Dark screen but good inverter : don't replace : repair it

A case that appears to me sometimes when repairing LCD laptop screens is typical:
It can be seen in several cases :

1 / The screen is very dark but you can see your desktop with a light, and/or you hear the windows sound.
First thing to change is the inverter board, because it's cheap, easy to change and work in 80% cases.
If you already did that and your screen is still dark you 'll have to change the whole CCFL : it's a cold cathode bulb at the botom of the lcd pannel that light up the whole lcd. dismantel is not very easy because you have do open the whole LCD pannel itself, but you can find an old ccfl for few buck on ebay. look for ccfl itself, or sometimes people are selling old broken lcd screens. you just need to check the size of the tube and the connector (only seen two types in my life).

2 / If the screen is going pink at startup, you can be sure that CCFL is dying. sometimes it lights for one or two seconds then it returns black. if you push the little switch that detects if the lid is open or closed you will see the screen lighted for one more second and then it turns black. here you are in the hurry to buy a new one.

3 / The Graphical processor is defective : you can see that easyly on a laptop by plug in an external screen :
- If you can see your desktop the GPU is good. your solution is #1 or #2 or defective wire.
- If you can't see anything don't hit the pc you can test one more thing : redirect the display to the external screen :
for that you have probably a key sequence on the laptop to do it. sometimes Fn+ F5 but it depends on the brand or the laptop model. hit the sequence one or several time to switch from external to internal or both displays.

4 / Just in case you bought an HP laptop you should be aware of the DV6xxx, dv9xxx and dv2xxx nvidia GPU problems.
there are notorious cases of HP laptops with nvidia gpu's overheating.
some of people are cooking the motherboard in the over but for my own I changed three times the motherboard. just for the story it worked best with linux.
if you have one of these hp laptops there is a bios update that should preserve the GPU by increment speed of the fan, but with or without it I loose two moterboards. sorry for that.

If you need experience on these models you can contact me cause I did a lot of work on it.
Hoping to help people, don't hesitate to write comments on this article.

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