test-drb September 2008

test-drb@ccmp.vtda.org

220 participants
323 discussions

by rikbos＠xs4all.nl

I'm bussy restoring a Ti SR-52 and having some trouble with the card reader electronics. I't's reading prerecorded cards fine, but is not writing data on the cards . And it does not transport the card fully through the card reader, I have to pull the card the last few millimeters before it gets free from the capstand. So I'm searching for a schematic diagram or service manual. -Rik

15 years, 8 months

Insulator/shielding in DEC power supply

by oldcpu2＠rogerwilco.org

Ian King said: > I'm reconditioning some H7100A power supply units in a VAX-11/785, and > I've come across something I haven't seen before. I'm hoping one of you > has. :) > > This particular PSU was labeled 'Memory Power Supply' and has additional > regulator boards for a 15v rail. Slipped between those boards were two > sheets of what looked like heavy-duty paper. However, one had > delaminated, demonstrating that it is a sheet of thin copper sandwiched > between two paper-like layers. That suggests to me that this was intended > more for EMI shielding than electrical isolation. I did not see these sheets in > another PSU that also had a supplemental regulator. > > Does this sound familiar to anyone? TIA - Ian In my VAX 11/750[1], each of two power supplies (2.5v and 5v) also contain this 'heavy' paper separator between adjacent boards. I've noticed that this paper is pretty thick, not quite what you'd call cardstock, but getting close. In my case, I haven't noticed any de-laminating, so can't confirm the copper foil inside, however, I have commented to myself a time or two that each sheet just 'feels' heavy. If there really is foil inside, I don't know how much EMI suppression it would do, since there is no connection of ground or other way to bleed of any incident energy. Rather, I'd guess they probably make pretty good reflectors of EMI, instead. But what do I know, I'm hardly a hardware guy. - Jared [1] Was brainless when picked up almost a year ago, but I've since gathered a set of all of the CPU boards, memory and other necessaries. Just picked up a DEUNA, but still need the cab-kit for it. Fixed the faulty 5V power supply, but now the 2.5V PS is goofy; presently working on that. At this rate, I'm now hoping to fire the whole system up for the first time, sometime before, oh, I don't know, maybe before Christmas?! :)

15 years, 8 months

vac tubes / was Re: Schematics of Atanasoff-Berry > Computer

by wbblair3＠yahoo.com

Gordon JC Pearce wrote: > > Did all the tubes disappear or something? LOTS AND > LOTS of tubes were > > They're still being made, mostly in the former USSR. > After Mullard > stopped producing valves in the 1980s, a company in the > USSR bought the > whole lot up and shipped it across. If you buy a Sovtek > ECC83 or EL34, > it's exactly like an old Mullard one. Here's the list of modern manufacturers: http://en.wikipedia.org/wiki/Vacuum_tube#Modern_manufacturers

15 years, 8 months

ENIAC vs. ENIAC-on-a-Chip IC implementation

by wbblair3＠yahoo.com

gerhard.kreuzer at liftoff.at wrote: > I think about a FPGA-version of ENIAC, so ist relativly > easy to get the hands on a replica. > > Is there goood documentation available? Is the ENIAC on > a chip project online, that meens, all the docs? The project is generally described here: http://www.ese.upenn.edu/~jan/eniacproj.html But the best technical description of it by far that I've found is in the book, "The First Computers--History and Architectures," MIT Press, eds. R. Rojas, 2000. The relevant pages are online with Google Books here, starting on p121 of the book: http://books.google.com/books?id=nDWPW9uwZPAC&dq=The+First+Computers--Histo… The 207 page ENIAC patent is here: http://www.scribd.com/doc/4960983/ENIAC-Patent-US3120606

15 years, 8 months

Anyone want a SS5?

by alanp＠snowmoose.com

As previously mentioned, I have a Sun SparcStation 5 that I rescued from my uncle. I have gone through it and here are the details: SparcStation 5 32 Meg memory 2G disk Solaris 2.6 installed Sun 5C keyboard Sun Compact 1 (ball, not optical, three-button) mouse 15" Color Monitor (Model 447L) I booted it, ran OPB diagnostics, installed Solaris 2.6 and everything seems to work fine. Located in the Seattle, WA area. Price: Make offer alan

15 years, 8 months

Mullard valves. Was Re: Schematics of Atanasoff-Berry Computer logic circuits?

by roger.holmes＠microspot.co.uk

On 2 Sep, 2008, at 20:22, cctalk-request at classiccmp.org wrote: > > Message: 28 > Date: Tue, 02 Sep 2008 20:11:25 +0100 > From: Gordon JC Pearce <gordonjcp at gjcp.net> > Dave McGuire wrote: >> On Sep 2, 2008, at 11:47 AM, bfranchuk at jetnet.ab.ca wrote: >>>> Us amp builders >>>> love them for their second-harmonicy crunch... >>>> >>> Still with out the guitar amp people, I don't think any kind of >>> valves >>> would be around for people like myself to play music through. >> >> Did all the tubes disappear or something? LOTS AND LOTS of tubes >> were > > They're still being made, mostly in the former USSR. After Mullard > stopped producing valves in the 1980s, a company in the USSR bought > the > whole lot up and shipped it across. If you buy a Sovtek ECC83 or > EL34, > it's exactly like an old Mullard one. I think they stopped production earlier than that, though they were probably selling their stock for some time after. Next to the Marconi- Elliott works at Rochester airport was (IIRC) a Mullard thermionic valve factory. Not to be confused with the Fisher fluid valve factory at the other side of the Elliott works. Around 1975/6 there was a period when due to car problems I used to wait near the Mullard works for my regular lift home and every night there was another batch of valve testing benches standing outside waiting to be collected. It went on for months, probably carried on after I got my car sorted out.

