I can't get a servo to move on the servo pin headers of a RAMPS 1.4 using the standard sweep code. The RAMPS 1.4 provides four servo headers tied to pins 11, 6, 5, & 4 each with power and ground (three pin header). I need help from someone familiar with this board. I can blink pin 11 on the first servo port so I know I have the right pin. When I tie a LED between the signal and ground on the port and run the sweep code the LED glows dim as it should with PWM. Yet when I attach a servo to the port - nothing (and yes I checked polarity). I have checked the power and ground pins on the port and it has a healthy 5v. I have even connected an external power supply to the RAMPS 1.4 so I know it has plenty of power. The same servos (I have tried 5) work on other arduinos. Any ideas what I am doing wrong? The RAMPS 1.4 board should be a powerhouse since it is designed to run 3d printers.