| i think time to try using another cable
and before try this :
open ur cable and remove +3v connection (from rj45)
phone will not starts to charge if u cut this pin, maybe it can help to boot
Keyboard
1-----------12
5 – TX
6 – RX
8 – (+) 3 Volts
9 – (-) Ground
br
<= The_Gorr => |