test-drb

test-drb@ccmp.vtda.org

101090 discussions

by peter＠vanpeborgh.eu

Guys, I seem to have lost contact with Rick Bensene of that museum for the last 10 days. Can anyone tell me if he is ok? Many thanks, peter

5 years, 10 months

PDP-11 tape question

by cclist＠sydex.com

I've been processing some PDP-11 9 track (800 NRZI) tapes and run across something that I don't recognize. Every file on the tape consists of a number of 512 byte blocks (okay, that's normal) but at the head of each file, there's a short block of 14 bytes. Usually, a short record like this is discarded as "noise" on many mainframe tape systems, but here it's consistently present. Here's what one of the records looks like: 15 34 fe 51 fe 76 01 01 00 00 01 80 10 00 Doesn't seem like a file name in RAD50 format, so I'm puzzled. Inquiring minds want to know... Thanks, Chuck

5 years, 10 months

Changing the number of file headers on an RSX volume

by cz＠alembic.crystel.com

So I'm working on this RSX11M+ system here and while working I ran myself out of file headers. Using the HOME /MXF command I was able to increase the number of headers, but only up to 4090. or so. Trying to go to 4100 gave me an error saying there were not enough system blocks or something. Currently I have 830 headers, but that's not enough in the long term. The volume has 541,944 blocks total, with 150655 in use. This is a system I generated on a smaller disk, then copied to the pdp11, then backed up with BRU MU0:=DU0: then restored to a larger blank disk. I guess the question is can I extend the number of blocks without having to re-init the system disk? I suppose I could flatten it by taking the system down to single user (shutdown, then p to start with the volume dismounted, mount the volume /for, then BRU mu0:=du0:), then format the volume with a really big assed MXF value, then restoring the tape, but would that flatten the volume info? Or do I need to just man up, put a second ESDI drive on this monster, copy the files to the second drive then format the first (big) volume right, copy the files with PIP, and do a VMR again to write the boot block? Or is there a better way to backup and restore the volume without doing an image backup using /for? Been a long time since I've done this stuff. Thanks! C

5 years, 10 months

PDP8 KV graphics PCB design

by roelof_klaas＠yahoo.com

I found somewhat fascinating pictures in a PDP8 small computer handbook. It is a KV graphics system. According to the book it was used to design new computer circuit boards. So I got very curious to that KV system. I found a maintenance manual about the system. It even had a joystick! I wonder if any of that PCB software has been rescued? Regards, Roland https://ibb.co/WVKCfMz https://ibb.co/TvYpP2v https://ibb.co/6mSZkdh

5 years, 10 months

IBM vacuum tubes

by decguy＠songdog.eskimo.com

While going through my assortment of old vacuum tubes looking for audio treasures, I found a handful of IBM branded ones. Mostly 5965, but there's one 5963 mixed in. These are dual triodes with the same pinout as common small-signal audio tubes such as 12AX7/7025/ECC83, but characteristics closer to 12AT7 or 12AU7. My RCA Receiving Tube Manual says they're designed to withstand being held in cutoff for long periods of time, and mentions digital applications. Anyone know what kind of IBM machine these would have been used in?

