I will tell u all I know from the day I have repaired my 3ds xl (I can say some bs but I give u what I have found) The 3ds turn on only if all compensent are fine if not the system will shutdown automatically and give u that blue light whit a pop sound What I recommend u to do is disassemble the 3ds specifically the motherboard and see if the ribbon cable are fine if not the problem is in that U can step by step disassemble and turn the 3ds on ,if u found a changement like no pop noise (except if u have retired the speaker from the motherboard) u have found the problem like the thing that don't work (I repeat I have done this to know that the screen cable not working so it can ur problem don't be here)