test-drb May 2020

test-drb@ccmp.vtda.org

163 participants
133 discussions

H7821 power supply in MicroVAX 3100, SCSI disk enclosures and others

by cctalk＠beyondthepale.ie

The recent discussion on BSC protocol prompted me to dig out my Microvax 3100 with DSH32 synchronous serial interface. It had been idle in storage for several years and it wouldn't power up, only giving a brief flash on the diagnostic LEDs and a quick twitch of the fans. There was a slight smell, like the stale air that comes out of a deflating tyre. I took out the H7821 power supply and found that five identical brown 1800uF 25V electrolytic capacitors on the output side had leaked. The SCSI disk enclosure where the machine's system disk lives required several power cycles to get it to run at all and it died as soon as the disk tried to spin up. It turned out to also contain a H7821 power supply which had a similar issue with the same five brown capacitors, although not as extensive as in the main unit. I found a second disk enclosure which had seen little use and grabbed the power supply out of that to put in the MicroVAX. It worked well enough to test with but there was a ring of goo around the bottom of one of the brown capacitors which was worst affected in the other units. Time to order a batch of replacement capacitors and figure out what else has been damaged. While it is not the worst I have seen, access to these power supplies for repairs is quite difficult and it is really difficult to debug them safely while they are running with the cover off :-( If anyone has anything with H7821 power supplies in them, I suggest checking on these capacitors. If anything with these power supplies is in storage, I suggest ensuring it is stored the normal way up as this should limit the ability of the goo to escape and spread around the power supply. And there I was thought I was being safe enough by removing the nicad battery packs some years ago... Regards, Peter Coghlan.

1 year, 10 months

PDP-11/05 microcode dump?

by jnc＠mercury.lcs.mit.edu

> From: Mattis Lind > Thanks Noel for sorting this out. Eh, de nada. But thank you. >> I wonder if the ucode in the two versions is identical? The uROM chip >> numbers should give it, (if they are the same on both versions, albeit >> in different locations on the board), but I have yet to check. Does >> anyone happen to know? OK, so the situation here is pretty complicated. To start with / make things worse, that CPU uses lots of PROMs. Lots and lots and lots and lots of PROMs. For the data paths board (M7260), both major versions appear to contain the same PROMs (going by the DEC part numbers), but the chip location (Exx) numbers are all different. For the control board (M7261), the C, E ('early' version) and F ('late' version) etch revisions each contain mostly the same PROMs, but apparently with slight differences between the sets of PROMs in each (as reflected in different DEC part numbers). For details see: http://gunkies.org/wiki/PDP-11/05#Control_PROMs to which I have just added all the gory details. As to getting the contents of all of them dumped in machine-readable form - oi vey! >> on the earlier version (prints for that version are in the GT40 prints >> online It turns out that I have hard-copy prints for the "C" etch revision of the M7261, which do not yet appear to be online; the GT40 prints have the "E" etch revision. I will scan the pages for that revision of the board, and put them up 'soon'. (I'm not doing the whole print set, it's about 1" thick, and most of them are for other things anyway, like MM11-L memory, etc.) Noel

2 years, 5 months

ISO earl TI DSP kits

by aek＠bitsavers.org

CHM doesn't seem to have much early DSP stuff in the collection Does anyone have any of the TMS32010/20/30 or C1x/2x/3x hw/sw kicking around? Other than the docs I've scanned there doesn't seem to be much on the web either.

2 years, 12 months

Font for DEC indicator panels

by jnc＠mercury.lcs.mit.edu

> From: Toby Thain > To get closer I'd need better images of the panels. Hi, I borrowed a DEC inlay from someone (a KA10 CPU bay) and scanned a chunk of it (as much as I could fit into my A4 scanner :-) at 200 dpi: http://ana-3.lcs.mit.edu/~jnc/tech/jpg/KACPUPanel.jpg I have a TC08 inlay, but it's currently being used in my QSIC display (until we can get the RKV11-F/RPV11-D inlay done :-), and I didn't want to yank it out. As far as I can tell, it's the same font on the two of them. > the closest I know of off the top of my head is Akzidenz Grotesk. The Akzidenz Grotesk Medium is indeed very, very close (other than the zero). Do you happen to know if that font available for use in non-commercial settings? Thanks! Noel

3 years, 1 month

Pro 350 Print Set

by robert.jarratt＠ntlworld.com

Manx lists MP-01394-00 as the Field Maintenance Print Set for the DEC Professional 350. I can't find this online and I was wondering if anyone has a scan of it by any chance? Thanks Rob

