Send it to the Toshiba tech service for repair. But that might be more expensive than buying a new one.
Why did you disassemble the device?
I have Toshiba MQ01UBD100 external drive 1TB , and I LOST the PCB board and I cannot find it anywhere , I tried replacement an exact PCB board and the disk powered up but not recognized .. after some search I found about ROM chip on the original board that must be swapped ..... what is the solution to this problem to use this new disk again ??