If the screen has an LED backlight, yes.  If it has a CCFL backlight, no - though changing the bulb is a difficult procedure.

Looks like it was available both ways - check your system's Original Configuration by service tag (support.dell.com) or your invoice to see which you have.

So do you know if Vostro 1520 laptop LCD screen it is with CCFL light or LED? Thanks

Thanks one more question then I found out I have a LED backlit LCD screen therefore

1) Is it correct that Even if my screen in not cracked or broken I need to order screen which comes with LEC backlight built in.

2) Does the LED back light inverter different than CCFL back light inverter?

3) Does the LED backlight screen comes with inverter board also?

1.  Given that you've mentioned nothing about the symptoms, it's impossible to say.

2.  LED backlit screens don't use inverters.

3.  See 2.

I am sorry I did not mention that my Vostro 1520 laptop screen is completely blank-black. I connected to external monitor and the laptop otherwise seems to work fine. So I am assuming my LCD screen LED lamp is blown. Therefore I want to find out if the LCD screen comes with built in LEDs or can I jut buy LED module separately because the screen itself is in one piece. Thanks

If your system has an LED backlight, and it's that backlight which has failed, the screen must be replaced.  The LED assembly is internal to the screen and cannot be replaced separately.

Have you checked the cable that runs between the display and screen?

Yes I see there are 2 cables. 1 ) Ribbon cable 2) A cable that goes from screen to inverter board below the screen.

Is it possible that this LCD screen with LED may be OK but this inverter board may be bad?

If you have an inverter, you do not have an LED backlight.  You must have a conventional CCFL backlight if there's an inverter board.  Yes, it's possible the inverter is bad but the bulb is OK.

If it's being listed as an inverter, it's not specified correctly.  LEDs use converters - not inverters.

If that's the board you have now, it's the right one.  If it's different, it's not - different model screens use different converter boards, and they're not interchangeable (if you have an LG screen, you can't use an converter from a Samsung, for example).

1) Is there a way to isolate if the problem is with this converter board or LCD LED backlit screen?

2) The LCD screen is Samsung

3) Or based on the symptoms there could be all together a 3rd issue?

I am assuming the board output to LCD screen is 10 Volt DC. Is there a schematic available to see which points the voltage should be measured?

Make sure the board is getting power (use a meter to test the cable). If it is, then there's a good chance the converter is bad.  If it's not getting power the problem is with the mainboard.

No, there are no schematics.  My guess would be you'd see 5V input, but it could be higher.  If you're seeing 10V at the output, it sounds like the converter is OK.