I figure this is a hardware issue, possibly a bad connection, or bad video card. But before I assume that I wanted to ask you guyz advice.
On a Pavilion dv4-2160us laptop, all the lights come on, the windows welcome sound plays, and I can see the desktop if I connect external monitor. (Or I could - it worked once, but I'm having trouble maknig it happen again.) But the laptop display shows nothing. During the boot process the screen goes from all black to dimly lit black a few times. When I use the dimming/brightening keys, the black screen slightly lightens and darkens. If I use the F4 key to cycle through the external display / laptop display combo settings, it never comes on, even when set to "both" or "no external". I tried opening the upper half to all angles. I removed the battery, unplugged and held the power button for 30 secs.