test-drb August 1999

test-drb@ccmp.vtda.org

161 participants
565 discussions

by edick＠idcomm.com

Assuming you've used a real wire, it certainly will keep the two points at the same potential. I thought you meant bypassing the already installed regulator by attaching a feed directly from the power supply, which indicates what I was thinking rather than what I should have been. What I was trying to envision is what kind of external booster they intend to put on a PC PSU. I can't imagine any worse sort of arrangement, though. By this I mean that the one functional component which seems to fail most is the power supply. WHile I've only had about half a dozen motherboards die over the years, I've got a 55-gal drumful of dead power supplies, on most of which the fan is what failed. In many cases, the fan fails and then the supply gets hot and dies. The common PC PSU is overdesigned by a fair amount. I doubt that a single 250-watt PSU is adequate for a typical S-100 setup. I know, that's 50 Amps on the +5! I've never seen one supply, even a 450-watt server supply that could approach its rated loading. They're out there, I'm sure, but I've never encountered one. Back to IMSAI's problem . . . I can't see financial justification for booster supplies from a PC PSU when you can buy a 450-watt open-frame switcher and set the outputs to the required voltage and be done with it. A day's work behind making the decision will eat up all the savings associated with using a PC PSU. Dick -----Original Message----- From: CLASSICCMP(a)trailing-edge.com <CLASSICCMP(a)trailing-edge.com> To: Discussion re-collecting of classic computers <classiccmp(a)u.washington.edu> Date: Tuesday, August 17, 1999 6:46 PM Subject: Re: imsai 2 >>I'm not sure that "jumpering across" the 7805 will be healthy for the 7805. >>Of course, if the input doesn't drop below the output during shutdown this >>may not be a concern. > >Maybe I was unclear on what I meant by "jumpering across": you put a >wire between pin 1 and pin 3 of the regulator. With such a jumper, >it's impossible for the input to drop below output at the regulator. > >Of course, you've got to remember to remove the jumper before putting >the resulting card back into a system with unregulated power busses! > >Like I said, regulated S-100 power busses were done by several manufacturers >in the early and mid-80's with great success. It's a non-issue. > >-- > Tim Shoppa Email: shoppa(a)trailing-edge.com > Trailing Edge Technology WWW: http://www.trailing-edge.com/ > 7328 Bradley Blvd Voice: 301-767-5917 > Bethesda, MD, USA 20817 Fax: 301-767-5927

25 years, 4 months

imsai 2

by allisonp＠world.std.com

<Anyway, why does it have to be one transformer? Why not a 12-0-12 for the <16V lines and a 6V one for the 8V line (those should produce DC voltages <within the range of any normal S100 board regulator). Such transformers <are trivial to obtain. Then you'd end up with the piece of crap altair supply... <There is a myth doing the rounds that PSUs -- even simple linear PSUs -- <are impossible to design. No idea where it came from... Because any error means all your silicon is junk. Also if you make a small error the core you using could get quite hot. Or maybe the ripple >from switching exceeds the reasonable level by say a volt or two. Then there are the high current ground loops that cause instability at something approaching max load or minimum load. The worst is when you forget the chopper side has 300V on it, S*!^^ d@**. The number of errors that can be made are far higher. Then again having designed a few, once you've done it you learn... mostly everything they taught you was far from enough. that and fixing all those that were really not so well designed. Allison

25 years, 4 months

Hacker tea (was Re: Late Nights and Caffeine)

by pete＠dunnington.u-net.com

On Aug 17, 15:04, Don Maslin wrote: > Subject: Re: Hacker tea (was Re: Late Nights and Caffeine) > On Tue, 17 Aug 1999, Pete Turnbull wrote: > > Actually, Tetley, and Taylors of Harrogate. > > Lovely little town - don't know about the tea. We spent a night there > some years back and had a truly excellent dinner at the Brasserie along > with some top notch jazz from a local group. Memorable evening. Yes, it's a nice place. I live in York, about 25 miles away -- and Taylors have a branch here too. They also own Betty's, which is a famous cafe. Actually, Taylor's are better know here for coffee than tea... If you're ever in that part of the world again, drop me line and say hello. -- Pete Peter Turnbull Dept. of Computer Science University of York

25 years, 4 months

DC300 Tape Repair

by wsmith＠gj.com

What's the best way to replace a broken belt in a DC300 tape cartridge? Is there a source for new belts?

