LCD Backlight Turns off after 1/2 Seconds from boot/wake.

Hello guys, I have a loyal PowerBook G4 used daily until 2012 when it was replaced with a MacBook Pro. Now, I use it sparingly, and plus its a nice addition to my Apple collection. A month ago, the backlight stopped functioning, and I eventually ordered a new inverter board and replaced it myself. Now, the problem is, whenever I boot the machine or wake it from sleep, the backlight only stays on for about two seconds before the backlight goes off. Any reasons why this might be? I don't think the CCFL bulbs are broken, as the display is bright (and was before the failure) and isn't flickering as it would with failed bulbs.