Hardwood T/S
Member
Hey! First post here, hope to be an active member of the community once I become a bit more experienced. 
2015 13" MBAir board, had some liquid damage on the I/O board and no light on magsafe even w/new I/O cable so I bought a new I/O board. No viewable liquid damage at all on main logic board.
Magsafe came on amber at first with battery plugged in, turned her around to power on--nothing. Unplugged battery, magsafe still amber. Tried removing components to see if they were causing a short, nope.
Eventually the magsafe light went out, so I decided to pull out the multimeter/schematic and start testing around normal power rails to see if something had shorted. While doing this I heard a pop on the backside of the board, flipped it around and saw small bit of smoke arise from center of the board. Couldn't tell at first what it was coming from, but eventually saw U7600 had a nice lil hole burnt on top of it near pin 12. Now magsafe light is back on, still amber, and the fan spins very intensely a few moments after being plugged in.
After double-checking and measuring all the other rails seeing if they were present, started checking the s0 rails. PP5V_s0 is there, PP3V3_s0 is not--showing 2.0mV consistently. So, this is where I'm at.
Honestly I wanted a bit of guidance and clearing up before continuing as well. Should I be measuring s0 rails right now, can I be sure the board is in an s0 state? Obviously U7600 is a problem, but would it have any affect on PP3V3_s0 (from the looks of the rails, no)? Where is PP3V3_s0 even created? and why did U7600 short so badly in the first place, how would I go about solving that?
Sorry for what may seem like many simple questions, but I would learn a lot from this experience! Thanks for reading.
edit - I forgot to mention, my PPDCIN_G3HOT and related 18.5v rails are all 15v flat. Same result with old I/O board, same result with multiple chargers. Not sure if this is a problem given all other always-present power rails are being created seemingly without problem?
2015 13" MBAir board, had some liquid damage on the I/O board and no light on magsafe even w/new I/O cable so I bought a new I/O board. No viewable liquid damage at all on main logic board.
Magsafe came on amber at first with battery plugged in, turned her around to power on--nothing. Unplugged battery, magsafe still amber. Tried removing components to see if they were causing a short, nope.
Eventually the magsafe light went out, so I decided to pull out the multimeter/schematic and start testing around normal power rails to see if something had shorted. While doing this I heard a pop on the backside of the board, flipped it around and saw small bit of smoke arise from center of the board. Couldn't tell at first what it was coming from, but eventually saw U7600 had a nice lil hole burnt on top of it near pin 12. Now magsafe light is back on, still amber, and the fan spins very intensely a few moments after being plugged in.
After double-checking and measuring all the other rails seeing if they were present, started checking the s0 rails. PP5V_s0 is there, PP3V3_s0 is not--showing 2.0mV consistently. So, this is where I'm at.
Honestly I wanted a bit of guidance and clearing up before continuing as well. Should I be measuring s0 rails right now, can I be sure the board is in an s0 state? Obviously U7600 is a problem, but would it have any affect on PP3V3_s0 (from the looks of the rails, no)? Where is PP3V3_s0 even created? and why did U7600 short so badly in the first place, how would I go about solving that?
Sorry for what may seem like many simple questions, but I would learn a lot from this experience! Thanks for reading.
edit - I forgot to mention, my PPDCIN_G3HOT and related 18.5v rails are all 15v flat. Same result with old I/O board, same result with multiple chargers. Not sure if this is a problem given all other always-present power rails are being created seemingly without problem?
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