So far, I haven't managed to find the hack for my JVC XV-N5, but I found some interesting things which could be one of the firsts steps.
Plugging and Powering from the player while holding I<< and >>I displays this : "REGION 2"
Plugging the player while holding Play and Stop, does this :
"TEST --" then displays "TEST E"
When pushing the Choice key on the remote, it displays this :
"23 56 13"
Pushing again does this :
"- - - - - - - -"
All LCDs lit
When "EXPERT" lite, pressing 3D Phonic on the remote does this :
Then pressing Subtitle does this :
Then when pressing Angle or Subtitle again we can simultaneously read :
"MJMO DE10", "MJMO DE09", "MJMO DE08"... and "MJMO DEOA", "MJMO DEOB"...
Pressing 3D Phonic again does this :
DATA 0000, then pressing Angle or Subtitle does things like "MJMO DEOD"
Pressing Menu does :
Now, pressing numbers button on the remote, changes 0000 0000 into many different codes, at this moment I think it is better not to press Enter, some wrong codes could be entered and I did not find how to enter 0000 0000 again.
When switching off and on again (without validing anything), the player keeps its keys.
Well, I hope that this small discovery will help some us to eventually figure out the hack for this player.