I've got a second-hand 15" G4 with a display problem- the top 1/3 of the screen is fine but the lower 2/3 is completely black. When I bought it the display seemed fine, and shortly thereafter I started getting intermittent lines showing up when I tilted the display. Moving the display a little would usually make the lines disappear, but then the lower part just went to black. When I attach an external monitor, the display on the external monitor is fine.
I've replaced the inverter cable and the display cable already; would this be an inverter board issue?