I turn on dell vostro 1520 and screen is blank. Screen shows to activity at all. On status bar between keyboard and screen POWER, CAP LOCK AND + indicator lights are lit solid. The NUM LOCK indicator is lit but flashing on and off.

SOURCE: Dell Vostro 1320 num lock flashing

it may be loose RAM take out your ram and put it back in making sure it is in tight.

SOURCE: dell latitude d620 once i turn on power the power

Is the laptop really turning itself off, or is the display just not doing anything?

It sounds like it could be a problem with the nVidia GPU used on the D620.

Dell has extended the warranty on the nVidia GPUs by 1 year. Call Dell and describe the problem.

See also: Dell and nVidia GPU

SOURCE: Dell Vostro 1510 Laptop; cant get anything on the screen

Same thing happened to me.
I stumbled on this link and the solution made sense to me.
http://en.community.dell.com/dell-groups/new-to-community/f/3511/t/19323146.aspx

What I did was to nudge in the Hard drive to make sure it wasn't loose and press down slightly on the processor even though it didnt feel loose.

Worked for me. Though I'd help someone else since someone else 's post helped me.

SOURCE: my dell vostro 1500 laptop

it sounds like your ac adapter has burned out and won't charge anymore. That's very common... that's why they are so cheap on ebay. Either that or your power plug on the motherboard is cracked or loose at the motherboard (2nd most common) and last bad motherboard (don't assume this unless last resort.)

SOURCE: press power button nothing comes

Copy and paste this link into your internet browser for the service manual for your laptop.
http://support.dell.com/support/edocs/systems/vos1510/en/SM/html/trouble.htm#wp1092170
The star icon (*) means flashing LED, the bold circle means on, the circle within a circle means off.
The LED's that they are referring to are the NUM, CAPS and SCROLL.
It appears that you have a problem with your LCD. Try connecting an external monitor to your laptop. If you get a display then your LCD display panel needs to be replaced. If no display then your motherboard needs to be replaced.