820-01949 Running Slow Fast Fan ASD Software Download?

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  • Comp_Pro
    Member
    • Jun 2020
    • 33
    • USA
    #1

    820-01949 Running Slow Fast Fan ASD Software Download?

    Hello all,

    I'm trying to repair this A2251 macbook pro. Board is 820-01949. The original issue was liquid damage which all cleaned up well and the board was not heavily damaged. Unfortunately after liquid damage cleaning the computer is running extremely slow and the fan is running at full speed. Even the cursor is lagging. Because of this I can't use the built in hardware diagnostic to give me a clue as to what is happening. Does anyone know if Apple Service Diagnostic software is available for this model? Any other clues which could help me out? Seems to me there is an issue with a temperature sensor.
    Tags: None
    • reformatt
      Badcaps Legend
      • Feb 2020
      • 1445
      • Australia
      #2
      All diagnostics require Apple GSX login now. Been that way for years so you'll have to go though each sensor individually.

      What treatment did you perform BTW? Did you take any photo's of where each location was before cleaning?

      Start by checking U5850/5870 amd the I2C lines for activity, and try another trackpad as well. Liquid damage often gets under a BGA, often resulting in the power input pad getting eaten away.

        Comment

        • Comp_Pro
          Member
          • Jun 2020
          • 33
          • USA
          #3
          I ultrasonic cleaned the board. Yes I noted where the liquid damage was. Would there be thermal throttling if the trackpad was the issue? I know that will give you the fast fan spin but can't recall if I've seen that slow down the processor speed. Checked U5850 and U5870 but couldnt' find anything wrong as far as rudimentary testing, will have to haul out my O-scope to check I2C activity.

            Comment

            • mon2
              Badcaps Legend
              • Dec 2019
              • 14549
              • Canada
              #4
              Just measure the voltage to ground on the smbus / i2c lines to see if they are stuck. Post the measurements.

                Comment

                • reformatt
                  Badcaps Legend
                  • Feb 2020
                  • 1445
                  • Australia
                  #5
                  Just as a FYI, ultrasonic cleaning of these newer boards is not recommended anymore (at least this is according to Paul S, formally of Rossman repair). Skip through to about 1:41:10.

                  https://www.youtube.com/watch?v=OgOi..._channel=PaulS

                  He claims this kills the NAND's. See if you can do a DFU revive to rule them out.

                    Comment

                    • Comp_Pro
                      Member
                      • Jun 2020
                      • 33
                      • USA
                      #6
                      U5850/U5870 I2C
                      Pin 9 SCL: 0.402
                      Pin 8 SDA: 0.400

                      Thanks for the heads up on the ultrasonic, did not know that. I've actually ultrasonic quite a few of them without any problem but will probably have to stop just in case.

                      I replaced the trackpad with no results. Still clocked down and has fast fan spin. Will attempt the DFU.

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