thinkpad 390x

[brobinsin]

I havea thinlpad 390x and the screen has gone blank!  I can still see a gray 
glow but nothing more.  I have hooked up another moniter and it works fine with 
the laptop.
My question is, does it sound like the video card went bad or the screen is 
bad.  I will be replacing the part myself so I would like to narrow it down 
before I start spending on parts
Thanks, Bill