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820-3437, Pulsing SMC_PM_G2_EN

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  • 820-3437, Pulsing SMC_PM_G2_EN

    I'm working on a pesky 820-3437 that had light liquid damage near the SMC. Replaced the nasty resistors/caps (isolated to the 3v42 areas near top of SMC), and got green light, but no fan. Tracked backwards and found that SMC_PM_G2_EN is pulsing quickly at low voltage (flipping from low-voltage to OL on multimeter quickly). My SMC_ONOFF_L is present (3.4v) and steady, but since SMC_PM_G2_EN was pulsing, I replaced the SMC, but no change. Still pulsing. I replaced U7501 and Q7520 just to make sure it wasn't causing issues, and no change--still pulsing SMC_PM_G2_EN.

    I also have fluctuating/pulsing readings for rails further down, but it all starts back at SMC_PM_G2_EN.

    Not sure how to proceed; any ideas? Thanks!

  • #2
    PPBUS stable at 12.6?

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    • #3
      Hey Duke, ppbus is stable at 8.6v, yes. No shorts on 3v42 or pbus.

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      • #4
        Must be corrosion somewhere else too. Check all rails for shorts, also check the usual U1950 and around U6100 and clock chip.

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