A hard drive is a system comprising mechanical, electronic, and magnetic functionality. When writing, the hard drive translates electronic signals into magnetic impulses which are stored as chains of magnetic values (either 0‘s or 1’s). When reading, the ‘translation’ process is reversed.
The printed circuit board (also known as ‘the PCB’ or ‘the controller’) provides power to the hard drive motor and provides all of the functionality that allows the hard drive to effectively manage the magnetic electronic translation process.
Any overvoltage to the hard drive controller will usually result in the controller failing immediately. Depending on the design of the circuit and the severity of the overvoltage, different on-board components may be affected.
In most modern hard drives, the controller contains information about the hard drive that is specific to the internal conditions of that particular hard drive, with the result that a direct replacement of the controller taken from a similar model hard drive will not work for modern hard drives. For data recovery purposes therefore, it is essential that the original controller card is fitted to the hard drive submitted for data recovery.
A controller issue is usually resolved by finding an exact match ‘donor’ hard drive, and removing the controller from it. The specific parameters of the damaged drive controller need to be extracted and installed onto the ‘donor’ controller, following which the hard drive should respond for data extraction.
In extreme cases, the pre-amplifier on the head assembly inside the drive may also become damaged, depending on the severity of the overcurrent, and the point in the circuit at which it is arrested.
While the original hard drive might be returned in working condition, it is not reliable enough for re-use. Recovered data is usually returned on an external hard drive.