Got gateway w340ua laptod with a dark screen i already change the lcd and the inverter and still is dark... any sugestion...also i can used with a external monitor no problem

sir,
even if you changed the back light inverter the fault remain as same, it seems to be the back light LED is damaged carefully remove the outer frame of the panel then dis connect the LCD then remove the frame of the defuser screen , take out plug your TV, check the LEDs

I'm pretty sure they go on the screen and into the motherboard someplace.

Just look at the old wires that are already on the screen. Normally there is a connection at the top of the screen, but it's more like a cable than a wire. And at the bottom of the screen a wire that plugs into the LCD Inverter.

Now the Wireless or Wifi wires sometimes run from the screen down through the motherboard and into the wireless card. Sometimes the wireless card is on the bottom of the laptop, sometimes under the keyboard.

Also I've seen webcam wires run from the screen area.

The used inverter maybe faulty. The inverter supplies high voltage to the CCFL lamp in the LCD screen, the CCFL lamp provides the backlight.
LCD screens and Inverters are available from this WEB site.www.lcdparts.net