Arduino Fried 2 times same testing station

Hello everyone i have a question.

At school i am having a project about 3D printing. For this we building an extruder that can print solder. I bought an arduino mega 2580 & an ramps 1.4 motherboard. At school and at home i tested a lot on the manually controlled power supply an it works al just fine. But suddenly on a specific controlled power supply the power supply was actinf weard, just giving 3Volt and 2 A while it should gave 12V. After trying again at the same testikg station my arduino couldnt find my com anymore. So i just bought a new one and started testing again. Still no problems at home and 2 other different testing stations. After all other testing spots were taken by other students we went to the same where we fried last time. The exact same thinf happend! Now is my question how is this possible? Could it be something in the powersupply? Pls help me!

Greets

Ooh and also my 8825 stepper driver was getting hot without even using it?.

Hi.

Is this an entirely different question from this one (click !) ?

A power supply set to 12 volts, dropping down to 12 volts and 2 amperes means the current is limited to either the settable limit or to a built in limit (which would be 2 A).
It's a different supply, but the same problem from your other thread.

Remove any shields or external hardware from your Arduino, and try to power it again.
If the supply still acts the same, your Arduino board has a short.
If not, add hardware one by one and try again between each step.
Might help you find the culprit.

Oh, and 2 A current just for an Arduino is way too high.
But your stepper and driver will probably be happy to take that.
Add an extruder and a hot plate to it, and 2 A will be not nearly enough to keep them happy.

When asking about this next time, please add a picture clearly showing your setup (it's not too easy to make a single picture to show that, and uploading may be tricky too).

Arduino is about learning software, but also about hardware, bridging the gap which has always been between the two of them.
I'm not sure what this school project of yours is about, but learning both is the way to go to my opinion.