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820 3435 no power, machine was liquid damaged, but over all the board looks to be in decant shape. I have G3 rails, I have s5 rails, missing s4. 0.00v on P5VS4RS3_EN_R, also 0.00v PM_SLP_S4_L...
Check carefully if there is power cycling on P5VS4RS3. Pluses will be very short and hard to catch on multimeter, best to use a scope. Checked all rails for shorts?
Pin 8 corroded on U1950 is also a common problem that will cause power cycling/pulsing.
Unfortunately I do not have a scope, with my fluke, it says 0v, but like you said maybe hard to catch. Pin 8 on u1950 looks great. Yes, I checked all rails for shorts.
Looks ok. Well without a scope we can only stab in the dark. Corrosion under SMC? Give it a light reflow with some flux, not full just 150C and let it cook a bit.