If you have a servo and you wan`t to test it and you do not have a remote control to do that, or want a tester to test it you can try making the following schematic of servo tester. You can se is based on a 555 timer. The circuit is very simple and cheap to make and it will work just fine. I will post other schematics of servo testers. You can al
so use this circuit to test low current brushless electric motors.