Take Off Stutter

[sniper101]

Hey guys. I'll try to keep it brief.

I picked up an RTR Axial Exo last weekend, stock servo went out as expected within the week. Today I put in a Hitec 7955TG, CC BEC, cut off the factory Deans plug on the ESC and soldered on a Traxxas to match my batteries, pulled red center contact from the receiver-ESC connector and tried my new Venom 3S 35C LiPo.

On the first take off, it stuttered away. Tried my older Dynamite 3S 20C, and it's doing the same heavy stuttering.

Any suggestions where to start troubleshooting? Thanks guys!

[sniper101]

Unplugged the BEC, and reconnected the power from the ESC to the receiver, now no stutter.

Thoughts?

[SINister]

Whats the voltage set to on the BEC. Factory is 5.1v which may be to low for your needs.

[afrofroggy]

Have you got a castle link to check ?

[sniper101]

I set it at 5.5V initially, then tried the factory 5.1V again.

I'll try 6.0v.

[sniper101]

I set it to 6.1v, and if there was a difference, it was small. Still stutters quite badly.

[SINister]

It should work even if the voltage is low, definitely at 6v. Could be either a bad servo/bec or a cold solder joint on the battery plug.

[sniper101]

It works fine with the BEC unplugged and the ESC powering the receiver and servo.

Assuming this means a faulty BEC somehow?

[jalans11]

I am having the exact same issue in my EXO. I called Castle today and they told me that I had a bad BEC and that I needed to go exchange it at my local shop. I will let you guys know if it fixed it tomorrow.

[Olle P]

Seems like the BEC output signal isn't smooth enough.
There should be at least a capacitor and preferably also a ferrite coil to reduce the high frequency noise.

[jalans11]

New BEC, same problem. Running the servo off of the ESC BEC. I guess we will see how long it lasts.

[sniper101]

Same thing. Just changed my BEC out for a new one, same issue is still there. Very disappointing...

Tempted to swap in the stock steering servo to see if that has any affect, and maybe the stock receiver from my SCX10 just to test.

[turbodan13]

I had the same issue, but on my Blitz. I'm running the Duratrax Element 3900kv motor/ESC combo (rebadged Castle units) on the Blitz, and added in the CC 10A BEC. Hooked up per instructions, and I had the same stuttering issue. Unplugged the BEC, reconnected the red wire for the ESC, and it was smooth running.
Now, here's the head scratcher of it all... I took the 10A BEC and wired it into my Exo, which is running a new CC Sidewinder 3900kv SCT system, and it works fine.

My only real theory, is that the Duratrax ESC's internal BEC wasn't jiving with the additional unit in the mix.