Best procedure for logic board water damage

You obviously took this to an idiot's repair shop where all they can do is swap boards because they can't use their brain! I am sorry for your experience - but you did a very good thing in running far far away! That was step one! Now onto step two; let's see if we can fix this board. :-)

Just copying and pasting this part from another post I made today.

Take board out and use toothbrush, a $1 baking tray from corner store deli, and 99% alcohol from the pharmacy. 91% will do if they don't have 99%. Brush GENTLY in circles. GENTLY.

Then put it in an oven at 220f for a few hours.

THIS IS NOT TO REFLOW SOLDER!!!!! That is a myth and fixes nothing. We are just trying to remove all remaining remnants of water. Alcohol displaces water and is a good cleaning agent, so immersing the board in alcohol to do the brush cleaning is important.

After the cleaning, into the oven for a few hours. Preferably an oven you never plan on cooking in again. Then try to turn it on after letting it cool off for fifteen minutes or so.

Obviously remove CPU heatsink and thermal paste before doing this so you don't get a bunch of thermal paste under the other components. Dry napkin is fine for this.

If it turns on great. If it does not turn on, measure voltage on PPBUS_G3H on F7040 should be 12.6v, measure for PP3V42_G3H on pin 2 of L6995 should be 3.42v, measure for PP5V_S5 on C7273 should be 5v, measure for PP5V_S3 on C7291 should be 5v.

From what you have posted, I am guessing your laptop has an 820-3115 board. Please confirm by looking around the fan area on the motherboard for small letters. If this is the case, please find yourself a boardview and a schematic for this motherboard. I cannot do this for you as these documents are illegal to distribute or possess, so some hunting is required. I hope someday to live in a better world where distributing documentation used to repair out of warranty products that the manufacturer gives you the middle finger on is not illegal, we'll see how it goes since that senate lobbying from last month, but I'm not holding my breath yet. Either way.......