Modern WD, Seagate, Hitachi, and Maxtor drives store unique, drive specific, "adaptive" information on the PCB. This information must be transferred to the replacement PCB. Sometimes you can be lucky with a straight swap if the tolerances are close. I've seen this happen in WD's case, but never for Seagate.
Samsung drives, OTOH, seem to be affected by two schools of thought. I witnessed a thread at HDD Guru where one experienced data recovery professional insisted that he always needed to transfer the adaptives, whereas his colleagues seemed to be saying that a straight board swap should work. I myself have seen user reports that fall in both camps. That is, some Samsung users have reported that a straight swap worked for them, whereas others have needed to move the serial flash memory chip.
BTW, I'm not involved in data recovery. I'm just an interested observer.
What is the problem with the original PCB? Sometimes there is an easy DIY fix.