Dell 5110 No display

Hello

 

I just received a new motherboard for my Dell N5110.

 

However I appear to be having some issues. The computer will power up but the screen remains black.

 

When I press the start button it sounds as though it is starting up but it doesn't boot properly and it goes quiet after a few seconds. The screen stays completely black. The three lights on the keyboard do light up in a sequence.

They light in the following sequence:
Left
Middle
Right
Middle
Left (Stays On)
Middle (Stays On)
Right (Stays On)
They all stay on for a second together and then all turn off completely.

The left and right lights on the front left of the laptop are also both on constantly.

Once the computer is on, when I press on switch the computer turns off instantly without any shutdown process.

 

Troubleshooting:

 

Verified no physical damage to parts

Display screen is also new

Pressing F8 or F12 during start produces no results

Removed power from the laptop

Removed cables

Removed batter

Held power button for 90 seconds

Let go power

Battery back in

Power plugged back in

Restarted device

No change

Tested with External monitor

No display on external monitor

Swapped ram

No change

Disassembled machine cleaned parts with compress air and reassembled

No change

LCD Display recently replaced was working

new motherboard as mentioned.

Any ideas?