RoBo 3D (RepRap Based) Wiring Issue

I recently attempted to upgrade the RoBo 3D, which is a reprap based consumer 3d printer, to a dual head extruder, and I really screwed something up. I am using an Arduino Mega with a Ramps 1.4 and a Full Graphics Display. My issue is that when I power on, the display fickers a lot and won't show anything unless the USB is connected, and the arduino gets very hot. I am unable to move any of the axes from the display as well. I am extremely lost and any help would be appreciated.
-Mohammed Al-Rashid (CounterSkil)

Sounds like something is drawing too much power from the mega2560's 5V line. Did you add any endstops or servos?

No, could it be the ramps board?

It is well known that the 5V regulator on an Arduino Mega cannot provide enough current to drive the backlight of a graphical LCD without overheating. See #1 at [reprap.org].

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Large delta printer [miscsolutions.wordpress.com], E3D tool changer, Robotdigg SCARA printer, Crane Quad and Ormerod

Disclosure: I design Duet electronics and work on RepRapFirmware, [duet3d.com].

Quote
dc42
It is well known that the 5V regulator on an Arduino Mega cannot provide enough current to drive the backlight of a graphical LCD without overheating. See #1 at [reprap.org].

Mine has been working ok with the full graphic LCD on the mega2560, with Vcc at 12.5V when unloaded, falling to about 12.0 with the bed and heaters running. No idea how close to the ragged it edge it is though, and I'll be happier when I drop the input to the mega to 9V or so via a buck converter.

CounterSkil, what voltage are you running the ramps/mega at? The most likely explanations are either that the 5V regulator on the mega2560 has failed, the 5V load on the board has increased for some reason (making it likely that the 5V reg will fail soon if you don't reduce the load), or the mega2560 is being fed too high an input voltage causing the 5V regulator to have to dissipate more heat and leading to thermal overload.

Ok, so it appears the voltage regulator was fried. I replaced the Mega board and things seemed to work at first, but when I select the preheat pla the hotend keeps heating up even after it reaches the targeted temp. Also, whenever I plug in the usb, the contrast on the LCD gets dimmer, even if the power supply is hooked up and running.