Grey screen w/lines - Inspiron 15-3521

Hi,

I replaced the screen on my laptop with a new one. I watched how-to videos so am positive I did it correctly. However, the new screen displays a grey screen with lines. Only once, upon repeated off/on tries did it displayed correctly but once I tilted the screen it went back to lines.

I've Googled and done these tests:

1. Re-checked my screen connections 3X. There is only one 40-pin connector to the screen. It doesn't look to be damaged. Note my old screen was cracked and did not display anything so switching back to test will not help. Also, I am positive it is the correct screen for my laptop.

2. Installed Dell System Detect but when I clicked on icon in task tray, nothing happens. But when I click on Dell Support, it recognizes my laptop.

3. Ran Dell self-diagnosis and it only showed SMART Short Self Test - Failed WHD16-28O. Every other test passed. From what I read, that is a drive issue and not screen display related.

4. Laptop LCD Built-in Self Test (pressing D key & power button and Pre-Boost System Assessment). I could not try either because the laptop screen does not display.

5. If I press lightly in the right bottom corner of the screen, I can make the lines config to other lines. The screen will not display but it does change the non-configuration. Pressing on the edge of any other part of the screen will not make this happen.

6. Checked the Graphics adapter driver and switched to an older version because I read in other posts that  when they upgraded to Windows 8.1 they had similar problems with their screen. After switching driver version back to older version, their screen displayed again. Mine did not.

7. All the available Windows updates are installed.

Please note that when I connect an external monitor, via HDMI, the second screen will display as normal. The laptop and its functions will work using an external projected screen. It is how I am currently using my laptop.

Any information you can provide if this is an hardware, software or screen issue is greatly appreciated. If the screen is bad, I will need to return it quickly before return policy expires. Thank you.