Arduino atmega2560 chip overheating 3 days till project due

Hi all! So iv'e been working on a 3d printer for some time now and ive made it completely from scratch, although it has been loosely based off of the prusa i3 in terms of wiring and motors. I have a 30amp 12v power supply and which is running 5 stepper motors and a hotend, but no heated bed at the moment. I have 3 arduino megas currently, two of which (the sainsmart and genuine arduino) work, and another Chinese knockoff that has a bootloader problem that I don't know how to fix. I have a generic ramps 1.4 board that I ordered from amazon and but currently I dont have wired to anything but power. At first when I would attach my mega to the ramps board and have it draw power from the PSU through the D1 diode the 5v regulator and the atmega2560 chip would get extremely hot (to hot to touch) and I would quickly unplug everything. After that I cut out the D1 diode and powered the arduino separately through my laptop usb port. Unfortunately that did not fix the problem of the extremely hot atmega chip. I can run blink and a stress test that makes the arduino calculate prime numbers without it getting hot, but as soon as I attach it to the ramps board within ten seconds it is burning hot. I have searched both boards for any types of shorts without luck.

p.s. Strangly enough, when I attach the knockoff board it does not get hot, but it isnt usable to me either. It seems the chinese board is build slightly differently though, is this a difference of generations or iterations of the arduino boards that could cause this problem?

... could be a bad capacitor, resisitor, short, regulator or processor - either you manage to find it, or change the board

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Viktor
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Aufruf zum Projekt "Müll-freie Meere" - [reprap.org] -- Deutsche Facebook-Gruppe - [www.facebook.com]

Call for the project "garbage-free seas" - [reprap.org]

Check your mosfets really are mosfets, seen one that had 7805 in the place of mosfets

Also take a full high res picture of the ramps, both sides for us to see if there is anything obvious

So I decided to take the whole ramps board apart and put it back together piece by piece with the power on (I k ow, bad idea) and waited to see if it would get hot. I was all going well until I put the third stepper driver on. Turns out that's what was making the atmega chip so hot for some reason. Currently ordering some new ones off of amazon, hopefully this fixes the problem! Thanks for you advice though guys!