test-drb August 2019

test-drb@ccmp.vtda.org

161 participants
150 discussions

by charlesmorris800＠centurytel.net

Is there any standard pinout for 20 ma current loop using a DB-25 connector, analogous to the well-documents RS-232 serial interface? My PDP-8/A drives an ASR-33, and having just restored an ADM-3A I want to be able to unplug the TTY and plug in the ADM. I somewhat arbitrarily put the transmit data + on pin 2 and receive + on pin 3, and picked two uncommitted RS-232 pins for the - legs of both loops. The ADM-3A receives on pins 23 & 25, and transmits on pins 24 & 17. Polarity doesn't matter since both pairs use bridge rectifiers. If this is some kind of de facto standard, I'll change the bulkhead connector on the PDP-8 and the TTY to match. Otherwise I'll just make yet another unique cable to hook up the ADM-3A to the PDP-8 as it's wired. Or would you recommend I use a different connector entirely? The reason I used the DB-25 to begin with is that I had a DEC rack-mount plate that already takes one. Maybe a Jones 4-pin would make more sense. thanks for any tips. -Charles --- This email has been checked for viruses by Avast antivirus software. https://www.avast.com/antivirus

5 years, 4 months

GW-DEC-1: A New DEC Prototyping Board

by jnc＠mercury.lcs.mit.edu

> From: Brent Hilpert > I've seen pieces of HP high-end lab equipment from thru the 60s that > used tin plating on the PCB edge fingers, mating into gold-plated edge > connectors on the backplane. ISTR that DEC used bronze contacts in their backplanes, but basically all the boards had gold-plated fingers. (I think I've seen a few power supply boards that had tinned fingers.) I think the bronze was preferred since the contacts bend back and forth as cards are inserted/removed, and bronze is more durable; and being part tin, has the same corrosion characteristics are the tin. Noel

5 years, 4 months

RXV21 questions

by dj.taylor4＠comcast.net

I have 2 RXV21 RX02 controller boards.? They were bought to be used with the RX02 emulator, the one on github by AK6DN. Finally, I finished one of the emulator boards and tried it out on a PDP-11/03 and found that one of the RXV21? boards worked and the other didn't.? I assumed the one board was bad. Yesterday I tried the RX02 emulator in a BA23 with a 11/53 cpu (I also tried a 11/23+) cpu.? What I found is that the one that worked in the 11/03 didn't work, while the other board kinda worked.? I could do a DIRECTORY and DUMP from RT11, but I couldn't boot the RX02 in the microPDP-11. Today I ran into Chuck Dickman's web site that talked about the Etch versions of the board and which would work in a microPDP-11. He showed how to convert an Etch 'D' board to work in a microPDP-11. I have Etch 'C' - this is the one that works in the 11/03, and an Etch 'D'.? My 'D' board isn't exactly like the 'D' board he shows. What are the changes to the 'D' board that he outlines?? What is exactly the reason why the 'C' works in the 11/03 and why an 'F' or modified 'D' is needed for the microPDP-11? Doug

5 years, 4 months

ADM-3A question

by charlesmorris800＠centurytel.net

Today the replacement 'LS193 arrived, so I put it in the previously-installed socket and the screen is now 24x80 again :) I'd been testing with the dip switch in half-duplex mode... For final test, I put it in FDX, connected to my HP protocol analyzer, and what do you know, no serial data out. The 1488 RS-232 driver was blown (TTL-level data going to it, but the RS-232 line was stuck in spacing). Not an uncommon failure with static discharge and incorrect cable hookups... I destructively removed it, again installed a good dip socket, now waiting for THAT chip (a variety of other line drivers in my drawer, but not 1488/1489). Meanwhile I noted another slide switch S8 ("GT/LK") near the DB-25 connectors. It is not referenced anywhere in the documentation, nor in the schematics! The wiper of the switch also goes through a hex inverter to a 74LS32 chip, ALSO not in the schematic or circuit description. This signal originates at the flip-flop that generates KBLOCK\. Finally, input pin 10 of the removed 1488 is supposed to be tied to pin 9, with the RTS output on pin 8. But pin 10 goes In fact, the PCB artwork at the end of the tech manual shows no connections except +5 and ground to that chip (position C2 I think), and it doesn't show the slide switch either. This is likely something for the auto-tester that LSI used to check these boards on the production line, although I don't know if the extra circuitry was added or removed during production. Anyone have internal documents on this? I'm just curious since it only appears to affect the keyboard lock functions which I'm not using anyway. --- This email has been checked for viruses by Avast antivirus software. https://www.avast.com/antivirus

