APM output problem

I found one of my motors is always beeping ( the one connected to ch4 output, I did ESC and radio input calibration).

Then I measure the voltage of ch4 and chs 1,2,3 with transmitter off.

I found the voltage of ch4 is 1.7 volt lower than ch1,2,3. Is that normal? what may be the problem?

Thank you in advance.


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  • Did you try swapping Ch4 to another motor/esc combination to see of the problem persists?  It may just be a bad ESC, as well.

  • You need an oscilloscope to really see what comes out of the ports.

    There are many freeware 'scope programs that utilizes the sound card in your computer/laptop , and it is more than fast enough to display the type of pulses used in a typical RC system, like the Quad.

    You don't need a fancy 'scope probe either, just wire a 10K resistor in series with a 100nF cap, put that into an old pen, solder a sharpened paper clip to the end.

    Not perfect, but good enough :-)

  • 3D Robotics

    You can't analyze PWM output with a voltage meter--it's a square wave. You need a logic analyzer.


    If you've got a dead channel, you probably have a soldering error, so double check that.


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