HDs in USB cases, external back ups can run way hotter. About 50% of the used drives I can repair when I pull the circuit board off. There's tiny spring loaded contacts, etc, that contact the board from the HD housing for motor power and read/write heads. The pads on the board can oxidize a bit and go 'open' stopping the drive. Carefully 'scotchbriting' these tiny pads, blowing off the debris and spot cleaning with alcohol can bring back a drive.