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820 2915, no picture on the screen

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  • 820 2915, no picture on the screen

    Hey,

    this board before the problem mentioned in topic, works well but showing problem's like tipical GMUX on mac15 - 2009 boards. First i put the board in other mac pro 15 who knew it was good.. don't solve the problem.. next replace a connector for new one and don't solve again the problem..

    aftwards i reball the GMUX but when i tried to put it on the board i missed! stayed a line up. i Turn on the board and I did not hear the tipical sound. I noticed that I was not well soldered.

    Now i try with original and 1 off donor board(Ebay) , the machine start i hear the sound but no picture..

    in Your's opinion GMUX Dead? PCH?

    i put a pen drive and blink like a normal start!

    Thank you

  • #2
    Do you get external video?
    Check resistance to ground at GPU side of the caps placed into data lines between CPU and GPU; C8020-35, C8055-70, 32 values to compare.

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    • #3
      This has a dead GPU simple as that. Waste of time

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      • #4
        No, GPU it's good! Before reablling GMUX, i test with Heaven benchmark 10min and the machine didn't turn OFF! Usually if they have a problem with VRAM or Graphic chip the machine goes off 3 - 4 sec with heaven benchmark .. It's my way of testing these models!

        2informaticos, i noticed that i don't have PPVCORE_GPU = 0V and GPUVCORE_EN = 0.130V .. .

        GPUVCORE_EN comes GMUX!! Are these chips heat sensitive? usually i use 400C* in my heat station!! in 2008 and 2009 models i never have this problem!! but i will shop a used GMUX from ebay and replace!!

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        • #5
          Test the mentioned caps.
          If you get OL on any of them at GPU side, that means broken trace, or bad solder under GPU.
          No need to bother with GMUX then.

          You should get similar values on every data lines pair.
          There are two values possible, but every pair should be very similar...

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          • #6
            already test all caps and i have similar values on every data lines pair!!! yes it's very similar!! values around 1.091M - 94K Pair...

            GPU don't get's Warm!! i hear the tipical sound and pen drive blink but no image and no external video!

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            • #7
              You must compare values in diode mode, not ohm scale.
              If are really similar values, that doesn't assure GPU is still OK.
              You can have now bad GPU, or GMUX...

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              • #8
                OK !!! Problem Solved!! i Have a working board here and test all testing points around MUX and i notice pin129 (MUX) have a diferent resistence!! i turn on the board and i gets only 1.5V compare a working board 3.3V!!! i follow the line in schematic and i found a R9600 burned!!

                But don´t solve the firs problem!!!

                https://drive.google.com/file/d/1cF0...ew?usp=sharing

                I'm sure it's not the connector or the LCD! because i have 2 another working machines here and i test the board in both!

                reballing mux, replace the connector .... what can be??

                thanks

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                • #9
                  If it's not a bad GPU today, it's a bad GPU tomorrow....tralala

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                  • #10
                    JohnB8812 have you had any situation like that?? or anyone have a problem like that ??

                    i heat the Graphic chip a bit and nothing change!!

                    i need to be sure..

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                    • #11
                      Force Intel graphics with software like gfx card status.
                      If you get good image, then is GPU issue for sure...

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                      • #12
                        https://drive.google.com/file/d/1H0I...ew?usp=sharing

                        with only integrated graphic same history.. i will replace again for a new lvds connector! then i will replace the Gmux because is the original Gmux! what you think??

                        in external monitor works perfectly!

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                        • #13
                          Hey guys again, this board is making me crazy!!

                          Already replace for a new one LVDS connector, GMUX, And Graphic chip for new one!! Same History, the picture off the screen is the same as a put up!!

                          anyone have more ideas?? thank you

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