Black screen on start up diognostics "help".

Here is a walk through of what I have already done. 1: noticed I only had one led light on when start I start it up. 2nd I took it to a Imac certified technician for diagnostics. 3rd: found that my rear ram banks were bad and the front two worked. 4th: found that my graphics card was bad. 5th: due to bad graphics card further diognistics could not be done. 6th: with ram in the right spot and the graphics card out I get led diognostics lights one, and two on when I start up. 7th: found a working graphics card. 8th: with new card in and all put back together I get all four lights on butt still black screen. 9th: I purchased a thunderbolt cable and hooked it up to my tv via hdmi cable, and got nothing. 10th: since I got no video on the tv I switched out the backlight board with a different one. 11th plugged everything back up and valla! I got a blue screen. Things to note:. I have a new unformatted ssd drive in place of the old one. I get chimes and everything seams to start up normally. I have reset the pram.

Question: my lcd display looks good. Have these gone bad before? I have 2 of them here and neither one works. What are my possible solutions? New question: do I kneed a start up disc to format and install the OS? If not how do I do in?