I have a Dell Inspiron 1521. Windows vista home basic 16-bit
Upon powering up, the screen is bright all the way up to the windows login screen. The screen does this whether the laptop is plugged in or not. when it gets to windows login, the screen goes so dark i can barely see the screen. (like 1% brightness) I have to hold it in the light just right to see it.
If I plug in an external monitor, the external monitor shows me the display just fine and occasionally, the screen on the laptop will go back to full brightness (with the external monitor plugged in).
I have checked all power settings in both windows and the catalyst control center and everything seem to be in order (at 100% brightness).
Any ideas on what's going on?
The only other thing I can think of is to backup all data and format the hard drive to hard-reset all settings but, I hope it dosen't come to that.
I've had something similar happen. there is a hot key that you can push that turns off the backlight if you can find the key combination try pressing it I'm betting your backlight is shutting off for some reason
The hot keys are the FN + UP Arrow to brighten the screen.
But as u say that the external screen works good the issue may be with the LCD Invertor...U can actually try reseating the lcd invertor once..
remove the hinge cover...then remove the screws for the keyboard , just lift the keyboard but dont unplug the connector below the keyboard...Now if look on the top right corner where the keyboard rests under that u will find the lcd invertor...just unplu and replug back again...restart teh system and check ...if the lcd still doesnt work it needs to be replaced...
check the below link to remove the hinge cover and then the keyboard...