I finally got time to assemble my flybarless 450 trad heli, I swear sometimes Hobbyking is slower then monkey spit rolling uphill.  And I bought the Assembled APM2 with out GPS back in June, it arrived July 10th.  

  I hooked up everything per the wiki and the discussion here.  Installed the correct firmware for Trad Heli. and calibrated my radio.  I pulled the main rotor, tail blades and started testing and all I got was throttle with no servo movement.  I checked my Throttle Pitch curve 50 50 50,  So I adjusted to 0 25 50 75 100 on both throttle and pitch.  Still nothing from the servos.  I pulled the APM and added JP1 hooked it all back up and still nothing.  I charged up the little 1 cell battery that I use for radio setup,  applied 4.2v to the servo rail on the APM with jumper 1 removed and there i got servo movement.  I don't have a working multimeter at home so I was unable to check voltages.  

I am using a 80 amp Turnigy Super Brain for my ESC, Overkill I know but it has so many options that even the options have options.  It is governed with data logging and a hefty BEC BEC: 5V/4A (Switching BEC, supports above 4 digital servos).  That provided exactly 5.0 volts.  I performed the mechanical setup with out the APM installed and all 4 servos are good and move properly without the APM installed.

I have the blades set  for 0* pitch at 50% swash throw and perfectly level.  


I am using 3 x Digital Solar Servo D220 for my swash, and 1 Digital Solar Servo D221 for the tail rotor.


Is there a separate step for digital servos?   Is my APM defective? 

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Just reread through the Wiki, and Digital servos are not only supported but recommended. 


     So I think what's happening is that the servos aren't moving because you're not providing power to the output servo rail.  Is that correct?  It's best to keep the power going to the servos (i.e. the rear servo rail) and the power used by the APM's CPU and radio separate.  I fear the servos will add a lot of noise if you join the jumper to make the servo rail and internal power on the same circuit.

And just in the interest of completeness since this thread is relevant:

On anything other than a 450, I really recommend using a servo power breakout board of some kind.  The circuit traces on the APM are NOT designed with big digital servo loads in mind!  You will quite possible burn out a trace and your servos will be dead in-flight.  Not cool.

Thanks guys,  I am going to build this tonight and it should solve my power problem.   Since it is just a 450 I am going to use the ESC BEC with a Y wire to split power between the RX and APM and the servo's.  But on a larger heli it could have its own BEC.   


The problem with just using a Y wire is that the voltage drops caused by the servos moving around will affect the main APM...maybe it'll be ok...but i had very bad luck with power problem until i switched to a separate castle creations pro bec with two separate outputs.

I STRONGLY concur with Randy here. I fly a TREX 450 Pro V2 3GX. I was feeding the 6V from its BEC into a $25 5V switching regulator, and it STILL browned out on me, causing two crashes before I wised up, and hooked the regulator directly to the battery.

The best BEC is still highly unlikely to be able to provide clean enough power to the APM on the same curcuit as that hungry tail servo. It's TOTALLY worth the extra weight to get an additional switching regulator.

If you decide to stick with the BEC running both the servos and the APM, before you fly it, flick the sticks a few times to induce as much movement as possible, especially in the tail servo. If the controls freeze, that's what you can expect in the air.

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