820-00165, liquid damaged FRU, U1930 / R1931, Spins up, no boot

Paul Daniels

Super Moderator
820-00165 supposedly replaced with a new board a couple of weeks ago. Clear signs board has seen liquid damage and was ultrasonic'd and put back in to service as it probably booted "then".

Now the unit will only green/orange light & fan spin. The fan spin runs for about 10 seconds, then stops, then starts again, and about 7~8 minutes later stops completely. LED on USB will flash once on initial power, and then when the fan spins up again after the 10 second lull point but never again.

PPBUS_G3H 8.6V, 3V42 present too. All other rails present that I've bee able to test, including CPU at 1.8V

Bubbling corrosion on the tracks for U1930 / R1931, as well as corrosion under R8152.

Problem might be that CPU_VCCST_PWRGD is being pulled down slightly to 0.98V from 1.05V, I've removed U1930 and R1800 and the slight pull down still occurs, leaving either the PCB or the CPU causing the slight pull down.

BIOS, SMC, RTC Gen, PCH HSIO Switch ( U8005 ) all checked/replaced and appear to be okay.

Feel like I'm missing something blatently obvious.
 
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Paul Daniels

Super Moderator
PLT_RESET_L is also present (3V3), starting to run out of ideas on this one. Might have to put it aside for another day ( tested the chassis with another board, all okay ).
 

Paul Daniels

Super Moderator
PPVCC_S0_CPU_PH1 is 12.6R - so it's possibly marginal, but overall I think it's time to just let this one drift away. Hard letting go.
 
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