if ye do is change your PSVita Brick
it remains black except Home button
waiting battery pack empty (not mandatory)
(try several times) Security mode > used Charles > FW choice
example editor FW 3.60 > 33 2E 36 31 (omitting only important > 2016_0323/sd_4190a24e21086c240221cc009cde1ef2)
have forgotten what > please edit pre of