While working normally with my 15 inch MBP (2006, CoreDuo) the other day, the display began to flicker and then, within about an hour, the backlight turned off. The display was still working and I could control things in the right light, but it was too dim to work seriously. I was able to hook up an external monitor with no problems and it is working normally.

I assumed the backlight itself had failed and ordered a new one from this site and replaced the display (thanks to the videos). The replacement seemed to go fine. However, when I rebooted, the new display had exactly the same problem as the old display - still no backlight, but everything else worked normally.

The backlight on the new display has flickered on for a few seconds twice: once when I was changing the automatic adjustment to ambient light settings (they are now off) and once when I hooked it up to my TV to watch a soccer game from the internet. It did not stay on for more than a second or two in either case.

Prior to the failure of the first display, I had not made any hardware changes in several months. I am still running Leopard and did not upgrade to Snow Leopard yet. The machine's software appears up to date. When I was replacing the display, the internals of the machine looked fine - none of the cables were obviously damaged, but I'm not sure that I could detect such damage.

I would appreciate some guidance on some other potential causes of my problem and/or ways to troubleshoot this issue.

Thanks.

Backlight issues are usually going to be caused by a faulty inverter board before the actual backlight goes out. So I would try a new inverter board, if that doesn't fix it, it can be either the cables coming into and out of that inverter board or worst case scenario the main logic board.