Was scratching my head a bit for this one so posting it here as I've seen nothing like it elsewhere. Fault presentation is 5V on both USB ports, loops from 0 to 0.1A repeatedly. No apparent shorts, and board is clean other than a corrosion spot directly under the CPU (I'm guessing from dead insect decomposing). Components affected are C8126, C8127, R2107, R2106, R2109, R2108. The worst damage was the two caps and R2107. Caps just fell off and nothing left of the pads. Pads for the resistors all looked ok so I thought how lucky is that.
So replaced all 4 resistors but the fault still persisted. Used the power sequence from the FlexBV 820-02016 Macbook Air board to check, everything is ok up to PMU_RESET_L, so went back to the area originally affected. Found R2107 not reading right (measured 0.42 in diode mode, should be 0.32). So pads just disintegrated when I took the resistor off again. I have the via visible on the top pad, but nothing on the bottom. This connects data line SPMI_NUB_MPMU_CLK_R and that goes directly to the CPU and there is nowhere else to bypass it. Not sure what else to do but wave the white flag.
So replaced all 4 resistors but the fault still persisted. Used the power sequence from the FlexBV 820-02016 Macbook Air board to check, everything is ok up to PMU_RESET_L, so went back to the area originally affected. Found R2107 not reading right (measured 0.42 in diode mode, should be 0.32). So pads just disintegrated when I took the resistor off again. I have the via visible on the top pad, but nothing on the bottom. This connects data line SPMI_NUB_MPMU_CLK_R and that goes directly to the CPU and there is nowhere else to bypass it. Not sure what else to do but wave the white flag.
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