I recently disassembled my dell xps l501x to change a fan and clean the insides. Having put it all back together, there is nothing happening to the screen when I turn it on. Also nothing when connected via HDMI calbe to a monitor.
Hi, what I can suggest, is disassemble the laptop again, look if any cable is not connected like it should. If nothing happen, with just the main board, an external monitor and adapter, look if it will boot with the power button.