Coolmax shuts off after a few seconds

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  • Pentium4
    CapXon Be Gone
    • Sep 2011
    • 3741
    • USA
    #1

    Coolmax shuts off after a few seconds

    I got this thing cheap brand new and decided to recap it, so I did. When I plug it into a computer, it gets stable 5VSB but when I hit the power button it will turn on for about 2 seconds and then shut off. When hitting the power button again it will not turn on until power has been pulled and the PSU is plugged back in. When it powers up for that 2 seconds, the 12V reads ~12.16V every time.

    I can't find any shorts....although the soldering side looks bad (including mine ) Any ideas? I would appreciate any feedback! Let me know if I need to take some better pictures.

    (Side question) On the 12V it has two 16A schottky's in parallel but it has no shunts and only one group of 12V wiring, does this mean that it will only work as a single rail @ 16A but will be more efficient than just one 16A shottky?
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    Last edited by Pentium4; 04-23-2013, 04:08 PM.
    Tags: None
    • 999999999
      Badcaps Veteran
      • Sep 2006
      • 774
      • USA
      #2
      Re: Coolmax shuts off after a few seconds

      Is this happening powering a load or unloaded, and how much load? I'm guessing too much or too little load on the 5V rail.

      Two schottkys in parallel can't be assumed to provide 100% of their summed current, but would be more efficient under 16A AND will allow higher than 16A. One will inevitably have a slightly lower forward voltage than the other and pass more current but this will cause it to heat up more, raising the forward voltage till there is (not an equilibrium but still) a reasonable sharing of current between the two. It's unlikely they will be the bottleneck on 12V current though you didn't mention the (probably false) specs Coolmax gave the unit.

        Comment

        • Pentium4
          CapXon Be Gone
          • Sep 2011
          • 3741
          • USA
          #3
          Re: Coolmax shuts off after a few seconds

          Thank you for the informative response, Coolmax claims 26A on the 12V. My test machine is a Pentium 4 Prescott @ 3GHz, 2 RAM sticks and a CD ROM drive so maybe you are right and there isn't enough 5V going through it, I will try plugging in some hard drives

            Comment

            • Pentium4
              CapXon Be Gone
              • Sep 2011
              • 3741
              • USA
              #4
              Re: Coolmax shuts off after a few seconds

              You, sir.....were spot on! We have life So I'm guessing there was too low of a load and the 5V sky rocketed and tripped the OVP?
              Last edited by Pentium4; 04-25-2013, 03:54 PM.

                Comment

                • 999999999
                  Badcaps Veteran
                  • Sep 2006
                  • 774
                  • USA
                  #5
                  Re: Coolmax shuts off after a few seconds

                  Yeah, seems that way. Too low for their cheap design. I suspect they probably use higher ohm value dummy load resistors trying to make their cheap original caps last longer by removing some of the heat they create.

                  Glad you got it sorted out.
                  Last edited by 999999999; 04-25-2013, 04:58 PM.

                    Comment

                    • Pentium4
                      CapXon Be Gone
                      • Sep 2011
                      • 3741
                      • USA
                      #6
                      Re: Coolmax shuts off after a few seconds

                      Yeah I was thinking about removing them. The original caps were Gold Link and CS...I doubt they would have lasted long

                        Comment

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