MacBook Screen Going Dark

I have a 2008 MacBook Santa Rosa/Penryn model. My screen started to go black on the left half and within 2 to 3 seconds it would go fully dark. If I closed the lid it would standby, then upon opening, it would sometimes flicker on or stay on for a few seconds, only to go black again. Most times now it doesn't even come on, just stays black. After some research, I shined a bright light to confirm that I can still see the image of my screen with a light, so I assumed it was an inverter board/inverter cable problem. I bought the parts, did the install, and once the last screw got put in, bahhhhh problem still there, no difference. Hooking it up to an external monitor works just fine, but I still want to fix the internal display. Any suggestions? Could it be the backlight bulb in the LCD? Mac wanted 300 or so to fix it before they knew the issue, so I have only dropped 50 bucks plus free labor into it so far, so I am willing to repair more if someone can give me some advice as to how to narrow this down to the culprit.