Announcement

Collapse
No announcement yet.

Dell U2711 2 seconds to black

Collapse
X
 
  • Filter
  • Time
  • Show
Clear All
new posts

    Dell U2711 2 seconds to black

    Hello,

    I have the above monitor which turns off its backlight 2 seconds after powering on. The screen still holds all the content, only the backlight is off.

    Now before that (even today) the monitor had the problem to turn its backlight off after around 30 minutes. Before switching off entirely the backlight changed brightness (like once a second).

    When switching off and back on the monitor would stay on for a while before repeatedly showing the behaviour described above.

    Now I changed the five main caps (low esr, but no name brand) on the power board (470uF, 35V) and resoldered the transformer taps on the inverter board. Furthermore I measured the secondary windings of the transformers, all reading between 4.6 and 4.7 kOhm.

    Trying to use the monitor now it switched the backlight off after 2 seconds. I thought it could be the no name caps I used and reinstalled the old caps. Still the screen goes black after two seconds. What could have gone wrong? Should I need to install brand name caps?

    I hope that the tubes are not faulty because they ran today for half an hour or even more.

    Thanks in advance!

    #2
    Re: Dell U2711 2 seconds to black

    Hi elagil - thanks for helping on the other Dell thread - I have no practical experience of these big monitors. When you said on the other thread you had cleaned the bulb connectors was it actually on this monitor?
    Have you any pictures of the boards? if so can you post them using manage attachments.
    There are people in the forum who can spot problems from the pictures and if there are no pictures may just move on to the next thread
    Please upload pictures using attachment function when ask for help on the repair
    http://www.badcaps.net/forum/showthread.php?t=39740

    Comment


      #3
      Re: Dell U2711 2 seconds to black

      No this is actually another monitor! The other one was a u2410.

      Here are some pictures of the power supply and inverter boards. I could not spot anything unnormal on the boards.
      Attached Files

      Comment


        #4
        Re: Dell U2711 2 seconds to black

        Those pictures seem to have been compressed quite a bit. Follow this link for full resolution images (watch out, they are huge..): http://coda.pw/dell

        Comment


          #5
          Re: Dell U2711 2 seconds to black

          The voltage that goes to the inverter is 24.10V when no lights are on and drops very slightly to 24.05V for those two seconds. Might that be a broken tube or something? I do have a spare tube of a U2410 around here.

          Comment


            #6
            Re: Dell U2711 2 seconds to black

            Turns out it was AGAIN an arching tube. It was charred on one end! Seems to be quite a common issue with these dell monitors that have those rubber clips to hold the tubes..

            Now it runs perfectly fine again.

            Comment


              #7
              Re: Dell U2711 2 seconds to black

              Well done!
              I was just looking for a way to test the transformers knew I had seen it
              https://www.badcaps.net/forum/showth...l261a12&page=1

              Anyway you dont need it now.

              Perhaps Prdp will see this and look more closely at his lamps.
              Please upload pictures using attachment function when ask for help on the repair
              http://www.badcaps.net/forum/showthread.php?t=39740

              Comment

              Working...
              X