lcd screen acting out? 12v problem? endstop short? IDK (3 replies)

So...a weird thing happened to me the other day, I was printing a new z axis endstop support (my endstops are the ones mounted in a pcb board, the ones with three wires.), everything is plugged in normally, then, when homing the z axis, and as soon as the endstop clicked, everything shuts down, and the printer disconnected from repetier. My first thought was that I probably plugged the wrong z endstop wires in the wrong pins, but everything was connected correctly.
Tried restarting the printer... when I plug in the ramps to the pc trough the usb port, everything lights up and works as normal, but as soon as I turn on the 12v power supply, the lcd screen kinda powers down, as if it doesn´t get enough juice, and the nema 17 motors don´t work. The funny thing is that when disconnecting the lcd screen from the ramps, everything works as usual, the motors move, the printer communicates with repetier, etc.
Reading around the forums I saw that a probable culprit could be the D1 diode, but it looks normal and it has continuity checked with a multimeter (At least I think I did correctly), other than that, I´m very limited in finding the problem due to my poor understanding of electronics.
BTW, I have a ramps 1.4 with an arduino mega 2560, an atx power supply with 18 amps on 12v.

Any help is more than welcome!!
Thanks a lot!!