terminal – Accidentally Uninstalled “AndroidSystem” Black Screen After Splash Image

A good friend hit uninstall on AndroidSystem icon (looks like a fan belt wrapped around a larger and a smaller circular object. AndroidSystem is the name of the icon). Since then, the tablet (a JP5s media device running jellybean) will show splash logo then go black.

Connecting to the tablet via USB in charge mode I cannot get root user. adb shell su returns nothing, but the cursor drops to next line and stays there. I have to hit control c to return to the shell prompt.

The troublesome tablet is rooted, USB debugging was enabled prior to the mistaken uninstallation. How do I get the root prompt to maybe do a factory reset by adb? The am and pm are not running.