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LCD black screen

Discussion in 'Troubleshooting and Repair' started by patrick_0207, Jun 22, 2010.

  1. patrick_0207

    patrick_0207

    3
    0
    Jun 22, 2010
    Hi, I have a dell 2407wfp monitor.

    The monitor is totally black, there is no image. Backlighting is off.
    I'm suspecting the mainboard is broken and needs to be replaced but before I order another one, I wanna make sure its the mainboard and not the lcd inverters.

    Is there any test I can do to figure out whether the main board or the lcd inverters are broken?

    The monitor powers on, I can switch inputs using the buttons on the monitor, but the screen is still totally Black.

    Thanks in advance!
    Patrick
     
  2. davenn

    davenn Moderator

    13,260
    1,748
    Sep 5, 2009
    Hi Patrick,
    is there any OSD (On Screen Display) ? that is ... can u see the menu if the menu button is pushed ?
    I'm just wanting to confirm that if its a HV PSU fault or an input fault.

    99% of the black screen LCD's that come through my workshop are because of the HV inverter has failed. and 90% of the time its because of the 1 or 2 electrolytic capacitors in that section that have dried out. You may even see them bulging at their top end. Definately the first thing to check

    cheers
    Dave
     
  3. patrick_0207

    patrick_0207

    3
    0
    Jun 22, 2010
    Hi Dave,
    There is no OSD at all, The screen is totally black. I heard that when the inverters fail, You can still see an image on the screen if you put it under a light. I tried that and there was no image at all.
    As for the PSU, I measured the outputs of the PSU and I had 19V on a couple of pins. The rest had 0V (Ground I'm assuming)

    Thats why i'm thinking the main board might be dead.

    I also did another test, I plugged in the monitor to my laptop (as a secondary monitor). The resolution on my laptop's screen dropped to 1024x768. I don't know if that helps.

    Is there any way I can test if electrolytic capacitors are dead? With an oscilloscope maybe?

    Cheers
     
  4. (*steve*)

    (*steve*) ¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥd Moderator

    25,178
    2,690
    Jan 21, 2010
    The best tool to use initially is the Mk:1 Eyeball.

    The next step is an ESR meter.
     
  5. patrick_0207

    patrick_0207

    3
    0
    Jun 22, 2010
    Hi,
    I took pictures of both the inverter board and the main board.
    There seems to be no bad capacitor on it.
    Is there any way I can figure out which one of the 2 boards is broken?

    Thanks
    Patrick
     

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