For 36 bucks delivered halfway around the planet, you can get a remarkable pile of gadgetry:
With a bit of persuasion, it can become a 3D printer controller based on a RepRap RAMPS 1.4 shield or serve as a generic stepper / servo motor driver with three honkin’ MOSFET power switches, two thermistor inputs, a variety of I/O bits from the Arduino Mega PCB, and a monochrome LCD with a knob.
The persuasion includes un-bending various header pins:
Correcting bowlegged pin strips:
And clipping offending pins:
The interference between the bottom of the RAMPS power connector pin and the top of the Arduino Mega coaxial power jack seems baked right into the original PCB layout, which is puzzling. If you don’t trim the pins, this is as close as the boards will get:
Well, of course, you could just jam all those headers together and bend the RAMPS PCB.
The bent pin near the Reset button connects to the
PS_ON output used to enable ATX-style power supplies. You connect the supply’s
5V_SBY always-on output to the
VCC pin, which powers the Mega and most of the logic, but not the stepper motor outputs or the heaters.
To make that work, remove D1 from the board where it’s snuggled along the header strip:
D2, next to the fuse near the bottom of the picture, provides reverse-polarity protection for the RAMPS board.
The servo motor power comes from the
5V pin. If you don’t need the
PS_ON output and
5V_SBY input, then jumper the
5V pins together. Otherwise, you could solder-blob those pins on the bottom of the board, which means the servos are always powered.
Configuring the latest 1.1.x version of Marlin should be straightforward …