bad VCORE pwm in soft start

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  • laoveja
    New Member
    • Jan 2015
    • 4
    • argentina
    #1

    bad VCORE pwm in soft start

    Hi i have a Biostar k8m800 micro AM2.
    it doesn`t POST and only have 300mV on VCORE.
    The PWM Controller in an ISL6568 and after check vcc = 5v and enable (pin ENLL) = 1.2v i think its ok but i dont know what component could be bad. The enable pin is connected to pin 15 of ATPA01G (no datasheet).
    Theres a pin PGOOD that indicate the status of the controller. its always low but i dont know if its by an fault or its always in soft start. i dont know where could be the fault. the caps dont look bad. any idea? i really want to learn how to fix mobos and this is the hardest that i try. thanks

    PWM Controller:
    http://www.intersil.com/en/products/...s/ISL6568.html

    POWER CHECK:
    http://es.aliexpress.com/item/ATPA01...224449455.html
    Last edited by laoveja; 01-14-2015, 04:50 AM.
    Tags: None
    • laoveja
      New Member
      • Jan 2015
      • 4
      • argentina
      #2
      Re: bad VCORE pwm in soft start

      PWM Controller:
      http://www.intersil.com/en/products/...s/ISL6568.html

      POWER CHECK:
      http://es.aliexpress.com/item/ATPA01...224449455.html

        Comment

        • cmia
          Member
          • Aug 2013
          • 37
          • United Kingdom
          #3
          Re: bad VCORE pwm in soft start

          post some pictures please
          can a mod move this into the motherboard section please.

            Comment

            • momaka
              master hoarder
              • May 2008
              • 12170
              • Bulgaria
              #4
              Re: bad VCORE pwm in soft start

              I agree with cmia, post a picture of *your* motherboard here (use forums built-in feature, NOT off-site such as imageshack or whatever).

              You could still have bad caps but they might just not be showing it. From what I've seen, BioStar really liked to use Chemicon KZG capacitors on the VRM low side on some of their motherboards. If that is the case with your, a recap would be highly recommended.
              However, given the problem, it could also be a bad FET on the VRM. With the CPU removed, check the resistance between Vcore and ground and Vcore and 12V rail on 4-pin 12V CPU connector. Let us know what you get.

                Comment

                • Sparkey55
                  Badcaps Legend
                  • Jan 2010
                  • 1523
                  • USA
                  #5
                  Re: bad VCORE pwm in soft start

                  Originally posted by momaka
                  I agree with cmia, post a picture of *your* motherboard here (use forums built-in feature, NOT off-site such as imageshack or whatever).

                  You could still have bad caps but they might just not be showing it. From what I've seen, BioStar really liked to use Chemicon KZG capacitors on the VRM low side on some of their motherboards. If that is the case with your, a recap would be highly recommended.
                  However, given the problem, it could also be a bad FET on the VRM. With the CPU removed, check the resistance between Vcore and ground and Vcore and 12V rail on 4-pin 12V CPU connector. Let us know what you get.
                  I have seen OSTs on BioStar mobos also.

                    Comment

                    • momaka
                      master hoarder
                      • May 2008
                      • 12170
                      • Bulgaria
                      #6
                      Re: bad VCORE pwm in soft start

                      Me too, but usually on the RAM and chipsets' rails.

                        Comment

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