documentation
for the IBM 2520 card reader? I know it's
a long shot. (I checked Al Kossow's archive
and don't see it there). Any leads would
be greatly appreciated!
Thanks,
Brian
=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-
_| _| _| Brian Knittel
_| _| _| Quarterbyte Systems, Inc.
_| _| _| Tel: 1-510-559-7930
_| _| _| Fax: 1-510-525-6889
_| _| _| Email: brian(a)quarterbyte.com
_| _| _| http://www.quarterbyte.com
I've removed (as of tonight) all the parts out of the chassis,
documenting
where everything goes. I cleaned the chassis very carefully. Once the
card cage/
backplane was out, it was obvious that these parts were in beautiful
condition,
if not more than a little bit dusty. A couple of bent pins in back were
easily
corrected, and the entire assembly sits waiting to be reinstalled in the
chassis.
The TU58, unfortunately, did not fare quite as well, as the mice had
chosen
it as their nesting place. After finally managing to get the tape that
was in it
loosened up, it came out coated with mouse fur and mouse droppings etc.
The rollers are entirely wound up in this stuff. It sits in a box
awaiting later
attempts at cleaning. I hold out little hope.
The power supply, which seems to consist of a controller and two
actual PSUs, looks solid from the outside, and also what I can see of
the inside.
It appears to have large battery packs in the bottom of it. These,
certainly,
would be dead after all this time. Are they important? Maybe theyre not
even
batteries...
The H7112A looks solid, but again, I haven't explored inside.
Everything in the system
has a light coating of New Mexico red clay dust.
The blower/motor assembly from the bottom of the cabinet awaits
cleaning.
The blower itself turns freely, which I'm taking as a good sign.
The cards are pristine, L0002, L0003, L0004, L0008, L0007, L0016. There
are 8 memory boards (M8750), several bus grant cards, a card labeled
"M9313"
and one labeled "M9202." I also found in the bottom of the system an
M9014 Unibus to H854 adapter that wasn't plugged in. I also have a
DELUA.
-----Original Message-----
From: Zane H. Healy
Sent: Tue 10/29/2002 9:35 PM
To: cctalk(a)classiccmp.org
Cc:
Subject: Re: Bringing up a 10 years dormant VAX 11/750
> I just a couple of days ago picked up a VAX 11/750. This machine has
Cool!
> been stored
> in a damp shed for ten years or so, has had mice living in it, and the
> usual assortment of spiders, etc.
Oh, SHUDDER! It sounds like you're in for an interesting restoration
process.
> to the control panel and TU58 tape drive. I'm in the process of
cleaning
> all the components,
> but am in search of some advice on this process, especially the power
> supply. How long
> should I let the power supply dry out from its prior damp condition,
and
> what should
> I do to bring it up for testing without risking damage to other
> components? I wish to
> do this methodically and carefully.
Unless this is a powersupply that needs a load on it when you power it
on
(anyone know?), I'd recommend having it totally disconnected when you
power
it on. I'd also recommend you have someone else standing by with a C02
Fire
Extinguisher for safety.
As for how long it needs to dry before powering up, I'm not really sure,
if
you've got it in a warm, heated location, I'd say a week or two should
be
plenty (probably doesn't need that much but it's better to ere on the
side
of caution).
Something to do in the mean time is to look for corrosion and to get
everything good and clean. I'm most concerned about your powersupply
and
backplane. Also take a look at the rollers in your TU58. While the
following is for a PDP-8, you might find it useful.
http://pdp-8.org/revive.htm Definitly read up on what Aaron has to say
about Backplanes.
Zane
BTW, I've found my VAX 4000 reports errors and will not boot
if the KZQSA is not properly terminated.
--
Eric Dittman
dittman(a)dittman.net
Check out the DEC Enthusiasts Club at http://www.dittman.net/
