[Ti] G4 Grey Screen - replace motherboard or screen?

[maf291 at nyu.edu]

Hey all--

I have a G4 Titanium 667 mhz where the screen started to show jumpy,  
moving static, all horizontal lines that would fuzz in and out, like  
fuzzy reception on a TV, and now just boots to a clean grey, no  
apple, no spinning no nothing.

Connecting to external monitor confirms computer still seems to be  
functioning normally.

There is no visible damage to the screen or hinges as I have been  
very careful with them, and actually replaced the screen & hinges  
after it broke.

Wondering if people think it's the motherboard that's damaged? or the  
video card?

all advice much appreciated thank you!

m