820-00138 1 second apple logo

Today I receive a Macbook A1398, board is 820-00138. Problem start with a water spill over the keyboard.
Customer clean the board before bringing to us. Macbook turns on, you get the apple sound a few seconds later apple logo shows for a second and Macbook turns off and starts to bootloop, always showing the apple for a second. Booting presing commands for PRAM does nothing, if you start with a pendrive and alt key, MAcbook shows the drives, if you select the internal ssd the Apple shows longer, a quarter of the loading bar, then bootloop starts.If pendrive is selected loading bar goes almost 3 quarters, the bootloop.

In the inside board looks really nice, almost no dust, but I found signs of water in two places, in Q3080 and the capacitor next to it, I clean with flux and hot air, maybe I need to change 3080.
he other place is in Q6060, and C3532 both with just a little oxidation, not shorted and fans work normal.

Should I continue looking for water damage, or is most likely a EFI/BIOS problem?
 

2informaticos

Administrator
Staff member
You should be sure no corrosion remains on the board first.
Also try booting in SMC bypass mode.
Disconnect internall SSD when test USB OSX.
Try new full BIOS file, with clean ME.
Is OK to try first only clean ME on original.

Disconnect KB/TP and test USB OSX; don't worry about max fan speed in this case, is just for test.
 
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USB OSX without KB/TP boots normal. With internal SSD loads half way and turns off, but with another SSD works fine, I think problem is OSX and not the SSD, will try to fix OSX later.

With the new SSD, I reconnect everything and apple logo 1 second and bootloop. I disconnect TP and macbook boots, but KB is not recognized.
With USB KB and mouse I can log in the machine.

Also try new KB and TP and machine don't boot up, just 1 second logo and bootloop. If I only try new KB machine boot, but KB is not recognized.

I search again for corrosion, and C5125 was cleaned, one side is black and the other is normal, so water was in that part of the board at some point. Can U5110 be the problem?
 

2informaticos

Administrator
Staff member
U5110 issue will not allow machine to start.
Is OK if you get AVREF_SMC.

KB doesn't work if TP is not connected, as normal behaviour; check schematic and try to understand why not.

Try known good TP flex and inspect TP connector on the MLB.
Do not trust new chinese TP flex; try more, if first still the same.
 
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