JR DS8411 Problem:

I am flying a 36% AeroWorks Edge 540, vintage about 2002, with two DS8411 servos on the rudder and two on the elevator (one Futaba 9202 servo on each aileron). I've always flown this airplane with a 5000 Mah Nihm flight pack as the sole power source for the receiver and servos with no problems. Now I've decided to upgrade my power system to redundant A123 batteries, so I tried to use two 2300 Mah 6.6 volt packs through redundant switches. The Futaba servos worked fine, but the DS8411s did not work properly at all, glitching like crazy and refusing to take signals from the receiver. I immediately returned to the 4.8 volt single battery pack power system, and the problem went away. I tried adding a second 4.8 battery pack through the second switch; this did notrecreate the problem; everything continued to work just fine. Next, I disconnected both 4.8 volt battery packs and reconnected one of the 6.6 volt A123 packs through an old 5.1 volt regulator I had lying around. No problem! Everything continued to work fine. I found several different voltage regulators from several different vendors via the Web, and ordered two matching 5.4 volt regulators because I figured this voltage would be low enough to allow the DS8411s to function properly and because these were the least expensive ($19.95 ea.) I could find. Imagine my chagrin [] when I connected one of the A123 packs through the regulator and found that I was still getting considerable glitching! I reconnected the same battery, replacing the 5.4 volt regulator with my old 5.1 volt regulator and the problem went away!! Apparently, my DS8411 servos don't like any voltage much over 5.1 volts. [&o]

My question is do I have some particularly quirky DS8411s or have other people experienced this voltage anomaly? I've searched here at R/C Universe and on one other site dedicated to giant-scale flying and have not found a specific answer to this question though I did read one post from a flier in Great Britain who found a written warning packaged with his DS8411s stating that he should use only 4.8-volt systems, not 6-volt systems with DS8411 servos.

I'd prefer not to have to send these four servos in for diagnosis if others have already conquered this problem by restricting voltage. Please advise. Thank you.

I'm not sure if Mike has tinkered with A123's yet and I'm just converting my models, but I'll tell you that I have a 33% Edge with two 8411's in the elevators. I just changed out the Duralite Li-Ion/regulators for dual 2300mah A123 packs. I've not flown it yet, but I had no difficulties setting up the model and did not notice any eratic servo behavior while setting things.

The A123's do have a 6.6 volt nominal voltage, but that is less than a fully charged 5 cell NiCD or NiMH. I only have one model converted to A123's that has a servo which is not very happy and it's an analog from a different manufacturer. But it was also having the same difficulty with the freshly charged 6 volt NiMH that was replaced by the A123.

Maybe Mike can address the issue from the servo performance/requirements side but IIRC, Danny Snyder who used to run the JR manufacturer support forum in the radio section, said that while the official recommendation was for no more than 6 volts, there hadn't really been any issues with slightly higher voltages.

What radio system are you using? If its a Spektrum/JR DSM sysytem and you have a JR amplified Y-harness on those servos, that is your problem. The Amplified Y harnesses with stsyem DSM on higher than 4.8V will cause that. Simple solution is just replace them with non amplified Ys.

The 8411 is fine on 6V or 6.6V. That isnt an issue at all.