If you like to really dig in, Google search for 3 phase brushless DC motor controller driver, and look at the Allegro and On Semiconductor (and your vendor, if you can identify) datasheets and application notes for examples of circuit operation. You will see that most of the chips require a low value external current sense resistor that determines the current limit for the high current needed to deliver startup torque. You can attempt to locate this resistor and verify it is intact, soldered well, and that the phase drive and hall effect sensors are connected well (might be good to unplug/replug the motor to controller board connections). You can also monitor the 5V and especially the 12V power to make sure they are not current limiting/folding back under the startup load, or substitute a really formidable power supply. No computer is needed, the question is whether the drive will just spin up, and most will try without any SCSI bus connection.