Arduino fuse or mosfet getting hot / no display output (3 replies)

Hi folks,

I'm pretty new to the RAMPS topics, so please forgive my newbieness in some points :)

I hooked up my RAMPS shield to an Arduino Mega, powered it via USB and flashed the latest Marlin firmware (no settings made yet).
Additionally I connected a mechanical entstop (X_MIN) and the full graphics LCD.

As soon as I connect both +/- connectors (the green ones on the shield) to a 12V power supply, the fuse or mosfet (I'm not 100% sure which one it is) near the Arduino power input jack gets hot very quickly.
Also, the display lights up, but no output is given.
There is no load on the ramps (stepper drivers installed but no motors connected) except the display.

Is there a reason for the heat-up of the above named components?

Thanks in advance