septillion:
The HD 1800A is indeed a very tiny cute servoSo you're probably fine if you add a decent capacitor across the power supply and/or decouple the Arduino power.
More force = more current
Big position change = servo tries to move as fast as possible = more currentAt start up you probably don't know where it is aka Murphy tells you it's far away.
:D. Sorry I don't know that much about electronics. Why should I use capacitor, to protect the system from sudden current changes? BTW now I noticed, doesn't the converter already have a capacitor?