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Thread: My Altair 8800a project

  1. #1

    Default My Altair 8800a project

    I thought I share my work:

    Over the past three years I've made some S100 boards for my Altair 8800 build. Two years ago I've bought an empty optima case from Ebay. To make
    a working 8800a computer I worked on the PCB's and the frontpanel (artwork). First the artwork. Luckily there's a good scan online (https://www.vintage-computer.com/ima...tpanelscan.jpg) for
    designing a new frontpanel. I've made a new version in GIMP by selecting, tracing and pixel editing to get a clean frontpanel for printing. I think it's a nice attempt if I say so myself.

    I've printed the frontpanel on aluminum so there's a metal feel to it. I've integrated the logo strip because the printing company (photo on aluminum) can print transparent pngs.

    frontpanel-artwork.png

    Then the pcbs. When I started with the pcbs I never made anything in Kicad. Now I'm somewhat of a pro . Some of the schematics from MITS are messy (as you probably know) so for
    example with the 8080 CPU I've bitmap converted the pcb scans to trace the tracks after I've made the schematic from the manual. I did this with every pcb. The boards are not a replica or a pixel
    perfect clone. This is because I chose for a schematic / PCB approach rather then a scan / gerber. an advantage is that you can easily make changes. (For example, A 8080 CPU pcb change with the clock mod)

    8080 CPU (works, KiCad replica. needs cpu clock tuning. Schematic cleaning necessary):

    cpu8080.png
    cpu8080-3d.png

    Front Panel (works, KiCad replica. Schematic cleaning necessary):

    frontpanel-pcb.png

    For the main board I've used scans available on the internet. This board is also remade with Kicad:

    mainboard.png

    Then I needed ram. I like using old boards and old ICs so I started with a 1k static ram board. It's a simple board but I don't have the pcb scans. The board is finished and working. Protect / Unprotect works.
    MITS 1k static ram board (works, Kicad new design based on pictures. No original traces):

    1kstaticram.png

    For the PSU I used an original PS DB supply pcb and bought transformers to use the system with 220volt. I've scans available when I stripped the PCB but it's better to use a switching power supply these days.
    I worked on my Altair for a very long time. Now I'm at the point where I can play kill the bit on my machine. I'm not a electrical engineer. Just a network IT-er with a passion for old machines. Keep that in mind when looking at the Kicad images

    At this moment I'm working on serial communication. The schematics for a 2SIO board are messy and I've made a prototype from the manual with problems. I would love to get pcb scans from a bare pcb. That would be really great. In the last couple of weeks I've made two
    other serial boards. The Solid State Music IO-4 and a MITS SIO-A board. These two boards are arrived last week and I'm waiting on the last ICs to test the boards. The traces on the IO-4 are autotraced so not that nice. For now that's enough.

    MITS SIO-A:

    sio-a.png

    Solid State Music IO-4:

    SSM-IO4.png

    The last project I'm working on is the Tarbell Cassette Interface. I've a finished schematic plus a PCB traced from the manual (very difficult thing to do!). The KCS mod is not included. I need to test this pcb in the coming weeks but a working serial board is my priority.

    Tarbell Cassette Interface 1001:

    tarbell-cassette.png

    I don't know if people are interested in the PCBs. I will setup a site when people are interested. I know Grant's very nice clone is neater but a more affordable alternative is desirable I think. If you do not want to work with 74xx logic, I would like to refer to the Altair 8800c
    Maybe someone can help me with bare pcb scans from 1k static ram, SSM IO-4 or the 2SIO card. I would love to trace those boards to Kicad perfection and also find the problem with the 2SIO board.

    Regards,
    Martijn from Holland.

  2. #2
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    I had been considering doing something like this myself so it's fun to see what you have done here.

    More affordable alternative is definitely something I am interested in also.

    Quite a project for a first go a KiCad!

  3. #3

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    Thank you. I'm sorting the files and cleaning up. Maybe a Git repo, I don't know yet.

    It's been fun to build something like this. I was lucky to buy an optima case. a working system is way too expensive for me. The problem
    is a nice alternative case. Some people used 19inch racks but I don't like that.

    I forgot to add some pictures of the system:
    IMG_1418.jpg
    IMG_1417.jpg
    IMG_1416.jpg

  4. #4

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    Lots of good work already. Fun!

    Mike

  5. #5

    Default

    Will you be posting your KiCAD files?

  6. #6

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    Thanks for the nice reactions. It's a lot of work. The past few weeks I've been working on my SIO-A board. No luck. I think the card is working but when I use the test program from the computes notes I can select the card on address zero but
    the input instruction gives 174 and not zero or one. I need to debug the card. Maybe a wrong clock signal? I worked my way to all the errata sheets and I think I've done all the changes...

    I've included links for the Gerber files for the CPU and frontpanel for now. Let me know if you'll need other boards or if there are any problems. I need
    to setup a site / Github for all the files. The Kicad files (schematic) are so messy to release just yet
    [URL="https://computerarchive.org/S100/projectfiles/"]

    The SSM or Tarbell is a work in process so I'm not ready to release them. I don't know if the cards work yet.

    Is there someone willing to de-solder a SIO-A (rev1) or 2SIO board to make a scan with a scanner? A high resolution scan with the components would also be nice.

    Martijn

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