Back lighted screen but black, works on external video

Bruce Chapman you do not have an inverter per se. You have a backlight circuit on your motherboard. Your model uses an LED screen LCD inverter flex cable that you want to take a look at. Also, in a darkened room and with the computer on and having the OS on the desktop etc. shine a flashlight at an angle and see if you can make out some silhouette's on the screen. That will give you the definite answer that it is your backlight. Download the service manual for your computer from here If your cables are all okay and properly seated, check the motherboard for obvious damaged components. You will need to get the make and model number for your motherboard to see if any schematics are available should it become necessary to look at some board level repair like the backlight driver etc. It might be beneficial if you post some pictures of your motherboard etc. with your question. It will allow us to see what you see. Use this guide Adding images to an existing question for that