Just to add some more info... I tried to start the diagnostics tool (holding the Fn key while powering up), and while it says that it will start it ... it turns off before running it, doing the same noises and lights.

I also tried to do the cold boot, by unplugging the charger and the battery, and pressing the power button for 50 seconds... but no luck... it still does the annoying sound and lightning drill.

I accidentally booted the computer with no screen plugged in... and it did the exactly same sound and lights!

So:

* when blinks 4 ambar, 1 white and beeps intermitently, it seems to be that there is no screen detected

* there seems to be a reason why even having a screen connected (and having output: the dell logo and the colors with the screen test) it makes the same symptom.

Since it appears the screen is OK, that would leave the mainboard as the faulty part.  Whatever impact damaged the original screen must also have done damage to the system board.

Thanks Ejn63,

It doesn't make sense for the mainboard to be faulty, as it is working with the previous part.

Is the replacement screen identical to the original one?

Did you ever fix this? I have the exact same problem after replacing the screen.

Did you ever fix this? 

I'm having the same problem