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820-01598 EDP cable was disconnected whist testing new screen. No image, no backlight

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    #1

    820-01598 EDP cable was disconnected whist testing new screen. No image, no backlight

    MBP2019 A2159 Board 820-01598

    Hi Everyone! My very first question and ask for help! Thanks in advance!!!
    I was testing the new screen on this MBP but the time I was maging to turno the mac over, the EDP cable got loose.
    I disconnected the power, reconnect de EDP cable, holding with screws the screen this time.
    Turns on fine, everything works fine, but no image (I used the flashlight) and no backlight at all.

    Done SMC and PRAM reset. Nothing changes.
    Tested other functional aftermarket and original screens. Nothing changes.
    Don´t have other EDP cable for testing. It´s coming in some days.
    No shorts anywere.
    SMC_LID / Hall function works as the touchbar works ok (i guess)
    Image fine in external monitor.

    Tested all components and I´ve found this:
    PPVOUT_S0_LCDBKLT: 0v
    Q8400: gate LCDBKLT_EN_L: 12.5v (doesn´t drop)
    Q8401: 0v all pins

    But what scare me are these two signals that come from the processor and its 0v both:
    EDP_BKLT_PWM and EDP_BKLT_EN

    Any ideas? Very apreciated the attention and help.
    Tags: None
    #2
    Re: 820-01598 EDP cable was disconnected whist testing new screen. No image, no backl

    new screen on this MBP
    There are some articles and concerns about compatibility of replacement screens. Is this screen under test 100% compatible with your machine?

    Comment

      #3
      Re: 820-01598 EDP cable was disconnected whist testing new screen. No image, no backl

      Originally posted by mon2 View Post
      There are some articles and concerns about compatibility of replacement screens. Is this screen under test 100% compatible with your machine?
      Yes! For sure. I´ve already tested it before got disconnected. And I have some original cracked screens for testing as well.
      Thanks for the question!

      Comment

        #4
        Re: 820-01598 EDP cable was disconnected whist testing new screen. No image, no backl

        Check the following voltages to ground:

        PP5V_S0SW_LCD
        I2C_DISP_3V3_SDA
        I2C_DISP_3V3_SCL
        EDP_PANEL_PWR_BUF_EN


        PS: Miss RIO ! Actually got lost while walking along the beach. Then crossing through streets without a map. Ended up on the other side with rocks and crashing waves. Rented a helicopter on Sugar Loaf. Pretty sure got the tourist discount.

        Comment

          #5
          Re: 820-01598 EDP cable was disconnected whist testing new screen. No image, no backl

          Originally posted by mon2 View Post
          Check the following voltages to ground:

          PP5V_S0SW_LCD:
          I2C_DISP_3V3_SDA
          I2C_DISP_3V3_SCL
          EDP_PANEL_PWR_BUF_EN

          Hey Mon2! Thanks for your reply! Im little scared with the EDP_BKLT_PWM and EDP_BKLT_EN as they come from processor.

          Follow all measures, including the ones you asked for:

          EDP conector J8500:
          Pin4: EDP_PANEL_PWR_BUF_EN: 3.31v
          Pin6: DP_INT_HPD: 3,29v
          Pin10: TP_LCD_IRQ_L: 0v
          *Pin16: EDP_BKLT_PWM: 0v
          Pin24: I2C_BKLT_SDA: 4,80v
          Pin26: I2C_BKLT_SCL: 4,87v
          Pin28: I2C_DISP_3V3_SDA: 3,3v
          Pin30: I2C_DISP_3V3_SCL: 3,3v
          Pin34: I2C_ALS_SDA_R: 1,8v
          Pin36: I2C_ALS_SCL_R: 1,8v
          *Pin43: PPVOUT_S0_LCDBKLT: 0v
          Pin44: PP3V3_S0SW_LCD: 3,3v
          Pin45: PP5V_S0SW_LCD: 5,12v
          Pin46: PP5V_G3S_ALSCAM: 5,12v

          U8400:
          LCDBKLT_SW: 0,1v
          LCDBKLT_FB:0v
          *BKLT_EN_R: 0v
          BKLT_PWM_KEYB: 0v
          LCDBKLT_FET_DRV_R: 0v
          PP5V_S0_BKLT_A: 5,12v
          PP5V_S0_BKLT_d: 5,12v
          BKLT_SD: 12,42v
          ISNS_LCDBKLT_P: 12,6v
          ISNS_LCDBKLT_N: 12,6v
          BKLT_SENSE_OUT: 0,05v
          BKLT_SDA: 4,80v
          BKLT_SCL: 4,88v

          Im waiting for a new edp cable to arrive for testing.

          PS: Miss RIO ! Actually got lost while walking along the beach. Then crossing through streets without a map. Ended up on the other side with rocks and crashing waves. Rented a helicopter on Sugar Loaf. Pretty sure got the tourist discount.
          AAAhhh!! Rio is amazing!! And you´ve seen all from the sky! Unique experience!
          Im from São Paulo and Im moving to Ubatuba beach (north shore, close to Rio state) next month! You´re welcome to visit and stay at home!

