Screen goes squiggly, then black. have been able

Best thing to try is a external monitor if one is available - if not then run the test....turn system off..as soon as u power back on hold down the FUNCTION key..wait till u see the test running on the screen before u let go of function !!! it will only take a couple of min to know .....when u see this test run just wait until it asks u if u see color bars..whether u can or cannot does not matter..we want to press N for no on the kb....next u will get the color bars if u can see them the mb is fine and u need to replace the lcd..if no bars were seen then u replace the LCD