The Computer Of Yesterday, Today

There are a handful of computers that have become true museum pieces. The Altair, of course, is tucked away in the Smithsonian’s warehouse waiting for some time in the future when Apple’s legacy fades or until there’s a remake of War Games. Likewise, the French Micral and American SCELBI are important historical artifacts, and even a modern component-accurate reproduction of an Apple I could fetch a decent amount of cash at the right auction.

There’s something special about these old kit computers – even though the instructions for these machines provided volumes of documentation, no one is building these machines anymore. You just can’t buy the PCBs, and sourcing period-correct components is hard. [Brad] is an exception. He found original, untouched PCBs for the cover story of the July, 1974 edition of Radio-Electronics. It’s an unbuilt Mark-8 minicomputer. Now [Brad] is in a position no one else has been in since the 1970s: he can build a vintage minicomputer, with a TV Typewriter, from scratch. He’s documenting the whole thing.

Since this is the first opportunity this century anyone has had to build a truly retro minicomputer, [Brad] is going all-in with this project. For an interface, he’s building [Don Lancaster]’s TV Typewriter, a device introduced in the September 1973 issue Radio-Electronics. When combined with an old CRT TV, the TV Typewriter becomes a serial terminal. While today something like this could be built around a single microcontroller, constructing the TV Typewriter is no small feat: it’s spread across four boards, uses character generator ROMs, and is currently housed in a beautiful red oak case.

Just because [Brad] is building an ancient computer using ancient parts doesn’t mean he can’t get a little help from modern technology. He’s applying white silk screen to his custom TV Typewriter boards using the toner transfer process. Yes, apparently you can get toner cartridges filled with white (and neon!) toner, and this works well enough to replicate the look of professionally silk screened boards.

This is one of the greatest retrocomputing projects we’ve seen in a very long time. This is a true retrocomputer, complete with custom transformers and gigantic linear power supplies. When this project is complete, [Brad] will have a museum piece, all thanks to a lucky find of an eBay auction and a lot of hard work.

16 thoughts on “The Computer Of Yesterday, Today

  1. I built a TV typewriter in high school with 2 other guys. We did the board with photo-resist, and didn’t quite line up both sides. We didn’t have plated through holes, so I hand soldered sockets on both sides (destroying about half the sockets in the process). Keyboards were hard to come by, so for a few months we used 7 toggle switches and a push button for a keyboard (a great way to learn ASCII).

    It took most of the school year to build and troubleshoot it. The friends built a SWTP 6800 and used the TV typewriter for a couple years. The amount I learned during that process was incredible.

    1. I took an electronics program in high school (late 70’s) and we had Don’s book. The TV typewriter was our my the range of my paper route income until I got a real job. Then I had plenty of money and no time (sigh).

      My real regret was not purchasing a Heathkit back then while they were still in business. I did purchase a Sinclair ZX-81 kit for $99, and still have it (I will never sell it, given the USAF thought it was a great idea to engrave your SSN on everything of value!)

  2. The Smithsonian had the Altair on display at one point. I have pictures of it. I haven’t been down there in awhile, so maybe it’s not there anymore. But it definitely has been on display before if it is not now.

  3. The original tv typewriter mostly offered potential, rather than usefulness. It was standalone, I don’t think it had any interface, so you could type on the keyboard and see the characters on the screen, but not much else. It took a later iteration before it could be used with a computer, but then when the original was published, no home computers.


  4. My first “real” computer was a Microtan 65 from Tangerine systems. It was 6502 based and I still have it together with a Tanex expansion board and a homebrew non volatile (battery backed up) memory board that I made. The idea was to use it for a home control system but I never got that far. It took a year to get the memory board working because of address bus timing issues. That was when I learned that debugging hardware was much harder than debugging software! GPIO was very hard to implement and I was working on an acoustic coupler for remote control over the telephone. After that I got a TRS-80 model 100 which was a little easier to work with and the Microtan was put aside. I love the fact that today you can concentrate on building functionality without having to solve too many underlying problems on the way. In the old days, I learned a lot but hardly ever got something to work as I wanted because it usually involved building a lot of tools and infrastructure before real world capabilities could be implemented. Ah for the good new days :-)

  5. Kudos to [Brad]! The Mark-8 and Lancaster TVT are both epic projects, and a real challenge to get working. I tried to build a Mark-8 and failed. I was just too young and inexperienced at the time to pull it off.

    Josh Bensadon *did* build a working Mark-8. He had it at the 2015 VCFMW show in Chicago. Very impressive!

    If you want to build a vintage microcomputer kit, take a look at the Z80 Membership Card. . It has the look and feel of a “lost” 1980 kit, right down to the vintage parts and manual printed on greenbar paper.

  6. For a remake of War Games, you’d want an IMSAI-8080 rather than an Altair.

    If I wanted an 1970s microcomputer kit, I’d pull it out from under the desk and power it up. Now if only the tapes would load.

    EXPLORER-85 VER 1.4
    COPYRIGHT 1979

  7. I built the Mark 8, Dr Suding’s cassette data recorder adapter, connected the Mark 8 to a baudot TTY, and build Lancaster’s TVT. Used a 1964 Motorola lug-gable TV with the TVT. These were good for training in 1974. Today I’ll take modern components and systems.

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