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Problem with Video and custom VGA switch. XP is disabling VGA?

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  • Problem with Video and custom VGA switch. XP is disabling VGA?

    I don't know what to really search for because I don't know what terms would bring up the problem I'm having. I tried searching a few things but I could not find anything like the issue I'm having because I built a custom switch for my VGA and USB cables.

    Let me start out with the hardware I have thats relevant to the issue.

    Lilliput 701-GL/NP/C/T the new one that actually does not break after a few minutes of use.

    Jetway J7F2WE2G-OC-PB motherboard

    Custom USB/VGA 2 port switch.

    Can-View device for OBD2 data

    I made the custom USB/VGA switch so I could switch between my PC and my Can-View device. I tried other switches but they always messed up the USB and VGA signal. So I built a custom switch with some relays to do the switching. This caused a physical disconnect between the devices. This works fine except when I let my PC boot to windows with the switch on the Can-View. This means the VGA is disconnected from the PC during the whole boot process. When I let this happen I get a black screen and a "no signal" error on the LCD when I switch over to the PC. If I switch to the PC when it first kicks on and stay there until it fully boots I can switch to my Can-View and back to the PC with no problem. My guess here is that either the mother board or windows is to blame.

    So my question is, is there a way to tell the mother board or windows that there is a monitor hooked up so it wont kill the video signal when there is not a signal there on startup?

  • #2
    I did a little more testing and I'm sure its windows thats causing the issue because if I leave my switch on the PC while the BIOS boots I can see everything. If I switch back to my Can-View right after the BIOS finishes and keep it there until windows boots I switch back and get a "no signal" error.

    Does anyone know how to tell windows to NOT disable the VGA when no VGA is present?


    • #3
      So can anyone explain why Windows XP is disabling my VGA when no monitor is hooked up? Or is it the mobo thats disabling it? Does anyone have a solution to this issue?


      • #4
        Have you tried 75 ohm termination on the RGB lines when the PC is not connected to the VGA?
        This can fool the PC into thinking a screen is still attached.
        Old Systems retired due to new car
        New system at design/prototype stage on BeagleBoard.


        • #5
          Well I think I found the problem. I think it was the windows update version of the video driver. I uninstalled the windows update video drivers and installed the ones from jetway. I then disabled the S3 system tray thing. I also just for the heck of it installed a generic 1024x768 LCD monitor driver for the lilliput.

          So far it will boot just fine with the switch on the Can-View. When XP finishes booting I switch over to the PC and the video comes up just fine.

          One problem solved now on the the others.