If you tried to restore your iPad, but it has been in recovery mode with black screen and has left you this error in iTunes: The iPad has been unable to be restored (Error 1604), do not worry, have a solution:
We connect our iPad to your computer and open iTunes
Restoration started again
At the time the iPad begins to restore and the screen turns black, remove the following processes (Ctrl + Alt + Del on Windows):
iPodService.exe
iTunes.exe
Return to open iTunes and restore.