Dark spots on screen - Powerbook 180

[tonata]

Hi,

I have an old PowerBook 180.
After 10 minutes of use dark spots start to appear on the screen in the corners. First on the left and then on the right.
Please see photo below:

It is dark, but still kind of visible (like inverted color).
What is it? How can I fix it?

 

[Doq]

Tunnel vision.

It's a common problem on the early active matrix PowerBooks. As far as I know, there is no known fix other than a full replacement; though temporary solutions have been discussed and documented. [1] [2] [3]