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MSV11

by useddec＠gmail.com

Hi Doug, If you are going to VCFMW, I can bring you a DEC M8044 for $25. Need anything else? Thanks, Paul

6 years, 11 months

Heath/Zenith Z100 technical...

by jules.richardson99＠gmail.com

I just picked up a board set from a Zenith Z-100 (not sure if it was a 110 or 120 model) which had been junked. I threw this out on the sebhc mailing list too, but perhaps someone here knows: a) If the machine's keyboard is completely passive (i.e. just a bunch of switches), or if there's any intelligence to it, b) If the system will start up with no boards plugged in (other than the bitmap display PCB) - i.e. no S100 FDC or winchester, c) If "yes" to the previous, whether the mainboard/bitmap board will function on just +5V and +/-12V (i.e. without the S100 +8V and +/-16V rails) Trying to power up what I have might be fun, but I'm really not sure about the lack-of-keyboard issue - if it's just switches and decoded via the mainboard then rigging something might be possible, but if there's some kind of higher level serial protocol involved then maybe it's too much hassle. I don't have a S100 bus machine kicking around to power things with at present (but of course rigging something would not be too difficult). I'm not sure what kind of details the documentation went into, either - I've got a Z-89 and the docs there are extremely technical, with full schematics, but I'm not seeing any equivalent online for the Z100 series (there seems to be very little out there about them at all - came too late in the S100 era, perhaps?) cheers Jules

6 years, 11 months

Ferroresonant transformer supply repair

by kylevowen＠gmail.com

Has anyone replaced the capacitor in a ferroresonant power supply with much success? My current understanding is that the capacitor and transformer are mated as a pair, so replacing just one of them would require careful consideration. The PDP-8/I I'm working on has a 704A in it, with a GE 8uF 660V capacitor. It measures a couple of nF on my capacitor meter, and I was told by the previous owner that it's dead. Any advice? Thanks, Kyle

6 years, 11 months

Ferroresonant transformer supply repair

by malcolm＠avitech.com.au

>Thanks! Someone else pointed me to Mouser as well. Was hoping to find something in stock, but I guess I can wait and go with Mouser; after all, the PDP-8/I has >been waiting well over 30 years for a new capacitor! > >Kyle It looks like Farnell/element14 have a couple in stock -> https://au.element14.com/search?st=8uf%20660v Element14 Order Number 2668607 Malcolm

6 years, 11 months

Looking for schematics of QBUS 32KW memory module.

by vintagecomputersmn＠gmail.com

Hello, A few weeks ago I ordered a Sigma 400255 for my H11A LSI-11 computer with the hopes of getting a 8" floppy hooked up for VCFMW. For the most part, all the tests I ran from the ODT seemed to be AOK. The one this I couldn't do it boot RT-11 from my TU58 emulator, as it would crash every time. Every since I was able to boot RT-11 on my machine it has been unstable and prone to crashes, but i chalked that up to the TU58 emulator, and not the machine itself. Since I needed to boot from to TU58 in order to INIT and make a bootable RT-11 disk for my system, I looked for other causes for the crashes. I ran the VKAA XXDP test, which passed fine. I then ZKMA test, which lo and behold listed back there were numerous bad addresses all over memory. The only memory modules I have are 3 nearly identical 3rd party 32KW memory modules. The one that I have in the system right now came with it, and is the one with memory errors. The other two are ones I bought on eBay that are in rather poor condition and currently do not work at all. I was hoping to transfer some of the 4116 chips from my nonfunctional units over to my semi-functional unit, but I cannot find schematics for any of the boards because they don't have any marking identifying marking on them. If anyone knows where I can find schematics for these boards, that would be wonderful. I am including a picture of one of these boards below. https://i.ibb.co/sQwZw0j/32kwram.jpg Thank You, Gavin Tersteeg

6 years, 11 months

ISO old AST mainframe comms driver software

by aek＠bitsavers.org

AST-coax, AST-432, AST-SNA, etc. IBM comms products circa late 80s I'm in the process of pdf-ing the manuals this afternoon. The only product disk I have is AST-3780

