820-00138-A w/liquid damage, magsafe responds but no power?

[Hardwood T/S]

Liquid damage pretty extensively on the I/O board, but the main logic board was mostly untouched--only slight corrosion around U7330, nothing on backside.
Cleaned her up, no change in magsafe (goes green, then amber), fans do not whir. All main power rails are there, PP5V_S0 and PP3V3_S0 are virtually not there, at .001 or 0.0mv. ALL_SYS_PWRGOOD is also missing, as you could guess, 0.0v.
Diode mode shows .286v for 3v3_S0, .388v for 5V_S0, so no shorts on those lines I think. Not sure where they are created, that'd be my next path.
Would Q8131 be suspect? I'm getting a healthy 3.3/3.4v on CHGR_VFRQ but nothing coming out of pin 1, PM_SLP_S3_R_L. I think that because U8180, the 'S0 enable' chip, has a healthy 3.3v on pin 5, but absolutely nothing on the other pins, including PM_SLP_S3_BUF_L.

 

[2informaticos]

Post SMC_ADAPTER_EN, PM_BATLOW_L, S5_PWRGD, PM_DSW_PWRGD, PCH_DSWVRMEN, PM_SLP_SUS_L, 3V3_SUS.
Also post exact voltage for PPBUS_G3H.

Are you using original 85W Magsafe 2 charger?
Try to start in SMC bypass mode.

 

[Hardwood T/S]

3.388 - SMC_ADAPTER_EN
3.347 - PM_BATLOW_L
3.383 - S5_PWRGD
3.417 - PM_DSW_PWRGD
3.229 - PCH_DSWVRMEN
3.349 - PM_SLP_SUS_L
3.351 - 3V3_SUS

12.57 - PPBUS_G3H, you think this one is a little low? Know it's supposed to be 12.8 but didn't seem too far off.
Using OG charger, not a knockoff. I'll report back with SMC bypass.

edit - no luck with SMC bypass.

 

[2informaticos]

MLB should start without RIO board connected.

Trigger SMC_ONOFF_L signal and check for any reaction at PM_PWRBTN_L.
Also check if any of PM_SLP_Sx_L signals react; one pulse at least.
Monitor ALL_SYS_PWRGD too...

 

[Hardwood T/S]

PM_PWRBTN_L responds--reoccurring pulses as long as SMC_ONOFF_L is bridged.
PM_SLP_S5_L responds--one pulse when bridging. I'm assuming the others do too.
ALL_SYS_PWRGD response, same as PM_SLP_SX_L--one pulse when bridging. What does this mean... )

 

[2informaticos]

Then you must get pulse at the big coils too; maybe not for CPU.
Check if any coil has no reaction at all.
Look at U1950 for corrosion.
See if pins 7 & 3 react too.
SYSCLK_CLK25M_SB tries to appear?

 

[Hardwood T/S]

U1950 looks fine, pins 7 & 3 along with SYSCLK_CLK25M_SB pulse with bridging SMC_ONOFF_L.
All the coils devoid of signals to begin with pulse when bridging except for one--L3095. You can see if I'm missing any, I tested these:
L7520
L7430
L7870
L7310/20/30

L7130, 7560 and L7630 all have signals before bridging, w/7130 having 12.57 and 7560 3.3. L7630 has a signal, but it's a very weak 2.5mv, probably a short on PP1V05_S0? Not sure.
edit - diode mode shows .090v on L7630, definitely sounds like a short right? Maybe not, other boards test around .07v diode mode there...

 

[JohnB8812]

Liquid near U7330 is no bueno this sounds like a dead CPU..

 

[Hardwood T/S]

Don't say that John if that was the case, wouldn't the CPU_PHASE coils not be pulsing when I bridge SMC_ONOFF_L? Also all the main power rails for ISNS are alive and well.

edit - if it's important info, when plugging in the charger PP5V_S0 and 3V3_S0 aren't immediately at 0.0v, they rapidly descend from a relatively small voltage and settle at 0.0v.

 

[2informaticos]

SYSCLK_CLK25M_SB should be check with o-scope, or frequency meter; there must be 25MHz oscillation.

L7630 must also pulse with all other coils, when SMC_ONOFF_L is triggered.

Try new BIOS file.