Not a typical backlight issue

My Dell Inspiron 1150 had a problem with the display. I could barely see the screen, after initially seeing the Dell logo clearly with a new reddish pink hue to it when the computer first booted. The pinkish hue went away quickly though and I was left with a darkened display. I rebooted several times, but still the same result. Long story short, the problem was solved by replacing the LCD screen.

The new LCD screen had been working fine for a couple of weeks. However, recently when I unplug the AC adapter the screen once again fades to a faint black screen. It is only a problem after the AC adapter is unplugged. I can run off the battery and never have a problem.

Thanks!