Here’s a helpful, practical guide for using a Hitachi HDD repair tool (often referring to Hitachi Drive Fitness Test (DFT) or tools for HGST hard drives).
Best for: "Magnetic reversal" (pseudo-repair). This tool claims to reverse magnetic decay. While scientifically debated, it is very effective at creating a temporary stable state to copy data off a dying Hitachi drive. It does not physically "repair" the drive but remaps sectors. hitachi hdd repair tool