25 years, 4 months

imsai 2

by jeff.kaneko＠juno.com

On Tue, 17 Aug 1999 16:11:10 -0600 "Richard Erlacher" <edick(a)idcomm.com> writes: <Stuff SNIPped> > What puzzles me is why the IMSAI folks decided to use a switching > power supply when the box and everything else already supported the needs > of the S-100 with the previously available and now quite inexpensive > unregulated supplies of yesteryear. Well, for a given wattage, switchers are smaller, lighter, and more economical to produce. I imagine if they resorted to the old iron-core transformers of yore, they would have had a difficult time finding a supplier for them. When they did, the part would probly cost as much as the rest of the materials put together. Makes perfect sense to me. Jeff ___________________________________________________________________ Get the Internet just the way you want it. Free software, free e-mail, and free Internet access for a month! Try Juno Web: http://dl.www.juno.com/dynoget/tagj.

25 years, 4 months

imsai 2

by chris＠handsoninc.com

Thanks to someone on the list, I saw the url for the people making a "new" imsai. I couldn't help but wonder: Will the fact that you can buy a new one for $995.00 finally curb the pricing on places like ebay for the vintage ones do you think? Jay West

25 years, 4 months

S100 box (was Re: imsai 2)

by allisonp＠world.std.com

<Say... trade for neat PDP-8 stuffies or similar? B^} < <-jim Smoking wacky weed? I have two NS*, one Altair, a CCS, Compupro and one of my own nightmares (split bus so there are three s100 busses that only share power). Then there were a dozen or so Intergrand and TEI cases I practically gave away. Allison

25 years, 4 months

[Fwd: Lear-Siegler ADM3A with Retrographics (Tek emulator) plus spare parts] (fwd)

by jimw＠agora.rdrop.com

Forwarded from the 'net. Replies to original poster please. This is very cool... If I was closer, I'd grab it! ---------- Forwarded message ---------- Date: Tue, 17 Aug 1999 11:38:25 -0400 From: Rich Kulawiec <rsk(a)gsp.org> Subject: Lear-Siegler ADM3A with Retrographics (Tek emulator) plus spare parts I have an original relic of the computing of the late 70's and early 80's here: it's an ADM3A (the ASCII terminal that looks like a Volkswagen Beetle) that has had a Retrographics board dropped into it so that it can emulate Tektronix graphics. (I've never used that functionality, but I can provide you with the notes that were given to me on how to make it work.) It's in the light blue/dark blue two-tone that LS liked to make these in...it's almost indestructable...and it's relatively heavy. I also have a box of spare parts which includes 1 or 2 extra ADM3A boards (gotta love all that TTL logic!) plus whatever else I gutted from the extra ADM3A's that were sitting around. It also works: I used it to boot a Sparcstation last week. Make me an offer (and please be sure that it's enough to cover shipping costs, or you can pick it up near Philadelphia or Baltimore) and the entire pile o'stuff can lend an authentic air to your retro-computing environment. My email address is below. ---Rsk Rich Kulawiec rsk(a)gsp.org

