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Old Dec 05, 2012, 09:45 AM
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More Flights = Less Crashing
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United States, WI, Beloit
Joined Nov 2012
5,147 Posts
Pull out a digital voltmeter if you have one, and start checking feeds
to the individual servos. When they have no load (no blades to put
tension on them) they should all be at the same supply
voltage. If one is lower than the others, even by just a little, it is drawing
too much current, and is probably defective.

Of course, all your servos need to be the same for this to have any
meaning, and you should temporarily remove the servo horns.
You don't need a $300 meter for this, a $30 Radio Shack special
will do just fine.

Keep in mind, we are looking for voltage drop... the difference will
be very small, possibly as little as 0.1 volts. But more than likely it
will be around 0.3 volts or more.

Check the feed as close to the servo as you can. Sharpen your meter
probes to a needle point, and just poke right through the insulation of
the servo lead.

Be careful not to short them (on my servos, the positive and ground
wires are right next to each other).

A better way to check would be to use an old servo extension cable,
cut it, and put an amp meter in series.
This way you could monitor current draw directly, even under load.

If I remember correctly, most servo spec sheets include maximum current
draw figures.

I gotta get some work done, be back on later.

Good luck!


To be honest, I think minbari has already figured it out. If the problem only
shows up under load, it makes perfect sense. Many servos freak out when they
can't go to the position you instruct, and that will happen if they do not have
enough torque for the application.

But it does not explain the ESC getting hot on the bench with no load.
If the ESC gets hot with the servo horns removed, I would suspect a
faulty servo or ESC.
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Last edited by Steve_; Dec 05, 2012 at 10:31 AM.
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