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Thread: Ultra-low-resistance cable for Kaypro keyboard

  1. #1
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    Default Ultra-low-resistance cable for Kaypro keyboard

    This topic was previously discussed in 2013 at here: http://www.vcfed.org/forum/showthrea...keyboard-cable

    I have several Kaypros but n-1 keyboard cables so I went to an office supply and bought a telephone receiver cord as a substitute. It worked for one machine (a 10) but not for others (a II and a 4/83). The Kaypro TSM (Aug. 85, p 13-1) mentions that "The impedance of the connecting cable can be a critical factor in proper operation of the computer. Replacement of the standard cable with a phone cord can create malfunctions in signal transmission to the computer. This is because the wire in phone cords is too small: therefore, the impedance over the total length of the card can be too high for reliable operation."

    I measured my replacement cable against one of Kaypro's own. Although low in impedence (<10 Ohms) it was an order or two of magnitude higher than Kaypro's (0.1 Ohm). I have also read that the early Kaypros had slightly undernourished power supplies (mine is nominally 60 Watts) and since the cable provides +5V to the keyboard I suppose that even 10 Ohms of resistance might cause unstable operation of the keyboard system.

    So much for theory. My question is more practical: Does anyone know where I can get an ultra-low-resistance cable, preferably coiled, preferably in the same length as the Kaypro standard (nominally six feet extended) and preferably terminated with the RJ9 connectors?

    Thanks for your replies.

    -CH-

  2. #2

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    Quote Originally Posted by clh333 View Post
    So much for theory. My question is more practical: Does anyone know where I can get an ultra-low-resistance cable, preferably coiled, preferably in the same length as the Kaypro standard (nominally six feet extended) and preferably terminated with the RJ9 connectors?
    RJ9 is the four conductor, not six conductor modular plug, right?

    I'm asking because I have some NOS keyboard cables but they have the six connector plug on one end and the usual 5 pin DIN on the other.


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  3. #3
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    Rj9 = rj22 = rj10 = 4p4c.

  4. #4
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    You'll need a "Monster" brand Kaypro keyboard cable. NOS.

  5. #5
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    Quote Originally Posted by rittwage View Post
    You'll need a "Monster" brand Kaypro keyboard cable. NOS.
    Thanks for your reply.

    Monster, out of SF, replied to my inquiry saying they do not make such a cable. I was unable to find one on eBay, either. Know of a place to look?

    -CH-

  6. #6
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    Quote Originally Posted by Stone View Post
    RJ9 is the four conductor, not six conductor modular plug, right?

    I'm asking because I have some NOS keyboard cables but they have the six connector plug on one end and the usual 5 pin DIN on the other.


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    Thanks for the offer, but I think the cable won't work with my application.

    -CH-

  7. #7
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    Quote Originally Posted by clh333 View Post
    Thanks for your reply.

    Monster, out of SF, replied to my inquiry saying they do not make such a cable. I was unable to find one on eBay, either. Know of a place to look?


    -CH-
    I'm sorry- the smiley face wasn't obvious enough. Monster cables are always good for a friendly argument. I'm not sure what is special about that cable, but I'm sure we can find a proper substitute. You might have to find a wiring guy to crimp some ends on a less flexible cable or something, though.

  8. #8

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    I replaced my coiled Kaypro 2X keyboard cable decades ago. For me, the coiled cable was a pain. You can't ever take full advantage of the true electrical length, and the cable kept getting caught in the stand and restricting keyboard placement. I forget if it actually started to fail or I just had had enough and replaced it with a straight cable.

    I crimped a couple 4p4c connectors on some decent, stranded, phone cable and watched the length carefully.

  9. #9
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    Thanks for your replies. I'm pretty much resigned to rolling my own.

    -CH-

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