Display is very dark and can barely be viewed. Brightness controls don't do anything. Any suggestions? It is a Dell latitude 505.

Function Keys 'Fn'. One is Function Brighter + and one Darker -

How do I adjust the brightness on my Dell Latitude laptop?
You can press the following keys to adjust display brightness: Press and the up-arrow key to increase brightness on the integrated display only (not on an external monitor). Press and the down-arrow key to decrease brightness on the integrated display only (not on an external monitor).

Using the Display: Dell Latitude D630/D630c User's Guide

http://www.solano.edu/technology100218/data/D630/display.htm#:~:text=You%20can%20press%20the%20following,not%20on%20an%20external%20monitor).

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Shannon Wagner.,
You can try increasing the brightness using the FN keys on your keyboard. <Fn><F11> Decreases brightness on the integrated display only (not on an external monitor). <Fn><F12> Increases brightness on the integrated display only (not on an external monitor). If needed start the computer and tap the F2 key to enter the bios. Navigate to the Video Section and you will see where to adjust brightness.
LCD Brightness This option (represented by a slider bar for On Battery and On AC) sets the panel brightness when the ambient light sensor is off. Thank You,
Dell-Jesse L

It sounds like if your screen stays lit fairly well during BIOS that is would be an issue with the Operating systems settings themselves. If you are using windows i would look for any options that may have something to do with display lightness darkness contrast anything really. Also see if you can hold the Fn key on your key board and locate a sun or light bulb with an up arrow beside it. While holding the Fn key press the light bulb or sun several times and see if that helps.

Look for a key labeled "Fn" (blue lettering) on the lower left side of the keyboard

Hold the "Fn" key and then use the Up/Down arrows to adjust brightness.

If that doesn't work, reboot your laptop and get into the BIOS. There is a screen for brightness. I don't recall how it is labeled, but it's one of the last pages as you cycle through the BIOS options.

Hold the Fn key and press the up arrow.

replace either your cold cathode screen lamp or, your inverter board in your display

CHECK THE INVERTER... THEN THE CABLE OF VGA..AND CONNECTION

there is a inverter in LCd that makes your lcd bright white shine. when it breaks down you see black screen. something happens on lcd you cant see clearly  you should go to service and need to be changed INVERTER.
pls rate

Set turn off hard disks option to NEVER in Control Panel / Power Options.
This is documented in Dell somewhere but I can't find it again.

check your power cord and make sure it's plugged in all the way, and if it is, check your brightness setting.

Usually it's the Fn key + an arrow key. Make sure the brightness is up all the way