Yesterday I tried to flash the latest firmware
Because of stupidness this was not really successful and my TAB didn't start after the flashing...
also pressing the power + volume down show's no effect.
the display turns on only when it's powered by the charger displaying 2 icons of a phone and a computer
I looked then through many forums and found at xda-developers patomas who had the problem.
Following solution worked:
1. wait until the TAB discharge (about 1 Day)
2. Start Odin and connect th tab to the computer
3. wait about 10 minutes, TAB connected to the computer
4. flash normal FW (I chose the XWJJ4)