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Old Aug 30, 2012, 12:46 AM
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Noob here, just got my first Heli and it's was DOA out of the box

Hey everyone,

I just picked up a Double Horse 9117 from my local fair in MN. I practiced for about 3 days with a small unit to get the hang of flight, Now it was time to take out the big dog. So I did my first charge and prepared for launch. I turned the helicopter on then the remote. After about 3 seconds, a servo on the side started buzzing and spinnging until it broke the connector buckle. If I turn the helicopter on with out the remote it's fine, but right when I turn the remote on, the servo starts spinning, and doesn't stop.

Do i have a bad servo or motherboard? Any thoughts?

Thanks
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Old Aug 30, 2012, 01:24 AM
Fly Runaway Fans
United States, TX, Fort Worth
Joined Jan 2009
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Sorry to hear.

Do the instructions specify to turn the transmitter ("remote") on AFTER the heli? Some do but many insist the transmitter be on first.

Even if "heli first" is what the instructions say, what happens doesn't narrow the problem much. That is, the heli may do nothing until it sees the TX. So when it does wrong (servo) it could be the TX telling it to, or it could have just been waiting to go wrong.

There will be a model thread for 9117. Try the search in the 'micro' section.
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Old Aug 30, 2012, 03:44 AM
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Letchworth, Great Britain (UK)
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Welcome to the forum

Most radio controlled models require you to switch on the transmitter first, and then the receiver in the model. But like arbilab has said, check your manual to be sure.

But then your description of a servo "spinning" seems to indicate that it's broken: A servo should not normally spin continuously -- it should only travel through about 45 or 60 degrees either side of center and, often if it's getting no signal from the transmitter (because the receiver's been switched on first) it will simply go to one limit of its travel and stay there.
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Old Aug 30, 2012, 06:26 AM
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Originally Posted by abenn View Post
Most radio controlled models require you to switch on the transmitter first, and then the receiver in the model. But like arbilab has said, check your manual to be sure.
Just curious, but is this a hold over from the older crystal based radios? I thought the new 2.4ghz ones have the equivalent of a protocol handshake in the binding process. Isn't there an ID in each data string that gets sent to the helicopter and that in turn keeps other pilots from interfering with each other?
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Old Aug 30, 2012, 07:20 AM
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Yes, there is some kind of protocol handshake -- I'm not technical enough to know how it works.

But the issue with switching on the receiver first is it means the receiver could possibly, even with modern systems, react to some spurious interference, or even to a signal from another transmitter. And with electric-powered models, where the motor is also usually powered up at the same time as the receiver, there's the risk that the motor could start unexpectedly due to a spurious signal from the receiver.

Switching the transmitter on first ensures that the receiver and motor are controlled by your transmitter, rather than being under the control of some random electrons that might be floating around.
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Old Aug 30, 2012, 09:49 AM
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Quote:
Originally Posted by Hajile View Post
Just curious, but is this a hold over from the older crystal based radios? I thought the new 2.4ghz ones have the equivalent of a protocol handshake in the binding process. Isn't there an ID in each data string that gets sent to the helicopter and that in turn keeps other pilots from interfering with each other?
You are essentially correct. The receiver on the PCB has a unique ID chip that binds to the first transmitter it sees. But, they only make about 30 different unique chips. The transmitter will only bind to one signal at a time. There is no bind plug to prevent accidental binding to another transmitter.
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Old Aug 30, 2012, 11:31 AM
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Here is a video of the issue.

http://youtu.be/iXn613k2ziQ

Thoughts?
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Old Aug 30, 2012, 11:45 AM
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looks like a bad servo to me. the signal from the TX is telling it to go to a certain position and the pot inside the servo is never telling the servo it got there so it just keeps going.

if you can (and dare) swap the wires from the two servos and see if the problem follows the servo or the channel. if the servo still spins wildly, then the servo is 100% bad. if the problem switches sides to the other servo, then the TX or the RX board are bad.

take the other turnbuckle off first, just in case, but I bet the servo is bad.
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Old Aug 30, 2012, 01:02 PM
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It was the servo. I swapped the two around and it still spun. I will call the company and see if they will replace it. Other wise I think it's only a $5 dollar part. Thanks!
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Old Aug 30, 2012, 01:52 PM
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Originally Posted by schreif View Post
It was the servo. I swapped the two around and it still spun. I will call the company and see if they will replace it. Other wise I think it's only a $5 dollar part. Thanks!
I'm not familiar with your heli, but there's a youtube video that I ran across once about fine tuning a servo, it had to do with taking the servo apart and adjusting the pot. Before the guy fine tunes it, the servo just spins around. Not sure if it's the same issue your having but check it out maybe it will help you in some way.

Fine Tuning Servo Set Point (5 min 25 sec)
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Old Aug 30, 2012, 02:01 PM
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I would strongly suggest replacing both servos with better ones. That heli uses CCPM mixing, so both servos have to perform exactly the same.
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Old Aug 30, 2012, 02:22 PM
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are you sure about that? looks to be a fixed pitch heli to me.

I wouldnt argue about replacing both though. it does use the servos together for directional purposes.
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Old Aug 30, 2012, 02:28 PM
Different fly 4 different guy
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The DH9117 is a fixed pitch somewhat similar to the MJX F45.

regards . . . g
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Old Aug 30, 2012, 09:26 PM
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Quote:
Originally Posted by minbari View Post
are you sure about that? looks to be a fixed pitch heli to me.

I wouldnt argue about replacing both though. it does use the servos together for directional purposes.
It doesn't mix cyclic, but it does mix ailerons and elevators, so it's the same principle as CCPM, just one less servo .
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