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Thread: Monochrome DEC Rainbow keyboard and video cabling options

  1. #1
    Join Date
    Feb 2016
    Santa Rosa, California

    Default Monochrome DEC Rainbow keyboard and video cabling options

    I picked up a DEC Rainbow PC100-B2 for free at this most recent VCF West show, and it has a 10MB MFM HDD, no color video option, and no cables of any sort.

    I've got DB15 video cables I can hack up, and I understand this thing can output monochrome composite video. I have a couple of displays which can accept composite via a BNC input, but I also need to fashion a breakout cable for the keyboard. I have an LK401 keyboard, which should work, assuming I can fashion an adapter.

    I found this old archived VCFED thread here, which looks like it may have contained the information I am looking for now, however it's long gone:

  2. #2


    I went through this just a few days ago, but in the process I blew up an LK401....

    Find a copy of the Rainbow Technical manual from May 84 (EK-PC100-TM-001) and find table 3-6 for the video/keyboard pinout.

    You'll want pins 12 and 4 for mono video source and mono ground. Then for the keyboard; pins 7, 5, 14, and 15 for the +12V, Ground, Keyboard Receive and Keyboard Transmit respectfully.

    For the keyboard find any phone jack and wire up those 4 pins correctly. This is the example pinout I followed for the jack:

    The DECstation pinout is what you'll be wanting to follow. Check your work over and over again before you try it, because like I mentioned, I blew up an LK this way.

  3. #3
    Join Date
    Mar 2008
    Westchester County, NY


    See the little box in this album that was discussed in my original thread of many years ago : . Notice the phone jack on the side to plug the keyboard into. The little box plugs nicely into the back of the Rainbow ( The pinout can be found online with a trivial amount of time spent with Google.



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