3 years, 1 month

Monitors FTGH

by a.carlini＠ntlworld.com

The following four monitors are available free for pickup in the UK (OX17 postcode). All appear clean but are untested. All are believed to have been functional when stored but that was ~2002/2003-ish. Microvitec Cub. Seems to be in its original box. DEC VRT19-D3. Vision Master Pro 17. DEC VRC21-W3. Obviously with the current restrictions on movement these cannot be picked up, but they need to be gone soon after the restrictions are over. Expressions of interest offlist please. Antonio -- Antonio Carlini antonio at acarlini.com

3 years, 4 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

3 years, 5 months

Thinking of selling my PDP's

by charlesmorris800＠centurytel.net

I am getting closer to retirement (although not close enough) and I'm considering selling off my PDP stuff, especially if I downsize and move. Everything's working, but I just no longer DO anything with either system... the adventure was acquiring all the pieces, fixing them and learning the software :) Anyhow I have an 8/A with cloned Programmer's Panel (Vince Slyngstad and I made it around 2006) and limited function panel, 32K RAM board (also have core), Philipp Hachtmann's USB interface board, RX01 floppy, two RL02's, and a high-speed (optical) reel-to-reel paper tape reader. OS/8 is up and running. Several spare RL02 packs. It's all in a tall DEC rack with an H-(something) power control box. The ASR-33 is not included, I'm keeping that. Also an 11/23+ (11/03 chassis) in a corporate cabinet with two RL02's, a 16-line serial interface, VT-220 terminal. Also an RQDX3 which is connected to a loose 3.5" TEAC floppy drive. Have RT-11XM, RT-11SJ and TSX-Plus 6.50 (all 16 timesharing ports are working too). So, I am wondering if there's any market for them (preferably as complete systems). Shipping would be difficult due to the size/weight (I'm in rural south central Missouri). I'm not looking to give them away, or to part out, but would entertain reasonable package deals rather than deal with the "LQQK! RARE!!" bull on ebay. I can send pics to interested parties. Let me know, thanks! Charles

3 years, 5 months

Looking for Cobalt Qube cases

by laurens＠daemon.be

Hello, I'm looking for Cobalt Qube cases, preferably in North America. I would prefer non working Qubes as I don't want to deprive anyone of working ones. Doesn't matter whether it's a 1, 2 or 3. I'm looking to repurpose the cases. Thanks!

3 years, 5 months

Microsoft open sources GWBASIC

by commodorejohn＠gmail.com

Liam Proven wrote: > I don't know. There is a huge amount of tradition and culture in > computing now, and as a result, few people seem to have informed, > relatively unbiased opinions. There hasn't been much real diversity in > decades. > > 25 or 30y ago, people discussed the merits of Smalltalk or Prolog or > Forth; now most people have never seen or heard of them, and it's just > which curly-bracket language you favour, or does your preferred > language run in a VM or is it compiled to a native binary. Agreed. While I'm much more favorably disposed towards C than you are, the increasing homogeneity of almost all modern languages is discouraging and, I think, detrimental to the field as a whole. Forth and Smalltalk alike were eye-openers when I discovered them (and Smalltalk in particular was a breath of fresh air, after I'd spent years failing to ever really grok OOP with the likes of C++ and Java,) because both presented genuinely *different* and beautifully consistent ways to think about structuring and specifying a computer program. These days, though, outside of deliberately jokey ultra-esoteric languages, it's pretty much just a bunch of domain-specific Java/Javascript knockoffs from horizon to horizon. > I am just surprised that this (to me) rather inelegant design survived > and got to market, given what you've said about the same company's > ruthless drive for cost-cutting removed one PCB trace even though it > killed floppy-disk performance, or wouldn't use an extra ROM chip > because it was too expensive. > > It seems inconsistent. It's marketing - consistency there is a non-consideration, if not actively striven against. The whole saga with CP/M on CBM was a boondoggle - the CP/M cart existed because business customers wanted a CP/M add-in to run their spreadsheets and their whatnot, but it didn't end up being a good fit for reasons already stated (slow CPU, slow disk, 40-column only.) The 128 improved on those points, but not nearly enough to become competitive with the advancements CP/M machines had made in that time, and in the process wasted precious man-hours and drove up the cost and complexity of the unit - and all the while CP/M had been losing ground to MS-DOS in the business market for years! But marketing promised it, so it had to happen... :/

3 years, 5 months

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test-drb May 2020