Display black. Start chime works. Does not connect to external monitor

Hi

The display of my old workhorse is pitch black. It was dim 2 days ago and I could see a few things but now it has gone completely black. I tried connecting to an external monitor using VGA display but it does not connect. Someone suggested I clean the RAMs pins with a soft tissue which I did but that didn’t fix things. My universities tech support suggested that I replace the LCD display but why wouldn’t it connect to an external monitor even if the LCD is bust. What could be wrong?

Thanks,

Abhishek