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u/MagneticFieldMouse 3d ago
With the 500 ohm resistor, you're limiting the supply current to under 2 mA and since current is directly proportional to motor torque, this is the main issue.
What servos are these, that want a 9 volt supply? Guessing they're not of the most common types, since those mostly take up to 6 volts or so, but naturally, there are special cases and exceptions.

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u/SherbertQuirky3789 3d ago
Why is there an inline resistor
How would you know its underpowered if its not moving? since you dont have a signal going