Randomly turns on, but mainly not.

Its 820-3115-B model.

I had sometime now upgraded to 16gb ram, ssd and it was operating as clamshell mode 90%. Battery replaced but not that good quality and so did the charger, but everything was going well for quite some time. Maybe this new charger is about a month now.

So as I was using it, it stopped suddenly. Black screen. Pressed power button, nothing. So I read and watch some videos and took the m/b out, nothing too extreme or obvious, cleaned with isopropyl alchohol, applied a new thermal paste and away it went. Installed 2 apps to check temperature and everything seemed ok. Until I put it at sleep mode and after it never woke up again. I cleaned everything again, installed one ram module, left keyboard, battery, dvd out nothing. The fan is working but nothing. Then I clean again very well and it starts, then I shut down, try to power again, nothing. The m/b at a specific area gets hot and the fan always spins, sometimes quite a lot. So I have not solved the puzzle.

I'm not experienced locating short's, but I have a multimeter and can follow instructions. No voltage supplier though.

I'm watching some videos, but I dont seem to find my issue how to address.

I would like to find the issue and have this machine keep going.

Any help appreciated !