Water damage 820-00875-A Dead board

[Hatwatt]

Hi, took the board out and will be measuring just the board with an USB-C amp meter connected to a Powerbank.

Water damaged board with a lot of corrosion around the U3900 and a little bit next to the U2890.
USB-meter shows 5V for a few seconds and then powers off and back on again. This will continue cycling.
Checked the resistors and traces next to U2890 that seem fine.

Any help where to start would be greatly appreciated.

PS. Have played around a little bit with other Macbook boards, but still a total noob and these USB-C boards are totally new and intimidating to me.

Thanks!

 

[JohnB8812]

Anyway you can upload picture of the liquid damage? I would guess corrosion elsewhere as well. U2890 for sure can cause this issue if it's bad, so I would replace it from a donor 00875. PP3v3_G3H 3.3 volts? Any signs of corrosion near U31/200?

 

[2informaticos]

If cycles, usually means board tries to start and something blocks the charger and restart.
R7020 voltage?
Any short, PPBUS_G3H or other rail?
Post some voltages around U7000, 3V3_G3H...

 

[Hatwatt]

Thanks for the replies!

The board got some very sticky liquid on the areas I mentioned and looks very clean everywhere else. And it does not seem to be cleaned before.
Photos attached.

PP5V_S5 = 0V and missing. Sorry for not understanding where it is created.
(U7650?)

No shorts atleast on these rails. Should I measure more?
(Any tips which rails are good to measure shorts or should I just measure all of the S5/S4 rails.)

PPBUS_G3H
PP5V_S5
PP3v3_G3H

Here are some voltage measurements:

R7020= 5V

Close to U7000:

PPDCIN_G3H_CHGR = 5V
PP3v3_G3H = 3.4V
CHGR_ACOK = 3.4V
SMC_RESET_L = 3.4V
SMC_RESET_R_L = 3.4V

 

[2informaticos]

Any pulse at PPBUS_G3H, at least?

 

[Hatwatt]

I did not have a 00875 donor board to get a new U2890.
So I scrubbed the corroded places with alcohol and toothbrush and reflowed the U2890.
That did the trick and I got 15V from the charger and the board is working perfectly now!

So corrosion under the U2890 was probably the culprit.

Thanks for the help John and 2informaticos! Thread can be closed.

 

[JohnB8812]

Nicely done!