820-3476 Liquid damage, no green light

[hambook]

Hi all, I have an 820-3476 on the bench that came in with quite a bit of liquid damage. Took these photos before putting the board through an ultrasonic cleaner with sweepable frequency as per Louis's videos and dried it overnight. It's now pulling 7mA from the power supply. So far I've followed power from the charger and found that power gets all the way to U7090 and PP3V42_G3H is present with 3.42v just past this chip. I checked 3 more spots of PP3V42_G3H across the board and I got 3.42v at each spot. Seeing as there isn't a magsafe light and there is PP3V42_G3H I'm a little confused of what I should check next.

 

[2informaticos]

Did you try known good DCIN board?
Check continuity between U7000 and central pin of Magsafe connector.

Post exact PPBUS_G3H voltage and SMC_RESET_L.

 

[hambook]

Did try known working board. I do have continuity between center pin and pin 5 of U7000. PPBUS_G3H is 12.28v and SMC_RESET_L is non-existent.

 

[2informaticos]

Missing SMC_RESET_L explains the symptom.

Inspect U5110 area and post its voltages.

 

[hambook]

There were a couple rusted probe points and some corrosion, used alcohol + toothbrush and worked a lot of it away and then got the following from U5110:
1) 3.4v
3) 3.4v
4) 0v
5) 0v
6) 3v
7) 3.3v
8) 0.2v

 

[2informaticos]

Post diode mode to ground at pins 5 & 8.
Probably need to change U5110.

 

[hambook]

Pin 5 is 0.487 and pin 8 is 0.575

 

[2informaticos]

Change C5101.
If still the same, change U5110.

 

[hambook]

Replaced C5101, no change. Just changed U5110 from donor board, all voltages are the same and still no green light. I tried plugging in the board after removing the old U5110 but before putting the new one on and I did get green light.

 

[2informaticos]

Pin 4 should rise above 2.1V normally.
C5101 set the correct timing for SMC_RESET_L.
Probably more corrosion on U5110 pads/traces.