No need to replace this
Ahh ok . I was assuming it was the one you had to plug serial to usb into controller board for miner to start you mentioned earlier. From https://bitcointalksearch.org/topic/m.11717444
Yea when he said serial connecting it confused me even more but he just meant usb jig. From the pics it looks like he is bypassing tx/rx but not ground. That should only have to do with networking correct me if I'm wrong. I dont see how that would have anything to do with powering on the miner. Maybe try replacing the connectors from the hash board to the control board and see if their is a problem there just to rule that out since this is unlikely to be the case. You could flash firmware have you tried flashing and starting it like normal?