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Thread: VC8E point plot 74xx replica

  1. #1

    Default VC8E point plot 74xx replica

    Call me nuts or something...

    I've made a 74xx clone of the VC8E. I had a little bit debugging to do
    because one chip was date code 7421 instead of model 7421
    And I had an unused 7474 which was broken. I was quite surprised that
    I had no PCB modifications to do. I've added a +15 and -15 output on the
    board coming from the PDP8 power supply. It seems to run nicely on the PDP8 supply.
    But you can use an external high quality + and -15V power as well of course.

    I'm still waiting for the axial capacitors so you see a few electrolytics which
    will be replaced. But hey, it works!

    The design files will come on my Github on a later moment.

    If you have just a digital board or just the analog board you should
    be able to use my design to make it complete as well...

    Vince is working on a much more modern version with a cpld. Probably much
    cheaper to make. But I love this old electronics and that is why I made the redesign.

    And I'm done with the Ebay auction sniper sickness... So I've made a redesign
    of the M882 RTC and these are on their way as well. Now that nasty EAE

    VC8E Analog.jpg VC8E Digital.jpg



    Regards, Roland
    WTB: Case for Altair 8800 ...... Rolands Github projects

  2. #2
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    They're pretty .

    If you're nuts - so am I for making an LD12!

    I will be working my way around to the DACs for spacewar presently when I have a working LD12 - which may be a bit off yet as I have the front panel PCB to design (in progress) and the documentation (only just started).

    Dave

  3. #3
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    I expect there's a whole lot of people who would say we're all 4 bits short of a word.
    Keep calm and carry on (at least 'til October 31) ...

  4. #4
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    And where a byte is 6 bits and can be represented by a two digit number rather than have to resort to letters!

    Dave

  5. #5
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    Default

    Very nice! I love seeing hard-to-get things reproduced and/or modernized

  6. #6

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    Quote Originally Posted by daver2 View Post
    They're pretty . If you're nuts - so am I for making an LD12!
    Thanks! That LD12 is a very nice project too!

    Quote Originally Posted by glitch View Post
    Very nice! I love seeing hard-to-get things reproduced and/or modernized
    Thanks!

    My goal is to make it a more affordable hobby. Prices seem to get to unpredictable insane levels.
    Mattis pointed me to the prices of the M8650 serial card. I don't really get it because there
    is that USB version from Phillip Hachtmann. The disadvantage of that board is that it is USB only.
    I wonder if it is worth the effort to make that M8650 serial card in 74xx TTL logic as well...

    These 74xx projects are especially affordable for people having a bunch of standard TTL chips on stock.
    I had all the TTL chips in my own stock for the VC8E. Also the op-amps can be very cheap.

    There are a few cards on my wishlist which I'm thinking of to redesign.

    But I wonder if people here would like to built such cards too... I really have no clue.
    I keep the circuits as original as possible. But with chips like the 8235 you have
    to be creative and it depends on the design how you can replace them...

    The 74xx version of the M882 RTC is on it's way to me now...
    Currently I'm working on the RX8E. I've been asked for the TD8E and I'm thinking about the EAE.

    But then again, no clue if it is interesting for other people to build. My fun is to redraw them into
    an easy to rebuild board with easy to find components...

    Regards, Roland
    WTB: Case for Altair 8800 ...... Rolands Github projects

  7. #7
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    Roland,

    An combination I/O card that included RTC, two serial, Centronics printer port, memory, and bootloader would be really great. It would save a lot of slots, and save a lot of money.
    Member of the Rhode Island Computer Museum
    http://www.ricomputermuseum.org

  8. #8
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    Re the M8650, I've got several of them with DL1 (30 ns delay line) either broken off or missing altogether; I expect others do as well. A small daughter board with a modern-day substitute would be a welcome project.

    A double port serial card with SD card capabilities would also be high on my list of useful boards.

  9. #9
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    Quote Originally Posted by Roland Huisman View Post
    My goal is to make it a more affordable hobby. Prices seem to get to unpredictable insane levels.
    That's been our goal with the reproduction Ohio Scientific boards, too. I'm definitely *for* the democratization of vintage computing

  10. #10

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    Are there any documents or pictures of DEC cables?

    I've got this Tektronix 611 recently. I've searched for it because it
    has the setting on the VC8E board. And within a week I got this Tek 611.

    Tektronix 611.jpg

    Does anyone know where I can find the cable pinout?
    Otherwise I have to figure out the cable myself...

    Thanks!
    Roland
    WTB: Case for Altair 8800 ...... Rolands Github projects

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