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Futaba 617 Rx / Hitec 7955 servos - Compatible?

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Old 01-18-2011, 05:06 PM
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Capt Cash
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Default Futaba 617 Rx / Hitec 7955 servos - Compatible?

I currently use the Futaba 2.4g7C with a617 FAAST receiver. Would rather have the Aura 9, but for now it works great and isall I need. I'd like to buy some new Hitec 7955's and just want to make sure these are compatible? People are bound to be running Hitecs on this receiver right? Will I need to change the connectors?
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Old 01-18-2011, 06:22 PM
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Default RE: Futaba 617 Rx / Hitec 7955 servos - Compatible?

No you don't need to change the connectors, they will plug in just fine.

Doug.
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Old 01-19-2011, 07:21 AM
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Default RE: Futaba 617 Rx / Hitec 7955 servos - Compatible?

Curiosity got me about running digital Hitec servos on my 2.4 Futaba 617 Rx. I would not think there would not be any compatibility issues would there? I'm no expert so please correct me if neccessary but here is what I've concluded so far:

After some internet research I found some older threads about this scenario where Hitec servos were misbehaving or locking out due to the signal output voltage of some Futaba receivers being lower than the required voltage oftheservos. This would not be good, and even worse the problem would not present itself until the servo reached about a 120F operating temp (which could easily be done on a hot summer day) or is continuously under high loads at which point the servo would require a higher voltage than the receiver signal would put out. So you could easily have apotiental latent failureand never even know about it! This is one choke point I wouldn't want to have.

Good news is I think this is not a problem anymore. Some 2.4Futaba receivers would put out a max of 2.7v to the servos, while some Hitec servos required a minimum 3.0v when at max operating capacity therefore resulting in servo malfunction. If anybody knows any more or can elaborate on this please chime in.

Another similar scenario to this is not in compatibility of components but in using long servo leads, lighter guagewire,and/or y-connectors.In this casethereceiver signal voltage drops over the long leads to the servo and the result is jittering, twitching or lockout thatinmanyinstances will not be present under nomal range checks. Apparently aneasy fix for this is an in-linebuffer-amplifier; cheap insurance for boosting the voltage to the servos. I assume the Smart-Fly power boards will do this also.

So I've now given a lookand am leaning towards Futaba servos again. I don't want to start a war on the perfect servohere but the Futaba 9156 seems to be an awsome servo and comparable in perfermance and price to the Hitec 7955, yet you just don't see many Futabas on large scale aircraft? Heck, many of the larger well known internet RC retailers don't even carry Futaba servos but instead push Hitec hard. I think over the years Futaba was passed by Hitec in the large scale market due to pricebutit seems theyare catching back up. Futaba dosen't push the infamous "Titatanium Gears" like Hitec followers, but for those that have used this line ofservos,theyhave reported very long life spans with little slop ever developing and better centering over the Hitecs.
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Old 01-19-2011, 08:23 AM
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Default RE: Futaba 617 Rx / Hitec 7955 servos - Compatible?

The only FASST receiver that had that low 2.7 voltage was the old discontinue R6014FS 14 channel receiver, the same receiver that had problems with heat.

Doug.
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Old 01-19-2011, 08:40 AM
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Default RE: Futaba 617 Rx / Hitec 7955 servos - Compatible?

Okay a couple of thoughts.....

Over the years Futaba has done their fair share of messing with things which produce undesirable results particularly with other vendor/manufacturer's hardware and the signal line voltage is just one example, the other real common one was the sinking current on the R149DP rx's which would not allow you to run Hitec servos on a Y-lead.

That said; Hitec adapted their servos to run on the lower signal current of the R6014FS Futaba rx's, Futaba came out with various upgrades to that rx which included hiking the signal current voltage and those rx's are signified by first a white dot, then a gold dot on the sides of the rx's and finally the release of the 6014HS rx.

Second thought is that there are guys using the big Futaba servos and reporting good results but as you noted they are not cheap. There have been some issues reported with the Hitec 7950's running on un-regulated Li-Po voltages and long servo extensions but that seems to be pretty much isolated to the Spektrum/JR PowerSafe rx's for some reason not yet identified by Hitec. Those reported difficulties do not seem to affect the 7955 Hitec servos in similar installs.

