test-drb March 2015

test-drb@ccmp.vtda.org

167 participants
224 discussions

Implementing the Mandelbrot set on an IBM 1401

by lproven＠gmail.com

http://www.righto.com/2015/03/12-minute-mandelbrot-fractals-on-50.html?m=1 -- Sent from my phone - please pardon brevity & typos.

9 years, 4 months

Happy Birthday, PDP-8

by blstuart＠bellsouth.net

>From what I've been able to find, it was 50 years ago today that the PDP-8 was officially launched. So Happy Birthday to a machine that had such significant influence on so many of us. And a big Thank You to all those who helped to create it. In recognition of this anniversary, the PDP-8/M restoration I'm doing (on S/N 07082) reached the stage today where I connected a terminal and was able to push characters in and out of it. Even as I type this, it's running the print test program >from the maintenance manual printing ASCII characters on a terminal. Happy PDP-8 Day, everyone! BLS

9 years, 4 months

Re. Happy Birthday, PDP-8

by c.murray.mccullough＠gmail.com

It had a significant impact onsome of us. I remember in my high school electronics class in '67 seeing/watching the teacher use/ demonstrate it. I was hooked om computing ever since. Happy birthday indeed if it's appropriate to wish an non-entity such! Happy computing, Murray :)

9 years, 4 months

Two New Alternate-Version Scans

by silent700＠gmail.com

I've scanned and uploaded different versions of two manuals that already exist on Bitsavers. They are the HP RTE-6/VM Quick Reference Guide and the Intel MCS-48 User's Manual. Those interested in completeness or tracking historical changes may be interested. You can find them here: http://chiclassiccomp.org/docs/index.php?dir=%2Fcomputing/HP http://chiclassiccomp.org/docs/index.php?dir=%2Fcomputing/Intel Enjoy... -j

9 years, 4 months

Fix for sticky buttons on Tek 1240/41 logic analyzers

by jnc＠mercury.lcs.mit.edu

So one of my Tek 1240s had incredibly sticky buttons on the front panel (basically, _all_ of them would stick, and have to be pried out manually). I had _very_ good results with the following very simple procedure (which is _not_ in the service manual :-) to totally cure the problem. Your results may differ, since the problem may have different causes in other cases; in mine, there was lot of fine dust in the keyboard area, and it apparently had gotten into the button mechanism, which has a lot of sliding parts with tight tolerances. i) Remove the keyboard PCB: the Service Manual, Volume I (available online) explains how to get the keyboard out - roll up the logic cage, and then you can undo 4 small bolts, after which the keyboard just comes off. You will also need to remove two flat cables. Next, remove the scroll button (usual hex set screw holds it on the shaft), and then separate the cover from the actual keyboard PCB by removing the four hex stand-off posts. ii) Take the button assembly out of the PCB; it's just a press-fit, not glued - just push on it from the solder side of the PCB (may need a fair amount of force). The buttons consist of precisely 5 parts: the keytop, which comes off/on easily (I usually remove them, but you could probably leave them on), the housing, the shaft/actuator, a spring, and a gold-plated copper contact bar (which connects two gold-plated contacts on the PCB, to form the switch). iii) Immerse the button assembly in water, and _while immersed_, push the shaft/actuator back and forth a number of times. If it's totally binding, and won't come out at all, use a small object of some kind down the cylindrical shaft to get it to go back and forth. If there is an air bubble trapped in the cylindrical shaft, make sure to clear it - that shaft is one of the places dirt can get and bind things up. Pretty soon it should operate completely freely. iv) Needless to say, dry thoroughly before replacing... :-) In theory one could take the button assembly apart to clean it, but I'd be _really_ worried I'd damage the contact, or something. I just left it all together and dunked it in water, and that worked wonderfully. For the 5 LED buttons, it's basically the same. The LEDs are _not_ glued into the button assemblies, just inserted into the cylindrical shaft. _Carefully_ remove the LED from the shaft, and bend it back out of the way. Then proceed as above. Hope someone finds this useful! It's tedious, doing all 30 or so keys, but it works well. Noel

9 years, 4 months

VCF Southeast 3.0 - Call for exhibitors!

by kylevowen＠gmail.com

The Atlanta Historical Computing Society and the Computer Museum of America has been planning a great celebration of the 50th birthday of the PDP-8, 40th of the Altair 8800, and 30th of the Amiga 1000 in Roswel, GA, for the Vintage Computer Festival Southeast 3.0. However, we need your help in exhibiting! Last year, we had about 400 people through the doors between two days. We'd love for you to sign up and bring your hardware to show off to the Atlanta community. I'll be there with dueling PDP-8s (/E and /M) playing chess, as well as taking turns playing Spacewar! on age-appropriate hardware. I'll also show off my emulated version based around SimH. And that's just at my table! Steve Lafferty has summed up (quite nicely) the signup process for those who have not done it before. Check it out! http://tronola.com/html/vcfse3_exhibitor_info.html Here's the link on vintage.org as well: http://www.vintage.org/2015/southeast/ If you have any questions, feel free to ask me. Kyle Owen Member, AHCS

