The specs for the servo from: MKS Servos HV-767 Titanium Gear High Torque Digital Servo w/Aluminum Case (High Voltage) (Flybar Only) [MKS-HV767] - AMain Hobbies
states that the operating voltage is from 6-7.4V.
Since 1 of the 3 pins on the servo needs to be powered by a voltage in this range, should I just connect that pin to a separate power supply? Or is there a way to somehow increase the voltage on the arduno's 5V pin to 6V?
Servos should not normally be powered from the arduino it's self (but you can get away with it for one micro servo and a small load). So yes you need a second power supply and of course a common ground.
Mark
Typical way to power a servo.
Those are monster servos = 347-430 oz-in of torque. Standard servos provide only 44 oz-in
of torque, and normally draw on the order of 300 mA [although some people say 1-Amp].
So, you're gonna need some good sized batteries to power the monsters. As the other
guys mentioned, best to use a separate power source for the servos, and put some
filtering across the servo power buss, eg 100nF and 220-330 uF electrolytic, to cut
down on motor electrical noise from getting on the Arduino.