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Old Jul 23, 2013, 10:12 AM
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United States, TX, Fort Worth
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Set up receiver and DX7s

Hey guys,

I just got a used T-Rex 550E and a DX7s and I was wondering if someone could walk me through on how to set up the settings in the DX7s for it. Also, how to set up the receiver and which servos should be plugged in where on it; it's an Spektrum AR7200BX.

I'm asking because I'm pretty confident that the previous owner did not have it set up properly.

Thanks guys!
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Old Jul 23, 2013, 09:48 PM
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Bump.

No one can help me?
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Old Jul 24, 2013, 10:47 AM
Where's the swimming pool
spykez's Avatar
Joined Jul 2011
966 Posts
1. If you are not confident about the prior owner's knowledge, I would suggest taking a good look at the heli itself;
2. However, you may not be the best person to do that if you are asking for help on wiring up a Bx (no slight intended, we all start somewhere).
3. Thus, to avoid much pain and frustration, take it to someone ie local club, heli shop for a once over and help to set it up.


4. If you can't do that... this is tricky, only a last resort...I can only suggest tearing the heli down, to check mechanics, there's possibly a build guide or vid on some site, maybe helifreak, paying close attention to all tips. And look here for bx guides... http://helifreak.com/forumdisplay.php?f=239
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Old Jul 24, 2013, 11:20 AM
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Originally Posted by spykez View Post
1. If you are not confident about the prior owner's knowledge, I would suggest taking a good look at the heli itself;
2. However, you may not be the best person to do that if you are asking for help on wiring up a Bx (no slight intended, we all start somewhere).
3. Thus, to avoid much pain and frustration, take it to someone ie local club, heli shop for a once over and help to set it up.


4. If you can't do that... this is tricky, only a last resort...I can only suggest tearing the heli down, to check mechanics, there's possibly a build guide or vid on some site, maybe helifreak, paying close attention to all tips. And look here for bx guides... http://helifreak.com/forumdisplay.php?f=239
I figured out the wiring and that's all correct. Now I'm just having trouble getting the servos to keep the swash level when changing pitch.

I went through and leveled the swash with the servo arms at 90 degrees and the pitch at 0. I know I have to change the travel in my dx7s, but I'm not sure how to in and set the percentages correctly.
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Old Jul 24, 2013, 05:42 PM
Where's the swimming pool
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Under the servo menu section. Better RTFM ; )

Why adjust servo travel btw? You only tweak that once you get the heli up in the air to get ie the roll or yaw rates you want per how it flies.

Seriously get someone to check the bird and fbl out, don't want to plant it be because of something preventable, like your gyro correction wrong or some vibe that drives the bx crazy.
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Old Jul 24, 2013, 06:12 PM
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Originally Posted by spykez View Post
Under the servo menu section. Better RTFM ; )

Why adjust servo travel btw? You only tweak that once you get the heli up in the air to get ie the roll or yaw rates you want per how it flies.

Seriously get someone to check the bird and fbl out, don't want to plant it be because of something preventable, like your gyro correction wrong or some vibe that drives the bx crazy.
Well, I need to adjust the endpoints because I'm not able to get the servos to all move at the same time in order to keep my swash level. Ironically enough, I did read the DX7s manual and it told me that changing the Travel adjust would change the endpoints. :P (Is there a specific procedure on how to go about doing this?)

I know, I'm going to have it checked out before my maiden flight with it. I've flown CP before and I'm very aware of what the swash SHOULD do when moving the sticks in whatever direction. It's just setting up the Tx that seems to be the most overwhelming right now.
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Old Jul 24, 2013, 10:12 PM
Where's the swimming pool
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Briefly, for am at work.

Mixing is not done on radio.

Servo endpoints control rates on a 1-90 degree fbl gyro usually, like the bx.

Like a tail gyro absolute servo endpoints to avoid binding are done on the gyro itself.

