820-02841 - Keyboard and shutdown issues after liquid damage

[Zebulon]

I'm hoping to find some help with my A2779 14" MacBook Pro 2023 M2 Pro. Board 820-02841. I purchased the MacBook from eBay and the keyboard was badly damaged. The seller just said that the keyboard melted and the keys were falling off, the keys didn't work and trying to use an external keyboard the MacBook would just shut down during an attempted setup. I took a bit of a gamble with this one lol. Looks like a coffee was spilt into the keyboard and they tried to use a heat gun to dry it out or something and melted all the keys. Anyway, I purchased a new keyboard and backlight from moblilesentrix and very carefully stripped down the MacBook, removing the old keyboard and backlight. Cleaned the chassis up like new, installed and new keyboard and backlight, before anything else, tested the logic board in the chassis. The same problem as it was doing before the keyboard replacement. The MacBook booted up, no internal keyboard function and using an external Apple wired Keyboard I was able to try to login, but as soon as I selected English and next, the MacBook shut down. I was able to DFU restore using another MacBook, then get through account setup in safe mode, but after that, same thing would happen after restart (Safe mode or not). It also shut down in Safari in Options. Removing the logic board again, I started to have a close look under the microscope and found several components that were corroded in two areas. The keyboard expanders UT101 and UT102 I had replaced with brand new ones with the same part number from MoblieSentrix and any bad resistors, caps or pads were replaced with same value components, then I had to run a few jumper wires where a pad was corroded away, to components where they should have been connected and checked continuity to the front and back of the board to make sure everything was connected the way it should be. Everything looked good and checking any voltages I could think of confirmed it seemed to be ok. After putting the board back into the chassis, it was still the same. It did not recognize the new keyboard, although the backlight worked. I removed the board again and checked everything again, I noticed that under UT102 the board view showed several resistors and caps that were missing, but not marked as no stuff although the pads looked like they might never have had anything on them. RT123, RT124, RT111 and at least one more were not there. I could see in the schematic that it seemed they should be populated, so I replaced all missing components with the correct value parts, put the board back into the chassis and the keyboard worked. Only problems left were that no caps lock LED working and once again, entering my user name then trying to login, the MacBook shuts down. I hate to say this happens when I try to login, because it also shuts down it I boot into options and try to go to an actual website, like Apple's website. At this point I'm kind of lost, so any guidance would be very much appreciated. Long message I know, but I am trying to be as detailed as possible in case it helps. Hopefully I didn't forget anything.

 

[2informaticos]

"no caps lock LED working"
You should follow KBD_CAP_CATHODE trace; driven by UT105.

Seems that machine restarts only when more CPU cores are engaged.
So you may have a problem with CPU itself.

I recommend to inspect all I/V sensor circuitries, from pages 59-64.