Video problem. Pavilion ZE4805US laptop

Shine a flashlight on the dark screen to see if you barelysee the icons on the desktop. If so, then the LCD Inverter is bad.

Plug in an external monitor and see if the display shows up on it. It can beany kind of monitor even the old big fat crt monitors as long as it has a vgacable to connect to your computer's vga port. If so that proves yourvideo card is ok. The video will show on most systems when you rebootwithout you having to do anything. Some systems will require you to hit the FN(Function key) + F1 thru F12. Hold down the FN key then hit the correctkey for displaying on the monitor (F1 thru F12). The correct key willnormally have CRT/LCD on it or it will have the icon of a display.

If you see no icons by shinning a flash light and the external monitor works,then your screen is bad. If you see no icons by shinning the flash lightand nothing shows on the external monitor, then most likely your video card isbad.

Your laptop is probably outputting the video signal to the wrong monitor. When the screen goes black, try pressing the function key to switch the video back to the laptop screen. Refer to your laptop's manual on what key to press. Usually it is the Fn key and F4 at the same time for HP laptops.

That is either the backlight or its power supply.

This is a bit tricky as you can get it fixed under warrenty but they will likely ask you to send back the entire computer not just the monitor. It is also something that you could fix or several shops could but the repair cost really isn't much less than a new monitor. You are not stuck using an HP monitor so anything will work and you can get quite a lot bigger or better for about $120 and up. Repair cost is going to be $80-$100 so as you can see for just a few dollars more you have a new warrentied monitor.

The cable for the back light inverter board may have come off on the mother board side or on the screen side.

2) Failed inverter board.
3) Failed lamp.

Plug an ext monitor into it. If you now see desktop the monitor is faulty.

If still no go,onboard video is faulty / vid card

Try connecting another screen and change resolution & frequency level to like 60hz, then switch back to your hp monitor.

Try connecting an external monitor to the laptop, power up the monitor first then boot up the laptop. The video data will switch to the monitor automatically, check if the monitor dislays a normal image and see if the image stays on the monitor.
Also press and hold the Fn key and press the F4 key, these keys toggle the video output between the LCD screen and the video port.
Test to see if this functions correctly.
Get back to me with the results of the tests.

The easiest thing would be to check your cable for a bent or loose pin. Next put another external monitor on the laptop. The circuitry to provide video to the laptop screen and the external monitor are separate except that they share a video processor and video memory. There can be bad electronics involved.

you have an ext monitor connection which you can use another monitor or get s-video lead and connect to a tv.
use fn + f4(or f key that has little square icon printed on it)
this combination switches from laptop screen to ext screen/tv

yes, sounds like your system board is ka-put. (bad).