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Dell 2408WFPb No Display. Power supply seems good

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    Dell 2408WFPb No Display. Power supply seems good

    Hi All,

    I bought this monitor from a used site from someone who claimed this was broken with no power at all after a power outage.

    When I got home it worked fine. I used it daily for a while. However after every power outage it would die again. No power at all until it is left unplugged overnight. Then it will work fine.

    This was fine with me until I decided to label the breakers in my house and ended up flipping that breaker a few times with the monitor plugged in.

    After that day I have been unable to get the display to come back on. Even after leaving it unplugged for more than 24hr.

    Currently when the power cord is plugged in the light will be green for a few seconds before turning orange for a minute or so before switching back to green and staying there indefinitely. pushing the power button at any time does nothing to change this light sequence.

    https://www.badcaps.net/forum/showthread.php?t=18189

    I used the info and schematic on this thread to find that everything on the power supply seemed fine and that the mainboard wasn't providing a signal through pin 9 on CN701.

    power supply readings:
    IC701 VCC: 14.7V
    C606: 15.78V
    C605:156V
    C611:14.7V
    C622:26.1V

    When testing PFC chip
    IC651 VCC: 500mv and
    0V pn 9

    to troubleshoot I unplugged the cable from main and applied 3V to pin9 and IC651 VCC went to the proper range. 14V i think? C605 also was 400V.

    Does anyone have a suggestion about what to test next?


    Thanks in advance for your help
    Attached Files

    #2
    Re: Dell 2408WFPb No Display. Power supply seems good

    If you are sure its not the power supply, try heating up that ic on the main board refered to in that other post.

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      #3
      Re: Dell 2408WFPb No Display. Power supply seems good

      I did try heating up each of the IC under the heatsinks then plugging in AC power. didn't change anything. although I do notice that when plugged in the heatsink near the CN701 connector gets warm and the other one does not get warm at all.

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        #4
        Re: Dell 2408WFPb No Display. Power supply seems good

        One ic would get warm if it is the one that is operating while in standby. the other ic would likely get warm once the monitor is on.
        CN701 should have a voltage change when the power button is pressed, if it does not its because the main is not sending that command, without a main board schematic, check if you have a voltage at the power button and does it change?
        see if you can trace where it goes on the main, It likely connects to the main processor ic.
        The ic port reads the power switch being pushed and sends the power on command to the power supply. something is not working in that operation, bad ic connection (bga) bad ic, corrupt program? improper reset or noisy vcc to the ic.
        Last edited by R_J; 01-28-2019, 12:13 PM.

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          #5
          Re: Dell 2408WFPb No Display. Power supply seems good

          Thanks R_J,

          ill try and poke around for power around the ICs. but without a schematic it will be difficult.

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