25 years, 4 months

S100 box (was Re: imsai 2)

by edick＠idcomm.com

The thing to remember about the "good old days" of early microcomputers, etc, is that most of the work was done by people who had the courage to do it in spite of their complete lack of educational credentials and the accompanying conventional prejudice. But for these courageous folks, nothing might have been done for another decade, as the trend at the time was to BE CONSERVATIVE. These bold newcomers were opportunists, building S-100 because they got a good deal on 100-pin edge connectors, for example, not because it was necessarily the best choice from a technical standpoint. That's what brought these machines to within the reach of the hobbyist/experimentor who reinvented electronics engineering of the time. The fact that the power supplies were "crap" was because they were built with stuff the vendors believed, but only barely, would "work" though it was bought primarily because it was "affordable." "Work" was loosely defined, and what was an inconvenience to the folks who bought the first Altair boxes was a costly lesson to the folks who designed the things in an essential vacuum. Most of the guys I knew back then to be doing the design came from Math, the Sciences, even Industrial Arts backgrounds, and they were working from a perception of need, not from, with their own funds or funds begged or borrowed from people who knew no more than they about what might happen. Dick -----Original Message----- From: allisonp(a)world.std.com <allisonp(a)world.std.com> To: Discussion re-collecting of classic computers <classiccmp(a)u.washington.edu> Date: Wednesday, August 18, 1999 7:02 AM Subject: Re: S100 box (was Re: imsai 2) >> Then you'd end up with the piece of crap altair supply... >> >> -------------------------------------------------------------------- >> >> <VENT WARNING - proceed at your own risk> >> >> Ahem... (with regard to the last line immediately above) Get Stuffed! > >Thanky very much and, here's your sign! > >Let me introduce myself... > >in december of 1974 I got my copy of Popular Electronics as usual and lo >and behold there was Altair. Having some expereince with 8008 prior to >that and PDP-8 as well I wanted one and had saved some money. Off goes >order by then airmail! Arrived 4 weeks later (told thats a record too) >is 200th built Altair with a 4k memory and PIO. Built with in days and >I was for many weeks maybe months the first one I know of on LI to have a >machine. > >NOW, there is NO question the PS was crap. The first transformers (two of >them for both voltages) were horribly undersized for the load, the >filter caps not to mention the diodes were also pretty over loaded. By >time spring came I'd finally gotten my 88ACR and another 4k of ram and >watche the PS fry. The transofrmer for +-16 was too light and I found a >suitable replacement. The somewhat larger +8 core was stripped and >rewound to provide 7.5V and the caps were tossed for some nice 55,000mFD >units. > >LIke I said the design was CRAP!. MITS would later that summer send a new >pair of transformers that were better but still woefully undersized. > >The were first, not best! > >> If a capable group of people (please note the non-specific reference here) >> were available and were such hot $#!* in 1975, why didn't they produce >> something better??? > >They did. IMSAI was far better as was the Altair 8800B. Everyone that >follow surely learned from the errors from better poser supplies to >improved cooling and bus noise reduction. > >> Twenty-Five years after the fact it is far too easy to pronounce judgements > >I said that at the time and quite bluntly, however it was cheap and most >of the problems could be overcome if you didn't mind applying some havey >modifications. > >> on the past, judged against the current 'state of the art'. But was >> anything learned from it? > >On my part yes, I'm still here. They arent. > >> In comparison to todays cars, the Model T was CRAP but I don't see it >> constantly being held up to ridicule. It, like the Altair and many other >> early developments were done with the materials and skills that were >> available AT THE TIME to the PEOPLE who got off their duffs and DID IT! > >Actually in many ways that is not true and you know why. > >> And all indications are that much was learned from it, as evidenced by the >> rapid followups by improved units like the IMSAI, the SOL, and even the >> ALTAIR 'B' series. > >The Bseries was how many years later? By then everyone was eating MITS >lunch. > >> In every revolution, someone has to be the first... and guess what? RARELY >> are they the shining example of the art that it seems like some expect that >> the Altair and its ilk should have been. More often, they are the >> unskilled visionaries, the hacks, the garage bands, the hobbyists, or even >> just someone out to make a quick buck and bail. > >Yep, and all of the above applies. > >> Maybe this is why it has been so hard to get people really interested in >> the HISTORY behind computers. It has just happened all too fast, and there >> has not been enough time for the whole art (science if you prefer) to gain >> any respect. > >As a practicing engineer then and now while the idea of cheap facinated >me, I was surprized that things know to the industry were not apparently >know to those guys. It's why by early '78 that box was for the most part >permanenty retired. It is still in my collection and while first from my >engineering perspective it serves as shining example of HOW NOT TO DO >IT. It stays in the collection as MY first one and how persistance >allowed me to do things that were difficult then with the hardware >available (to me). > >> Or we get the people that came from the jobs that some of up would died for >> back then. Working with 'real computers', built by well trained (I like to >> believe) people in 'real companies', with a 'real goal' ahead of them... >> Reality check folks, that was a whole other world from the reality that >> some of us grew up in! > >Oh, guess my resume doesn't qualify. > >> So, (not that anything I will ever say is likely to stop anyone) call it >> what you will, but to some few of us who were still in awe of computers >> back in 1975, and the Altair or some similar device was the first computer >> that we could ever call our own, it was magic! > >It was majik. No question but as someone that was there there was more >magic in our dreams. Those dreams I may add were all to often spent >chasing a design of the machine error when the real desire was to crank >code! Or watching our really neat VDM1 demo fry as bus nise crashed the >machine. > >Like the Model T those of us that have driven one, worked on the engine >understand why it deserves to be preserved, driven and documented as it >it's effect on the world. It does not negate that it's a crude machine. >The later will never change but history knows that too. It's partly the >reason for the AAA and a lot of other inovations! > >With that in mind the computer equivelent of AAA was the Homebrew >Computer Club, LICA<Long Island Computer Association>, BCC <boston >computer Society> and so on. They were there to help those that couldn't >cope with the design errors, limitations or outright shoddy design on >their way to accomplishing a dream which wa often very different from >coping with a machine that didn't work as could be expected. > >Not a rant, just a loud, wake up! The good old days were more than simple. >VCF is dedicated to showing the full story, all of it including the dirty >sides like the World Power SCAM. > >Allison > >