6 years, 11 months

Announcing VCF Pacific Northwest 2020

by mbbrutman＠brutman.com

The Vintage Computer Federation is pleased to announce Vintage Computer Festival Pacific Northwest 2020! We will be at Living Computers:Museum+Labs in Seattle Washington on Saturday March 21st and Sunday March 22nd, 2020. To make this happen we are looking for exhibitors, speakers and volunteers. Last year we had 28 exhibits and 6 presentations. We had a great time, we broke the museum attendance record (again), and we are looking to have a good time again in March. If you are thinking of traveling from outside of the region there is plenty to do in Seattle while you are here. Local attractions include the Connections Museum, the Pacific Science Center, MoPOP, the Boeing factory tour, Mr. Rainier, etc. Victoria, British Columbia is also a short distance away. See a more complete list at https://goo.gl/3emMWH . Details about VCF PNW 2020 can be found at http://vcfed.org/vcf-pnw . The exhibitor registration instructions can be found at http://vcfed.org/vcf-pnw/exhibitor-registration . I'm happy to answer questions by email too. Regards, Mike mbbrutman at brutman.com or michael at vcfed.org

6 years, 11 months

Looking for schematics of QBUS 32KW memory module.

by jnc＠mercury.lcs.mit.edu

> From: Mister PDP > listed back there were numerous bad addresses all over memory. > ... > I cannot find schematics for any of the boards You can repair MOS memory boards where the board is basically working, but just has some failing memory chips, without schematics. First you need to create a map which translates memory chip # to bits. You have 32 chips in the array, so there are probably 2 32KB banks, each 16 bits wide. Pull a chip, and then try and figure out which bit it is; then repeat with other chips to try and figure out which bits are stored in which chips. (Unless the designers were insane, each chip will hold the same bit in all the words in that bank.) On yours, the memory chips are in sockets, which makes this less painful. (On boards where the chips are soldered in, a program which loops, storing a word with a single 1 bit, can be used to the same effect; the chip data sheet will tell you which pin is the data pin.) Usually a missing chip results in bits stored in that chip reading as '0', but it's possible they will read back as 1. Anyway, to test the first possibility, start by finding a location in the each bank that can be written to all 0's and all 1's (read back after writing to verify). Next, pull a chip, and then try writing all 1's to that word in the low bank, and read it back. If it now has a 0 bit, congratulations i) you've verified that missing chips read as 0, ii) that chip is part of the low bank, and iii) the 0 bit tells you which bit that chip is - fill in that entry in your chip<->bit chart. If not, try the high bank word, and see if it now has a 0 bit. If not, try writing 0's to the high and low words, and check for a '1' bit; if so, i) missing chips read as 1, etc. If neither is true, check back here! Otherwise, try pulling another chip, and work out which bit that one is, and add it to the chart. Repeat for all 32 chips - although if you're lucky, after a couple you might find a pattern, and be able to predict which chips hold which bits. (But not always; many are random; see e.g.: http://gunkies.org/wiki/Q-RAM_11 http://gunkies.org/wiki/NS23M for some.) If so, do a few spot tests of your predictions to make sure your pattern is correct. With the completed chart in hand, given a failing word (address and bad data), you can work out which chip is at fault, and replace it. Repeat for all memory errors. Noel

6 years, 11 months

Mohawk Data Sciences 6401 Schematic?

by coryheisterkamp＠gmail.com

Hey Guys, I recently picked up an MDS 6401 Key-To-Tape unit in NCR guise to park next to my keypunches. It's been in storage for a couple decades and is in pretty decent shape. Even has a tape on it from when the university that had it pulled the plug and sent it off for surplus. Found an internal date code of 1971. The unit does actually show signs of life, but I suspect a power supply issue. Does anyone have a lead on a schematic? This here is basically what I'm working with: http://www.thecorememory.com/NCR_C-735_-_MDS_6401_Memories.pdf Thanks, Cory

6 years, 11 months

Info on testing vintage power supplies

by aperry＠snowmoose.com

Can anyone here provide a pointer to info on testing vintage power supplies? Search results on the web may eventually lead to the kind of info that I am looking for, but I have to get through too many pages of modern PC power supplies first. Specifically, I will be testing the power supplies in my Sun 3/260, which has 24V, 12V and 5V. I am wondering things like what is suitable loads and do I need to put a load on all three or can I test them one at a time and what I haven't thought of with regards to testing them. alan

6 years, 11 months

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