Blank screen (not black) on HPg7

[ccbirm]

Gray screen with vertical moving bands at time. External monitor is fine. Device manager claims display is working. Can I replace lid or screen and get the display back?

 

[Phillip Corcoran]

If external monitor works okay, that means the laptop's graphics processor is okay, so it must be either the screen or the inverter which need replacing. I don't know enough about them to say which of those two has failed with confidence, but from your description I'd say it's the inverter.