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Burned out servo??

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Old 04-03-2018, 04:30 PM
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kevarc
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Default Burned out servo??

I have a DX18 with an AR9030T receiver running five HS5585MH servis and one HS5495BH throttle servo.
Using electrodynamics nano 6.6v 2500mAH.
I have five flights on the plane.
Plane sat for three for a couple months.
Went to the field and could not get the engine to start. Determined a servo or linkage problem.
In the shop there was very little movement in the servo.
Thought maybe a gear issue.
Went to take the servo out and noticed it was very hot. The servo extension connection was also hot.
Hmm bad servo.
Grabbed another 5495 plugged it in and was fiddling with the transmitter adjustments. Got a low receiver voltage alarm.
Turned around to see smoke in the plane. Crap!
Shut the battery off. The new servo fried.
Near as I can tell the servo extension was the problem.
Without the extension things seem to be ok.
Tore the extension apart but no apparent issues.
I did notice latter that the battery was not plugged into the battery port on the receiver.
Otherwise sure that matters.
Putting this out there to see if I am missing something.
What could go wrong with an extension to cause this problem?
Or do I have another issue?
Thanks
Kevin
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Old 04-04-2018, 08:22 AM
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Truckracer
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First, replace the extension if there is any doubt about that. From there I'd check 100% that there is no binding in the linkage or that you are hitting a hard end point on the carb. I'm not familiar with your radio but is there a high speed mode? If so and if active, you may want to set the receiver to normal mode as the servo may not be compatible with HS. From there, though unlikely, you may just have a bad servo(s). I'd suspect binding or endpoints first.
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Old 04-04-2018, 08:52 AM
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"I'd suspect binding or endpoints first."
+1!
That is a digital servo, so should be no problem with high refresh rate, but since high refresh rates don't do much for plankers, stick with the normal refresh rates.
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Old 04-04-2018, 10:01 AM
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Higher refresh rates won't cause issue. Most pilots won't feel the difference between high and low speed, sans for competition level pilots so yes, plankers can take advantage of higher refresh rates.

Check for binding and ensure your end points are set correctly, that is almost always the cause of servo failure. The servo should be pretty quiet both at full throttle and at idle, if it's making a lot of buzzing at either point then it's probably being driven too far.

Also, at full throttle, set the servo so that it does not hit the hard stop of the carb. You will want to back it off a few points from fully open so that the servo is not hitting the full stop when the engine is running and causing vibrations.

Last edited by Xpress; 04-04-2018 at 10:12 AM.
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Old 04-06-2018, 10:31 AM
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kevarc
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Thanks for the responses.
The second servo that fried was not even connected to any linkage and lasted 30 seconds.
I got another hs5945 and have it installed with a different extension and seems to work fine.
I have no idea what happened?
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