see the desktop only using a flashlight.

Hi all. I'm having a problem with the display on my Black 2007 Macbook Core 2 Duo. It doesn't flicker, but has gotten dimmer over time. I can now see the desktop only using a flashlight. Up to about 10 days ago I could see the desktop on 2 out of 3 boots, but then it would go black whenever I tried to do anything (open apps, etc.). I could see the desktop with a flashlight here, too.

Now it just boots to the dimmed desktop.

It works okay though. I have booted from external disk and I can also connect the Macbook to an external display, which works perfectly.

As it's the black model, I've found it harder to find the whole display at reasonable cost. Obviously better if I could just change the inverter, if that's the problem. Do you think it's the inverter? Or the bulb in the LCD? Thanks.