RAMPS power issues. (no replies)

Hi, I am having power issues with my RAMPS board and I am not very seasoned in troubleshooting circuitry. I have looked around the net and this forum but was not finding much in terms of how to generally go about testing what may be wrong with it.

I have tested the Mega and it works fine, I can even connect pronterface to the printer and get accurate temps as long as the 12v power supply is off. As soon as I turn it on, I lose the connection. With the power on there is no way to connect and move axes but the fans get power and the stepper drivers have a normal voltage at the pots. This makes me think it is power supply related (the PSU itself or the power supply circuitry on the RAMPS board) so I have tested that there is still 12v coming from the PSU and nothing on the board looks burnt but beyond that I am not sure where to start.

I was wondering if anyone could give me some pointers as to where to go poking my multimeter. Could it be a fuse? How do I test that? That sort of thing or even links to other guides if you have them. Any help is appreciated.

EDIT: Adding things I have found so i can keep them in one place.

- [forums.reprap.org] - Easily troubleshooting MOSFETs!