Fn with ^ key? Why? The Display Toggle-Over key is the F8 key.
Fn key plus UP Arrow key is to increase the Brightness.
You hold the Fn key down, and tap once on the F8 key.
(Of course there are at least 3 display options available;
A) Laptop internal monitor ONLY.
B) Laptop internal monitor AND external display device.
C) External display device ONLY.
You may have to hold down on the Fn key again, and tap once more on the F8 key)
You switched LCD screens with a working one, and it works OK.
Reason is you also switched the screen Inverter, too. Correct?http://www.ebay.com/itm/New-LCD-Inverter-Board-for-Dell-Vostro-1000-1500-Series-US-/280987325828?pt=US_Laptop_Screens_LCD_Panels&hash=item416c265584
The screen Inverter is mounted to an area at the bottom of the LCD screen, and behind the Display Bezel,http://www.dell.com/support/Manuals/us/en/19/Product/vostro-1500
Click on - Service Manual (1817 KB)
It's a PDF file. The computer you are using now has Adobe Reader on it, which uses PDF files.
After you click on Service Manual, it may take up to 30 seconds, before the first page comes up.
Click on Display.
An LCD screen does Not produce light,http://solutions.3m.com/wps/portal/3M/en_US/NA_Optical/Systems/BehindTheScenes/Optics101/
(Click on the monitor image)
It needs an additional light source.
A Backlight is the additional light source.
A Backlight can be a CCFL, (Or two of them); Or a series of LED's.
(Light Emitting Diode)
The Dell Vostro 1500 series of Notebook PC's, uses a single CCFL for a Backlight.
A CCFL is a Cold Cathode Fluorescent Lamp.
Similar to Fluorescent lighting used in homes, and businesses, but on a MUCH smaller scale.
Average thickness is -> 2mm. That is a little larger than 1/16th of an Inch.
Average length is almost as long, as the LCD screen is in height.http://www.laptoprepair101.com/laptop/2007/12/09/replace-laptop-backlight-ccfl-lamp/
View the last 8 photos.
It is just like Fluorescent lighting used in homes, and businesses also, because it has MERCURY vapor inside.
A screen Inverter is used to convert the power, (Electricity), from the laptop, for the LCD screen, and Backlight.
(NOTE* Does NOT apply to laptops that use LED backlighting.
There is NO screen Inverter used)
90 PERCENT OF THE TIME the fault is a bad screen Inverter.
Me? I would buy a screen Inverter, due to the low cost, and ease of accessing to replace, and replace it, and use the old LCD screen.
[ You did check Video Cable connections -> PHYSICALLY, (Try to plug in tighter), on the Video Cable motherboard side connection, LCD screen connection, and screen Inverter connection; correct?]
For additional questions, or to have me clarify anything I have stated above; please post in a Comment.