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by Wouter de Waal

Hi Tony and all >It might have run CP/M (which will run on an 8080, and therefore on an >8085). That needs RAM at location 0000 [1]. I know of CP/M, I even used CP/M (on my Apple) but I did not know it needs RAM at 0000. That's kind of strange, since everything that ran CP/M (OK, everything -80) has vectors at 0. I guess there was a reason behind it. I see the CPU board has a jumper "F000/F800" so I guess it does something to map that address to 0 after reset. W

9 months, 1 week

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Documentary on the SKALA computer of Chernobyl Nuclear Power Plant

by Sellam Abraham

This is a pretty interesting documentary describing the computer (SKALA) that ran the Chernobyl nuclear complex. https://www.youtube.com/watch?v=ZbaptQh2AM4 Sellam

9 months, 1 week

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Shelves / Rails for DEC Racks Questions

by Jay Jaeger

I have some open slots in some of my racks. I do have some old DEC rails, but I have a fair amount of equipment, from both DEC and other manufacturers, for which those rails are not suitable. Does anyone have any specific recommendations for shelving? (where equipment could just be slid on top of, if the equipment isn't too wide - some pieces are very close to 19 inches all by themselves, and were designed for front cantilever style mounting.) Would also be interested in specific recommendations for the following: DEC VR14 (I have one on a PDP-12 with proper rails, but have another to mount and don't have proper rails for it) HP 88780 (Perhaps a shelf is the best bet for these?) JRJ

9 months, 1 week

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VCF Swap Meet - Wall, NJ - Oct. 28, 2023

by Jeffrey Brace

Same place as last year in the big parking lot across from Brookdale and down the street from InfoAge Science and History Museums. We have Southern Monmouth County Firehouse museum selling food and drinks in the middle. This is a fundraiser for both museums (VCF and Firehouse museum) which are both part of InfoAge. All the info is here: https://vcfed.org/vcf-swap-meet/ Thanks! Jeff Brace VCF National Board Member Chairman & Vice President Vintage Computer Festival East Showrunner VCF Mid-Atlantic Event Manager Vintage Computer Federation is a 501c3 charity https://vcfed.org/ <http://www.vcfed.org/> jeffrey(a)vcfed.org

9 months, 1 week

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Re: Free Fujitsu M2444 6250 BPI tape drive

by Len Shustek

The drive is saved from the landfill! It was picked up by a classic computing fan at noon this morning. (And yes, it is Pertec-compatible.)

9 months, 1 week

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Theory of operation of DEC H7441 regulator?

by Tom Hunter

The DEC H7441 regulator is a relatively complex circuit using 2 x 555 timers, 2 x LM301 op-amps, 2 x transformers and 2 inductors I am struggling to understand how it is meant to work and was hoping to find a maintenance manual for it. Could anyone with such a manual please help? Alternatively is there another explanation of the operation of this or similar types of circuits? The circuit implements a switch mode supply. One of the two 555 timers operates as an oscillator, the second I think operates as a monoflop with the pulse length controlled via one of the LM301s. Overall the circuit seems very complex and while I understand parts of it, other parts are mysterious. In particular the top left section around Q1/Q2/Q3 and T1/T2 and E3 is most confusing. I did not find anything remotely similar in "The Art of Electronics" from Horowitz & Winfield. The H7441 schematics are available from here: https://deramp.com/downloads/mfe_archive/011-Digital%20Equipment%20Corporat… Thanks for any help or suggested reading material. Tom

9 months, 1 week

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Free Fujitsu M2444 6250 BPI tape drive

by Len Shustek

I bought this giant GCR tape drive on eBay five years ago, http://www.bitsavers.org/pdf/fujitsu/_brochures/M244X_Brochure_1984.pdf hoping to be able to use it to extract analog signals from 6250 BPI tapes to feed into my decoding program. https://github.com/LenShustek/readtape I failed to figure out how to get the right signals out, and eventually abandoned the project. I now need the space it takes, so I'm offering it for free before consigning it to the landfill. It's big (20" x 24" x 30" on the wheeled stand I built) and heavy (160 lbs) so I won't ship it. Pickup only, on the San Francisco peninsula.

9 months, 1 week

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DEC VT36 Color Graphics Display Control System

by Hans-Ulrich Hölscher

Hi, who knows details about the DEC VT36 Color Graphics Display Control System ( https://classic.technology/vt36-color-graphics-display-control-system/)? I'm looking for manuals for the VT36 as well as for the associated VAX-11/PROVUE or RSX-11/PROVUE software. Anyone with personal experience with the VT36 and/or PROVUE? Ulli

9 months, 1 week

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Re: Vintage Computer Systems for sale

by Stephen Pereira

Sorry Sellam, none of the websites I mentioned for information are mine. smp - - - Stephen Pereira Bedford, NH 03110 KB1SXE

9 months, 1 week

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Vintage Computer Systems for sale

by Stephen Pereira

Good afternoon to all, I am starting the process of selling off some of my vintage computer systems, so as to not burden anyone I leave behind. The systems I list here are available for viewing in Bedford, NH, just west of Manchester, NH. Anyone interested can send me an e-mail message and we can set up an appointment for you to visit. Cash and Carry, of course, and reasonable offers will be considered. Altair 8800c — $2500 I constructed this system early in 2019. I built the front panel and front panel interface boards, and soldered up the backplane. The rest of the boards were purchased assembled and tested. You can see the Altair 8800c story here: https://deramp.com/altair.html The system is fully tested and working, currently using virtual Altair disk drives via the Deramp application. Plenty of documentation. Single 8 inch disk drive in a dual drive cabinet — $500 This physical disk drive has been paired with the Altair 8800c in the past. Works fine. I included will be an 8 inch disk drive that used to be in this cabinet until the power supply failed. I believe this drive can be repaired. Included will be another 8 inch drive that is the wrong form factor to fit into the cabinet. Purchased on eBay, untested. Altair 680 — $2000 I acquired this system on eBay back at the end of 2018. It was not working, but a bit of troubleshooting discovered bad ram which was replaced. The least significant LED of the address display does not light, but I’ve tested that the proper signals are there. I simply did not want to risk changing out the LED. This system comes with the 4-slot riser, but the connectors are not yet soldered in. No add-in boards. Plenty of documentation. Complete SWTPC 6800 clone system from Corsham Technologies — $400 I acquired this system from Bob at Corsham in the middle of 2018. It is the complete setup, with the full 64K ram and the virtual disk drives. Documentation available at Corsham Technologies: http://www.corshamtech.com <http://www.corshamtech.com/> Northstar Horizon — $800 I purchased this system on eBay as a running system. From time to time I had problems with the top 8K ram on the Horizon 64K ram board. The 64k ram board has been replaced with a Compupro Ram 17 (or clone), works great, no problems. I will include the glitchy Horizon 64K ram board. FYI, a Deramp Virtual Sector Generator works great with this system, eliminating the need for hard sector diskettes. https://deramp.com/vsg.html Thanks for listening! smp - - - Stephen Pereira Bedford, NH 03110 KB1SXE

9 months, 2 weeks

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