Strange electrical behaviour with Ramps 1.4 (1 reply)

As this is my first post, hello to everybody!

A few weeks ago I purchased a full P3steel kit controlled with Ramps 1.4. I assembled it, connect it to my laptop and everything was working fine.
One day I had the idea of controlling my 3D printer from a raspberry pi. I opened printrun and connected to Arduino correctly, but as soon as I plugged in the 12v power supply the raspberry reboot and the screen was completely dark. The HDMI driver was fried and I assumed it was because of the cheap HDMI-VGA converter I used.
I abandoned the RasPi idea and continued to print with my laptop without further problem until today that I tried to connect the 3D printer to an old laptop running Ubuntu. Same thing happened, open Printrun, connect to Arduino, but as soon as the 12v power supply was turned on...
At least this time I didn´t fry the laptop, but instead the following Arduino USB component was burnt


I guess I´m having some kind of shotrcircuit that makes overcurrent to kill some components, but I dont get why with my laptop everything works fine, but when I use any other device I have those problems...
Any idea? Where should I look for the fault?

Thank you in advance guys!