Default [Q] Need help with sony l28t

My sony xperia l28t will not turn on. when i plug in a charger or usb the led will come on flash a black screen. then go off and repeat. nothing i have tried will work. i do not want to send it in or repair. ive tried everything ive been told someone please help. also ive been trying to use the sony companion but i cant keep the phone charged or on for more than a second.