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Dell E171FPb No Power?

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    #1

    Dell E171FPb No Power?

    I was given a E171FPb monitor that would not power up. After a few days of "free time" troubleshooting I have found that when the small connector for the LCD itself is disconnected I get 2 seconds on (backlight and power led only), then off, then 2 seconds on, etc. I'm sure that the inverter board is good. I have found no problems in the power board, but it feels like something isn't staying switched on. There's a ticking coming from the board when powered on, but I can't pinpoint it. Any ideas? Is it even worth fixing?

    Thanks.
    -In order to invent you need an imagination and a huge pile of junk.

    -The major difference between a thing that might go wrong and a thing that cannot possibly go wrong is that when a thing that cannot possibly go wrong goes wrong it usually turns out to be impossible to get at or repair.
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    #2
    Re: Dell E171FPb No Power?

    New Developments...

    The upper connector on the input board is power and control for the LCD. With that connector disconnected, I get a steady green LED. With it connected I get the on-off-on power. There is supposed to be +5VDC from the controller to the LCD, and it switches from mV to nothing and back as the PS clicks with the connector plugged in. I'll post what else I find...
    -In order to invent you need an imagination and a huge pile of junk.

    -The major difference between a thing that might go wrong and a thing that cannot possibly go wrong is that when a thing that cannot possibly go wrong goes wrong it usually turns out to be impossible to get at or repair.

    Comment

      #3
      Re: Dell E171FPb No Power?

      I think the problem is in the power going to the backlight board. When the backlight board is not connected I get +15VDC steady to it. When it's connected I get +28VDC counting down. I have resoldered all connections that are thru-hole, but have not yet got to the ones that are SMT. I noticed that the caps that feed the backlight board are slightly bulged at the top (35 VDC 1000 microfarads), but they don't seem to be overly bulged and are not leaking. The cap tester on my DMM goes nuts when i try to test them (probably out of range on my crap-o-matic meter). I also found a cap that is 16VDC 1000 microfarads that is slightly bulged as well (on top). Anyone else see this?
      -In order to invent you need an imagination and a huge pile of junk.

      -The major difference between a thing that might go wrong and a thing that cannot possibly go wrong is that when a thing that cannot possibly go wrong goes wrong it usually turns out to be impossible to get at or repair.

      Comment

        #4
        Re: Dell E171FPb No Power?

        I have also found (when it bit me) that there is 80VDC on the heatsink for Q601. I'm not sure why it's there, but it hurts.
        -In order to invent you need an imagination and a huge pile of junk.

        -The major difference between a thing that might go wrong and a thing that cannot possibly go wrong is that when a thing that cannot possibly go wrong goes wrong it usually turns out to be impossible to get at or repair.

        Comment

          #5
          Re: Dell E171FPb No Power?

          Any cap that is swelled up is enough of a reason to replace it and then you will probably find a few bad transistors too. AND you are so right about that 80 volts is enough to make you keep from checking for excessive heat on those heatsinks with your fingers ,I'm here to tell ya.Been there already ,shame is I will probably do it again.
          Dave
          I am pretty good at keeping a secret,it's the people I tell that can't keep their mouth shut!

          Comment

            #6
            Re: Dell E171FPb No Power?

            Can anyone tell me why there is 80V on the heatsink? I've been working on/in electronics for 16 years and have never seen that before.

            I ordered all new caps and a few transistors. Without having a real schematic I'm shooting from the hip, but all of the transistors tested good. The caps... well... the meter wouldn't read them. Is there a schematic out there for this unit? I haven't found one yet, but I might just have to make one if I can get this thing working.

            Cuda- Where in PGH are you from? I'm originally from Greensburg... small world, huh?
            -In order to invent you need an imagination and a huge pile of junk.

            -The major difference between a thing that might go wrong and a thing that cannot possibly go wrong is that when a thing that cannot possibly go wrong goes wrong it usually turns out to be impossible to get at or repair.

            Comment

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