Screen not working (PC works fine)

Hi,

I will try to explain the situation:

A few weeks ago, sometimes when I turned on the PC, the screen would not display image, after a minute, it would (the rest of the computer worked perfectly, if I connected it to an external monitor, you could use it with no trouble). After a couple of days, those times the problem occurred, it would not fix by itself, so I had to reset the computer and hope it would work (sometimes it did).

Then, a few days ago, the problem became permanent. Again, with an external monitor, there would be no problem.

Troubleshooting I tried is:

1. Remove the battery, let it rest for 5 minutes, drain the remaining energy by pressing the start button for 60 seconds (not connected to the power nor any peripherals). Then, plugging it to the ac power (still no battery) and turn it on. After this, screen displayed image again and lead me to a menu which let me "Continue" or "Go to configuration". I selected to "Continue" but lost image again and had to restart, but this time, image was completely gone again. I tried it several times but with no result.
2. After step 1, I started the computer by pressing shitf, f8 and the power button. Like the first time in the last step, I had image again, and could access to that menu, this time selecting the configuration option, which led me to the BIOS. I reset everything to default and saved and exit. Once again, when computer restarted, no image. If I tried it again, I would not have results.
3. Remove SSD.
4. Unplug keyboard.
5. Clean the ventilator.

Given RAM is sodded, there is no way to reconnect it. Is there any solution to this? It looks like a software problem to me, because if it were hardware related it would not start working depending in the start up option.

Really thank you