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    ASRock H61M/U3S3 Short

    Hello. First of all, I hope this is the right category for this thread.

    A friend of mine has got an ASRock H61M/U3S3 which does not power up and he has brought it to me to try to repair it.
    The problem is that the board does not power up: the PSU goes in self-protection for a short.

    Sadly, I have not found any schematics for this board, so I started looking for broken components. Actually, I have found out that a 1117 regulator placed near the ATX24 connector, which regulates +5V to +3.3V, is heating up when the board is powered. Moreover, an electrolytic 560uF capacitor on the +3.3V line and the PCH are warmer when powered. For these reasons, I had carefully desoldered the regulator and have discovered the +5V line is not shorted.
    Therefore, it is the +3.3V line which has problems.

    I have soldered back a new 1117 regulator but the PSU still shorts. So I have desoldered the electrolytic capacitor to exclude any possible cause, but the short persists.

    May the PCH be the cause of the short?

    Attached you can find a picture with the highlighted components.

    Thank you
    Attached Files

    #2
    Re: ASRock H61M/U3S3 Short

    you did not mention what power supply it is. have u checked the power supply itself to make sure its not the psu thats failed and tripping itself? i.e. shorting the green wire on psu atx connector to ground without any of the psu cables connected to anything?

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      #3
      Re: ASRock H61M/U3S3 Short

      You are right. My friend has given me his iTek 500W he had used with this motherboard. This PSU does not have a self-protection state, and continously "restarts" itself (that is how I have found out that some components were warmer). However, my friend had already tested the board with a Corsair 650W, which goes in self-protection state.

      To be sure it was a short causing this, I have used an Xbox 360 PSU, by connecting +5V (standby) and GND only. The PSU goes indeed in self-protection, revealing it is a shortcircuit.
      Last edited by MichR; 03-20-2016, 01:48 AM.

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        #4
        Re: ASRock H61M/U3S3 Short

        Can someone help me? I do not want to throw this board in the bin. Yes it is a bit old and cheap but still a 1155 board my friend can use.

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          #5
          Re: ASRock H61M/U3S3 Short

          To pinpoint the problem a bit easier, disconnect the motherboard from the PSU first. Then, using your multimeter on the lowest resistance setting (usually 200 Ohms for manual multimeters), measure the resistance between ground and each pin on the ATX connector. Do the same with the 12V connector for the CPU. Post the results here. That way, we can see which (if any) of the major rails has the short-circuit. We will continue from there once that is identified.

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            #6
            Re: ASRock H61M/U3S3 Short

            Hello, thank you for your response. These are the results measured with my multemeter (all referenced to ground):
            +3.3V - 214Ω
            +5V - 371Ω
            +12V - 6.7kΩ
            -5V - OL (>220MΩ)
            -12V - OL (>220MΩ)
            +5VSB - 122kΩ
            PSON - 8.5kΩ

            +3.3VSB (the output of 1117 regulator, as seen in the picture) - 470Ω (it is the resistor between 1117's ADJ pin and GND).

            As previously said, I am certain the +3.3VSB is somehow shorted, as desoldering the regulator solves the problem. +3.3VSB supplies power to the PCH. Perhaps the PCH may be the cause of the issue, but I do not understand why.

            Comment


              #7
              Re: ASRock H61M/U3S3 Short

              Originally posted by MichR View Post
              Hello, thank you for your response. These are the results measured with my multemeter (all referenced to ground):
              +3.3V - 214Ω
              +5V - 371Ω
              +12V - 6.7kΩ
              -5V - OL (>220MΩ)
              -12V - OL (>220MΩ)
              +5VSB - 122kΩ
              PSON - 8.5kΩ
              Okay, so pretty much everything looks okay (or at least nothing shorted).

              Originally posted by MichR View Post
              As previously said, I am certain the +3.3VSB is somehow shorted, as desoldering the regulator solves the problem. +3.3VSB supplies power to the PCH. Perhaps the PCH may be the cause of the issue, but I do not understand why.
              Then measure the resistance from the output of the 1117 regulator to ground and report back what you get.

              Both ceramic and polymer caps can short out sometimes, so if you are getting a short-circuit (I'd say less than 10 Ohms), you can try removing the polymer capacitors that were getting hot and see if you still get a short-circuit.

              Comment


                #8
                Re: ASRock H61M/U3S3 Short

                The resistance from the output of the 1117 is 470Ω (as written in the previous post, perhaps you have missed it) which is sum of the two resistors between Vout-Adj-GND (300+180Ω).

                One curious thing I have noticed is that the motherboard does not behave in the same way as before. I had left sit it for a while (until you replied) and now, when supplying +5VSB, the PSU does not short. The current on +5VSB rail is, however, about 1.3A. The even more curious thing is that the regulator does not heat up. Instead, only the PCH gets warmer. The voltage on +3.3VSB is 1.86V.

                In order to understand what is going on, I have repeatedly cleaned the BGA (of the PCH) underneath with IPA and sometimes the current on +5VSB reduces to .02A. The voltage on +3.3VSB in this case is 3.44V.

                Comment


                  #9
                  Re: ASRock H61M/U3S3 Short

                  Originally posted by MichR View Post
                  The resistance from the output of the 1117 is 470Ω (as written in the previous post, perhaps you have missed it) which is sum of the two resistors between Vout-Adj-GND (300+180Ω).
                  Ah yes, I did. Sorry about that.

                  Originally posted by MichR View Post
                  One curious thing I have noticed is that the motherboard does not behave in the same way as before. I had left sit it for a while (until you replied) and now, when supplying +5VSB, the PSU does not short. The current on +5VSB rail is, however, about 1.3A. The even more curious thing is that the regulator does not heat up. Instead, only the PCH gets warmer. The voltage on +3.3VSB is 1.86V.

                  In order to understand what is going on, I have repeatedly cleaned the BGA (of the PCH) underneath with IPA and sometimes the current on +5VSB reduces to .02A. The voltage on +3.3VSB in this case is 3.44V.
                  Interesting. I'm not really sure what can cause that. I doubt bad BGA could be the issue, but if you have tools to reflow it (a heat gun will do), you could try that.

                  Another thing you can try is to insert 3.3V from the PSU's 3.3V rail directly in that spot without the voltage regulator there. Then turn on the PSU manually (by shorting PS_ON wire to ground) and see if the PCH overheats/smokes (if it does, it probably was dead).

                  Just throwing ideas out here, though.

                  Comment


                    #10
                    Re: ASRock H61M/U3S3 Short

                    Yes I have got a hot air station I could use but not a good flux to use along with it (right now I have a homemade RMA flux).

                    Before trying reflowing the chip I would like to supply +3.3V as you suggested. What I am missing however is a proper power supply. As said, I am using a modified XBOX 360 PSU which outputs +5V/+12V with short protection.
                    Last edited by MichR; 04-05-2016, 11:55 PM. Reason: Typo

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