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Thread: VAXmate output to VGA Monitor

  1. #1

    Default VAXmate output to VGA Monitor

    Given that it seems unlikely that I will ever be able to replace the flyback transformer in the monitor for my VAXmate, my next option is to try to use an external VGA monitor driven from the I/O board.

    The I/O board produces RGBI, H and V sync. H sync is 26.4KHz, V sync is 60Hz. The RGBI signal amplitude is 5V, and VGA uses 0.7V, so I can't feed this direct to a VGA monitor.

    I have a VR241 which apparently might be able to work with these signals, but I don't want to risk damaging it.

    I have been trying to see if any converters exist that would go from these 5V signals to something that will work with VGA. I have an LCD monitor that will sync down to 24KZ, so I think I just need to get the RGBI signals down to the right amplitude.

    Does anyone know if such a converter exists? Or could I just use a resistive divider to bring the amplitudes down?

    All suggestions gratefully received.



  2. #2
    Join Date
    Feb 2011
    NorthWest England (East Pondia)
    Blog Entries


    We will have to stop meeting like this. I did a bit of googling and many circuits rely on the monitor being 75ohm resistive and use 330 ohm series resistors I am not sure all are. e.g.:-

    I think I would go for the level shifter. I would be rather more worried about the ability of the TTL in the VAXMate to source the 12ma needed to deliver 1v into 75ohms rather than the monitor over loading....

    Looking for Analog Computers, Drum Plotters, and Graphics Terminals

  3. #3
    Join Date
    Aug 2009
    Oslo, Norway
    Blog Entries


    The RGBtoHDMI is a very flexible converter, however it might be overkill if you already have a monitor that will work with the frequencies the VAXmate outputs.
    Plus it is another project to assemble.


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