We never repair old C2D laptops. We just go to groupon and get another if that's the machine and CPU the client wants. At this age all parts are beyond the service life and you would need a service manual (rare!) to answer the question about power supplies. All the shops I know will not accept this for repair.
I'm gonna start from the beginning. I have the option in my laptop to turn off the screen with the combination of keys FN+F5. The funny thing is the screen is never completely turned off after I press these keys. You can still see everything on the screen but it's extremely faint and barely visible. And you can see it only when the light in a room is on or in a daylight - you can't see anything if the room is completely dark. The screen is turned off completely only when I use an external monitor.
I also have an option to change the brightness of the screen with FN+Up/Down.
So here's my problem. I recently noticed that when the brightness was not set on maximum the screen was blinking in second or longer intervals (one second was brighter and the moment later was darker). Everything was OK when the brightness was at the highest level. There was no blinking at all.
Yesterday I wanted to make the screen a little less bright and when I pressed FN+Down the screen flickered which lasted about 0.2 second and "died".
The thing is I can still see everything on the screen - it looks like it has been just turned off using FN+F5. So it's not completely dead. And I can still use the laptop with the external monitor. Everything works fine beside the screen.
So here's my questions:
1. I'm pretty sure the screen ribbon/cable burned/broke. If so how can I see everything on the screen? Does that mean that the screen has two power supplies? How does it work?
2. What solutions would you suggest to solve the problem? I'm planning to open the laptop and check if maybe a loose cable is the problem. But I'd like to hear some advice first.
Looking forward to your thoughts.