820-00165 Board turning on, CPU VCore present but seems brain dead

overshoot

Member
Hi,

I've got that 2017 MacBook Air board which had a tiny liquid damage near U7600.
It would not turn on.

After replacing the chip, it woudn't turn on either.
Board would pulse twice and then nothing.

I've then decide to replace U1930 since it was near U7600 and got the board turning on but stuck at 0.4Amp which is not normal as this board usually draws 0.6Amp.
It seems it would even reset like the 820-3437 would do (RTC reset) but just once.
Plugging a screen would bring no picture (no voltage on the coil). On external screen, same thing.
A USB will light up.
PPVCore_S0_CPU is 1.8V.
Resistance to ground on CPU is 16ohms which seems fair enough.

I did replace the Bios with a similar 820-00165 model (same specs) but same thing. I did put back the original Bios chip for now.

Any help on which signal I should check?
Does it sound like a faulty connection between Bios and CPU?
 

JohnB8812

New member
Check all traces and components near U7600. That on off on on these is an awful symptom not one I've solved yet. I'm guessing CPU issue of some sort but best to check all that was corroded first.
 

overshoot

Member
Thanks!

I assume that U7600 and the surrounding area are fine since I am getting a nice and steady 1.05V, no?
Also, resistance to ground on that line is 240ohms which is equivalent to a known good board from 2017 (2015 usually have 160-180ohms)
 
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