820-00165 No PP5V_S4RS3


I get all power rails only up to PP5V_S4RS3. I do have 5V on pin 14 for J4800. Does this board need the keyboard/trackpad plugged in to make the rest of the rails work?
I have replaced many things so far, I don't have the complete list, but the board history is this was a parts board which did have some liquid damage.

I have replaced: U7501, L7520, U7100. Doesn't the PP5V_S4RS3 start from U7501?

Thank you!


Staff member
"I do have 5V on pin 14 for J4800"
Is not the proper point to check; 5V_S4_IPD comes from 5V_S5.

U7501 requires enable signal (P5VS4RS3_EN), to generate 5V_S4RS3.

Do you have 3V3_SUS present?
If yes, trigger SMC_ONOFF_L and check for drop pulse at PM_PWRBTN_L (at same time).


Sorry, I did test the lines (including for 5V_S5) leading up to the J4800 pin 14 which I meant to convey the proper voltage was making it that far.

I do get .15v from 3V3_SUS, which I would assume is too low. Where should I check, or what should I do next?


23/ 8.57
22/ 3.2
12/ 3.3
13/ 2.0
29/ 5.0
21/ 3.3

Earlier while troubleshooting, Q7520 got super hot where it came unsoldered, I have replaced this once already because I did have a short on it, but right now I do not have it on the board. While I had Q7520 up from the board, Q7430 also got hot (thermal cam), but is not getting hot anymore, but pin 1 is 8.57, Pin 3 builds up to .40 but then drops quickly.