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My xperia z2 tablet would not power on. When I try to charge it (wall charger or USB) the charging red led would start indicating it gets the electricity. However at that point the Sony sign would show up and it would blink twice and start restarting.
And like this every 10 seconds.
While starting to perform hard reset, the tablet would vibrate three times and do nothing.
This is how it looks like:
https://www.youtube.com/watch?v=e-OodxRYZ30&feature=youtu.be
Hi @Papapipo,
Sorry to hear this. 
Could you try pressing the volume up (+) key and the power key together and keep them pressed down for 10 seconds when you have the charger connected and see if that helps? If that doesn't work see if you are able to perform a software repair using PC Companion.
Thanks @Christofer for looking into this!
I tried and while I am holding the power button and volume + button (plugged in wall charger) the blinking stops. Is this a good sign?
However when I stop holding the combination after 10 seconds, the blinking of the screen repeats every 3 seconds instead of previous 10 sec.
Do you have any idea what is happening and how this could be fixed?
hi @uliwooly,
the charging is not really possible, as the tablet keeps restarting every 3 seconds and the battery does not charge at all. Or should I simply let it restart like that for two hours and see what happens? Kind of afraid to burn something important.
Btw, I don't see where @Christopher suggested to charge it 2 - 3 hours, only the software repair. Am I missing something?
how about if you connect the tablet to a wall charger > press and hold power & volume up until the tablet vibrates and/or it turns off.
make sure to remove both SIM and SD cards.
@uliwooly,
I did that. Tablet vibrates three times every few seconds. As soon as I let the buttons, it starts restarting again. There is no SIM nor SD card inside.
I will try to do the software repair and see if that helps.
Hi @uliwooly, @Christofer,
PC companion repair did not help. Acctually I got stuck. This is what was happening:
I followed the intructions until the point where the window appeared informing that my battery must be 80% full. I can't charge the battery and can't really check how full it is, so I jsut tried to continue.
The PC companion could not detect the Tablet as described in Step 10.
Tried the additional help information to turn off the buit in battery. Pressing the upper volume key and power key did not make the tablet vibrate three times. My guess, the battery is simply dead.
Interesting fact: when the tablet is attached to Laptop, the red button of battery is lighed up (not sure if its charging or just indicatign a direct contact to electricity), but when the tablet connected directly to the wall charger it keeps restarting. Good thing I can post now how it looks, hier is the video:
https://youtu.be/te-DIlXwUik
Any ideas?
In that case I'm afraid that it seems like your tablet is in need of service so I suggest that you get it examined further at an authorised service center. You can contact your Local support team for information on where to find one and how to proceed from here.