Question about Dell Latitude C840 Notebook

1 Answer

Screen takes several power up attempts to fire up

I have a Dell Latitude C840 that i have to repeatedly press the power button on off on off sometimes maybe 20 times for the screen to fire up. Everything else seems to be getting good power as the hd and cd drive both spool up as well as all the indicator lights coming on. My best guess would be something faulty in the lcd inverter board, maybe bad caps? I don't know. I'd like an experts advice before tearing into it. Thanks!

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  • 3 more comments 
  • av8tr_777 May 18, 2009

    To reply to benwabnick, yes thats exactly what it does.



    To reply to Geekman I will try reseating the cable and report back on that. as far as the other symptoms, The brightness color and picture are perfect and crystal clear once its on.



    Thanks for the speedy replies you guys are awesome!

  • av8tr_777 May 18, 2009

    Ok I reseated the cable from the lcd to the video card which did appear to not be pushed in all the way but no joy on the problem. I have noticed however and I don't know if this helps, but the longer it stays off the harder it is to get the screen to fire up. i.e. If I just freshly shut the computer off the lcd will come right on if I turn it right back on. If I let it set for say 5 min it might take 3 tries. If I let it set over night it may take up to 20 or so tries.

  • av8tr_777 May 18, 2009

    Ok I just tried hooking an external monitor as instructed by Geekman with some interesting results. When I turned it on with the external monitor hooked up while the LCD stayed blank as usual, the external monitor displayed lots of..I don't really know how to explain...but lots of all different colored pixels meshed with some lines flashing. Then after the on off on off routine a couple times I had the normal picture showing on both monitors.



    Thanks again!

  • av8tr_777 May 18, 2009

    Ran a memtest86+ passed 100%. So i'm off to ebay to hunt video cards :)



    Thanks to all of you...I really appreciate it!



    Oh yeah I forgot to mention this earlier but I have an LG Flatron LCD that does the exact same dang thing..I'll have to go look for the section here to post that one.





    Thanks again!!! :-)

  • Ben Wabnick
    Ben Wabnick May 11, 2010

    Does the laptop always turn on but once every so many tries the screen will come on?




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  • Dell Master
  • 32,281 Answers

If you hear the hard drive spinning and you think Windows is working but you can't see an image then :-
You could have a defective screen - a defective inverter or a CCFL lamp or simply the video cable needs reseating. After reseating the video cable and the problem is still there then :-
To determine if you have a LCD screen or video card problem, read this and follow the instructions.

Defective CCFL backlight, it may have the following symptom:

  • Screen flashs on red/pink and off.
  • Picture stays on in red and slowly be come normal.
  • Picture flickering with dim display or appear black.
  • Picture flickering on and off.
All these symptoms indicate that the LCD backlight lamp (CCFL Lamp) has reached the end of the life and all you need to do is replacing the CCFL lamp

Connect an external monitor to your laptop and power it up, if you see the normal Windows images then the video card and laptop is OK and the problem is definitely the backlight.

Dim image and/or dark display on the laptop's LCD screen indicates a faulty LCD backlight and it could be the inverter that supplies high voltage to the CCFL lamp or it is the CCLF lamp is nearly burnt out or burnt out, most likely this is the case.
The inverter can be replaced easily but the CCLF lamp is more time consuming and requires soldering skills.
Check out www.lcdparts.net for parts, repair service and DIY info.

Posted on May 18, 2009

  • Chris Hingee
    Chris Hingee May 18, 2009

    You seem to have a flakey video card or video RAM, the proof is that you can sometimes see a normal picture on both monitors.

    The video card uses part of the memory of the RAM module/s.

    Try reseating the RAM modules and or test them in another laptop or test them at your friendly computer shop.

    There is not much you can do if the video card is flakey/faulty as it is part of the motherboard, and most likely it will fail sometime in the future.

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