non-working buuton in K750i

[JeNeI]

In 5-10 minutes after phone switch-on keyboard (7,8,9, a return key, and <) cease to work.

Flashing does not help

If to switch off phone at least on 30 mines, then to include back - and again suffices only for 5-10 minutes of normal work. Then again keys do not work

What can be? maybe phone partially hardware dead?

Hello.You can check this way : press >*<<*<* then you go to Service tests and then Keyboard ==> now press all buttons and see what happens.If not working go to a phone service.