5 years, 4 months

Archiving information, was Re: ADM-3A question

by jnc＠mercury.lcs.mit.edu

> From: Eric Christopherson >> Anyway, the whole 'how do we find the info' is a part of why I started >> working on CHWiki, once I discovered it > Psst: it would've been a good idea to share the URL to CHWiki. Well, that passing reference wasn't an attempt to get people to go look at it, hence no URL! :-) I was focused on the abstract discussion about 'how do we make information accessible, if relying on search engines to find blog postings doesn't work'. I have on several occasions posted appeals to this list for people to contribute content to it, and gotten almost no response (with one notable exception), in terms of added content; that was a large part of why I merely mentioned it in an offhand way. > a site I was already familiar with, but not under the name you used for > it. Ah, formally it's the 'Computer History Wiki', except that's a lot of typing, so I've been using 'CHWiki' as a short, easy-to-type, name for it for some time now. > (It was a bit hard to find with Google, which just goes to show...) Yeah, I added "CHWiki" to the text on the Main Page to make it a little easier to find from the short name, after a previous case where I'd used that term here, to some people's confusion. But I see it still doesn't work well; I guess I'll have to add 'CHWiki' links from more pages. Using 'Computer History Wiki' as a search term only works slightly better, though; it's at the bottom of the first page of results for me, below a bunch of Wikipedia links. Noel PS: In response to a point raised in a private reply to me; the site is for _all_ historical computers: personal computers, mainframes, the lot. I myself have added a lot of PDP-11 material, but only because I'm very fond of them, and know them well. The field of historial computers is _way_ too broad for one person to cover in depth, which is part of why I previously appealed to people who knew/were familar with other corners of it to add detailed content in those areas.

5 years, 4 months

Google site ordering (Was: Archiving information)

by jnc＠mercury.lcs.mit.edu

> From: Christian Corti >> An additional issue, I think, is that Google is deprecating sites that >> use HTTP, versus HTTPS. > Not true, in contrary, Google even crawls through FTP sites :-) I did say "deprecate", not 'ignore totally'! :-) Here's what I know: An e-commerce site where I do a lot of business announced that they would switch to using HTTPS. I grumped, because I'd have to use a browser I don't like as much. The owner wrote back as follows: "next month Google will begin to demote all websites that are not https secure" I assume he knew what he was talking about (via his Web-site engineering people). I suppose I could research it, but I don't have the time right at the moment. I'd love to hear if anyone else knows more. Noel

5 years, 4 months

ADM-3A question

by charlesmorris800＠centurytel.net

I found a newer version of the tech manual on bitsavers, which does mention the mysterious S8 switch (as well as the S6 switch that fills the screen with 0's upon clearing). "The gated EXTENSION port mode, when selected by switch S8, allows selective transmission of data from the keyboard, in Half-Duplex mode, or the communication line through the EXTENSION port. GT: Enables gated EXTENSION port mode which allows ON/OFF control of the EXTENSION port. LK: Disables gated EXTENSION port mode which allows locking and unlocking off [sic] keyboard." The wiring is on the newer schematic, too. Another of life's little mysteries, solved :) --- This email has been checked for viruses by Avast antivirus software. https://www.avast.com/antivirus

5 years, 4 months

GW-DEC-1: A New DEC Prototyping Board

by systems.glitch＠gmail.com

Connor Krukosky and I have been working on laying out a new quad-height DEC protoboard, which can also be sheared down into a dual-height board. Full announce on the VC Forums: http://www.vcfed.org/forum/showthread.php?71177-GW-DEC-1-A-New-Quad-Height-… These should be available within a month or so. I'll be putting up a preorder soon to gauge interest in the production run, which as usual will have hard gold plating on the edge connectors. I haven't gotten a quote for the cost, but I expect them to be $30-40 each for production boards. They'll be available at VCF Midwest as well as online! Thanks, Jonathan

5 years, 4 months

cctalk Digest, Vol 59, Issue 13 (Curt Vendel)

by michael.99.thompson＠gmail.com

> > Date: Wed, 14 Aug 2019 12:06:48 -0400 > From: Curt Vendel <curt at atarimuseum.com> > To: cctalk at classiccmp.org > Subject: Re: cctalk Digest, Vol 59, Issue 13 > > Will... > > I?m still waiting for you and the Rhode Island Computer Society to get my > brand new in the box 9766, the Alignment disk platter, the box of spare > heads and the other unit 9766 beat up unit up and running that I gave you > to donate to RICS for free in exchange for you reading the dozen 300mb > platters I have and then once the data was read they could keep the > platters... > > So still waiting on that... hint hint hint > There are two vintage computer groups in Rhode Island, The Rhode Island Computer Museum <http://www.ricomputermuseum.org/>, and the Retro-Computing Society of Rhode Island <https://www.rcsri.org/>. In this case, Curt is talking about the Retro-Computing Society of Rhode Island. -- Michael Thompson

5 years, 4 months

Event Reminder: DEC Legacy is back on 9th-10th Nov 2019, Windermere UK

by mark＠wickensonline.co.uk

Just a quick reminder for those folk thinking about registering... The next DEC Legacy will take place Saturday 9th November 2019 - Sunday 10th at the Marchesi Centre in Windermere, North West UK. With a focus on Digital Equipment Corporation and their legacy of hardware, software and ethos I'm also extending an open invitation to those who are interested in SGI, HP, Sun, IBM and other high end hardware to come along and share their passion with us. Several formal presentations will be mixed with plenty of hands on time with hardware brought by enthusiasts. Enthusiasts are encouraged to bring along hardware and software to exhibit. The personal nature of the event brings a unique atmosphere within which friendships are easily forged. Registration is now open. Please visit http://wickensonline.co.uk/declegacy/ for more details. Kind Regards, Mark Wickens, M0NOM

5 years, 4 months

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test-drb August 2019