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Thread: Compaq Portable video issue

  1. #1
    Join Date
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    Default Compaq Portable video issue

    Apologies if this is a little long but there's a lot of info to give. I posted a while back about an issue with the video output on my Portable a while back and I couldn't figure it out then so I put it away for a while. So a few months back I just lost video completely on my Portable after a few weeks of it working fine. I bought another video card, tested and working, and that changed nothing. I had my friend test both cards and they both checked out ok. Yesterday I got a 100% working Portable and swapped monitors. The monitor from my first one had a bad cap and the vertical height is way off, so there's one thing wrong. The weird thing is I'm getting the same issue with my first motherboard and the known good monitor from the second. It seems to turn on fine but after a while it gives me 1 long beep and 2 short beeps which I believe indicates a video fault. Exactly the same as before.

    Every card in both machines checks out fine, both monitors check out apart from the vertical stretch on the one, 3 video cards are known good and both power supplies are good. What could this possibly be? I'm almost sure it's a motherboard problem now but I have no idea what could cause this. Bad eproms? Some bad chip? I'm stumped.

  2. #2

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    It's reporting a video failure. Not many options to try, but:

    Double check the motherboard DIP switch setting to make sure it matches CGA and Compaq internal monitor.

    Try a different slot for the VDU card.

    Connect an external monitor - probably won't help at all

    Good luck

  3. #3
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    Quote Originally Posted by resman View Post
    It's reporting a video failure. Not many options to try, but:

    Double check the motherboard DIP switch setting to make sure it matches CGA and Compaq internal monitor.

    Try a different slot for the VDU card.

    Connect an external monitor - probably won't help at all

    Good luck
    Unfortunately I checked all that and still nothing. This is very weird

  4. #4
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    Those computers are known to have problems with their tantalum capacitors. Mine had one explode in the power supply and another on the video board catch fire.
    Have you checked the voltages on the power supply?
    The tantalums on the main board where the power supply cable connects could be a problem also. A resistance check at the connector may show one shorted.

  5. #5
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    Quote Originally Posted by Chuckster_in_Jax View Post
    Those computers are known to have problems with their tantalum capacitors. Mine had one explode in the power supply and another on the video board catch fire.
    Have you checked the voltages on the power supply?
    The tantalums on the main board where the power supply cable connects could be a problem also. A resistance check at the connector may show one shorted.
    I checked every tantalum cap and none are shorted. I have not checked the voltages but the psu I'm using worked perfectly with another motherboard

  6. #6
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    I just tried removing the card completely and I got the same error code. So it appears that the video card is just not being recognized at all

  7. #7
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    A bad video switch on motherboard? E.g. Settings made for CGA, but because of the bad switch, BIOS thinks you have MDA, and beeps because it cannot find an MDA card.

    Just in case, according to [here], motherboard's video switches are on:
    Revision B BIOS: switch block SW1
    Revision C BIOS: switch block SW2

  8. #8
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    Hmm, I never thought about that. I'll take it apart and test the dip switches with my multimeter.

    I did just try using another CGA card, an IBM one out of my 5160, and a 5153 monitor. It seemed to recognize there was a card in it, as in it didn't have the error beeps and the screen went black as if there was an input, but nothing showed up on the screen.

  9. #9

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    Quote Originally Posted by RadRacer203 View Post
    Hmm, I never thought about that. I'll take it apart and test the dip switches with my multimeter.

    I did just try using another CGA card, an IBM one out of my 5160, and a 5153 monitor. It seemed to recognize there was a card in it, as in it didn't have the error beeps and the screen went black as if there was an input, but nothing showed up on the screen.
    Try pressing Ctrl Alt > to switch to external monitor: https://en.wikipedia.org/wiki/Compaq_Portable

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