Dell Inspiron N5110

Hello to the community,

Like the tittle says I have a Dell Inspiron N5110, before all this trouble happen it used to work fine I turned off and turn it on a couple of time.  after two days the computer turn on but with an error sign saying that the OS was not found, I run the diagnostic tool that the computer has built it in, the computer pass the test so I was like well there is a software problem, but after I restart it the computer wont turn on again.  I thought probably the computer run out of battery or something so I connect the power brick and still didn't want to turn on, I took off the battery discharge the laptop by pressing the power button then I plug in the power brick and try to turn it on but no luck at all. So I tested the power brick with a multimeter and everything is working fine as it should be, so I bought a new DC power jack and give it a try.  After i received the power jack I disassemble the laptop and install the new power jack, I connect all the cables and make sure everything was connected so i don't have to disassemble the laptop again.  The computer turn on but the screen didn't turn on it was pitch black so I left the laptop like that for a couple of days and give it a try later, the computer didn't turn on again and not even as before nothing was turn on, so my best guess is that my MOBO is dead or making short.  I hope someone can verify my deduction or came with a better answer or solution for this problem.