Water Damage a couple weeks ago, no MagSafe LED.

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MacBook Pro 13" Unibody Early 2011

Early 2011 Model: A1278 / 2.3 GHz i5 or 2.7 GHz i7 processor

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Lucas Roberts @lucasroberts

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Posted: Jun 17, 2015

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Water Damage a couple weeks ago, no MagSafe LED.

A couple of weeks ago, I left my Macbook Pro outside. I did not foresee rain coming and forgot about it. I ran an errand, and came back to my Macbook soaked. In the words of Forrest Gump, I am not a smart man.

I disconnected my battery, and put the macbook in a sealed container with dessicant. I left it for just over 72 hours and inspected to make sure it was dry (though I did not check for corrosion. Once again, not a smart man). I plugged it in and turned it on. The trackpad was crazy but other than that it was fine. After 10 minutes of use, it shut off. At that point, the MagSafe LED would not show.

The next day, I cleaned the corrosion off with a toothbrush and rubbing alcohol. The MagSafe LED still will not turn on and the Macbook will not power on or show any signs of doing so. Am I out of luck or is there something else I can try? Thanks.

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zzz @zzz30021

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zzz

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Posted: Jun 17, 2015

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You have an 820-2936 board so first step is to find a schematic and a boardview for it. Measure PP3V42_G3H voltage, then measure whether SMC_BC_ACOK is making its way to U6901, then measure for PP3V42_G3H on U6901. Also see if corrosion is near U4900 or U7000. Complete homework and we'll fix the board.

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Thanks. I will do this later tonight.

Jun 17, 2015 by Lucas Roberts

Ok, it seems there is continuity between SMC_BC_ACOK and U6901. I am not quite sure how to test for the PP3V42_G3H voltage. I am also not quite sure what you mean when you say "measure for PP3V42_G3H on U6901." I still see some corrosive residue near the components you mentioned.

Jun 18, 2015 by Lucas Roberts

PP3V42_G3H is 3.42v. If you don't get that from the number 3V42 you can get it from page 7 of the schematic where it lists voltage rails. Also, if you look at the schematic you will see PP3V42_G3H shows up on pin 5 of U6901. So, is 3.42v present on pin 5 of U6901? Is SMC_BC_ACOK present? Is it 0v, 1v, 2v, 3v, 3.3v?

I need actual voltage measurements to fix this through the internet. GO MEASURE!!!!

And obviously clean off the corrosion before plugging it in again.

Jun 18, 2015 by zzz

Ok, I just wanted to make sure I was measuring voltage correctly. Prior to cleaning off some more corrosion, I wasn't receiving anything on Pin 5 of U6901. Now I am receiving 3.45v on pin 4 and 5. Pin 1 and 2 (SMC_BC_ACOK on U6901) are both coming up at 2.35v however Pin 3 (also SMC_BC_ACOK according to boardview) is not registering at all.

EDIT: Thanks for keeping up with me thus far. I am totally new to working on electronics and still learning.

Jun 18, 2015 by Lucas Roberts

Nuh uh, this makes no sense. Pin 3 of U6901 is ground, NOT SMC_BC_ACOK!

This is a logic gate. Pin 5 of U6901 is the 3.42v power supply, and it will be passed through to pin 4 if SMC_BC_ACOK is present on pins 1 and 2.

U6900 is powered by the output of U6901. U6900 allows communication between the charger's ADAPTER_SENSE pin and the SMC via the SYS_ONEWIRE data line created by the pullup resistor R6929. But for any of this to happen, U6900 has to have 3.42v on the VCC pin.

What is the onewire circuit? https://www.youtube.com/watch?v=FLH2Ns7Z...

What is a pullup resistor and how does it create a data line? https://www.youtube.com/watch?v=iDIq43D6...

Jun 18, 2015 by zzz

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Ok, it seems there is continuity between SMC_BC_ACOK and U6901. I am not quite sure how to test for the PP3V42_G3H voltage. I am also not quite sure what you mean when you say "measure for PP3V42_G3H on U6901." I still see some corrosive residue near the components you mentioned. — Lucas Roberts
PP3V42_G3H is 3.42v. If you don't get that from the number 3V42 you can get it from page 7 of the schematic where it lists voltage rails. Also, if you look at the schematic you will see PP3V42_G3H shows up on pin 5 of U6901. So, is 3.42v present on pin 5 of U6901? Is SMC_BC_ACOK present? Is it 0v, 1v, 2v, 3v, 3.3v?

I need actual voltage measurements to fix this through the internet. GO MEASURE!!!!

And obviously clean off the corrosion before plugging it in again. — zzz
Ok, I just wanted to make sure I was measuring voltage correctly. Prior to cleaning off some more corrosion, I wasn't receiving anything on Pin 5 of U6901. Now I am receiving 3.45v on pin 4 and 5. Pin 1 and 2 (SMC_BC_ACOK on U6901) are both coming up at 2.35v however Pin 3 (also SMC_BC_ACOK according to boardview) is not registering at all.

EDIT: Thanks for keeping up with me thus far. I am totally new to working on electronics and still learning. — Lucas Roberts
Nuh uh, this makes no sense. Pin 3 of U6901 is ground, NOT SMC_BC_ACOK!

This is a logic gate. Pin 5 of U6901 is the 3.42v power supply, and it will be passed through to pin 4 if SMC_BC_ACOK is present on pins 1 and 2.

U6900 is powered by the output of U6901. U6900 allows communication between the charger's ADAPTER_SENSE pin and the SMC via the SYS_ONEWIRE data line created by the pullup resistor R6929. But for any of this to happen, U6900 has to have 3.42v on the VCC pin.

What is the onewire circuit? https://www.youtube.com/watch?v=FLH2Ns7Z...

What is a pullup resistor and how does it create a data line? https://www.youtube.com/watch?v=iDIq43D6... — zzz