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    #1

    a1990 no image

    I HAVE A1990 BOARD 820-01814 THIS BOARD WAS NAND IC SHORT I CHANGED NAND IC NOW BOARD IS POWER ON BUT NO DISPLAY SOUND IS COMING AND CAPSLOCK IS BLINK WHEN PRESS I CHECKED WITH EXTERNAL MONITOR BUT SAME DISPLAY IS NOT COMING
    IT GOES 1.3MA THEN COME 600 TO 700 MA I CHECKED NAND COIL VOLTAGE ARE OK SOMEONE HELP
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    #2
    anybody help what should i check

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      #3
      Review the multiplexer IC @ U9850. This is a critical component that routes the display data to either the outside or the internal LCD display assembly.

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        #4
        https://logi.wiki/index.php/MacBook_NAND_List

        You can't just swap out a NAND on a T2 machine. Has to be of the same configuration and location from a donor, or re-programmed by the JC P13/P15 programmer. Additionally all of the NAND's are striped as RAID 0 by the T2 and encrypted. As the SSD also contains the T2 BridgeOS, you need to perform a DFU restore to fix all of that.

        If the NAND firmware you installed doesn't match the rest of the config, or in the right location, a DFU will fail. Others have also stated that all NAND's should be replaced after a TPS failure, don't try to re-use any of them.

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          #5
          Originally posted by reformatt View Post
          https://logi.wiki/index.php/MacBook_NAND_List

          You can't just swap out a NAND on a T2 machine. Has to be of the same configuration and location from a donor, or re-programmed by the JC P13/P15 programmer. Additionally all of the NAND's are striped as RAID 0 by the T2 and encrypted. As the SSD also contains the T2 BridgeOS, you need to perform a DFU restore to fix all of that.

          If the NAND firmware you installed doesn't match the rest of the config, or in the right location, a DFU will fail. Others have also stated that all NAND's should be replaced after a TPS failure, don't try to re-use any of them.
          i changed nand controller ic not nand only nand ic was shorted

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            #6
            Originally posted by mon2 View Post
            Review the multiplexer IC @ U9850. This is a critical component that routes the display data to either the outside or the internal LCD display assembly.
            i checked j8500 only pin 1 and 3
            diode mode
            pin 1 =460
            pin 3 =462
            and i also changed u9850 with new one but same condition

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              #7
              External display also fails?

              Remove all power. Meter in diode mode. Red meter lead to ground. Black meter lead to point to test.

              Test each pin on this mux. Low measurements may be due to a short. No power during diode mode testing.

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