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Dell E177FPv dropping voltages

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    #1

    Dell E177FPv dropping voltages

    I have inherited two identical models of this monitor and can find very little mention of it anywhere and none in Badcaps forum. Both are completely dead as in no power light at all and no startup, flashes or image visible with torch. I have done the usual checks and fully recapped the boards, changed the C5707s and resoldered the transformers, checked the schottkys etc. Still dead. however I have found that the 5v voltage to the logic card pin is there and then over a couple of mins progressively drops to 0.2v. Also at the "hot" end of the board I can measure 15v at startup and this also drops slowly and progressively to almost zero after a couple of mins. This happens whether the board is tested on its own or with the backlights and logic board plugged in. Is this a normal switch off type function and I am chasing the wrong symptom (both boards do exactly the same) or is a faulty component leading to voltage drop?
    Any thoughts most welcome while I still have hair left!
    I am attempting to attach a library photo of the board as my camera is out of use at the moment in case someone recognises the board and the symptoms.
    Johnboy183
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    #2
    Re: Dell E177FPv dropping voltages

    Do you get about 160V DC across the main cap? Careful measuring this voltage!

    Did you recap the small caps as well? They are usually 1uF 50V or 2.2uF 50V? On other boards there is also a small cap that is usually 22uF or 47uF/50V.

    Is there a picofuse on the board? (your diagram is too small to see)? Picofuse is written as PF on the board. Example PF801. Test the picofuse for continuity.

    Originally posted by johnboy183
    Both are completely dead as in no power light at all and no startup, flashes or image visible with torch. I have done the usual checks and fully recapped the boards, changed the C5707s and resoldered the transformers, checked the schottkys etc. Still dead. however I have found that the 5v voltage to the logic card pin is there and then over a couple of mins progressively drops to 0.2v. Also at the "hot" end of the board I can measure 15v at startup and this also drops slowly and progressively to almost zero after a couple of mins.
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    Comment

      #3
      Re: Dell E177FPv dropping voltages

      Any major troubleshooting assistance will require bigger (and clear!) pictures of both top and bottom of the board, as well as a shot of the logic board.

      The power supply would not have any shut-off function. Retiredcaps suggestion of monitoring the voltage across the large cap is good. Also, look for bad solder joints. That's about the only explanation I can see for the behavior you describe.

      PlainBill
      For a number of reasons, both health and personal, I will no longer be active on this board. Any PMs asking for assistance will be ignored.

      Never be afraid to try something new. Remember, amateurs built the ark. Professionals built the Titanic.

      Comment

        #4
        Re: Dell E177FPv dropping voltages

        Also, what brand of caps did you use to recap?

        Originally posted by johnboy183
        I have done the usual checks and fully recapped the boards,
        --- begin sig file ---

        If you are new to this forum, we can help a lot more if you please post clear focused pictures (max resolution 2000x2000 and 2MB) of your boards using the manage attachments button so they are hosted here. Information and picture clarity compositions should look like this post.

        We respectfully ask that you make some time and effort to read some of the guides available for basic troubleshooting. After you have read through them, then ask clarification questions or report your findings.

        Please do not post inline and offsite as they slow down the loading of pages.

        --- end sig file ---

        Comment

          #5
          Re: Dell E177FPv dropping voltages

          Depends on what the old ones are rated for.
          So what are they?
          Mann-Made Global Warming.
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