If you are having power problems it can cause corruption problems if the drive is writing and gets stopped. Make sure your power supply is plugged into the wall and not the surge protector. That sometimes causes problems. I don’t know enough about Macs to recommend any software for help. Possibly something like this might help http://www.easeus.com/datarecoverywizard/free-data-recovery-software.htm it’s try and buy if it works.
Joe