5 years, 10 months

Malfunctioning VT240 - help please

by charlesmorris800＠centurytel.net

On 6/21/20 10:41 AM, Jon Elson wrote: > On 06/20/2020 09:41 PM, Charles wrote: >> On 6/20/20 8:31 PM, Jon Elson wrote: >>> >>>> I confirmed the bad one by removing the piggyback and the failure >>>> returned. Now I need to desolder the bad one without ruining the >>>> board. I may just cut the leads off close to the bad chip, and >>>> solder the replacement to the stumps. (Normally I remove the legs >>>> and install a machine-pin DIP socket). Or just solder the piggyback >>>> and leave it there... thoughts? >>>> >>> Cut the leads close to the body.? Apply a soldering iron to each >>> lead, and pull the lead out with tweezers, >>> simultaneously heating and pulling.? This is very gentle to the >>> board, just doing one at a time.? Then, you can vacuum out the holes >>> and install a new chip or socket. >>> >>> I've done this many times, and never wrecked a board. >>> >>> Jon >>> >> That's how I do it... the vacuuming is the problem. Someday I need to >> get a good vacuum desoldering station. Right now I just have a >> spring-loaded solder sucker (which I can do a pretty decent job with >> on most boards). But this high-density layout (2 traces between DIP >> pads) I'm a bit wary of. >> > Just be gentle, and you should be able to do it.? Also, in some cases, > you might heat from the opposite side from the solder sucker.? That > way, you can keep the soldering iron on the pad until you have > triggered the sucker.? But, yes, the hollow soldering iron with > powered vacuum is amazing the first time you try it.? I got one at an > auction years ago, it is much better than the regular iron and > plunger-sucker. > > Jon The small company I first worked for had a Pace unit. I remember not being impressed with it - frequent clogs, pads lifting, and not getting all the solder out, no matter how we set things. Still beat solder-wick though! I got it done, but pin 16 (which connects directly to the internal-layer ground plane) was a bear. From the feel of it and the heat required, the draftsman didn't bother to make pad reliefs. Anyway it's now socketed, so of course it will never fail again! I also made a small jumper on a 15-pin D-sub to connect Monitor Present L to ground, so that annoying "Monitor Error 9" message stops ;) On to the next project!

5 years, 10 months

Imsai and others in Montgomery, AL

by sales＠elecplus.com

https://www.facebook.com/marketplace/item/960320167759670/ Guy is cleaning out his shed because he is moving. Not affiliated with seller, etc. Cindy Croxton Electronics Plus 1613 Water Street Kerrville, TX 78028 830-370-3239 cell sales at elecplus.com -- This email has been checked for viruses by Avast antivirus software. https://www.avast.com/antivirus

5 years, 10 months

LK201 emulation

by paulkoning＠comcast.net

Gentlepeople, I've been having problems with broken LK201s, so as a workaround I created an adapter that connects to a standard PC USB keyboard and makes it look like an LK201. It's based on an Arduino (specifically, Adafruit Trinket M0, an amazingly tiny yet powerful small microprocessor). It's working at this point, though it needs a few small software tweaks to make it complete. I'm going to turn my breadboard into something slightly more polished. Question to the list: is this something that would be of interest to others? If yes, I can make the design available. Perhaps the PCB layout and parts list. I don't think I want to get into building units for others, though. paul

5 years, 10 months

New subscribers?

by ccth6600＠gmail.com

Are new subscribers to cctalk still accepted? My subscription request was left unanswered. With all the talk about the future of this list I wonder if I came too late. Thanks Tom Hunter

5 years, 10 months

Malfunctioning VT240 - help please

by charlesmorris800＠centurytel.net

> On 06/11/2020 02:29 AM, Mattis Lind via cctalk wrote: > >/If that would be the case I think the system would fail />/quite soon rather than on test 5. A guess is that this is />/a memory problem. / That was a good guess, everyone ;) I got some new 4116's and piggybacked (dry, no solder) two of them atop my suspects at E3 & E4. Didn't fix it. Of course :/ In the meantime I've acquired a nice HP 1630G logic analyzer complete with pods and cables. Setting it up was going to take quite a while since I'm not familiar with this model. So I decided to try a simple brute-force approach before the analyzer. I piggybacked another 4116 onto each soldered-in 4116, one at a time. Actually easy to do since with the leads properly formed, I didn't even have to solder it in place, just turn off the power and move it to the next chip. On the 16th, the last one of course, the terminal booted normally and works again. :) I confirmed the bad one by removing the piggyback and the failure returned. Now I need to desolder the bad one without ruining the board. I may just cut the leads off close to the bad chip, and solder the replacement to the stumps. (Normally I remove the legs and install a machine-pin DIP socket). Or just solder the piggyback and leave it there... thoughts?

5 years, 10 months

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