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820-0165 Fan spin about 1 sec, then off.

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  • 820-0165 Fan spin about 1 sec, then off.

    After fan stops pulling about 24ma from the charger.

    Going down the power rails I have everything till PP5V_S4RS3, on U7501 it is 5V
    while fan spins, then down to zero when fan stops on pin 2. It looks like something
    stops telling it to turn on. Any suggestions?

  • #2
    Sounds like possible power cycling. Does CPU VCore come high too when the fan spins?

    Comment


    • #3
      All the secondary coils get voltage, or pulse at least?
      ALL_SYS_PWRGD pulsing too?

      Comment


      • #4
        Assuming ALL_SYS_PWRGD is pulsing, which I'm betting it is, check U1950 and surrounding area. If that's clean, check everything coming and going from U6100.

        Comment


        • #5
          ALL_SYS_PWRGD goes to 3.3v then zero on pin 1 of U1950
          PPVCC_S0_CPU on R7320 pin 2 peaks at 1.8v then zero
          Both come up with fan spin, then go to zero when fan shuts off.

          Just to make sure I am saying this correct, the fan spin and the voltages come
          up when I connect charger, then about 1 second later the fan stops and
          the 2 above voltages go to zero. At this point the voltages on the rail page above
          PP5V_S4RS3 are all correct and present. Nothing changes that I have
          found once the fan spin stops. If I disconnect/Reconnect the charger I get the 1 sec
          fan spin then back to steady state until I disconnect the charger again. There
          is no cycling or any of the voltages not present going above zero again.
          Last edited by rsiesta; 09-25-2018, 06:14 AM.

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          • #6
            Pins 7 & 3 from U1950 pulsing too?

            Comment


            • #7
              Ok so power cycling ang history liquid damage etc?

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              • #8
                Both 7 and 3 act just like 1, voltage when charger connected for brief second, then nothing.

                Comment


                • #9
                  No history, I wish I had stuff brought in for repair, but I am learning on
                  boards listed as for parts or repair on ebay so I am probably buying donor boards .
                  I could find no liquids or corrosion on the board and no sign anyone had tried repairing it.

                  Comment


                  • #10
                    What you get on pin 2 of U1950?
                    If 1 & 2 pulse, then 7 must pulse too.
                    Be sure pin 8 receives 3V...

                    Comment


                    • #11
                      U1950

                      When first plug in charger (These are just watching display for highest value, before went to second values)
                      (Did not use max/min function)


                      1 3.4v
                      2 3.4v
                      3 3.4v
                      4 0.040v
                      5 3.4v
                      6 3.4v
                      7 3.4v
                      8 3.4v


                      After charger plugged in 5 sec and fan spin stopped, these stay
                      same till you remove and reconnect charger.

                      1 0.003v
                      2 0.059v
                      3 0.002v
                      4 0.002v
                      5 0.007v
                      6 0.002v
                      7 0.007v
                      8 3.44v

                      Comment


                      • #12
                        Is now time to check all SPI resistors and traces.
                        Also check U6100/01 for corrosion.

                        Comment


                        • #13
                          Checked all 22 of the resistors, they look good, checked all the pins on 6100/01
                          only the ones that should be ground were to ground. No visible corrosion.
                          Just have the traces to check left to do.

                          I take it this is failing when trying to load the bios?

                          Last edited by rsiesta; 09-25-2018, 06:59 PM.

                          Comment


                          • #14
                            Found bad pad and trace, ran jumper wire . The connection
                            between R7425 and pin 15 of U7400 was gone. Not really
                            corrosion but pad looked a little tarnished, scrape the black
                            coating off trace and copper looks like melted away.

                            I now have continuous fan spin, pulling about .6 amps but no chime or
                            display output. Back to seeing what point it fails now.
                            Thanks for help.

                            Comment

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