Like a tail gyro radio endpoints control rates apart from collective/pitch where that value usually correlates with collective pitch you dialled up on gyro setup.

If coming from flybar can see how you can get confused. Beware vibes and gyro correction! Good luck!
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Old Jul 24, 2013, 10:46 PM
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Originally Posted by spykez View Post
Briefly, for am at work.

Mixing is not done on radio.

Servo endpoints control rates on a 1-90 degree fbl gyro usually, like the bx.

Like a tail gyro absolute servo endpoints to avoid binding are done on the gyro itself.

Like a tail gyro radio endpoints control rates apart from collective/pitch where that value usually correlates with collective pitch you dialled up on gyro setup.

If coming from flybar can see how you can get confused. Beware vibes and gyro correction! Good luck!
I figured it out after reading the bx manual, go figure!

I have it mostly dialed-in, but I won't know until the maiden flight. But I actually won't put it up until I'm more confident the bx is right on.

Also, are the cyclic servos supposed to somewhat slowly go back to their normal position after moving the elevator/aileron stick and releasing? Yes, FBL systems are very new to me.
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Old Jul 25, 2013, 12:23 AM
Where's the swimming pool
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All axes are under gyro control, so, yes, your cyclic servos will not behave like a flybar heli's. Whether the behaviour is correct or ideal will depend on programming.

Radio setup ironically is dead easy, perhaps only a teeny bit more complicated than an mcpx.

Gyro setup is the tricky bit.

The bx forum I linked you should help.

Bench test the heli (safely) for vibes. More critical here than flybar helis.
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Old Jul 25, 2013, 02:23 AM
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Good Job Spykez....

I was going to chime in with response #1...But wow it was so much to write. I re-read it and new it would just confuse a first timer.

O.P..there are a few really good videos on on you - tube to help walk you thru it. Good stuff to watch.
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Old Jul 25, 2013, 06:23 AM
Where's the swimming pool
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Yep, Dejavu*Xion is right, some real good vids on you tube.

By the way, for a 550 with a CF frame, you have a satellite receiver right? ie spm9645?
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Old Jul 25, 2013, 11:06 AM
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Yep, Dejavu*Xion is right, some real good vids on you tube.

By the way, for a 550 with a CF frame, you have a satellite receiver right? ie spm9645?
I do not. It's a second hand heli and the previous owner changed out the CF to an orange fiberglass frame.

I've heard of people using a sat. but I'm not sure why; is it just incase the bx loses signal?
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Old Jul 25, 2013, 08:13 PM
Where's the swimming pool
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I do not. It's a second hand heli and the previous owner changed out the CF to an orange fiberglass frame.

I've heard of people using a sat. but I'm not sure why; is it just incase the bx loses signal?
Redundancy.

I'm no electronic engineer but if Spektrum say it is recommended for that size, I would do it. Glass fibre or not.

Do make sure whoever you bring the heli to see really goes through setup with you and walks over the heli with you; there are possibly other issues you may not be aware of.
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Old Jul 25, 2013, 08:30 PM
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Redundancy.

I'm no electronic engineer but if Spektrum say it is recommended for that size, I would do it. Glass fibre or not.

Do make sure whoever you bring the heli to see really goes through setup with you and walks over the heli with you; there are possibly other issues you may not be aware of.
I just realized that I have an extra receiver, but I don't know if its a sat: it came with my Blade 450 3D along with a DX6i.
Would I be able to use that?
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Old Jul 25, 2013, 08:46 PM
Where's the swimming pool
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An AR7200BX latest capable protocol is dsmx. I have only ever tried successfully binding it up with it's appropriate mate, a dsmx sat from spekky, spm9645.... Yes.. I have a few of them lol

The jrprr121x dsmx sat might also work buNt I have not tried it on an AR7200BX, i am more a v-bar guy, bicurious about msh brain...

your best bet is to get the original spekky sat but the jr may work. There's an orange one out now apparently but .... I might pass on that one.
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