|Are you sure what you bought on eBay was NEW and not a PULL in new packaging? Contact the seller. Yeah Right!!!!!|
Check the Users Manual for the Fn/Fkey combo to toggle from LCD to External monitor.
If not the Inverter, it could be the CCFL Back light tube itself, or a broken/loose wire in the LCD bundle from MOBO to LCD. Broken wires are common in the part that goes through the Lid Hinge. If you can see the Desktop image, it's not the LCD.
Double check all connections.
There is nothing to learn from someone who already agrees with you.