HSR-5995TG Hitec robot servos not working

Hello everyone!

I am new and have a question about my hitec servo not working with my usb arduino. Here you can see I have written a sketch (my first!) to try and rotate a servo to the middle position.

int ledPin = 13;   // select the pin for the LED
void setup() {
  pinMode(ledPin, OUTPUT);  // declare the ledPin as an OUTPUT
}
void loop() {
  digitalWrite(ledPin, HIGH);  // turn the ledPin on
  delayMicroseconds(1500);
  digitalWrite(ledPin, LOW);
  delayMicroseconds(18500);
}

So after connecting my other servo (a HS-5645MG I believe) to my arduino board pin 13 and then connecting the to the onboard power pins it worked! My problem is that the same sketch with the HSR-5995TG servo makes it generate ticking noises for awhile, moving the arm like the second hand on a clock. And then sometimes then the arm moves into position but then even after it gets into position it still makes noise; a sound simmilar to the chatter of a harddrive. I am really puzzled why one because a) I have close to no experience with servos and b) because it doesn't make logical sense for one server to work and for the other to not. At any rate thanks for any light you can shed on this, it is much apreciated.

Sorry for the double post but is it possible that my servo isn't getting enough current? I think I read in another thread that the Arduino only likes to give out 40mA at 5v, were my servo needs 300mA with no load (according to the datasheet). Should I get a separate power supply?

yes, you need an external power supply, servos draw too much current.

Ok, thanks! By the way, is this a typical response from an underpowered servo?