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Thread: Model I monitor as composite monitor

  1. #1

    Default Model I monitor as composite monitor

    Hello all,

    I have a Model I monitor with no corresponding computer, so I thought I might like to use it as a composite monitor. Has anyone done this? I've only found references to people using regular composite monitors with the Model I, not the other way around.

    I know that it needs a 5V supply in addition to the video signal. (How much power does that draw?) It occurs to me that it might be fairly simple to provide both from a Raspberry Pi, to start with.

  2. #2
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    Interested in a trade for an Apple monitor?
    Kaypro 1,2,II,2X,10 Apple IIe Apple IIgs Commodore 128d, 64 IBM 5160 Ampro littleboard

  3. #3
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    The reason for the 5v line is it's needed to drive an opto-isolator circuit; the Model I monitor was a *barely* adapted and very cheap "Hot ground" TV chassis. I doubt it draws much power but I can't say off the top of my head how much. If you supply that it should work, if rather poorly. (Radio Shack pretty literally just ripped the tuners out of a bunch of spare B&W TVs they had in a warehouse and did minimal patching beyond that.)

    I would definitely consider swapping it to a Model I enthusiast in favor of something like an Apple Monitor /// or other common monochrome composite monitor unless you're really set on using it in particular.
    My Retro-computing YouTube Channel (updates... eventually?): Paleozoic PCs

  4. #4

    Default

    I can see why phogren wants it, but, I wasn't suggesting this because I need a composite monitor. Rather, I've had this monitor for years already, and never done anything with it. I definitely see the merit in reuniting it with a Model I... kinda hoped to do that myself. But, maybe I can do both.

    I'm not planning on hacking it up. The adapter would be external. I've ordered a few parts, and I'll post if I make any progress. At this point, I don't even know if the monitor works, although it powers up, and the screen gets bright if I turn the knobs.

    The main thing I needed was clarification on the pinout. I found this chart:

    Code:
    The pin connections on the Video DIN plug are:
    
             2               1 - 5V dc (30ma max)
         5   o   4           4 - Composite video
          o     o            5 - Computer ground
       3 o       o 1
    but that seemed ambiguous to me. But, if I assume that the pin numbering is standard (as odd as it is), then a search on "din pin numbering" found images like this:



    So I think I can proceed.

  5. #5

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    Are you certain you need the 5V? I remember using one as a TV by connecting to a VCR composite-out, mainly because it was able to sync with "scrambled" cable channels (not perfectly, but enough to watch.)

  6. #6
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    Quote Originally Posted by Towmater View Post
    Are you certain you need the 5V? [snip]
    The optocoupler on the video interface board needs 5V to run.

    Tom

  7. #7

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    Proof of concept:



    It works. Kind of a fragile connection, I may clean that up.

  8. #8
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    I'm surprised the text looks that sharp

  9. #9
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    Default

    That type of 5 pin DIN connector is dirt common (it's the same one used for MIDI cables) so you should be able to make a finished adapter pigtail you can plug the unmodified monitor into easily enough

    That monitor does have a shedload of overscan on it; the original machine's 384x192 resolution was specifically optimized to keep the borders wide, so without tweaking the monitor severely you'll probably need to convince your source to scale appropriately if you want to see everything.
    My Retro-computing YouTube Channel (updates... eventually?): Paleozoic PCs

  10. #10

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    Quote Originally Posted by Towmater View Post
    Are you certain you need the 5V?
    I can tell you for a fact that it needs the 5 volts to work, yes. Disconnect the 5V, no picture.

    Quote Originally Posted by lafos View Post
    I'm surprised the text looks that sharp
    Sharp, but a bit flickery.

    Unfortunately the monitor is starting to smell just a little bit burny, so the experiment is suspended for now. Still, pretty good for a 42/43-year-old* CRT, with probably all original parts.

    * Depending on which sticker you believe. Maybe it was built as a TV in 1977 and converted to a monitor in 1978, I dunno.

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