Segate told me that each controller board is "married" to the HDD to which it attached, and the tracks and cylinders are unique to the controller board that is attached to it. I bought a controller board for a Segate external drive that was exactly the same model code. It did not fix the problem (clicking) and my data remains locked in the inaccessible drive! There is a data retrieval company (Crucial Data Recovery Support) which will "attempt" to recover your data (no guarantees). They charge $750 if they are successful (from 1 - 100%) and $0 if they cannot recover any data at all (0%).