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Dell Dimension 4550 - Bad Audio Caps?

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    #1

    Dell Dimension 4550 - Bad Audio Caps?

    This computer has the worst audio quality that I've ever heard, so I wanted to try recapping the sound section. There appear to be three electrolytic caps in this section, one 10uF 35V and two 100uF 25V. I want to replace the 100uF caps with a larger value, but I want to know if they still need to be 25V or if I can decrease the voltage. Also, I can't tell if the 10uF cap is polarized or not.

    The VRM caps need to be replaced as well. Two are bulging, and one of these has blown the bottom out and spewed brown stuff all over the board. Also, this computer still runs prefectly.
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    #2
    Re: Dell Dimension 4550 - Bad Audio Caps?

    The caps next to the CPU will be replaced with Nichicon HMs and the 100uF caps will be replaced with 150uF Panasonic FRs. These appear to be the output coupling caps for the headphone amplifier, so increased capacitance should be better.
    Should I buy a non-polarized 10uF cap just in case the original is not polarized?

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      #3
      Re: Dell Dimension 4550 - Bad Audio Caps?

      Those small uF high volt caps in things like audio and USB are sometimes there to stop EMI or voltage spikes [from user error] from coming into the system through external jacks and cables. They over-kill the voltage so the cap doesn't blow from a static spike [like plugging in an audio or USB cable after dragging your feet on the carpet]. The small uF is because EMI from wires acting like antennas is at a higher frequency than ripple from a SMPS.

      If the caps are not connected to a port then the higher voltage is simply to use a cap with a higher ripple rating. In that case a 16v cap is fine. Less if you want to actually check voltages. Usually the only small ones actually on +12v are associated with the fan header but you have to check the voltage to know for sure.

      HM is serious over-kill for those though.
      Panasonic FC; Chemicon LXZ; or Nichicon PW would be fine.
      There are probably between 1 and 2 dozen series in that range that would be fine I'm only mentioning what I usually get.
      Some audiophools actually like panny FC and FM and they are sometimes advertised as audio caps.
      .
      .
      Last edited by PCBONEZ; 05-13-2011, 01:17 AM.
      Mann-Made Global Warming.
      - We should be more concerned about the Intellectual Climate.
      -
      Be who you are and say what you feel, because those who mind don't matter and those who matter don't mind.
      - Dr Seuss
      -
      You can teach a man to fish and feed him for life, but if he can't handle sushi you must also teach him to cook.
      -

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        #4
        Re: Dell Dimension 4550 - Bad Audio Caps?

        Assuming it's a sleeved cap, if the 10uF has no stripe then it isn't polarized.

        You could replace those Vcore caps with 820uF poly w/ESR at .010 ohms of less for a longer lived system.
        You already have enough other poly in there that 4x820uF would do fine.
        Mann-Made Global Warming.
        - We should be more concerned about the Intellectual Climate.
        -
        Be who you are and say what you feel, because those who mind don't matter and those who matter don't mind.
        - Dr Seuss
        -
        You can teach a man to fish and feed him for life, but if he can't handle sushi you must also teach him to cook.
        -

        Comment

          #5
          Re: Dell Dimension 4550 - Bad Audio Caps?

          He wants to recap the KZGs around the VRM with HM. That's fine.
          "We have offered them (the Arabs) a sensible way for so many years. But no, they wanted to fight. Fine! We gave them technology, the latest, the kind even Vietnam didn't have. They had double superiority in tanks and aircraft, triple in artillery, and in air defense and anti-tank weapons they had absolute supremacy. And what? Once again they were beaten. Once again they scrammed [sic]. Once again they screamed for us to come save them. Sadat woke me up in the middle of the night twice over the phone, 'Save me!' He demanded to send Soviet troops, and immediately! No! We are not going to fight for them."

          -Leonid Brezhnev (On the Yom Kippur War)

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            #6
            Re: Dell Dimension 4550 - Bad Audio Caps?

            Agree.
            Mann-Made Global Warming.
            - We should be more concerned about the Intellectual Climate.
            -
            Be who you are and say what you feel, because those who mind don't matter and those who matter don't mind.
            - Dr Seuss
            -
            You can teach a man to fish and feed him for life, but if he can't handle sushi you must also teach him to cook.
            -

            Comment

              #7
              Re: Dell Dimension 4550 - Bad Audio Caps?

              I'll have to check again to see if the 10uF cap is polarized. If it is polarized, I already have one, but it is a "Samhwa" brand and is dated 1997.
              The 100uF caps appear to be connected to the headphone jack.

              Comment

                #8
                Re: Dell Dimension 4550 - Bad Audio Caps?

                After looking at other repairs that failed, I don't want to recap this board. My soldering iron is a junk, and I would probably damage the board while removing the caps and cleaning the holes. I have discovered that the soldering iron must be held on each joint for several seconds to get the solder to melt on multilayer boards. This computer is too old to be sent in to be professionally recapped, and my parents can't even stand to be without a computer for the time it takes to clean the dust out of it.

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