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00165 - 2.7V on SMC RESET L

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    #1

    00165 - 2.7V on SMC RESET L

    History is "Coffee spilled on keyboard. Dim apple logo for a while now dead." There was liquid damage on backlight driver, surprise. BIOS, RTC area was also hit, pgood guy Q8150 and U1950. Also damaged was U5600 but not liquid, more voltage surge.
    I have replaced BIOS chip, U1950, U5600, R7121/2
    Currently
    3v3_s5 - 3.3v
    3v3_sus - 3.3V
    RTC G3H - 3.3V
    5v_s5 - 5.1V
    5VS4RS3 - 0v EN - 0v
    SMC_PM_G2_EN - 3.4v
    SMC_RESET_L - 2.77v

    I'm a little foggy on the exact order and dependency of SMC, PGOODs, RTC Bios.
    Tags: None
    #2
    Re: 00165 - 2.7V on SMC RESET L

    Green light on Magsafe?

    Double check SMC_RESET_L. If it is really 2.77V instead of 3.42V, check for any liquid corrosion on J6100. If that's not it, you may have an issue with R5100, U5110, U7100 or SMC.
    (Usually 2.7V is found on SMC_MANUAL_RST_L, not SMC_RESET_L.)

    Measure exact voltage on PPBUS_G3H.

    Also, SPI ROM almost never dies. The resistors and traces do. Put the original one back, or at least use the dump of the original one on the new chip.
    Last edited by piernov; 08-01-2019, 07:54 AM.
    OpenBoardView — https://github.com/OpenBoardView/OpenBoardView

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      #3
      Re: 00165 - 2.7V on SMC RESET L

      SMC_RESET_L is 3.39V
      PPBUS_G3H - 8.60V

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        #4
        Re: 00165 - 2.7V on SMC RESET L

        It's SMC MANUAL RST that's low, but isn't it normally 3.4V on a working board?

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          #5
          Re: 00165 - 2.7V on SMC RESET L

          Nothing to see there then, everything is fine. I assume green light is present.

          Missing PM_SLP_S4_L then I guess?
          Check if there's at least a pulse on in when plugging Magsafe in. (use oscilloscope if your multimeter is slow)
          Make sure PM_BATLOW_L is high.
          OpenBoardView — https://github.com/OpenBoardView/OpenBoardView

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            #6
            Re: 00165 - 2.7V on SMC RESET L

            Light on charger is present. Green at first, Amber b.c no battery.
            PM_SLP_S4_L pulses, multimeter caught it go up and back down. Missing while powered.
            PM_BATLOW_L - 3.315V

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              #7
              Re: 00165 - 2.7V on SMC RESET L

              Check if CPU VCore pulses too. If it doesn't, check for a pulse on ALL_SYS_PWRGD and PM_PCH_SYS_PWROK.

              If CPU VCore pulses, you most likely have an issue with SPI ROM, or SPI resistors and traces (or stuff on J6100).

              If CPU VCore and PM_PCH_SYS_PWROK don't pulse, but ALL_SYS_PWRGD does, you have an issue with U1950 circuit.
              OpenBoardView — https://github.com/OpenBoardView/OpenBoardView

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                #8
                Re: 00165 - 2.7V on SMC RESET L

                I measured a pulse on CPU L7310 and then when I plugged in power to measure for pulse on ALL_SYS... fan spin.

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                  #9
                  Re: 00165 - 2.7V on SMC RESET L

                  Ok it's back to not working, L7310 is definitely pulsing, I also measured a pulse (sort of) on PM_PCH_SYS_PWROK but the fan spun that time, and it looked like the rail only reached 0.116V? Going to try and get a read on ALL_SYS_PWRGD. I am one handing the probes so I don't think I've gotten a good read.

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                    #10
                    Re: 00165 - 2.7V on SMC RESET L

                    Thank you for your help, I'm sure I'll look back at your wisdom from this post in the future.
                    I must be on the right path if it's turning on while I'm probing that circuit. I will post what the problem was if I find out anything.
                    Probably about to do a little replacing (new ISL since I used a donor, lifting U1950/continuity checks, probably should change Q8150)

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                      #11
                      Re: 00165 - 2.7V on SMC RESET L

                      It was pgood, Q8150 was lifted/ one pin not connected.

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