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Asus A7N8X bad caps + non-low-esr replacements?

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    #1

    Asus A7N8X bad caps + non-low-esr replacements?

    Hey there,

    My motherboard (Asus A7N8X-DX) seems to have finally failed. It will no longer POST, and although it turns on, nothing happens, no beeps, just sits there. I have determined its due to bad caps since about 7 of 9 of the larger caps (3300 uF, 6.3V) have bulged and/or are leaking electrolyte. The problems had been getting progressively worse until now it just won't boot.

    I plan to recap this board and hopefully this should fix the problems. My question is, I have a bunch of United Chemicon KMG series caps that could replace the caps. The caps that are bad are near the processor/bridge (I believe this is VRM?). Can I use these caps I have? How bad is it to use non-low-ESR caps, or should I just get some low ESR ones? Here is the datasheet for KMG series:


    If I do decide to get some Low ESR caps, I sourced some potential options that would be the most easily available. I can get:

    United Chemicon KY or KZE (6.3V)
    Panasonic FC or FM (6.3V, both more expensive than chemicons)
    Nichicon PW or HE (10V, also more expensive than chemicon)

    Which is preferable of the above? All have a minimum diameter of 12.5mm which isn't great but is probably doable. The KMGs I have are 10mm diameter, but yeah, dunno if they'll be good enough.

    Any help is appreciated.
    Tags: None
    #2
    Re: Asus A7N8X bad caps + non-low-esr replacements?

    what caps should i buy?
    https://www.badcaps.net/forum/showthread.php?t=2280

    lower esr and higher ripple is better

    only low esr caps on vrm output please otherwise badcaps type symptoms
    capacitor lab yachtmati techmati

    Comment

      #3
      Re: Asus A7N8X bad caps + non-low-esr replacements?

      Search the threads in this forum may get some helpful.
      My SAMXON Capacitors Database HERE!!

      X-CON is a new brand for SAMXON's Polymer Capacitors.

      Comment

        #4
        Re: Asus A7N8X bad caps + non-low-esr replacements?

        pm topcat for samxon cap prices.
        capacitor lab yachtmati techmati

        Comment

          #5
          Re: Asus A7N8X bad caps + non-low-esr replacements?

          Thanks for your help guys.

          I ended up going with the United Chemicon KZE 3300uF 6.3V caps. I replaced 5 caps beside the processor (whole row) and one cap (out of a row of 3) nearer to the AGP slot. However, unrelated, while I was removing the processor I accidently slashed across 8 of the copper PCB traces. I figured the board was fucked but I actually managed to repair it by fly-wiring over the affected area with tiny wires. From my multimeter checks it looks like everything is connected properly and nothing is shorted.

          However, I'm now having strange problems. My computer normally runs at 166 MHz FSB with a 11x multiplier (~1800 MHz total). I'm now finding that the computer won't boot at any multiplier past 8.5. I can run it, at the highest, at 8.5 multiplier on any FSB (100, 133, 166, even 200 but its not stable). As soon as I set it to 9x, it won't save the BIOS settings, and once booted it reverts to CPU safe mode of about 700MHz.

          Any idea what would cause this problem/how to fix it? Possibly something to do with the new caps, or is it more likely due to the improvised wiring?

          Comment

            #6
            Re: Asus A7N8X bad caps + non-low-esr replacements?

            Are all the traces repaired properly (all continous and none shorted)?

            Comment

              #7
              Re: Asus A7N8X bad caps + non-low-esr replacements?

              well the KZE are not very low esr but they are not bad specs so i dont think they are the problem.

              with the repair you have added another unknown into the equation. congrats though for repairing 8 traces, i know how hard that is.

              there is a possibility that the repair is the problem. the thickness of the new wire is adding impedance to the circuit or they are not connected properly. whether that is the issue i dont know. i know it is possible to get stable after repairing a few traces.

              you also have a board that was not posting and then you recapped it. there is a possibility that something is damaged in the vrm circuit before the recap although i find it strange that the board would post if that is the case.

              one other item is the caps, did you do a full recap of all the bad brands 1000uf and above?

              its a difficult one.....
              capacitor lab yachtmati techmati

              Comment

                #8
                Re: Asus A7N8X bad caps + non-low-esr replacements?

                I'm gonna double-check the traces, but from what i could tell with the multimeter (which was tough with normal test leads) the traces were reconnected properly.

                I didn't replace all the large caps, because many looked OK (no signs of leaking/bulging). The computer is fairly unstable in general now, but the multiplier problem is really weird. I guess I'll try replacing all the large caps.

                Comment

                  #9
                  Re: Asus A7N8X bad caps + non-low-esr replacements?

                  I'm a little late to this discussion, so forgive me if it's already been resolved.

                  If I understand correctly, it sounds like you used 12mm caps, and I assume the originals were 10mm? If so, you may have had to leave the caps not completely seated to the board to make them fit. I've found that stability is sensitive to having short leads and good solder joints. If you have long leads or bad joints on your caps that could be enough to make it flaky. Also, with the damaged traces you mentioned, you might have to make especially good joints to compensate for the increased impedance.
                  I've had lots of success with KZE capacitors but at the 3300uF size I'd go with something that is available in 10mm for a snug fit against the board.

                  Comment

                    #10
                    Re: Asus A7N8X bad caps + non-low-esr replacements?

                    would it not be possible to use conductive silver paint to repair the damage?

                    I used this on my RAM modules who's pins had been burnt off, after snipping the carbonized burnt pins I just painted pins in their place and the RAM's never worked better.
                    Rubycon Rubycon Rubycon

                    Comment

                      #11
                      Re: Asus A7N8X bad caps + non-low-esr replacements?

                      The problem with conductive silver paint is the application and the quality of the compound.
                      If good quality paint is used, you can cover the other traces with small stripes of Tesa film. So you can cover trace after trace wihtouth making shorts.
                      Any way, my succes rate with this was not very high, but those boards i have tried it had always very very small traces wihtout mutch space between.
                      But on Ahtlon XP`s this was the method of choic.

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