9 years, 4 months

Huge IBM 1800 find (and need some help)

by johannesthelen＠hotmail.com

I hope this is not too long story, but I'd like to start from beginning... I was selling and donating my 80's computer collection away, because I really couldn't get anymore kicks of home computers (gateaway theory is right, Commodores are step to mainframes ...) Anyways, I asked every buyer have they seen any thing big, old computers anywhere here in Finland. One guy gave hint of some truck sized IBM, which he had seen at his old job. He told it is probably going to scrap yard and he sent photo of it. I was stunned, FULL 1800 SYSTEM. Next step was find boss who decide what is going to happen that IBM. I called him and asked how's IBM. Firstly he thought I'm gold digger. After some talk, he became convinced I'm real deal. Sadly, he told me that IBM is in their private museum, and not for sale or not planned to donate anywhere. But he invited me to see that IBM. I was little dissapointed, but better than nothing I thought. After couple months, I went to there to see IBM. Boss had changed at that time, there was new guy. He also understand historical value of that big iron, no doubt it. We drove plant where that IBM was. When I see it, I was stunned. It was absolute spectacular! It was stood 30 years after service in dry and warm warehouse, same place where it installed early 70's. It have stood still almost long as I have wander this world! Time was stopped that room, it looks like we have got back to 80's on time machine. 2311 disk packs was left probably just where they are 30 years ago. Here's pic: https://drive.google.com/open?id=0B_DR111cK6W-NnRINlhESk5aNUk&authuser=0 System contains 1801 CPU, 1803 additional core storage unit, 2841 drive adapter, couple 2311 hard drives, 1826 data adapter, 1443 printer, terminals, card readers/punches, etc... It is giant system! Now comes twist to plot, this new boss suddenly asked: "When you could make pickup for this IBM?". I'm not that type guy, who can get be quiet that easy, but I could just stutter something like "I can pickup every you want". :D So, I was so excited, own IBM 1800, that is just what I have always wanted, own mainframe :D (...360 would be even better but this would do the trick as well ;) We have not that much computers back 60's or 70's. like below 200 at 1970. So you can imagine how rare big iron is here and it is totally unlikely you could find anything this good at Finland these days. ************** But now comes the problem. This IBM is in second floor. There is only (wide) staircase down to street level. So cabinets have to partly disassemble to light those "little" bit. I would need some kind of document of wireharness and schematics, so I get it back together. Also good pictures inside of cabinets would help, so I know what is waiting me there. And by the way, what weights so much these units? CPU weights 907kg, why? Is power supplies so heavy or is there lead poured to structure ;) ? I'm picking this up next week, at least small items, so I would need some good advices also. Rolling cabinets via stair case is not option ;) Also any help to bring this back to life is welcome! Thaaaaaanks! - Johannes ThelenFinland Before microcomputers blog (Finnish) http://ennenmikrotietokoneita.blogspot.fi/

9 years, 4 months

Mac SE/30 making zipping and buzzing noises

by marc.verdiell＠gmail.com

A classic case of Mac SE leaking electrolytic caps. Soon your sound will disappear completely. Then your Mac SE/30 won't even boot. You can confirm looking for shiny leaks traces around the caps. Very easy to take care of. Replace all of them, as they will all go bad. But there aren't many of them, I think I counted just 11. Most of them are of the 10 uF variety if I remember. Surface mount with leads hidden underneath the caps, a bit annoying to remove, but you can pretty much break them off the board carefully. The leads should break off at the cap and stay attached on the board. Then desolder the lead remnants and clean off the old solder with copper wick until you get pristine pads. Clean any spilled electrolyte under the caps thoroughly. Replace them with regular 10 uF ones - or whatever value is needed. I used standard axial through holes ones, just soldered the bent leads on the traces. It's even written on the board where the + go! Thanks Steve Jobs. If I could attach pictures of the before and after, I would... I can send them to you off line if you want. Actually I see your email, I will. Marc On 20/03/2015 6:39 PM, <dave at 661.org> wrote: > I'm gradually restoring a Mac SE/30. Today I got a new PRAM battery > and installed it. There was no battery leakage, so I'm good there. > The machine seems to run just fine. The big problem now is that even > though nothing should be emitted from the speaker, I'm getting zips, > buzzes, and burbles from it depending on what the computer is doing at > the time. I'm quite sure the the sound circuitry is somehow picking > up RF noise from the system bus. What does this symptom indicate? > Should I recap the whole machine? > > David Griffith > dave at 661.org

9 years, 4 months

A challenge from the Spectrum BASIC manual is finally achieved

by lproven＠gmail.com

30 years after it was set by Dr Stephen Vickers. An orchestra of a dozen -- networked! -- original ZX Spectrum computers plays Mahler's 1st symphony. A rather lovely 10min film: https://www.youtube.com/watch?v=LxPXLIALJJI -- Liam Proven ? Profile: http://lproven.livejournal.com/profile Email: lproven at cix.co.uk ? GMail/G+/Twitter/Flickr/Facebook: lproven MSN: lproven at hotmail.com ? Skype/AIM/Yahoo/LinkedIn: liamproven Cell/Mobiles: +44 7939-087884 (UK) ? +420 702 829 053 (?R)

9 years, 4 months

IBM 5100 Restoration in progress

by santo.nucifora＠gmail.com

Hi All, Long time reader, first time poster. I am in need of some assistance in trying to revive an IBM 5100. It is a Basic 32k version that was in rough shape. You can see pics here: http://vintagecomputer.ca/ibm-5100-before/ I've been able to clean it up but when I fire it up I see a single "A" on screen. I can't seem to get into any diagnostic modes. The single "A" indicates an issue with the F2 Base I/O card. Some of the ICs do have some rust on them but I'm wondering if it might be the "bridge connectors" between the Base I/O and Controller (CPU) card. Are they directional or can then be swapped or turned around? I may have not kept them in the correct orientation but I don't see any mention in the Maintenance manual. I, pretty much, need someone who has one to take a picture of the top of their Base I/O and Controller cards. Any help is much appreciated. If someone happens to know a common issue that would make the "Bring up Program" stop at A, I'd love to hear about it. Thanks in advance, Santo

9 years, 4 months

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test-drb March 2015