no system partition - lost adb connection while updating
I got the update (with system.img) from the Google site. The problem is fixed now - so much time wasted. First I wrote an update.zip file that formatted the system partition (to fix the corruption) &amp; write out the files in system.img. That seemed to work, but my tablet would only boot to Recovery. I suspect the formatting - perhaps a boot flag was needed. In the end, I discovered that I was wrong about not being able to flash. AUGH!! I could have fixed this so easily. Once in Recovery, if I rebooted into the Bootloader, I was connected. I reflashed the system partition &amp; all is well now.

On the plus side, I learned a lot (trying to see a silver lining from so much wasted time). I know how to write flash updates that run in Recovery mode, and I know a lot more about the features of TWRP. I think I could wake up any soft-bricked device at this point. :)