MBP Mid 07 2.2

The screen on my MBP went black.

Trouble shooting:

- Tested hard drive on external enclosure, it's good.

- Swaped out RAM, tested good.

- Connected external display, also black.

- Reset NVRAM, heard start up sound twice, screen stayed black.

Is there any other trouble shooting I should try before deducting it's a graphics card issue?

Thanks,