HP ProBook 4440s - Screen lit but all black, no video

[emax4]

I just purchased a used HP ProBook 4440s. It was purchased with the previous owner not knowing what was wrong. I turned it on, and the screen lights up, but it's all black and doesn't display anything. I can tell when the screen is black due to no power to the laptop and when the monitor itself is on but nothing to display (like waiting for the BIOS with a flashing cursor).

I have tried both a 1 GB and a 4 GB RAM stick in the slots. HP advises to remove the battery, hold down the power for 15-20 seconds, leave the battery out but plug in the power adapter, then turn it on. I tried that but get nothing. I also hooked up a monitor using a VGA cable and an HDMI cable (different monitors), made sure I was selecting the right video input source, but still get nothing with the screen lit and no video.

I was hoping to start small and just purchase a replacement internal video cable for a few bucks on eBay, but wanted to check with the experts first regarding my next step and plan of action. Thank you!

EDIT: I should add that this has an i3-3110m CPU (3rd generation) with HD 4000 graphics built-in to the chip, not relying on a separate graphics chip on the motherboard.

 

[grana92]

Last time I had this issue was because of a faulty RAM stick, try to switch them around, test both RAM slots

 

[emax4]

I tried that with a good, known 4 GB module. I tried it in both locations. When I switched it from one to the other I removed the battery, held down the power for 20 seconds, left the battery out and plugged in the charger, then turned it on. I also tried holding down the function key and pressing the contrast keys, and they work. While it's lit up and black, I can adjust the "brightness" or contrast of the black screen.

 

[grana92]

So in other words, the display is working but it's not receiving any data from the system? Check the data cable connection, they are usually very fragile and can be a pain i the a*s to adjust them correctly (so they would fit into the socket).

 

[emax4]

So in other words, the display is working but it's not receiving any data from the system? Check the data cable connection, they are usually very fragile and can be a pain i the a*s to adjust them correctly (so they would fit into the socket).

Prior to posting this thread I had disconnected and reconnected the video cable, which is already in the stock wrapping, from the motherboard. Should the next step just be me replacing the same cable since they're cheap? On eBay they're under $15, and now that I've seen the whole cable I can try disconnecting and reattaching the cable on all ends, but am thinking it will not fix anything. What do you think?

 

[emax4]

Because I couldnt get video I assumed that perhaps the CPU was shot somehow. So I ordered another one, put it in = black screen. Prior to this I had purchased a replacement video cable and installed it, tried it = same black screen. I'm thinking there's an issue with the logic board at this point, no?