HP Pavillion dv6700 problem

Since the replacement of the USB requires the removal of the display assembly, did you remember to reconnect display panel cable under the top cover on the upper left. Check to see if you inserted and seated the cable completely. Page 69 of the maintenance and service guide.

As I am not currently at home I cannot verify, but as 100% sure I connected it and 90% sure its seated properly. Not sure if this will help, but I was not getting a post so I removed ram and did get the missing ram post beeps. So if indeed the cables are are connected and seated properly I don't know what else could be wrong besides the display itself, which costs more than I am willing to spend right now. Any other ideas or troubleshooting steps will be greatly appreciated.

I would check the cable again and make certain you did not bend the display ribbon cable, they are fragile and if bent will fail. The cable itself is not expensive. I would try to connect an external monitor, which will determine if the GPU is working. Since you only disconnected the display cable, I doubt, the screen itself, the invertor or the backlight has failed.