Is there a chip at location U12 on PCB? If not, then a PCB swap probably won't work. If U12 does have an 8-pin flash memory IC, then this chip needs to be transferred to your replacement board. It stores unique, drive specific "adaptive" data.
I am looking to do the same with my Western Digital 1TB externall hard drive. My husband tried to use the power cord for my laptop (19 volt) with it (12V). The blue light does still flash (but dimly) when you plug it in but the computer does not recognize the drive at all and the light does not stop flashing.
Does yours do this? I hope you'll let us know if you find a card and it works. I'm looking for someone that has the exact same unit to buy.
jljteacher: if you're really lucky, the over-voltage may only have damaged the circuit of the external case, and not the HDD itself inside. Have you considered opening the case, removing the HDD and connecting it normally to a computer as an internal drive to see if it can be used?
The quick answer is that there is usually an easy DIY repair that should cost you nothing.
The usual fault is a shorted 12V TVS diode at location D4 on the PCB. The simple solution is to cut it out with flush cutters. However, before taking any drastic action, obtain a digital multimeter and take some measurements.
Set your multimeter on the 200 ohms range and measure the resistances of both components. Also measure D3 and R67.
R64 and R67 should measure close to 0 ohms. If either is open, then bridge it with a wire link or blob of solder. If either D4 or D3 measures close to 0 ohms, then it is shorted, in which case cut it out with flush cutters. The drive will work OK without it, but it will no longer have overvoltage protection on the affected supply. Be absolutely sure your PSU is OK.
If, for continued protection, you wish to replace the diode, then a 5V TVS diode can be substituted with an SMAJ5.0A, and a 12V diode with an SMBJ12A. They can be ordered from Farnell, Mouser, Digikey.
If you need help identifying the components, upload a detailed photo or scan of the component side of the PCB.