Boots to white screen/video out works great

Hello all

So my Imac 17 inch Intel recently screen stopped working...no new software or hardware was place into it. During my troubleshooting I notice the Imac continues to works fine if use video out. I tried settings different screen resolutions, but still no luck, did notice that the screen reacts to adjusting the brightness. I have done the resetting of PRAM and SMC. I do not have the original CD's..but found a website that has the AHT file, will try to run AHT and post results, in the meantime...any suggestions would be great...thanks