XPERT SI-4501-HV servo jitter

[prokyon]

Take a look at this YouTube video - servos are 1.5 years old, around 100 flights:

XPERT SI-4501-HV jitter at center (0 min 57 sec)

Two front cyclic servos came from Gaui X5 Premium Edition combo - those are the bad ones. The rear cyclic one was replaced a few months later - that’s the good one. Servos keep jittering around center.

[prokyon]

Here's another video of a different person with the same problem:

Xpert SI-4501 jitter (0 min 41 sec)

[rfauske]

Worn/Damaged pots it looks like.

Have you tried to contact the dealer or Xpert ?

[prokyon]

The two failed servos are from Gaui X5 Premium Edition combo. I already contacted the dealer about replacing other items when the combo got to me, so I've run out of "please replace this" asks :-)

I can try contacting XPert, but these are 1.5 years old now, so way past warranty. Plus it's not like I want replacement ones anyway.

[jadams]

Sorry to hear about the issues. Have they been tested in another setup or with just a receiver and no gyro?
No servo is bulletproof and with every electronic device failure is eventually going to happen. Not saying that 100 flights is excessive tho and I would personally like to see them last longer. If you have proof of purchase I would recommend contacting a rep named Art Hughes either through Facebook or on the xpert rc Facebook page. He might be able to help resolve this issue.

Jordan.

[ryanha]

Had the same thing happen to mine (also from the X5 premium combo) after 250 flights.

Here are a couple videos.

Xpert SI-4501 jitter (0 min 41 sec)

(check out at around 30 sec)

Elevator servo jitter (1 min 16 sec)

I contacted XPert and they did a trade-in upgrade for me to the SM-5401s.

One thing to note if you are using the mini-Vbar is that there are issues with some modern brushless HV servos (including the SM-5401s). The issue is described here: http://www.vstabi.info/en/node/1422. I did not have this issue with the 4501s but I did have it with the 5401s.

--Ryan

[prokyon]

Thanks Ryan - very informative. I hope MKS HBL665 don't have this problem... those are the replacement ones I'm going with.

Receiver LiPo is arriving in the mail soon - I'm going to hook up the removed XPerts to servo tester and post vids at 8.4V.

[ryanha]

Just make sure to bench test your new servos using the procedure that mikado recommeneed. Essentially set pitch pump to 100 and pump the cyclic up and down rapidly for 60 seconds. Then check vbar logs and make sure there are no errors.

Even if this test passes there is a chance of having the mini vbar internal voltage regulator kick in during hard 3d which will show up as a brief power outage.

Ultimately I had to add a capacitor as recommended by mikado and the problem which was easy to reproduce with the new servos has gone away.

--Ryan

[prokyon]

Thanks, I'll definitely bench test.

On my 450s (also VBared), I swore in some maneuvers I was getting power outages and helis would become unresponsive for 1/10th of a second. I figured it was just the battery not keeping up with the loads and sats losing power for a split second. I didn't see any errors in the logs.

So I added a 6800mF capacitor to my X3 and I don't see any problems anymore. Perhaps the Gaui servos which I had on were also supplying reverse current.

On the X5 I'm running an OptiPower backup guard, which I'm guessing has its own capacitors, so I should unplug that when I'm doing the tests.

[ryanha]

If you run with an ultra guard that may have the same effect as adding capacitors. So if that is how you typically fly it, then I would say you could just do the bench test with the ultra guard connected. If you don't get any errors in the log, you should be good to go.

Of course, if you want to know whether the servos have the potential to cause issues then I guess you could bench test without the ultra-guard just to have that data point.

Another tip is when you do your re-maidens with the new servos start with an easy flight and do 3-4 batteries doing progressively harder and harder moves, checking the logs after each flight. Also you might want to do it pretty high up just in case it happens under load.

Also post your results if you don't mind. I am interested to see what you find.

--Ryan

[prokyon]

OK, I tested the servos using iCharger 308 Duo and running a receiver LiPo at 8.3-8.4V through J2 port. I tried pulses in the range 1170ms to 1830ms and mimicked VBar cyclic frequency of 144Hz.

The 60 degree times seem to be right to the specs. I got about 0.102s to 0.106s for all three servos, although sometimes the test would fail and other times I would get something like 0.211 seconds. Is this normal?

I tried to replicate the jittering around center - I can't. I stepped the servos with 0.5ms pulse while applying load to the servo horn with my finger - I can't seem to get them to jitter around center. Actually, even with the VBar, once they warm up a bit they don't jitter anymore.

I'd like to get someone else's opinion on this

[prokyon]

Testing XPerts without LiPo at 5V - speed test never fails (obviously the times are slower). As soon as LiPo is plugged in, even at 7.6V, half the time the test fails, and frequently the servos show 0.211 seconds or around there for travel time.

Motor also sounds very buzzy, almost overdriven with the LiPo...

[williec]

prokyon,

iCharger is a very nice charger. However, it's servo test function was not the optimum option as it gets the "speed" reading by calculating the current draw which is not the real speed reading. There was a video posted in Xpert USA's Facebook page on June 17 explaining how the speed specification was done in our company.

As for the jitter issue, we will ask Art to chime in later. We are still catching up our work after a long week of Ircha.