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RGBs video signal unstable

Discussion in 'Troubleshooting and Repair' started by Simon_m74, Jun 7, 2018.

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  1. Simon_m74


    Jul 25, 2016
    On my Virtual Reality machines, there are two types of LCD`s used in the headsets - depending on the machine version.
    On version uses Epson LCD`s, while the other uses Panasonic.

    The machines also output to an external display via a 9pin Dplug - CGA (RGB & sync)

    On an old CRT, this works fine, with either a system for Panasonic of Epson.
    With LCD`s, using either a CGA to VGA, or CGA to Composite - with an Epson system its fine, but on a Panasonic system, the video output is unstable.
    Effects like no sync on some LCD`s, or vertical shaking or odd colours..

    I have found a manual with a note in it... so I hope this helps you help me making the video stable on a Panasonic system.

    In the manual, it states that the video output is:
    Type : RGB Analogue
    Volatege : 1v Pk to Pk
    Impedence : 75ohm
    Connection 9 pin D-type
    Line period : 64 nano seconds (15kHz)
    Field rate : 49.92 Hz
    sync voltage : 0.3v
    Now the interesting bit:
    Sync type : Printed as Combined Sync (+ve) - I believe this is for the panasonic screens
    The `combined` has been crossed out, and hand written as Neg Going TTL. Which I imagine is for the Epson screens

    Now, my hope is, that I can get a stable output on Panasonic systems, as most of my machines are Panasoinc systems.


  2. Simon_m74


    Jul 25, 2016
    any ideas?

  3. kellys_eye


    Jun 25, 2010
    I'm confused.
    What do you want? A stable OUTPUT or a stable video INPUT?

    The whole wording of your query just doesn't make sense (to me) and I can't figure out what you've got, what your issue is or what you want.

    The video signal needs to match the monitors requirements - obviously. Either convert the video signal to match the monitor or use a monitor that accepts the video.
  4. Simon_m74


    Jul 25, 2016
    Sorry for confusion,
    Right - the output from the VR machine, shows to be unstable when connected to an LCD panel, but fine on a CRT monitor/TV.
    Depending on the LCD panel/TV I use, I get from best, a good image, that slowly jumps up and down a few pixels, to randomly going out of vertical sync, random large black horizontal bars and random colours, usually heading towards purples.
    I have recently read that as a scart RCBS connection, uses the composite line a the sync - and that a lot of `modern` monitor/TV systems require a resistor on the sync line, otherwise the voltage is too high.

    I have installed a resistor - but have not yet had time to plug it in to check - I hope to tonight,
    The resistor / sync line being too high - does to me sound like its what could cause the instability ?
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