RAMPS fried 2 MEGAs. Now only powered through USB.

I've managed to fry two MEGAs (with two different RAMPS boards in two different printers, actually, but the symptoms are identical).

The Arduino (and the LCD) can no longer be powered through the RAMPS. It only comes alive if I plug it into USB. If I use USB, it seems to behave more or less correctly (shows up as a serial port on my computer, I can upload code, I can connect with PrintRun/Pronterface and issue

Before the second one fried in this way, I did notice that the Arduino was getting pretty warm in the area between the USB connector and the coaxial power connector. The voltage regulator and the over-current protection chips live there, and I've read that a fried voltage regulator is usually the culprit, so I'm all set to order some AMS1117 5v SOT-223 chips. Do these symptoms (RAMPS power no longer powers the Arduino but USB still does) consistent with a fried voltage regulator? Or does it sound like it's something else?

A fried voltage regulator on Arduino Mega/RAMPS is a common problem. Arduino/RAMPS was never designed to drive graphical LCDs, servos, or anything else that takes more than a small amount of current from the +5V rail. See #1 at [reprap.org]. If you are building a serious 3D printer rather than a budget one, buy better electronics.

Edited 3 time(s). Last edit at 03/16/2018 03:10PM by dc42.

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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].

Definitely a dead voltage regulator

And despite our local dodgy car salesman above trying to flog his wares...

The most common cause is endstops plugged in backwards so the switch shorts +5v to gnd (also alot of people have been zip tieing the endstop board to the rods shorting the board out)

If you have a 20x4 lcd these are normally fine, but the glcds can draw to much current and can eventually kill the voltage regular.