Last; if you are looking for servos that big, it would suggest you want to run a GS gasser setup? If so, may I strongly suggest you do not plan on running these size servos on Y-harnesses especially reversing type Y-harnesses, verify that your rx and battery system can handle the amperage needed to run these big servos and pay attention to all of your electrical components like switches, wire guage sizes, connector types and available current paths into the rx.
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Old 01-19-2011, 09:56 AM
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Default RE: Futaba 617 Rx / Hitec 7955 servos - Compatible?

These servos are intended for a 88" span 30% Sbach 342 with DLE-55. I hear many folks use a servo such as the Hitec 7955 /Futatba 9156on this and larger planes for doing both hard 3D and sport flying. A little less torque will suffice I know, but the price is not all that much cheaper for say a 200 oz-in servo over a 340 oz-in servo.

I've always used heavy duty minimal length extensions, HDswitches, and never Y-connectors, etc. Receiver power will be from two unregulated A123 batteries. I do use a Smart-Flyservo syncronyzierfor the twin elevator servosas my Futaba 7C does not support this. So far it has performed excellent in my other planes.A Smart-Fly Power board would also be nice, but I just can't really justify it in a 50cc size model right now.

At the moment all I have for radios is my Futaba 7Ctransmitter along with 3fairly new617 FAAST receivers so I'll probably stick with these. I'm assuming a set of new Hitec 7955 servos will work just fine on this receiver as that was my reason for this post, but I'll probably go with the Futaba 9156s now. I can get either for $100 shippedfrom Tower Hobbies after discounts.
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Old 01-19-2011, 10:11 AM
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Default RE: Futaba 617 Rx / Hitec 7955 servos - Compatible?

Your 7C 2.4 will support 2 elevators, I use channels 2 and 5, then go to the AILEVATOR function on page #45 (I think) of the manual.

The old 7C does not have this feature.

Doug.
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Old 01-19-2011, 10:25 AM
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Default RE: Futaba 617 Rx / Hitec 7955 servos - Compatible?

Well thats good to know.But canI can trim each half also and not use any of my custom P-mixes?

I'm currently using all three P-mixes for knife edge coupling so I can't use those if needed. (two mixes for aileron-to-rudder on ch 1, and 6.And one mix for elevator-to-rudder on channel 2)
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Old 01-19-2011, 10:28 AM
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Default RE: Futaba 617 Rx / Hitec 7955 servos - Compatible?

Yes you can trim each half, and is a built in feature. no need for a mix.

Doug.
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Old 01-19-2011, 02:04 PM
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Default RE: Futaba 617 Rx / Hitec 7955 servos - Compatible?


ORIGINAL: Capt Cash

These servos are intended for a 88" span 30% Sbach 342 with DLE-55. I hear many folks use a servo such as the Hitec 7955 /Futatba 9156on this and larger planes for doing both hard 3D and sport flying. A little less torque will suffice I know, but the price is not all that much cheaper for say a 200 oz-in servo over a 340 oz-in servo.

I've always used heavy duty minimal length extensions, HDswitches, and never Y-connectors, etc. Receiver power will be from two unregulated A123 batteries. I do use a Smart-Flyservo syncronyzierfor the twin elevator servosas my Futaba 7C does not support this. So far it has performed excellent in my other planes.A Smart-Fly Power board would also be nice, but I just can't really justify it in a 50cc size model right now.

At the moment all I have for radios is my Futaba 7Ctransmitter along with 3fairly new617 FAAST receivers so I'll probably stick with these. I'm assuming a set of new Hitec 7955 servos will work just fine on this receiver as that was my reason for this post, but I'll probably go with the Futaba 9156s now. I can get either for $100 shippedfrom Tower Hobbies after discounts.
Get the 9157s instead of the 9156. Same price at Tower right now and if you use code 014bw you can get a pair for $205. They are almost a 100 oz. stronger than the Hitec 7955. I just got 4 of them.
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Old 01-19-2011, 02:08 PM
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Default RE: Futaba 617 Rx / Hitec 7955 servos - Compatible?

