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820-3330 no video

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  • 820-3330 no video

    I got this board witch has been messed with a little...It got a sticker with (bad video card/Bios)
    Hopefully GPU has not been reflowed.
    I took a look at it and here is my findings:

    Initially quarter fan spin...nothing to do with charging sense resistor
    L3508 completely burned...but thats not a big deal.
    Wrong 2011 lcd plugged in...
    Looked for knocked off component and found R8802 in another position! between R8802 pin1 and c8823 pin 1. R8802 pin 2 was not anymore connected.

    Corrected all this stuff and still board with all signals power cycling...

    Decided to quickly test a bios from same donnor board and actually it chimes! but still no video! Usb mouse with red light.

    U8900 had very bad looking original solder joints. I decided let's touch up and reflow all the solder joint, It looks really great but nothing changed, still no video...

    Tried some PRAM and checked for image but nothing.

    Then I thought maybe bios should have it's original ME, so I tried a backup from the original bios and it's not detected by programmer. When I solder back bad original bios chip it has same diode mode reading than the donnour testing one...
    Actually it looks like it does'nt turn on but no short!! When I remove original bios it doesn't change anything, it continue power cycling.

    Is it worth spending time for this? If so how can I confirm if it's a bad ME bios chip causing that or a bad U8900?

    Note: I confirmed U8900 is receiving GPUVCORE_EN 3.3V and GPUVCORE_PGOOD at 3.3V. Found also PPVCORE_S0_AXG to be 0,89V, so it looks very likely that U8900 is working properly.

    Thanks for any advice

    Last edited by jadao; 10-24-2018, 10:29 PM. Reason: Corrected a mistake in the description of initial issue

  • #2
    Did you test for external video.
    Instead of mouse, test with OSX pendrive; if flashes, there is USB activity for sure.

    "GPUVCORE_PGOOD at 3.3V"
    That means GPU power supply works good.

    Post some voltages at J9000; correct LCD plugged in, of course...


    • #3
      Yes I tested with external monitor, it doesn't work.

      However I am sure there is activity,, it chimes, I can PRAM the board with external kbd.
      I also see flashing activity with my usb live os hdd,
      When I boot holding option key, I can see Caps Lock key light on.

      Voltages on J9000:
      PP3V3_SW_LCD=0V I am missing LCD_PWR_EN = 0V



      • #4
        Try this dump as is, don't change ssn yet.
        I cannot assure is good, as I got it from vinafix...


        • #5
          Hi 2informaticos, thanks for the dumps I downloaded it, but I can't open the compressed file, it seems broken.


          • #6
            What is the difference between 8MB and 4MB?


            • #7
              Apart of 2x4=8???
              I didn't exactly understand you.
              Try to explain you better...


              • #8
                Sorry, for some reason it’s missing a line,
                Since I can’t open your dump, the compressed file is reported as corrupted (maybe it’s my win xp system , I’ve downloaded from Vinafix a bios to test. They had a 8MB version and a 4MB.
                I just took a standard 8MB version.


                • #9
                  So I tested another bios (with no warranty wether clean ME or not) and samed thing...
                  it chimes, it's able to PRAM but no image/backlight...
                  Any suggestiona? Thanks

                  I notice also fans doesn't ramp up due to missing trackpad, it just run quiet as if trackpad was connected??
                  Last edited by jadao; 11-04-2018, 08:37 PM.


                  • #10
                    Any suggestion about this one before I give it back? Thanks
                    Don't know if on this model fan ramp up progressively to maximum when trackpad is disconnected… I think it should if TS0P is located on the trackpad…
                    I don't know if this is most likely related to bad ME region or other additional issue...


                    • #11
                      No external video discard a problem with internal LCD.
                      You must have a GPU related issue.
                      Change U8900, just in case...


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