Won't charge won't turn turn on, charger LED change intensity

Hello after 4month remaining unused (it was working last time it was powered off) my 5130 won’t charge/turn on anymore, the top right led never turns on the only thing that happen when i detach the charging cable from the tablet is that the charger (genuine DELL) LED lowers it’s intensity for 1sec than go back to normal intensity.

What i’ve tried:

-replacing main battery

-replacing micro USB power cord

-use the docking station to charge/turn it on

-deatach the CMOS battery for some mins

-keep power button pressed for over 30sec

-keep pressing power and volume/up down keys

It seems just dead… any suggestion?