iPhone 3GS won't boot at all

My iPhone 3GS won't boot at all. I bought it off of ebay, and it was listed as water damaged. Only the water indicator in the dock connector was active, but the other one at that top of the phone was not active.

I took the phone apart, soaked it in alcohol, gently cleaned it with a toothbrush, and finished it off with CRC electrical contact cleaner. I even removed the logic board shielding during this procedure.

If there's a simple cable I can replace to get it working, I'd be happy to do so. The one cable coming out of the display that doesn't "click" in seems to be burned, or something like that. I've attached photos for reference.

I cleaned up the copper side of the cable, but the back side that appears to have a black dot - I can't clean that side. What cable is this, and is it causing my problems?