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Dell C840 flickering LCD... video card?

Discussion in 'Hardware' started by cettolox, Apr 12, 2008.

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  1. cettolox

    cettolox Thread Starter

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    Hi,

    I have a classical "flickering" display problem on my Dell C840 laptop. Since I cannot understand if the problem is relate to the lcd or to the inverter or to che graphic adapter, I am asking here for advice.

    These are the syntoms:

    • the lcd flickers and shows random patterns
    • it gets worse as time goes by (if the pc is cold it happens after 20mins, if it's warm it happens immediatley)
    • it gets worse or better if I twist the base unit
    • it gets worse or better if I lightly push or pull the lcd (see here http://www.youtube.com/v/AbHDsUnY5PA )
    • as the patterns on the screen get worse, at a certain point WinXP freezes and reboots
    • I get the same problem if I connect an external monitor
    • I get the same problem if I connect to the laptop via VNC or LOGMEIN (remote desktop). (I think this excludes the lcd and inverter, since it means that the corrupted patterns are sent via tcp/ip to a remote controlling machine....
    • I tried with no success to change operating system, to work disconnecting all the disconnectable hardware, to change RAM dimms, to remove all pieces and to assemble back, even to change the whole motherboard.
    I suspect a video card fault (I think onboard video memory broken).

    Thanks,

    /Stefano
     
  2. leroys1000

    leroys1000 Banned

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    Sounds like the video card is overheating.
    Can you hear the fan running inside the laptop?
     
  3. Rich-M

    Rich-M

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    I would try vacuuming out grates underneath and wherever they exist from the outside only and see if that helps.
     
  4. Triple6

    Triple6 Moderator

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    The laptop has a Geforce4 440 Go GPU, generally those are removal. So it may be an issue with the connections between the card and the motherboard, so maybe reseating the video card will help - would sure make sense if touching the laptop has an effect on the display. Thats if the above suggestions of the cleaning out the vents doesn't help. Dust buildup will cause overheating and eventually damage the GPU.

    But being an upgradeable graphics card you can replace it if needed.
     
  5. kiwiguy

    kiwiguy

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    Certtainly appears to be mechanical in origin rather than dust, the flexible cable that connects the screen bay be damaged.
     
  6. cettolox

    cettolox Thread Starter

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    To all... thanks for the suggestions. As I said I replaced the whole motherboard, so I cannot be a dust issue (I cleaned everithing).

    Also, I repeadtly plugged out and in the DIMMs and the graphic board, so I don't think it's a contact/connector problem.

    It could be the flex cable as reported, but I tried to move it in all directions and did not notice patterns on the screen caused by this movement.

    And the fans are allright.

    So, I already changed the motherboard, without solving rhe problem (I am going to sell it again on ebay). So the next candidate I think is the video board. I hope to have some more luck.

    Thanks.

    /Stefano
     
  7. dancerjeff

    dancerjeff

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    I also have a dell c840, P4 2.0 GHz, 1G Ram. And have the same problem.

    When using the laptop logged in locally, the screen is drawn with odd boxes or just messed up, I end up with the blue screen. The blue screen is about a video dll giving a page fault in non paged memory, I can send a screen shot if needed, but I currently don't get it (see below).

    I think it is something with the video card, but I tried to solve it with software.

    I found out that if I don't the video card, it does not freeze (But then you cant really use the laptop). However if you use Windows XP with remote desktop (No VNC or Log me in), the os does not use the video card, but run all the graphics in memory. (The laptop stays in the login welcome screen, while in use). I have been able to use the laptop. I have been using the computer all day and it has not frozen, being logged-in remotely.

    This is not really a fix, but it is a work around for saved an otherwise unable laptop. Your laptop becomes a desktop with no monitor.

    You said you tried remote desktop, have you tried MS remote desktop built into xp?

    It sounded like you tried replace the video card, but this had no effect (did I read this right?)
     
  8. cettolox

    cettolox Thread Starter

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    I do agree, the problem must be related with the video card. The fact that vnc/logmein do not work is because they send to the remote PC exactly the main screen of the host, while the Remote Desktop sends the image of the screen related to a "parallel/concurrent" user, not the one that is watching the host's screen.

    I have replaced the motherboard, with no result. Now I am quite sure that I have a faulty video card, and I have purchased a new one on ebay (quite cheap). I am going to try it in a few days, I'll let you know the result.

    /Stefano
     
  9. dancerjeff

    dancerjeff

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    This is going to sound crazy, but I got it fixed and it is working, and my laptop has been running the 3D flower box screen saver for the past 20 minutes no problem.

    Here is what I found. The main cpu has a nice heat sink thats lead to two fans, and does a good job of keeping the cpu cool. However the GPU (graphic card), does not, its heat sink is actually the keyboard!. My dell c840 video card had a protective sticker on it. A white sticker (it was also held in by two strews, that were also keeping the video card on the motherboard). The white sticker also had a sliver square on the button side right above the GPU. I first thought was was part of the heat sink, but taking it off, and GPU has better contact with the keyboard heat sink. (My other dell c840 does not have this sicker). My guess it this batch of Dell c840 never had this sticker removed, (most dell c840 do not not, I know that at least three dell c810 do not have this sticker).

    To remove the sticker, take off the keyboard, unplug the cable to the display, then unscrew the screws to the video card, take of the sticker. Then put it all back together.

    My question is for you, does your video card also have this protective white sticker covering it?
     
  10. cettolox

    cettolox Thread Starter

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    This IS crazy, I am happy you got it working. My video card has the white sticker, I also tried to pull it off, but it was so hardly glued I was afraid to brake something. Now I am going to try again and I'll report back tomorrow.

    (anyway, if this works for me too, I have a spare motherboard and a spare video card to sell back on ebay.. :-()

    Thanks,

    /Stefano

    PS please tell us if your laptop works beyond the 20 mins you told us
     
  11. cettolox

    cettolox Thread Starter

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    No way, I took off the sticker and the problem came after 5 minutes.... maybe my video card memory is really broken.... anyway I am still waiting for the new card, I'll let you know.

    /Stefano
     
  12. cettolox

    cettolox Thread Starter

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    Problem solved replacing the video card.

    Thanks everyone.

    /Stefano
     
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