DougV, thanks again for the info,

I maycontinue to usemy servo sync on the elevators however. I wouldassume on the Futaba7Cthat you cannot individually adjust eachof the elevatorscentering and endpoints in both full up and full down movements. The Smart-Fly allows me todo this which is nice when you have elevator throws over 40 degrees or so.When this is the case asis with my setup,I've noticed thatthe smallest little difference in your linkagescreates a magnified effect when at maximum deflections. Again not a huge deal and I suppose you could mechancally tweak the linkages, but it is nice to electronically have theelevators matched at maximum throw. The Smart-Fly Eq II has helped me tremendously for fine tuning inthis area. I have no experience with higher end radios but would hope that they have thiscapability built in.
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Old 01-19-2011, 03:12 PM
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Default RE: Futaba 617 Rx / Hitec 7955 servos - Compatible?

i did use for a long time 617 on my 50cc with 7955 all around without any problems. Use the rx later on my electric and installed the 6014 but i dont remember any issues with any fasst rx with hitecs.
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Old 01-19-2011, 04:35 PM
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Default RE: Futaba 617 Rx / Hitec 7955 servos - Compatible?

Using Ailevator, you have each Elevator half on a separate channel, as was mentioned, so you can adjust Endpoints, I would think.
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Old 01-19-2011, 04:36 PM
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Default RE: Futaba 617 Rx / Hitec 7955 servos - Compatible?

The 7C should allow for individual EPA and sub trim for each channel.
FWIW, I use Hitec servos, both analog and digital almost exclusively on FASST receivers, from the little 4 channel, to the 8 channel model, though the majority are the good old R617FS.
Best of luck,
Pete
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Old 01-19-2011, 04:46 PM
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Default RE: Futaba 617 Rx / Hitec 7955 servos - Compatible?


ORIGINAL: BuschBarber

Using Ailevator, you have each Elevator half on a separate channel, as was mentioned, so you can adjust Endpoints, I would think.
Your thinking is correct BuschBarber.

The centeing can also be adjusted with the servos considering that the mechanical linkages rarely have a possible adjustment smaller than 0.0089 inch.

Zor



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Old 01-19-2011, 04:53 PM
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Default RE: Futaba 617 Rx / Hitec 7955 servos - Compatible?

Thanks!!

I have set up one 7C, for a friend of mine, to use Ailevator. I have used Ailevator, many times, in my 8AUPS and 9CAP, but I found that it's implementation in the 7C was not as intuitive when it came to picking the channels to mix. We had to call Hobbico to get the answer.
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Old 01-19-2011, 04:53 PM
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Default RE: Futaba 617 Rx / Hitec 7955 servos - Compatible?

OK, hows about in Metric, Zor
Pete
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Old 01-19-2011, 05:03 PM
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Default RE: Futaba 617 Rx / Hitec 7955 servos - Compatible?


ORIGINAL: pilotpete2

OK, hows about in Metric, Zor
Pete
I will assume you are being funny and not sarcastic.

Just multiply by 25.4 . I do not know how to multiply ___ Hee Hee .

Zor

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Old 01-19-2011, 05:06 PM
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Default RE: Futaba 617 Rx / Hitec 7955 servos - Compatible?

That is mm. I want cm.

I am just kidding!!!
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Old 01-19-2011, 05:12 PM
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Default RE: Futaba 617 Rx / Hitec 7955 servos - Compatible?

Thanks again all for helping clear up any issues with the Hitec servos. I'll try and play with my Futaba 7C radio and possibly eliminate the elevatorservo sync now. If I don't need it I'll certainly take it offmy currentplane. I always go backto the KISS method whenever I can!
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Old 01-19-2011, 05:13 PM
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Default RE: Futaba 617 Rx / Hitec 7955 servos - Compatible?

I was just kidding Zor
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Old 01-19-2011, 05:14 PM
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Default RE: Futaba 617 Rx / Hitec 7955 servos - Compatible?


ORIGINAL: BuschBarber

That is mm. I want cm.

I am just kidding!!!
This 0.0089 inch on a 2 cm horn represent 0.6476 degrees of servo or surface rotation.

Can be significant particularly on elevators.

Ha! Ha! He He ___ fun but true.

Zor
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Old 01-19-2011, 05:16 PM
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Default RE: Futaba 617 Rx / Hitec 7955 servos - Compatible?


ORIGINAL: pilotpete2

I was just kidding Zor
Pete
That is how I took it.
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Old 01-19-2011, 05:17 PM
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Default RE: Futaba 617 Rx / Hitec 7955 servos - Compatible?

Thanks!!
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Old 01-20-2011, 05:24 AM
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Default RE: Futaba 617 Rx / Hitec 7955 servos - Compatible?

Well all I can say is that when I was using Hi-Tec HS6965 servos with my Futaba 617 I got a most unpleasant centering BUZZ. Swiched to Futaba 9550 digital and no more problems...so that's my anecdotal story.
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