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Thread: Kaypro 2x video issue

  1. #1

    Default Kaypro 2x video issue

    Hi all,

    I was recently gifted a pristine Kaypro 2x computer. It's a beauty, complete with manuals and disks, and it works. But it does have one minor issue. There are thin horizontal (and slightly diagonal) lines running from top to bottom of the CRT display. They are not bad enough to obscure the display but they show that something is slightly wrong.

    Any thoughts on where to look first? Eventually the entire system should probably be re-capped, but that's a big job and it'll probably be a while before I can do that.

    Also, there is a lithium battery on the mainboard, and it hasn't leaked. But I'm thinking I should remove it?

    Thanks!

    - Earl
    We discuss retro computers of all shapes and sizes on the Retro Computing Roundtable (RCR) Podcast. Listen in at http://rcrpodcast.com.

  2. #2

    Default

    Quote Originally Posted by retrobits View Post
    Hi all,

    I was recently gifted a pristine Kaypro 2x computer. It's a beauty, complete with manuals and disks, and it works. But it does have one minor issue. There are thin horizontal (and slightly diagonal) lines running from top to bottom of the CRT display. They are not bad enough to obscure the display but they show that something is slightly wrong.

    Any thoughts on where to look first? Eventually the entire system should probably be re-capped, but that's a big job and it'll probably be a while before I can do that.

    Also, there is a lithium battery on the mainboard, and it hasn't leaked. But I'm thinking I should remove it?

    Thanks!

    - Earl
    Impossible to make an educated guess of the video issue without a photo of it.

  3. #3

    Default

    Recapping is one thing, a far more urgent subject are those gold colored (and cracked) RIFA X2 and Y2 capacitors at the primary side of the power supply. These are just timebombs waiting to go off. Replace these as soon as possible. They will not cause immediate damage to the computer but the smoke and smell if they fail is horrible.

  4. #4

    Default

    Quote Originally Posted by gertk View Post
    Recapping is one thing, a far more urgent subject are those gold colored (and cracked) RIFA X2 and Y2 capacitors at the primary side of the power supply. These are just timebombs waiting to go off. Replace these as soon as possible. They will not cause immediate damage to the computer but the smoke and smell if they fail is horrible.
    I wouldn't be too worried about those.

    The great thing about the line power supply voltage, is that it has a very low internal resistance and it can supply the 110V to a 1kW bar heater.

    So if the Rifa X2 caps start to draw current and smoke, there is plenty of energy available to vaporize them and plenty of time to turn off the power before they start lighting up like Christmas tree lamps, smoking more than Humphrey Bogart on Casablanca, and stinking out the house.

    You can just remove the X2 caps as they fail.

    In this day and age there is little point in replacing them, when there are truckloads of SMPS's supplies running on line power (drawing current on peaks distorting the nice sine wave) and powering every appliance and energy efficiency lamp for every man and his Dog, the subtleties of keeping RF interference off the line power is well out the window by now, just throw the Rifas in the bin. You can prove this easily by trying to run a shortwave radio in most homes these days and wonder where all the RF hash is coming from.

  5. #5
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    Default

    Another Diag Software url is: http://www.slor.net/kaypro/res/Dists-2/kpdiag/

    Larry

  6. Default

    Quote Originally Posted by Hugo Holden View Post
    So if the Rifa X2 caps start to draw current and smoke, there is plenty of energy available to vaporize them and plenty of time to turn off the power before they start lighting up like Christmas tree lamps, smoking more than Humphrey Bogart on Casablanca, and stinking out the house.
    If you happen to be home, or in the room when this happens, then yes, there's enough time.

  7. #7

    Default

    In my experience they tend to fail, when they do, shortly after power up.

    Though many years ago I was sleeping in a room that had a Singer electric sewing machine in it. It was switched on, but not running. There was a Rifa cap in parallel with the foot pedal control, suddenly maybe around 2am, the machine started at full speed because the Rifa cap shorted out spontaneously, it was actually pretty scary and for a moment confusing as to how it happened.

  8. #8

    Default

    Quote Originally Posted by Hugo Holden View Post
    Impossible to make an educated guess of the video issue without a photo of it.

    It sounds like retrace lines to me. It can often indicate a worn CRT, where the brightness has to be turned up beyond the normal settings for a usable picture.

    Sometimes it can be fixed by adjusting the "screen" control on the flyback, if it has such a control (I don't really know anything about the internals of the Kaypro).

  9. #9

    Default Kaypro 2x video issue (pictures added)

    Attached, please see pictures of the video issue I'm having with the Kaypro 2X.

    In one picture, I've turned the brightness down all the way. You can still see the horizontal slanted lines on the screen.

    In another picture, there is text on the screen from the MITE terminal program. On this screen, you can see that on lines with text, there is a horizontal streak of green on the entire line.

    In the final picture, with some inverse text, some bending of the screen is also evident. (Note on this picture that the extra brightness in the middle is the camera - it doesn't look like that in person.)

    EDIT: One thing I'm going to try - the Kaypro technical manual describes a brightness pot on the CRT board. It's possible that is turned up too high, causing the distortion. I'm going to try (carefully) adjusting that.

    Any thoughts appreciated, and thanks again!

    - Earl
    20200619_195852_result.jpg20200619_200109_result.jpg20200619_200718_result.jpg
    Last edited by retrobits; June 19th, 2020 at 09:43 PM.
    We discuss retro computers of all shapes and sizes on the Retro Computing Roundtable (RCR) Podcast. Listen in at http://rcrpodcast.com.

  10. #10

    Default

    Adjusting the brightness may get rid of the retrace lines, but not so sure if it will fix the other symptoms (it might).

    It may be possible that all 3 symptoms are caused by one thing, so after you've tried the brightness pot, start looking around the video board and power supply for bad capacitors. They often give themselves away by leaking, bulging, or getting hot. Another cause is large components (big resistors, transformers) getting bad solder joints.

    If the boards are joined by plug & socket connections, check them out too. The earlier Kaypro II was prone to that trouble.

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