MacBook Air 820-3437B ALL_SYS_PWRGD Missing

[ACS-Repair]

I have this MacBook Air 820-3437-B that came back several months after cleaning up some corrosion around the ALL_SYS_PWRGD area. Last time this was all that was missing and it required a couple of jumpers to restore the signal.
This time the computer will not come to S0 state. ALL_SYS_PWRGD is missing at U1950, and so is PP3V3_S0, and so PM_PCH_SYS_PWROK. PM_SLP_S4_L is also at 0v. I've looked this board over carefully and I believe that I have found and corrected all of the corrosion.
It begins to be a chicken and egg when trying to follow the loops for these signals. It's hard to say which one is affecting the other. I'm sure there is a priority list somewhere.

This is what I have:
PPBUS_G3H = 8.6v
PP3V42_G3H = 3.42v
PP3V3_S5 = 3.3v

SMC_RESET_L = 3.4v
PM_SLP_S3_L 0 0v
PM_SLP_S4_L = 0v
PP1V05_S0 = 0v
P1V8S_S3 = 0v
P5VS4RS3_EN - 0v
P1V05_S0 - 0v
PP1V2_S3 - 0v
PP3V3_S0 - 0v
PP1V5_S0 - 0v
PP5V_S0 - 0V

At the PCH, I have the following:
PCH_SUSACK_L = 3.3v
PM_SYSRST_L = 0v
PM_PCH_SYS_PWROK = 0v
PM_PCH_PWROK = 0v
PM_RSMRST_L = 3.3v
PM_PWRBTN_L = 3.4v
SMC_ADAPTER_EN = 3.4
PM_BATLOW_L = 3.3

I would appreciate it if someone could show me where to start.

[mon2]

Re: MacBook Air 820-3437B ALL_SYS_PWRGD Missing

https://www.it-tech.com.au/mac-q-a/pm-slp-s4-l-timing/

[ACS-Repair]

Re: MacBook Air 820-3437B ALL_SYS_PWRGD Missing

Perfect, thank you!! I'll let you know how I make out.

[ACS-Repair]

Re: MacBook Air 820-3437B ALL_SYS_PWRGD Missing

So, I checked the 11 signals from the list in the link and found this...

1. PPVRTC_G3H 3.3v (3.3v)
2. RTC_RESET_L 3.3v (3.3v)
3. PCH_SRTCRST_L 3.3v (3.3v)
4. PCH_INTVRMEN_L 2.84v (3.3v)
5. PCH_DSWVRMEN_L 2.83v (3.3v)
6. SYSCLK_CLK32K_RTCX1 32kHz (32kHz)
7. PP3V3_S5 3.3v (3.3v)
8. PM_DSW_PWRGD 3.4v (3.3v)
9. PP3V3_SUS 3.3v (3.3v)
10. PM_BATLOW_L 3.3v (3.3v)
11. PM_RSMRST_L 3.3v (3.3v)
+1. PM_PWRBTN_L 3.3v (3.3v)

PPVRTC_G3H 3.3V (3.3v)

According to this checklist I should have PM_SLP_S4_L to enable my main voltage rails and ALL_SYS_PWRGD. unfortunately this is not the case. The only deviation is that PCH_INTVRMEN_L and PCH_DSWVRMEN_L is lower than expected. While not correct it shouldn't make a difference.
I'll need to keep looking...

[mon2]

Re: MacBook Air 820-3437B ALL_SYS_PWRGD Missing

See if you can do a smc bypass:

https://boards.rossmanngroup.com/thr...lp_s4_l.53151/

[ACS-Repair]

Re: MacBook Air 820-3437B ALL_SYS_PWRGD Missing

Thanks mon2. I did an SMC bypass and found a 1/2 second fan spin after about 4 seconds. After that, nothing. I must have another corroded trace somewhere and I'll need to look them all up (the 11 on the list) to make sure that they are getting to where they need to go.

[piernov]

Re: MacBook Air 820-3437B ALL_SYS_PWRGD Missing

https://logi.wiki/index.php/User:Pie....2C_what_do.3F

[ACS-Repair]

Re: MacBook Air 820-3437B ALL_SYS_PWRGD Missing

Thank you for that piernov, it was a big help. While I did find that all of the points in the Wiki referred to were good, it did point me to corrosion on one of the pads for C1910 (PPVRTC_G3H). I removed the capacitor, cleaned the pads, and replaced it. Doing this has made a difference because I'm now seeing pulsing voltages on PP5V4_RS3 (L7520) and PP3V3_S5 (L7560). I believe that PP3V3_S5 was solid before and PP5V4_RS3 was not present. PM_SLP_S4_L is now pulsing, where it was not present previously. Lots of EN are now pulsing... This may have been a step back so I'll need to backtrack to see why this happened.

[ACS-Repair]

Re: MacBook Air 820-3437B ALL_SYS_PWRGD Missing

It appears to be a short on the PP5V_S3 line (L7520). Not sure where that came from but I can see all of the main rails pulsing like a heartbeat. I don't remember touching anything that had to do with the 5v supply but that's the next focus.

[ACS-Repair]

Re: MacBook Air 820-3437B ALL_SYS_PWRGD Missing

So that one was on me. I inadvertantly swapped the DC-IN board and had a 2012 one connected, which is no good. So I'm back to where I was. Changing the capacitor hasn't made any difference but it needed to be done.