Why my phone suddenly turned off and has to reaction.?

i have an xperia l1, days ago my phone suddenly turned off and has no reaction to any key (even power +vol up).

after connect my charger ,charge led start blinking slowly.

for the solution i try to change my battery but problem is still there.

i can’t find any other solutions or even pcb schematic to check mainboard…

is there any solution..?