Is probably not the ramps but the mega. Unplug the ramps from the mega, and put 12v into the mega dc power jack. I suspect you will still see your 2.45 volts on the 5v lines.
The cause.
The mega has a voltage regulator see top left of diagram [
arduino.cc]
The ncp1117, its a 3 pin device, 3 legs on one side and a big tab on the other. Normally just above the power socket.
These can get damaged... a common cause is shorting +5 to gnd
They are surface mount but quite large and easy to replace if you can solder.
Edited 3 time(s). Last edit at 08/24/2014 07:27AM by Dust.