Mac Mini A1347 (820-5509) PM_SLP_S5_L missing

[microitech]

Hi everyone,

I've been troubleshooting a Mac Mini A1347 (820-5509) that came in for a simple thermal paste replacement, but it turned into a challenging repair. I've made some progress, but I'm stuck at a point and could really use some advice from those more experienced with this board
Worked fine for a week, then started powering on intermittently.




What I've done so far:

• Found PP3V3_G3H in short.

• Removed and replaced an AND gate (74LVC1G08) and an OR gate, which were causing issues on the line.

• Found VREG5 at 26 ohms on TPS51980. Replaced TPS51980.

• Now I have stable PP3V3_G3H and PP5V_G3H.




Current situation:

• PM_SLP_S5_L is stuck at 0V, as is PM_DSW_PWRGD.

• SMC seems operational (SMC_RESET_L is 3.3V, PM_P3V3_G3H_PG is 3.3V).

• TPS51980 isn't generating PP5V_S4_REG, likely due to no enable signal on EN2.




Looking for advice:

I'm stuck at this point and would appreciate any pointers on how to continue troubleshooting. What should I check next to get the SMC to release PM_SLP_S5_L and advance the power sequence?


Thank you in advance for taking the time to read this and for any advice

schematic:

https://drive.google.com/file/d/1ufr...ew?usp=sharing

[microitech]

UPDATE:

PP3V3_G3_RTC shorted to ground = Game Over, BAD PCH