820-00281: Not turning powering up

[macRepairAmb]

This board came in with no sign of liquid damage but won't power up. Only things i've found so far is PP3V3_S0 reading 2.8 and the ssd chips are warm (not hot), but the red spot in the picture is ready about 104 degrees (F). So i ran the board through the ultrasonic just case there were some hidden corrosion, no change in temp or voltage reading of PP3V3_S0. With lifeboat board taken out, the ssd isn't warm anymore. PP5V_S0 is 5.1.

other measurements noticed in comparison to another board with other issues is LA640 and 650 are both reading 1.8ohm and on the another board i get 4ohms. Not sure if this means sometime

Any suggestions

 

[2informaticos]

"but the red spot in the picture is ready about 104 degrees (F)"
Which picture?

GPU and CPU core rails may have small differences in resistance to ground; depending of exact chip type.
But if you have exact same chips in two boards, the readings should be very close.

What is the CPU core behaviour?
Do you note a drop to 0.6V from 1V or so?

Without J9600, 3V3_S0 still low?
Post U8295 voltages.

BTW, as you get even S0 voltages, board turns on; doesn't boot is the problem.

 

[macRepairAmb]

 

[2informaticos]

That is a ground, or unconnected pad...

 

[macRepairAmb]

No activity on cpu core rails.
Without J9600, 3V3_S0 still low at 2.8

PP3V3_S0_LEFT - 0.12
PP3V3_S5 - 3.3
PM_SLP_S3_L - 3.3
P3V3S0_CAP - 1.7

Measured pin 5 of U8295 and it's shorted to ground. Searching for the source now.

 

[2informaticos]

Remove the chip and check if short disappears.
If yes, change U8295.
If not, continue to search for the culprit.

 

[macRepairAmb]

Believe I've isolated the short to U2800. It shorts out C2975 to 78. The short is also present on L2950. With L2950 pulled, pin 1 reads 1.20ohms while pin 2 which also ties back to U2800 reads 40ohms.
Before i pull this chip, any suggestion on what stencil to get for this chip and possibly where i can get it?
Can I remove this chip/disable it and the board still run, just without J3300 and if so, do you happen to know how to disable it so it's not looked at by the system?

 

[2informaticos]

Try to separate U2800 from the power rails where it generates short.
And check if the behavior changes.