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HP DV6810us - no boot, no power, bad power mosfets?

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    HP DV6810us - no boot, no power, bad power mosfets?

    Hi everyone,
    I have an HP Pavillion DV6810us, aka DV6700, aka DV6000. It has an AMD cpu and NVIDIA chipset. The problem is that it will not boot at all. No fan or hard drive spinning, no lights, no beeps, nothing.

    I know that these laptops typically have overheating problems and the graphics card will need to be reflowed, but I don't think that's the problem because the laptop is not even powering up or POSTing. I did remove everything and try to turn it on without, but it's the same exact thing.

    My main suspect is the PPM or VRM chips, as those are typical causes of this no power symptom. However, I suppose it could be a capacitor or driver on the mobo also. Also, the DC adapter works fine, and the charging ring and light turn on when plugged in.

    On my laptop, the power mosfets are different than the ones in the link above. the FDS6679 is a 4856a, and the AO4407 is a 6679gm. I know I can go ahead and unsolder these and test them outside the circuit, but if I did that I might as well just put new ones on, and also, I don't want to risk doing a bad solder job and ruining the rest of the board.

    So basically, is there a way to go about testing the board without unsoldering anything? I have a DMM with diode and capacitance functions and a block diagram/schematic available (see attached). I really don't want to replace the board because I want to be able to sell this computer for a new one and putting a new mobo in would be too expensive and not worth it.

    Any help would be greatly appreciated!

    Thanks,
    JGAN
    Attached Files

    #2
    Re: HP DV6810us - no boot, no power, bad power mosfets?

    Usual dv6000 series is hard to repair, because if you repair one thing, after few days or just hours, gone another thing.

    Try all coils on board tested with multimeter with OHM test, black on - and red on coil if you got reading 0 or 0.01 coil is shorted, but first check if got 5 and 3 volts

    Comment


      #3
      Re: HP DV6810us - no boot, no power, bad power mosfets?

      Thanks for your reply primoz,
      I checked the schematic and found "5VPCU" and "3VPCU" on there, but I don't know how to locate them on the motherboard? Also, when I find them, am I supposed to probe between the point on the motherboard and the DC jack, or what?

      I'm not exactly sure if this motherboard has coils - at least not the ones that are on desktop computers. If it does, what do they look like?

      I have attached a couple of high res images of the mobo for reference. One shot is the top, the other is the bottom.
      Attached Files

      Comment


        #4
        Re: HP DV6810us - no boot, no power, bad power mosfets?

        Follow "5VPCU" and "3VPCU" in the schematics, look for a coil at which they are connected to, then look for the same serigraph on the board.

        Comment


          #5
          Re: HP DV6810us - no boot, no power, bad power mosfets?

          Thanks ablacon, I was able to find the inductors on the mobo and tested them by putting the negative end on the negative part of the dc jack and the positive end on one side of the inductor. They all tested fine; in the K ohms range (except one, which was at .5K).

          I did not find the literal 5VPCU or 3VPCU serigraph on the mobo though, did I need to? If not, what is the next step? I tested the voltage between the inductor and negative lead when plugged in, and they matched up (5v, 3v).

          Thanks for helping a newbie
          Last edited by JGAN; 08-25-2012, 07:51 PM.

          Comment


            #6
            Re: HP DV6810us - no boot, no power, bad power mosfets?

            Hi. If this board as your, and you got readings 5 and 3 volts and no shorted coils is like (my opinion) 70% chance to bad chip, bad contact or sodler under the cihip join together under the nvidia chip, is only one.

            Dot marked is places where you can put black - miltimeter probe
            square mark is where usual find the 3 and 5 volts
            big square mark is nvidia chip
            Attached Files

            Comment


              #7
              Re: HP DV6810us - no boot, no power, bad power mosfets?

              Sorry, I'm not sure I fully understand you... You think that I have a bad NVIDIA chip? Because I don't have a problem with the screen. Also, I get 3.35v on the power switch.

              Comment


                #8
                Re: HP DV6810us - no boot, no power, bad power mosfets?

                I mean If you got power, and no one of coils shorted, then is problem somewhere else, and on board with nvidia graphic is a a lot of times problem on chip.

                Yes is possible, I got same problem 2 times, after reballing nvidia chip is work again, because solder balls under chip is bridget. Im not say is in your case 100% this problem.
                Last edited by primoz1; 08-26-2012, 03:32 PM.

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                  #9
                  Re: HP DV6810us - no boot, no power, bad power mosfets?

                  Could it one of the mosfets that control power? Specifically PQ30 and PQ3 (Pg. 34).

                  *EDIT*
                  I just checked PQ3 and it has the correct voltage (11v-12v). I will check PQ30 next.

                  *EDIT #2*
                  PQ30 has ~18v from the drain to ground. The led on the DC jack works also, so I don't suspect that PQ30 is bad.
                  Last edited by JGAN; 08-26-2012, 05:18 PM.

                  Comment


                    #10
                    Re: HP DV6810us - no boot, no power, bad power mosfets?

                    I also just tested PQ50-PQ54 and they all checked out - PQ54 didnt have any voltage from pin 4 to ground, is that normal?

                    Are there any other steps I should take?

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