Question details:

I am having a problem with my n6600. When I switch on,it works properly for some time then it does slowly become white screen and turn off power by itself. sometime it will turn off and reboot by itself. but when during phone conversation never turn off power no matter how long the conversation is. and never turn off as well when no sim card insert. i have check the battery, no problem. i have done full format (press the 3 buttons&on button) so many times, still the same.

Answer:

Try to reformat your phone by performing a Deep Reset ( press *#7370#) .

If you still can't solve the problem it could be a hardware problem. Take your phone to a repair shop.