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820-3437 chime no video or backlight

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  • 820-3437 chime no video or backlight

    Hi All.
    Thia is liquid dmg board near LCD Connector. I have replaced the LCD connector and U8300 as it was not looking good.

    I dont get any voltage on data lines in R8361, R8362. Also EDP_PANEL_PWR is 0v. I cheked the LCD pins in diod mode and it seems ok with working board connector reading.

    Appreciate your help.

  • #2
    This is eDP panel, so pins 18/19 of J8300 should get voltage at least in the first few seconds.
    Pin 14 must go high in this time.
    PCH requires DP_INT_HPD signal for correct LCD detection.
    Check L8304 and traces to R5670.
    Be sure U8300 is properly soldered and check for short, or low value to ground, on its pins.

    Confirm consistent USB activity.
    You hear chime, but board can get stuck there...

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    • #3
      Hi, THank you for your quick reply.

      Pins 18,19 of J8300 I get 3v just for a second. L8304 trace to R5670 is fine. tested with ex monitor USB's working fine. Checked the resistors around J8300 they all fine.

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      • #4
        DP_INT_HPD comes high in that second when you get 3V at J8300?

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        • #5
          no it doesnt come high in that second .0v

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          • #6
            Check if R8360 is OK.
            Be sure to have good traces and solders for J8300.

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            • #7
              I replaced R8360 and R8350 as 8350 was 50k. I placed and check R8350 was 98k. then powered and same as before. Then I checked R8350 again and its 50k.

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              • #8
                J8300 traces are fine.

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                • #9
                  "R8350 again and its 50k."
                  Onboard measurement is not relevant in this case.
                  High value resistor is affected by other components.

                  Do you get external video?
                  Try disconnecting LCD and give time to enter OSX...

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                  • #10
                    HI, it works with external display. boot couple of times with osx . replaced the LCD connector again. Replaced SMC thinking SMBUS_SMC_0_S0_SDA AND SCL pulling down. none of worked. still the same situation. should i get 3.3v with out the LCD on R8362 &R8361 coz I cheked with a working board it stays for a while. but this board just for half a sec.

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                    • #11
                      Normally 3V3 should stay few seconds, without LCD connected.
                      Replace all the caps from the liquid affected area.
                      Also check for corrosion all resistors.

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                      • #12
                        Hi Solved. Thank you so much for your guidance. As you said I replaced all the caps affected area still was the same. Then I replaced the C8320,C8321,R8318,R8317. Display works.
                        Another successful guidance by 2informatics. Thank you Sir.

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                        • #13
                          Just to know is DP_INT_ML_C and P required to create DP_INT_HDP?

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