Answer: the client did not do the PCB board firmware transfer before swapping the PCB board.
Swapping the PCB board is a very common way and easy to fix a hard drive for data recovery purpose.
Talking about swapping the hard drive PCB board, it is very obvious to think to find an identical good hard drive donor PCB board to replace the bad one to fix the hard drive. It is so true from the outside. But it is not always true for the inside. What is the inside of a hard drive PCB board? The inside of hard drive PCB board is the firmware( BIOS) of the hard drive (not the computerís BIOS), which is the hard driveís basic input/output system. In the hard drive PCB board firmware( BIOS), there is a set of data called hard drive configuration data. This hard drive configuration data recording the detail of the hard drive disk information, which is unique for each hard drive. The original hard drive needs this unique configuration data to work. So before put the donor board to the old hard drive, we have to transfer the PCB board firmware( BIOS) from the old board to the donor board. Then the old hard drive can find its own configuration data from the donor board. At this point, with the new donor board, the old hard drive can work properly.
Hard drive PCB board BIOS transfer
The hard drive PCB board BIOS is either in one or two independent SMD memory chip on the board or integrated into the PCB board Main IC (normally the biggest square chip on the board).
Because the hard drive PCB board is damaged, we cannot work from the port of the PCB board. So we have to work on the chip directly.
If the PCB board firmware( BIOS) is in the independent chip, we can swap the memory chip to transfer the board firmware( BIOS).
If the PCB board firmware( BIOS) is integrated into the Main IC, we have to swap the Main IC.
Working on the SMD memory chip or Main IC needs professional tool and experience.
Here is an example of how to swap the Seagate hard drive PCB board and BIOS transfer.