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Panasonic PWD7 flickering problem when using VGA

Discussion in 'Plasma TVs' started by ulrik, Apr 1, 2005.

  1. ulrik

    ulrik
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    I have the following:
    - Panasonic TH-42PWD7UY
    - PC with Windows XP Media Center 2005 and ATI 9550 graphic card

    I have the PC connected to the monitor with a VGA cable. I have two main problems:
    - The picture flickers (you will notice it more in dark areas)
    - The ATI graphic card reports 848x480 as supported resolution, when it should be 852x480

    I have tried many different resolutions and frequencies on the PC, but the picture always flickers. I tried connecting the PC to the montior using the composite output on the graphic card and that gives me flicker free picture, but picture quality is obviously less than when using VGA.

    Has anyone experienced similar problem when connecting PC to a plasma screen? Any ideas what may be wrong in my setup? I am totally lost here, so any help is appreciated.
     
  2. MAW

    MAW
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    What refresh rate? It will run 72Hz for you (USA based?) but you might have to tell it so, it might be running at 48Hz or 50Hz. Flicker bothers some even at 60Hz, crank it up.
     
  3. ulrik

    ulrik
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    The TV is bought in the USA yes.

    It flickers at all refresh rates i set it to. I have tried 60,72,75,85 etc (at 800x600) and I have tried the same at 848x480 (although 72 is not available in the resolution).

    Got any more ideas for me? Why doesnt the computer report the monitor as 852x480?
     
  4. MAW

    MAW
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    Don't know on the reported res front, what's wrong with running it at 848? Does it still flicker then? Also worth trying is 1280/720, this being true 16/9.
     
  5. GranPremio

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    Not sure it is the refresh rate. I have a 50PHD and noptice 50Hz flicker like mad, however it is usually visible in the brighter areas of the screen, not the dark areas. Sounds to me more like a cable or card issue, have you the opportunity to test both?
     
  6. ulrik

    ulrik
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    No, nothing wrong actually running it on 848x480, just wondering why it doesnt show up as 852x480, which is the native resolution of the TV.

    Yes, it flickers at both 848x480 and 1280x720 at the different refresh rates.

    Do I need to adjust the TV in anyway?

    Does anyone know if I need to configure my ATI graphic drivers in some special way?

    - ulrik // ... still waiting for the magic solution
     
  7. ulrik

    ulrik
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    I have tried two VGA cables, both result in the same flickering.

    I also tried hooking up my laptop to the monitor. It worked fine for a while (several mintues), but then some Intel dual monitor graphic drivers kicked in, and the picture started flickering as well (i believe the intel drivers kicked in when i changed the resolution from 1400x1050, which is the resolution of the laptop monitor, to a lower resolution. Changing it back to the orginal resolution did not fix it back).

    It looks to me like I am missing some setting in my graphic drivers... but I dont know.
     
  8. lisag

    lisag
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    Hi,

    This is odd....
    The graphics card can only display resolutions that are divisible by 8, which is why it can not display the native res of 852 x 480... is the flickering really, really noticeable or just faintly noticeable? Have you tried uninstalling and installing the graphics card and updating the drivers.

    I have a 37" PW7, and use the resolution 1280 x 576 @ 60hz via DVI, and had 1280 x 720 @ 60hz via VGA - and never had any flickering problems.
     
  9. ulrik

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    It is really really noticeable. More in dark areas though.

    I have tried to uninstall the drivers yes. The odd thing is, that when i boot up the computer w/o the drivers installed, the picture is flicker free, but as soon as I install the ATI drivers the picture starts to flicker again :-(
     
  10. cboy

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    u tried different catalyst drivers?
     
  11. ulrik

    ulrik
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    Well, I was not able to find older versions of the drivers on the ATI page. Maybe I should try to downgrade a few versions?
     
  12. lisag

    lisag
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    It certainly does sound like a driver issue but the fact that your laptop replicated it with a different card and drivers is puzzling.... I wonder if it is a fault with the panel or the vga input?

    lisa
     
  13. stevelup

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    Hi

    The other thing you need to do is make sure you have correctly set the timing on the display. If the clock phase is sufficiently out, you can get a nasty shimmer on the image.

    Do the following:-

    1) Make sure your PC is set to 848 x 480 mode
    2) Open paintbrush
    3) Image->Attributes and set it to 848w, 480h and Black and White (important)
    4) Fill the window with the 50% dither pattern (I've attached it for reference)
    5) Switch Paintbursh into fullscreen mode (CTRL+F)

    Now adjust the vertical size and horizontal size until there is minimal banding on the screen. Once you have found the ideal setting, you will still probably see one really large stripe running right across the screen.

    At this point, use the Clock Phase setting. All of a sudden, the picture will snap into super sharp focus and you will be able to see every single dot in your 50% dither pattern.

    Hope this helps.

    Regards,

    Steve
     

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  14. Cummo

    Cummo
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    Hi ulrik,
    I posted some time back with the same observations on my old series 5 SD Panny and my series 6 HD Panny. No matter what PC/laptop/graphics card combination I've used, the screens will only refresh at 60Hz. You can nominate higher rates and they are accepted by windows, but the 60Hz. flicker still remains.
    I notice flicker on my HD panel with a 50Hz video signal which is completely removed with a Lumagen Vision feeding it 60Hz but a PC signal at any refresh rate has flicker. I put the removal of the flicker by the Lumagen at 60Hz down to the fact it is also using progressive scan processing of the video signal
     
  15. cboy

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    wat about fitting 1 of those cathodes supplied with the plasma aint they supposed to do sumthing?
    like reduce interferance?
     
  16. ulrik

    ulrik
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    Thank you all for your help, I really appreciate it.

    I have continued to experiment with the VGA input on my monitor. My last test was to try my computer on my friends TV (he has the same type of plasma screen as I do - bought at the same time). At his place the image did flicker at 800x600 at 60hz (but still less flickering than on my TV at same resolution/refresh rate), but was flicker free at 800x600 at 85hz as well as 848x480 at 85hz (well, it wasnt 100% flicker free, you could, if you really really wanted to, notice some minor flickering, but nothing that bothers you). Strange huh?

    Anyway, I finally gave up with the VGA port on my TV and installed a DVI input in slot 1 and tried connecting my computer via the DVI. And guess what, I get this beautiful image via the DVI input - no flickering :D

    It is still a mystery why the VGA input flickers on my TV, but I am now a happy TV owner using the DVI input instead ;-)
     
  17. lisag

    lisag
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    :smashin: Well done!
     

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