Mission planner 1.3.5, APM: Copter V3.5.3, Pixhawk 2.4.8. Hexacopter configuration.
This is a similar problem to one discussed over a year ago but I see no resolution in that post https://discuss.ardupilot.org/t/two-motors-spin-at-the-same-time-when-motortest/7668
Here is my issue:
This is a brand new build. I have everything connected and just wired up the motors. I did ESC calibration all together and can ARM the machine and all the motors spin and respond to throttle.
When I attempt Motor Test I get the followtng:
1) When throttle at default 5% only motor 2 (PX output channel 1) spins independent of which motor I select to test.
2) When I up the throttle to 10% each motor responds as it should except motor 2 spins along with each. So Test Motor 1 gets 1 & 2 spinning the same speed and the same duration.
Test Motor 3 gets 2 & 3 spinning
Test Motor 2 gets just 2 spinning.
3) I swapped the output channels of PX 1 and 3 to see if the fault was in the ESC or the wiring to the motor. The result is now that the new motor connected to PX output 1 is the offending motor. I conclude the error is the output from Pixhawk.
I have removed the 5v power to the rails and the zener connected across them to make sure and nothing else is connected to the back of the PX other than RC in.
Any suggestions of how to debug this further? I am not inclined to try to fly with one motor behaving badly.