25 years, 4 months

More available equipment / Chicago rescue opportunity

by ware＠interaccess.com

The moving truck arrives Monday, and I still have far too much stuff. If anyone in the Chicago area is interested, I have the following equipment available free to a good home (of course, interesting token small trades or cash won't be turned down...) DEC RL02 disk drive w/packs DEC 6-bit A/D converter (likely to be incomplete - made with single-height flip chip modules. Was used with an 8/e.) Assorted DEC power supplies (single and multi-voltage outputs) Apple II+ with Disk II drives Apple IIgs Apple Disk II drives Apple Macintosh IIci Apple Macintosh Plus (qty. 3) Apple Macintosh SE Apple monitors - II, IIc, RGB, Mac Assorted monochrome and color monitors Assorted PC clone cases, parts, and power supplies AST 486 desktop (stripped) Compaq 386 desktops (qty. 5) Compaq Portable II (one data line on ISA bus stuck low?) Data General/Hitachi 20" monitor (fixed freq for AViiON, RGB+sync on green, slight xdm login screen burn. Same model used with some SGI systems) Magnavox Odyssey2 (qty. 3) Okidata LaserLine 6 printer (w/extra toner) Sony 16" Trinitron monitor (fixed freq, RGB+h&v sync inputs) Keyboard for Commodore 128D VTech Laser 128 (poor cond.) 8" and 5.25" floppy disks Various non-computer electronics (JBL speaker components, assorted a/v equipment, old test equipment) There are also many other items that I may be willing to part with if someone is interested, including the following: DEC PDP-11/24 Luggables - Compaq, Panasonic, Sanyo, etc. Other Apple II-series and Macintosh systems and peripherals I will not have time to pack and ship any of this equipment before the move, so pickup in Chicago (Lakeview/Lincoln Park area in the city) would be greatly preferred. I may be able to make some of the smaller items magically reappear in the SF Bay Area in a few weeks (for the cost of freight) if there is no local interest, but I can't do that with the larger items. Help! -- Scott Ware ware(a)interaccess.com

25 years, 4 months

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test-drb August 1999