I managed to get an as-is PowerBook 140 for $35 shipped, seller reported it dead, but with my 3a PowerBook adapter it does power on and boot from the hard drive. The only issue it has is a very dark screen that brightness and contrast adjustment does not affect much.

The lights are good, and for a second or two after power on, everything lights up properly but a second before the happy Mac it goes dim. At the right angle, you can see what it is displaying.

Is this a cap issue, screen issue, or cable issue?