          Comment

            #6
            Re: 820-01598 EDP cable was disconnected whist testing new screen. No image, no backl

            A sad update:
            I measured diode mode on J8500 and found the pin 1 (EDP_AUXCH_N) is shorted to GND (diode mode is 0.008 and should be~0.261).
            It is right next to Pin 43 (PPVOUT_S0_LCDBKLT) which is 50v.
            The conector, when got loose, shorted these two pins and killed the CPU...

            Am I right with this diode reading, right?

            Comment

              #7
              Re: 820-01598 EDP cable was disconnected whist testing new screen. No image, no backl

              Such a low diode mode reading will be from a short condition.

              If you are able to see any video on the external monitor then the CPU is ok but not holding my breath.

              Can you confirm it?

              Comment

                #8
                Re: 820-01598 EDP cable was disconnected whist testing new screen. No image, no backl

                Playing smoothly with sound.
                Night shift works too.

                Now I found that´s a very comum problem with liquid damage. The oxidation shorts these two pins, sending 50v directly into the CPU.
                Rossmann Talked about this several times.

                Do you know the best solution for this? Buy a board? Another mac? Try to find someone who changes de cpu?
                What you would do in situations like this?
                Thanks a lot for all advice and attention!

                Comment

                  #9
                  Re: 820-01598 EDP cable was disconnected whist testing new screen. No image, no backl

                  From the details in the thread, it does appear that the video section of the CPU is defective but yet the CPU is booting. To me, that is somewhat odd. A high transient short would have probably killed the entire CPU.

                  Double check that the connector and compression contacts are solid enough to mate with the cable. Post clear and zoomed up pics of the cable end and the mating connector.

                  If the CPU is really damaged then you need to work with a local shop that is confident enough to perform the BGA rework. We own a very high end BGA rework machine for this process but still not comfortable to replace such a complex BGA device. Have some very patient clients waiting on us to repair their submitted boards. We have now replaced 13*13mm BGA devices with success and can do this in under 5-10 minutes. Proper heating (top & bottom) and then proper alignment of the BGA balls is key. The service fee and risk factor of replacing the CPU may be cost prohibitive. Personally do not know yet if the CPU details are tied down to some encryption on the logic board.

                  Also some bad luck discussions on finding a reliable vendor the cpu replacement itself. Perhaps seek-ic can provide a reliable and working CPU. You may want to ping rewatech or Master Liu (both in Shenzhen) to confirm if the cpu can be replaced on this logic board before proceeding.

                  He did not reply to my questions about a year or so ago. We are not worthy and were unable to walk on the rice paper without leaving footprints (David Carradine / Kung Fu).

                  Safer bet may be to seek out a replacement, working board that is not icloud locked.

                  Wait on other comments but that is what I believe is your current position on this repair. With regret, these boards are extremely tiny and fragile by their design. Starting to get the handle on using tweezers under our table 4k microscope and can handle 0201 with ease but takes lots of practice. Essentially a cellphone tech made to appear as a laptop - as noted by Louis and others.

                  Comment

                    #10
                    Re: 820-01598 EDP cable was disconnected whist testing new screen. No image, no backl

                    Thanks for all explanation Mon2! Tomorrow the new EDP cable arrives so I will teste it and send pics.

                    I give me some hope... Technicians Ive asked for help told me that the problem is this shorted area of the CPU caused by a leak of the backlight tension to the neighbor line.
                    Dont you think that the diode mode in that line directly to the cpu showing zero confirms a blown area of it?
                    But if you have some insight let me know please. Ill apreciate.

                    Thanks a lot

                    Comment

                      #11
                      Re: 820-01598 EDP cable was disconnected whist testing new screen. No image, no backl

                      Yes that does sound logical. Be sure the check is without the LCD connected to rule out the display as a fault. Be sure the pin being measured is not shorting to ground at the connector level. After these checks, the video driver pin on the cpu is only to blame. Just weird that a segment of the CPU is defective while the rest works. Like a wounded component. Perhaps consider to sell the logic board under this condition, it works only with the external HDMI connection.

                      Comment

                        #12
                        Re: 820-01598 EDP cable was disconnected whist testing new screen. No image, no backl

                        Originally posted by mon2 View Post
                        If you are able to see any video on the external monitor then the CPU is ok but not holding my breath.
                        No, damaged CPU is damaged.
                        OpenBoardView — https://github.com/OpenBoardView/OpenBoardView

                        Comment

                          #13
                          Originally posted by Dancauac View Post
                          MBP2019 A2159 Board 820-01598

                          H

                          But what scare me are these two signals that come from the processor and its 0v both:
                          EDP_BKLT_PWM and EDP_BKLT_EN

                          Any ideas? Very apreciated the attention and help.
                          Dear., Did you ever get this logic board 820-01598-A board working.. As I have the same problem as you had previously, NO BACKLIGHT & No ENABLE signal to turn ON U8400 (Backlight Driver chip). According to the schematics, ENABLE signal is directly generated from the CPU. Asking All, is there any other way round to get this voltage out of the CPU or by applying voltage to the enable pin & turning this chip on ???

                          Comment

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