Makes poping sound and turns off.

A fw days ago I was playing my 3ds Xl and I closed the screen then I came back my 3DS made a poping noise and shut off. I mannaged to turn the brightness down to 1 and it dosn't turn off although the top screen appears to be on full brightness. So I tore it appart and I found that if i play with the ribbon cable it will come back to the 1 brightness. You know how the 3DS XL has 3 positions well it works fine on the 1 position but the other 2 start causing the problem (by 3 positions i mean:1 the first click, 2 the second click 3 all the way back). I got the New 3DS XL and I am trying to get the old one working so I can sell it. So I will not use nintendo's repair service. (They wanted $140 to fix it). Please Help! I have looked all over the internet but nothing is helping.