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Thread: How do I interface a TRS-80 Model I to a TV or Composit video monitor?

  1. #1
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    Saraland, AL just north of Mobile
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    Default How do I interface a TRS-80 Model I to a TV or Composit video monitor?

    I recently acquired a TRS-80 Model I Level II 16k with a power supply; but I don't yet have a Tandy Video Monitor. In searching the Web, I have run across a few references on interfacing a Model I video output to a TV or Composit Monitor but there are no details on how to do it. The Din-5 provides sync, video, +5 and ground. What is the schematic to feed these into a composit RCA jack on a TV or monitor?? Any help would be appreciated.

  2. #2

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    Connect ground (pin 5) to the shield of a piece of coax (terminated in an RCA connector), and the video signal (pin 4) to the tip. You will then have a standard compsite video out.

    Do NOT CONNECT ANY OTHER PINS. There is 5V lurking there that can cause smoke to come out.

  3. #3
    Join Date
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    Yeah, I used to make the cables all the time by just taking and old AT keyboard cable and soldering an RCA jack to the wires that corresponded with pin 4 (data) and pin 5 (ground). Plugged right into the video output jack.

    BTW, an ordinary AT style keyboard extension cable is great for using as a monitor cable extension on the model 1.
    Legacy Computers and Parts

    Sales of, parts for, and repairs to, Vintage and Legacy computers.

  4. #4
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    On the topic, but slightly different question. As you know, I received the TRS-80 Model III with a smashed monitor this summer, and I haven't had the time or motivation to try find another tube. However there is a cable from the motherboard to the monitor circuit board. I have downloaded some service manuals, but didn't look into them. Does anyone know if the Model III on this connector also has a "standard" video output that I could tap and feed into another monitor? If yes, I may be able to locate the pinout, but as long as I don't know if I should expect to find what I'm looking for, I may look in vain.
    Anders Carlsson

  5. #5

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    Quote Originally Posted by carlsson View Post
    On the topic, but slightly different question. As you know, I received the TRS-80 Model III with a smashed monitor this summer, and I haven't had the time or motivation to try find another tube. However there is a cable from the motherboard to the monitor circuit board. I have downloaded some service manuals, but didn't look into them. Does anyone know if the Model III on this connector also has a "standard" video output that I could tap and feed into another monitor? If yes, I may be able to locate the pinout, but as long as I don't know if I should expect to find what I'm looking for, I may look in vain.
    I have no answer for your question, but I feel your pain. I too got a Model III that wasn't packaged correctly and the monitor imploded. My solution was to track down a Model IV and use the III for parts.
    =============================
    Bill Loguidice, Author
    Managing Director, Armchair Arcade
    About Me

  6. #6
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    Even if I can get video from the computer, it probably will be NTSC at best. Maybe I'll find time in November to look into this. First I need to follow Druid's advice how to adopt the unit to 220-ish voltage.
    Anders Carlsson

  7. #7

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    Quote Originally Posted by Druid6900 View Post
    Yeah, I used to make the cables all the time by just taking and old AT keyboard cable and soldering an RCA jack to the wires that corresponded with pin 4 (data) and pin 5 (ground). Plugged right into the video output jack.

    BTW, an ordinary AT style keyboard extension cable is great for using as a monitor cable extension on the model 1.
    My apologies for resurrecting an old thread, but I just have to say thanks for this. My old Model 1 video cable disintergrated at the DIN end last week. I googled to get some repair advice and came across this post.

    A few days ago, I sourced an old AT keyboard at work gathering dust under a lab bench and snipped off the cable. Before retiring tonight (and after cleaning up after Xmas festivities) I made a new video cable with the said AT lead and the advice above.

    It works a treat!
    ------------------------------------------------
    My vintage collection: https://classic-computers.org.nz/collection/
    My vintage activities blog: https://www.classic-computers.org.nz/blog/
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  8. #8
    Join Date
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    Not a problem. Glad it worked out for you and you can see what You're doing now
    Legacy Computers and Parts

    Sales of, parts for, and repairs to, Vintage and Legacy computers.

  9. #9

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    Do I have to have a switchbox to hook my trs-80 to a TV or can I directly connect my cable to it?

  10. #10

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    Quote Originally Posted by tweetykiss View Post
    Do I have to have a switchbox to hook my trs-80 to a TV or can I directly connect my cable to it?
    Ooh. Necroposting.

    Which TRS-80 are you talking about? The Model 1 uses composite video, and you need only build a trivial cable to go from the 5 pin DIN on the back to an RCA plug that you can hook to the composite video input on a modern TV.

    The TRS-80 Color Computer, on the other hand, is a completely different animal. The Color Computer 1 and 2 have only RF modulators, so you need either a switchbox or an adapter to go from the RCA connector to the screw-on F connector on the TV's antenna input.

    The Color Computer 3 has composite color video already - just plug it into a composite monitor.

    -Ian

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