15 years, 8 months

WANTED: AIM-65 PASCAL and/or PL/65 ROMs

by tosteve＠yahoo.com

Please let me know if anyone can send me the AIM-65 PASCAL and/or PL/65 ROMs. Either originals or copies. Thanks- Steve.

15 years, 8 months

DataDock 7000

by rups1967＠googlemail.com

Dear All, I am restoring a Data Dock 7000 that was languishing neglected in a dusty corner and I wondered if anyone has any information regarding these "wee beasties". Regards, Rupert.

15 years, 8 months

Schematics of Atanasoff-Berry Computer logic circuits?

by wbblair3＠yahoo.com

> > A multi-stage direct coupled vacuum tube circuit.? Fun. > Yes, be prepared for some fun, in both senses of the word: it is fun to play > around with, but the implemention of tube logic can be problematic or > unreliable, at least in the way the ABC tried to implement both NAND and NOR > gates with resistive input circuitry. > > Atanasoff makes it sounds easy in his paper, but if one reads it closely > it's not quite so, at least as measured by modern standards where one comes > up with a gate design and then simply repeats it ad infinitum. After reviewing the ASM circuit on your web page, it became readily apparent to me that it would likely be a major challenge to fill in the blanks for those missing resistor values and end up with something that actually worked reliably. > The ABC reconstruction and the original required (at least some) hand-picked > resistors in the gate circuits. I bought the excellent book ?The First Computers ? History and Architectures? mainly because of its content on Konrad Zuse?s relay-based machines. However, in its included paper on the reproduction of the ABC, the authors state: ?In building add-subtract modules, we found the circuits very demanding of precise resistor values. We have evidence that Berry hand-selected resistors from bins until he found ones that worked, and we attempted the same tactic. In measuring the characteristics of 10% resistors, we discovered the distribution about the nominal value shown in Fig. 3. (It?s a graph of a bell curve between -10% and 10% with a big notch in the center of the curve). Apparently, the manufacturer had already segregated the resistors close to nominal value. Hence, we found it necessary to use 1% tolerance resistors.? So, here?s a 14 gate, multistage, direct coupled vacuum tube circuit that apparently requires various hand-selected values of 1% resistors to work properly. Whew!!! I think I?m going to start with something a great deal simpler, like a single flip flop or astable multivibrator using an inexpensive 9-pin miniature dual triode at low voltages to see if I can even get that to work. > Some of the issues: > > 1. Tubes can be insufficiently non-linear. Driving between saturation and cutoff >? can take a bit of swing and saturation is soft (curved). > > 2. Plate circuit impedance is high. If the difference between the plate circuit > impedance (lower better) and the grid circuit impedance (higher better) is > ? ? insufficient, then different fan-outs in the logic circuit (loading), and > ? ? varying tube/component characteristics, can pull the logic levels away from > ? ? the design targets and upset everything. > > Going to the low plate voltage is a nice idea from a practical view but I > wonder if it may compound issues of point 2 above. It will reduce the voltage > shift between the plate and grid circuits that needs to be accomplished, but it > may also reduce the voltage swing between the 0/1 logic levels. How it works > out in the balance will be interesting. Thanks for that info and it will be interesting indeed to see if this will work. I was surprised to find nothing on low voltage tube logic when there?s so much on the web about low-voltage tube audio circuits of all kinds. True, tube logic is a fairly esoteric subject with no usefulness beyond that of a novelty, but with all of the audio low voltage stuff, I?d expected some tube enthusiast somewhere to have already done something on the logic side just for the heck of it. > Straying completely away from technical issues, and I'm somewhat loath to > mention this, but the animosity engendered by the early-70s court battle > continues decades later. The somewhat nasty inter-personal battle > found it's way into the Amazon book reviews as recently as 2004. > Another bizarre twist in the ENIAC patent saga on the legal/social side. Yes, I saw that when I went to look at the Amazon entry for Burks' "The First Electronic Computer." Wow, it?s a long-time, knock-down feud for certain. Bill

15 years, 8 months

HP200LX, e-text and vertical reader

by feldman.r＠comcast.net

Vertical Reader (1.11, the file is VR100.zip) can be downloaded from the HPLX S.U.P.E.R. ftp site at http://super.hplx.net/anonftp/pub/. For my personal taste, I found the lines in VR too short, so I wrote a "Horizontal Reader". It's not as polished as VR, but I can send the program and Turbo C source code to anyone who would like it. There is still a moderately active mailing list for the HP 200LX. The link for information is http://eberl.com/HPLX. The old HPLX information center at http://super.hplx.net/ is still up, but most of its links are broken. If you need to get a 200LX fixed, go to http://www.palmtoppaper.com/store/asp/prodtype.asp?prodtype=27 (in the US; there are others in Europe who do HPLX repairs). Bob

15 years, 8 months

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test-drb September 2008