blinking power LED - help

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  • RandyG
    New Member
    • Dec 2009
    • 4
    #1

    blinking power LED - help

    Hi motherboard experts

    Does anybody know what it means, when upon turning on the power supply (rear switch) the mobo power LED blinks slowly?

    This is a desktop board - MSI K8NGM2-FID (aka 7207)

    I have a clone of this computer (had to recap it too) - it doesn't blink on standby (was my first thought too)

    When you switch on the case POWER SUPPLY, the motherboard power LED almost immediately starts blinking slowly. This is prior to hitting the mobo power switch. Pressing the mobo power switch makes no difference at all.

    No post, no beeps, no fans, just blinking power LED.

    Already tried swapping the power supply, cpu, and ram, replacing the bios battery, (and hitting the bios reset button a couple dozen times).

    The motherboard has 5v at this point, it doesn't appear to even try to start the power supply at all, with the mobo power on header switch.


    I recapped it a while ago. My badcaps kit was missing quite a few caps (the 470s and smaller) but they test ok with my trusty old BP esr meter.

    It was having problems powering up prior to recapping, and had a couple crappy CPU power caps.

    After recapping the computer worked perfect for 3 or 4 days , then it shut itself off with this blinking power led about 1 minute after powering up from standby one night, and has been dead ever since.


    Could the bios have scrambled itself? Could that cause this?
    Last edited by RandyG; 05-21-2010, 04:18 PM.
    Tags: None
    • delaware74b
      Badcaps Veteran
      • Apr 2009
      • 628
      • USA
      #2
      Re: blinking power LED - help

      It's possible the BIOS is bad or the southbridge got burned from the past power supplies. I had a customer who had a similar issue with a bestec where the 5vsb went bad. I replaced the power supply and the board died a year later. My recommendation: see if the power supply will start on its own, go back and check the caps that weren't replaced when you recapped it and anything 100uf and up.
      Stupidity should be a crime, especially for drivers. I have NO patience for them.

        Comment

        • kaniki
          Badcaps Veteran
          • Dec 2009
          • 514
          #3
          Re: blinking power LED - help

          The power supply should not be the problem. or should i say the only if it is one at all. He already said that he switched it with a known good one. so if it is bad, then the problem is definitely more then just the power supply.

          I would check to make sure that all the solder joints are solid. also, I dont know how you solder but maybe some excess flux got under the cap and is slightly shorting the board out. I have had that happen once. It worked fine when I recapped, but then started messing up days later and would not boot, post, or anything else. I took the caps out and found that there was a little excess flux under a couple of the caps that caused the problem. I cleaned it and re-soldered the caps in and no problems since then.

            Comment

            • RandyG
              New Member
              • Dec 2009
              • 4
              #4
              Re: blinking power LED - help

              the power supply doesn't turn on though. None of those caps are getting voltage yet.... all that's powered up so far is the +5vSB (and couple volts on the ATX PS_ON# pin). And something is making the LED blink... lol

              What controls the power supply PS_ON? I've been googling for that all morning.... is there a "CPU Power sequence controller" on a 939 board?

              Or does the bios have control between pressing the power button, and PS_ON ?

              I'm pretty good with electronics... I have a couple scopes, and likely anything I need to trace it out. (I do microcontroller AVR type stuff for a hobby)

              I just don't have any clue where to begin and can't seem to find any reference on the web to get me started.

                Comment

                • RandyG
                  New Member
                  • Dec 2009
                  • 4
                  #5
                  Re: blinking power LED - help

                  It still blinks the same, even with the bios chip out - so it's not that I guess.

                  I measured every electrolytic cap on the board. The only one with power on it is up by the outside edge of the pci slots... which makes sense since pci is supposed to get 5v standby power.

                    Comment

                    • kaniki
                      Badcaps Veteran
                      • Dec 2009
                      • 514
                      #6
                      Re: blinking power LED - help

                      I would say that it is the same on a 939 board as it is on any other board. All that turns is on is shorting out the 2 pins or wires that are down the middle of the main power supply power pack that goes to the motherboard. So it should be pretty much the same no matter the brand or model. There has to be something one the board that is not powering up right though. If you are getting the light on then that means that it is getting power and you said it is the same no matter which power supply that you try. The 12v and other voltages should not come into play until you turn or push the power button on. You could try shorting out the power line while it was attached and see what happens, but if something is really shorting out bad, then that may also fry the board if it isnt already. I wish i could help you more but that is about all i know.

                      here is some info about the power supply's

                      http://www.helpwithpcs.com/courses/p...nc-pinouts.htm

                        Comment

                        • RandyG
                          New Member
                          • Dec 2009
                          • 4
                          #7
                          Re: blinking power LED - help

                          Thanks kaniki

                          I hot-flashed the bios in the working board, just for fun... made no difference

                          I did short the ps_on# pin yesterday for a second with no cpu/ram in it, and fans spun up.

                          Kinda afraid of smoking stuff trying to power it up that way though

                          It appears the Winbond chip controls power on / off , the PS ps_on#
                          and the LEDs, including the one that's blinking. So... either it is screwed, or it's flash data is screwed, or it sees something it doesn't like and is refusing to power up the board

                            Comment

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