Arduino over heating..still!

After using my printer for a couple months I had an Issue as to where my heated bed would start to warm up instantly upon power up and would not stop. After deducing the problem is coming from my ramps I ordered one off of amazon. Upon hook up everything seemed ok but a couple minutes after powering up extruder and heated bed (wish I would have only done one or the other but...) the larger of the poly fuses caught on fire :/ I replaced the fuse and triple checked my voltages and polarities and everything was connected properly so I powered up the printer with only incoming power connected to ramps. This caused the arduino to get very hot..too hot to touch..on the back side of where the usb connects of arduino mega 2560. Thinking I had fried my ramps I purchased another from a more reputable supplier. After installation I am STILL having an issue with my arduino getting too hot to touch, almost 2 or 3 minutes after start up. Ive seen people on instructables putting heat sinks on top of arduino between usb and dc reg. inputs but I dont feel this is a proper solution. I am at a loss and printing is still at a halt. Any info would be appreciated, thanks for reading.

It's seems to be the Arduino's voltage regulator.
Are you powering your Arduino through Ramps (D1 diode). This power is limited to 12 volts, if more you can fry voltage regulator.

A heatsink, maybe help, bit it is not the solution.

Sorry for my english.

Your arduino is fried no two ways about it.

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Welp, I am still at a loss as to why my original RAMPS fried after months of operation...but it seems I was sorely mistaken in what I thought was D1 Diode..I thought it the 2 pins located next to the Chiclet fuses and assumed "removing" diode from the circuit was achieved by removing a jumper from the pins extruding from RAMPS. Wrong ....removed the D1 Diode from underneath stepper driver and viola...back in business...now to find out why there is smoke coming from my extruder