Thanks for getting back to me.
The Energy Saver box was checked and I unchecked it. Unfortunately, it didn’t help.
Here, again, is what’s happening: I click Time Machine to back up my internal and external drives and the backup drive starts clicking and blinking. Time Machine will say something like "backing up 104 Mb of 720 GB and the backup drive clicks for a while. Sometimes it will only be 10 minutes, sometimes longer. Then the drive will spontaneously disconnect. When I unplug and re-plugin the drive, my MacBook Pro will see the disk again. Time Machine will be saying something like “Waiting to finish download” when the disk has disconnected. When I reconnect the backup disk, Time Machine will go back to saying it is backing up stuff again, but then sooner or later, the disk will disconnect again.
Here’s a more specific description of the last time I tried to get the disk to back up: I reconnected the disk and both my external drive and back up disk were quiet for about 4 minutes. Time Machine said “Preparing for Backup”. Then both disks blinked for a few seconds. Then the external drive disk fell silent and the backup disk blinked and clicked away. The external drive disk blinked a few times but mainly stayed quiet. This time, Time Machine said it was backing up X bites of 288.90 GB. Over the course of about 10 minutes, this continued. Time Machine got to the point where it said “Backing up 860 MB of 288.90 GB”. At that point, the backup disk spontaneously disconnected.
I’m suspecting that the disk is faulty. Unless you have another suggestion, I’ll try a different D-DRIVE USB. I bought 3 of them to go from my present 2 TB set up of one external disk and two backups (along with Backblaze) to the same setup with 4 TB. I am using one of the new G-DRIVES as my external disk drive (and it’s working fine). Unless you suggest something different, I’ll unbox the third D-DRIVE and see if it works with Time Machine.
Please look this over and get back to me about any new ideas to get this drive working or to unbox the third drive and try it.