Dell Inspiron 15R 5537 not starting and black screen

I have a Dell Inspiron 15R 5537 and it suddenly stopped working. When I press the power button sometimes it blinks HD led, stays on for 3 seconds (I can see in the led) and then turn off. Other times it blinks HD led and then stays on with a black screen. Other times it blinks screen as if it was trying to turn on and then goes to black screen. I tried: Clean physically RAM memory; Disconnect HD; Turn on without HD; Turn on without RAM memory; Turn on only in battery; Turn on only in AC without battery; Turn on in AC with battery; Turn on with a external monitor plugged; Turn on pressing F2, F10, F12; The notebook dont start without HD or RAM memory. The external monitor dont show anything. Plugging or unplugging HDMI cable makes no difference on notebook or TV. I can't access BIOS because my BIOS has password and it dont even show the blue box to insert password. I can't run hardware diagnostics. Yesterday I was using and the battery was gone, it turned off, then I plugged AC power and it wasnt turning back on. Today it was working fine, I've let the notebook on and then when I came back the screen was black and now I cant turn on.