A1707 board with PM_BATLOW_L at 0.8V (after blown cap on PPBUS_G3H)

[overshoot]

Hello,

Working on another old MacBook, an A1707, which came for, another... (drumroll please) blown capacitor on the PPBus rail.
Prior to replacing the blown capacitor, I got 20V with 80mA but no PPBUS. Found the shorted cap, replaced it, same symptom however I am now getting PPBus at 12.5V.

I'm missing now PM_SLP_S4_L and PM_BATLOW_L is sitting at 0.8V.
It's being pulled down by either the SMC, the PCH or one of the 2 Thunderbolt controller.
I have already replaced the SMC and the ISL6259.
I am afraid I am dealing with a bad PCH.

This signal comes from PP3V3_S5 through a 10k resistor which then connects to the SMC, PCH, etc...
I've cut the trace to the PCH only and the PCH side is at 0.3V while the other side remains at 3.3V, in other words, the PCH is pulling down that signal.
Anything else I can try from your experience?

 

[2informaticos]

Did you check diode mode to ground on PCH side?
Compare with good board.

Do you get 3V3_S5/SUS?

 

[overshoot]

I do have PP3V3_S5 and PP3V3_SUS yes.
Ok I'll check around the PCH in diode mode.

 

[overshoot]

I went around the PCH, measuring the nearby resistors and they all seem to have similar values to a working board.
I don't see any big differences.

Some more measurements:
PM_SYSRST_L is at 3.4V
PLT_RST_L is at 0V
PM_RSMRST_L is at 3.3V
PM_PWRBTN_L is at 3.3V
PCH_SRTCRST_L is at 3.1V
RTC_RESET_L is at 3.1V

Is there anything else I can try?

 

[2informaticos]

I mean to check diode mode to ground around PCH; on its power rails and suspected signal lines.