Joel_L

Hi,

I mostly fly on 6M and am setting up one of my planes to fly with my 12Z using 2.4GHz for the fist time. I am using a 6008HS in an electric jet. What I notice is that when I first turn on the receiver ( TX is already on and transmitting, and the RX has been linked to the TX ) is that the servos go off center and jitter. They will do that until I move the sticks, then all is fine. I'm using a Jeti optically isolated speed control, CC 10A BEC, and HiTec HS85 servos. The receiver is not in the HS mode. I notice slightly less jitter when using a receiver battery pack and not the BEC though the problem is still there. Any thoughts as to why this happens?

Thanks

Joel

DaddySam

My Feedback: (9)

I have had some jitter with a few Hitec servos, just as you describe. If you can, try with some other servos and see if that is the issue.

Joel_L

Thanks, still seems odd. Another thing I noticed, if I don't move the sticks, I can move the servo arm like the servo is not being driven. Once I move it just a bit, it jumps into place and works normally from there. I have heard of issues with HiTec and the 6008HS that doesn't seem to be a problem with the 617FS. I might try one of those.

Joel

Joel_L

Hi,

If anyone is interested, I looked at the signal driving the servos on both an 617FS and 6008HS.

The 617FS

servo pulse rate is 62Hz wich is similar to what servos have gotten for a long time
The rise time of the pulse is 330 nS

For the 6008HS in normal mode

servo pulse rate is 71Hz, a little faster than expected

The rise time is 18nS, could be an issue depending on what the receiver in the servo amp looks like

Both of these could cause issues for some older design servos

I also look at what the 6008HS looked like in HS mode,

servo pulse rate 142Hz ( 2x the the rate of normal )

The rise time was the same at 18nS

So even though the 6008HS has a " normal " mode, it is still a little fast. I also tried an experiment where I slowed down the edge of the 6008HS. The old HS81( it is not an HS85 as I said in the original post ) servo was much happier. Still buzzed when things were turned on but settled down on its own.

So in the end, the 6008HS is a little fast even in the normal mode for some older servos.

FYI

Joel

Joel_L

BTW, everything works perfectly with the 617FS, so that receiver stays in the plane with the old servos ( not easily changed, glued into a foam jet ).

DaddySam

My Feedback: (9)

FWIW, I use lots of different types of servos, mostly Futaba and Hitec, from S148's to digitals, micro to 1/4 scale. The only servos I had do this were the HS-81 servos, which had previously been installed as landing gear door servos. I had thought that they had been somehow damaged by that use, but now I think it is the rx issue you're talking about. Thanks for doing that analysis. I don't have the technical expertise or equipment to do such a test.
Thanks again,
Sam

Silent-AV8R

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To be accurate, this is not an "issue" with the receiver. It is an issue with how some non-Futaba brand servos work. Futaba makes certain that their products all play well together and that means in general they work with most servos. But they cannot guarantee that every servo made will work flawlessly. They can only do that for their own products.