OK, well, lets do this....with all EQ off, plug in all cables and turn on the external monitor. Make certain monitor is set to HDMI input.
Boot up laptop, pressing (not holding) F2 repeatedly until it beeps. Did you get a display, or did it shut down? If it shut down, then post back and we will go to next step. Are you good with opening up the machine? Did you already do that? If so, take out all of the ram, and boot. Does it still shut down?