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Sproggy MK2.5 Wont Boot

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  • Sproggy MK2.5 Wont Boot

    Have built the sproggy 2.5 power supply and the voltages are fine, but the board won't boot.

    The processor (P166) gets warm, the system draws 2A of current, but the hard disk won't spin.

    Just causes a clicking sound from the PSU, that goes away when I unplug the HDD.

    Have a 1k + 100uF power good delay in case that is the problem (PC chip TXPRO) but makes no difference!

    Any suggestions anyone?

    ANY help apreciated!


  • #2
    Hi Moobie,
    I had the same problem with a home brew PS that I built. What I found out was when I used the same +12 volts for the computer and HDD, I heard a clicking noise from the HDD and the PC wouldn't boot. When I separated the +12 volt supplies for the PC and HDD by using a second +12 volt supply, the problem went away. The result is I am now listening to mP3s in my car.
    Make sure that you have enough filtering on all of your voltage outputs.
    Good luck



    • #3
      Ok i've spent the after noon (almost) tearing my hair out over this.

      The mobo and graphics card post and boot fine, but the hard diak just won't spin up.

      Even if it is the only device attached to the PSU it still cliks, the LED comes on but the drive won't spin!

      There should be more than enought current avauble on bothe the 5 ans 12v lins but it just won't spin!

      Any further ideas?


      • #4
        Does the hard drive work if you hook it up to a normal power supply? An obvious question, but I guess it had to be asked...


        • #5
          Hi andy yes it does, well both of them do, for some reason they just won't quite work!

          When I say both I mean i have tried 2 different disks.


          • #6
            Didnīt you swithed the ground wires? Each one has his own ground wire (makes 2). One must connect to 5V part and the other to 12V part. If this doesnīt work measure the current passing to the HD.



            • #7
              This problem is allmost certainly caused by the large startup current drawn by the hard drive. Most modern drives spin very fast and require a heafty dose of current to get them going(I think IBM shows a graph of current over time for the spinup of there drives in the data sheets). My only suggestion would be to try a capacitor connected across the 12V supply very close to the plug on the drive(soldered to the back of the plug would be good). Try around 1000uF and dont go too high as too much capacitance on the load side of a switch mode regulator can cause problems. I had the same problem with seagate drives and it was fixed by using shorter, thicker cable and a capacitor.


              • #8
                When i gave out my design on the PSU some people came back to me telling me that the +12v rail wouldnt work with large HDs. The problem obviously was in not enough current was supplied to spin the drive. The +12v rail was based on LM2587 IC which can give out 2amps @ 12v. So looking at the datasheet of the drive some of them required only 1.2amps however they still wouldnt work.
                The problem was that i had a 10uH inductor on the output of the 12v rail. That was placed there to filter the output volage. But instead of doing that it worked as a extra load on the 12v rail.
                Simply removing the choke fix the problem.
                So check to see if you have any inductors in your 12v rail if so try getting rid of them. Flyback regulators dont like them much

                System Comp V3 - In progress.
                Low power MB with C7 CPU, DC-DC PSU, car ECU link, USB TV, GPS, 7" TFT, Wireless, Voice.