It's not the first time I've seen that happen. It sounds like the hard drive might have died. If so, it's probably either a firmware or electrical fault with the drive. The Seagate Barracuda 7200.11 drives are infamous for their sudden deaths due to buggy firmware for example.
I would be weary of replacing the PCB if the drive has indeed died. Some models of hard drives will not accept replacement PCBs, even when they come from the exact model and have the same firmware. You may need to research this first to see if doing this is effective before you try it.