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    #1

    Identifying a failure... help?

    Hi all,

    New here, still have to update my profile. Quick version - I'm Kyle, college student, have been soldering for years. Recently acquired a broken 19" LCD TV for $10, recapped it, and now it's perfect. This led me to go get about 12 more LCDs, from 17" displays up to a 32" LCD HDTV. Most are obvious bad caps, a couple have me stumped (of course, the newer/nicer units )

    I have a Dell 19" widescreen LCD, from about 2007. No visibly bad caps. When plugged in, I hear a faint :tick: :tick: :tick:. Maybe its a faint "click". Anyway, it sounds like it is coming from the big cap in the mains voltage section of the board. It's a CapXon (i know) 120uf 450v(L) cap. The clicking remains for about 5 seconds after the plug is removed.

    Should I just recap the power supply based on the fact that it is composed of CapXon, TAICON, and no-name caps? Or, does it sound like something else could be fried?

    Thanks for any and all assistance. I should be able to post photos if needed, just don't have a camera with me right now.
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    #2
    Re: Identifying a failure... help?

    Originally posted by koerneka View Post
    Hi all,

    New here, still have to update my profile. Quick version - I'm Kyle, college student, have been soldering for years. Recently acquired a broken 19" LCD TV for $10, recapped it, and now it's perfect. This led me to go get about 12 more LCDs, from 17" displays up to a 32" LCD HDTV. Most are obvious bad caps, a couple have me stumped (of course, the newer/nicer units )

    I have a Dell 19" widescreen LCD, from about 2007. No visibly bad caps. When plugged in, I hear a faint :tick: :tick: :tick:. Maybe its a faint "click". Anyway, it sounds like it is coming from the big cap in the mains voltage section of the board. It's a CapXon (i know) 120uf 450v(L) cap. The clicking remains for about 5 seconds after the plug is removed.

    Should I just recap the power supply based on the fact that it is composed of CapXon, TAICON, and no-name caps? Or, does it sound like something else could be fried?

    Thanks for any and all assistance. I should be able to post photos if needed, just don't have a camera with me right now.
    Wrong area; ask a moderator to move it the 'Computer Display Troubleshooting' section.

    The symptoms indicate one of two possibilities. The most likely is the startup cap for the SMPS controller. This is a small (typically under 100 uF) cap near the SMPS controller. A second possibility is a short on one of the outputs of the power supply.

    As a general rule, we suggest replacing all electrolytic caps in a power supply (with the exception of the 150 uF, 450 volt one) unless they are a known high reliability brand.

    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

      #3
      Re: Identifying a failure... help?

      Originally posted by PlainBill View Post
      Wrong area; ask a moderator to move it the 'Computer Display Troubleshooting' section.
      Oops, sorry about that I saw the "electronics theory" portion of the forums but didn't keep reading.

      Originally posted by PlainBill View Post
      The symptoms indicate one of two possibilities. The most likely is the startup cap for the SMPS controller. This is a small (typically under 100 uF) cap near the SMPS controller. A second possibility is a short on one of the outputs of the power supply.
      When I upload a pic or two, would anyone be able to help me identify this?

      Originally posted by PlainBill View Post
      As a general rule, we suggest replacing all electrolytic caps in a power supply (with the exception of the 150 uF, 450 volt one) unless they are a known high reliability brand.

      PlainBill
      Makes sense. However, the 120uF (anyone know the Mac key combo for this character?) 450v is a CapXon, which even in my limited experience has been a complete crap brand. Should I order that as well?


      On a positive note, I did successfully recap a 32" Vizio today =D

      Thanks Bill =)

      Comment

        #4
        Re: Identifying a failure... help?

        Originally posted by koerneka View Post
        When I upload a pic or two, would anyone be able to help me identify this?
        Yes we can identify, but if you want the monitor to last a long time, most here suggest you replace all the electrolytic capacitors on the power board. Please use the manage attachments function to upload your picture and please do not post inline.

        However, the 120uF (anyone know the Mac key combo for this character?) 450v is a CapXon, which even in my limited experience has been a complete crap brand.
        Capxon has a poor reputation on this board. However, the largest filter capacitor rarely, but not never, fails regardless of brand. The largest cap will probably cost around $2 to $4.
        --- 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: Identifying a failure... help?

          Sounds good. There are probably only about 10-12 caps on the board, so replacing them shouldn't cost too much. The monitor cost me less than $5 to buy, and might be put into daily use, so I have no problem with what.

          I'm not sure what the controller mentioned above is, however.

          And good to know that the filter cap probably isn't the bad one. I'll check Newark's prices on it, as they handled my last order pretty well, and their online ordering and customer support were great.

          Thanks guys!

          Comment

            #6
            Re: Identifying a failure... help?

            Originally posted by koerneka View Post
            I'm not sure what the controller mentioned above is, however.
            PlainBill is probably refering to the SMPS controller IC or chip. It is usually a 8 pin IC.

            The little cap will feed voltage into this IC (somewhere between 10 and 16V DC). If the little cap is bad (little caps rarely bulge/bloat) the voltage across this cap will be either low or fluctuating. The clicking (SMPS trying to start) is the clue to why he suspects the little cap.

            A good quality Panasonic FR/FM or FC cap is only about 33 cents. If replacing the little cap doesn't resolve the problem, it could be the SMPS controller IC is bad.
            --- 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

              #7
              Re: Identifying a failure... help?

              a very common value for that startup cap is 35-50V 47uF. just as a hint (doesn't mean it has to be that value)

              and like plainbill said, a short on the secondary (output) side of the PSU could also cause that ticking sound (PSU trying to start up, runs into a short, shuts down, repeat)

              edit: for the ยต symbol, try option+m (on windows, right alt+m)

              http://www.wikihow.com/Make-Symbols-on-a-Mac
              Last edited by Scenic; 04-19-2011, 02:01 AM.

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