mmabc

My Feedback: (1)

I just bought a Futaba 7C 2.4G radio used.I've got the radio and two R617FS receivers. I've got a 25 year old Ugly Stick, and I want to get back into RC.
What it had was four servos along the lines of Futaba S131SH. From what I can tell, I won't be able to use those.

The little postage stamp size receiver is definitely not what I expected! There's no battery input on the receiver. That's different! I assume battery power goes directly to the servos, but the radio manual doesn't say anything about that. I don't understand how that works. How do the servos connect to the battery, switch and receiver?

I need to figure out everything else I need to buy for the plane electronics. Can someone explain to me exactly what I need to order and how I will hook everything up?



,

JohnBuckner

My Feedback: (1)

Your battery plugs into the switch/charge harness and the lead from the switch harness plugs into the bottom Rx port marked 7 or CH 7. Actually you can plug the power from the switch harness into any unused RX (servo) port. If you need all 7 channels then the switch plugs into a Y harnesss and the other leg the servo will plug to. Then the single lead from the Y harness is plugged into that last port marked 7b. That 'b' means battery.

John

JohnBuckner

My Feedback: (1)

mmabc is the reason you said you obviously can,t use those futaba servos because they have plugs that look like this?

John

mmabc

My Feedback: (1)

Thanks John. I think you've answered one of my big questions.I don't know why they didn't explain that in the manual or at least labelling on the receiver. And no, the connectors on my servos are the same as they are today. They will plug into the new receiver. I would assume then, as I've been hoping, that I can still use the servos. That will keep my startup costs down.

I would guess all I need now is the battery. I see there are a several different types of lithium batteries and sizes, plus there are voltage regulators. What should I buy? It's a 60 size plane.

BarracudaHockey

My Feedback: (11)

Get a 5cell NiMh or NiCad

Yes, the servos should work.

jester_s1

If you want to go lithium (you don't have to) get a LiFe in pretty much whatever size you want to get it in. I have a .60 size Ultra Stick that uses about 100 mah per flight. So a 1000 mah battery is enough for 6 flights with plenty of safety margin left. NiCd's still work as well as they ever did though, and they'll work with a basic wall wart charger.
Are you talking about using 25 year old servos that have been sitting for a long time? They may be ok, but more often that not they'll be unreliable. At least do an hour of testing on the ground (wiggle the sticks while watching TV) before flying. Servos have improved a lot since then though, so for about $60 you can have a new set of Hitec HS-425 servos that will be stronger, center better, hold better, and they'll be new.

JohnBuckner

My Feedback: (1)

Dittoes on this. If you run a 2.4 radio, its my opinion that runing a four cell or 4.8 volts is a brownout just waiting to happen and it does not matter which major brand system you have.

All my airplanes run five cell packs and I use Nimh which are great if you use packs that are around three times the capacitys that we formerly used with Nicd's and the size/weights usually come out close and some a little smaller than the Nicd's. In other words for say a sixty sized airplane that we formerly used say a 600mah Nicd I would use an 1800mah Nimh or larger. My only exception to this is just two of my airplanes that are controlline ships that I now use 2.4 systems to control throttle and in the case one that has a second servo to operate a stooge release. These airplanes are fine with four cell packs having only two small servos and will never be more than sixty feet away

Those servo plugs I pictured are the old Futaba 'G' plug and those will not plug to a modern Rx without an adapter or a plug change. Since you have the modern J plug then there is no reason not to try those servos. They are probably an older series but no reason not to give them a shot.

John

mmabc

My Feedback: (1)

Can I use an old nicd battery charger for the nimh?

RCKen

My Feedback: (9)

Technially you can use it, but if you don't have much experience with the battery types I wouldn't recommend it. Ni-mh chargers use a little bit different type of detection than Ni-cd's do. You would be better off picking up a charger that is designed for Ni-mh's. In fact, there are plenty of chargers on the market now that are reletively inexpensive and are loaded with features. Most of these will charge Ni-cd;s, Ni-mh's, lead acid, and lithium chemestry batteries. You'll never go wrong with one of these chargers as they will serve you later on down the road if you expand into other types of batteries that need charged.

Hope this helps

Ken

rcjetflyer0718-RCU

My Feedback: (1)

Many of the 25 year old servos will not take 5 cell receiver packs, especially JR. As far as brown out with 4 cell packs the only brand that has this problem is Spectrum. I fly Futaba, Hitec, and Airtronics on 2.4 and I have never had a brown out with a 4 cell pack. I belong to the 2nd largest rc club in the USA and I have never heard a non Spectrum user complain about brown out.

CGRetired

My Feedback: (1)

Spektrum no longer has a problem with so-called brownout. That problem was eliminated several years ago. All of the Spektrum line radios are just fine. I have both the DX6i and DX7 and have NEVER had a problem with so-called brownout.

CGr

JohnBuckner

My Feedback: (1)

In regards to the original poster his radio is 2.4 and as such I am of the opinion that 4.8 packs are just a brownout just waiting to happen therefore my personal recommendation stands. Further I do not believe its just a brand thing and I beleve it has everything to do with and is generic to 2.4. Now I definitely do not beleve its first is limited to just Spectrum and that Spectrum fixed anything much but instead education got a whole lot better. And that means much more careful charging techniques and practices than we formerly tended to use as well as a definitely safer 6 volt packs of much higher capacitys than we formerly tended to use.

You say you are a Hitec user RCJetflyer and that's wonderful so am I (extensively). If you read very carefully between the lines in various places in the manual you will find yes you can use 4.8 but rather strong reccomendations for 6 volts. Its obvious these veiled comments are mearly for the various brands trying to compete with each other. We would be deluding ourselves if we beleved we are immune to brownout because we use brand X or that brand Y fixed it.

I believe brownout still happens (any brand) in most cases because of new folks combined with very poor charging practices I see this a lot and it greatly helps simply by in most cases with the few exceptions I used in my former post, to use 6 volt packs of capacitys of around three times what we formerly used in the past with 72 systems.

John

BarracudaHockey

My Feedback: (11)

To add to what John correctly said, if you drag any system down below its required operating voltage it will reboot.

Spektrum originally had an issue where it took 3 seconds to re-link. That issue was addressed ages ago, so all of the current systems INCLUDING 72mhz, are susceptible to the same issue, dragging the voltage down below what the receiver can operate at.

What's different now? Higher torque servos, and digital servos that pull more amps than "back in the day we never needed 5 cell packs..." that everyone seems to be using today.

That said, a 5 cell pack is a cheap insurance policy for any radio installation. Most servos made since music started showing up on CD instead of cassettes can take 5 cells with the exception of a few special use servos.

jester_s1

Spektrum still has an issue with brownouts that other brands don't. Yes it's true that any 2.4ghz receiver will reboot if the voltages gets low enough, but the threshold is set lower on all the other brands. Spektrum reboots at 4 volts, which one can easily reach with a 4.8 battery that is in good condition and a second of high servo loading. I've seen testing where Futaba will work down to 2.5v, and Airtronics says their receivers will work with full range down to 2v. I don't know about Hitec, but since there haven't been any anecdotes that I'm aware of about them rebooting I assume their threshold is pretty low too.
When Spektrum was first released, lots of people lost planes due to the 3 second reboot time after falling below 4 volts. Mind you, that was planes flying with the 4.8v battery that Spektrum included with the system. No warnings about voltage sag were given in the manual or the Spektrum website until a rash of complaints started to surface. Spektrum's response was to make the reboot time quicker instead of making the voltage threshold lower, so at best it's a bandaid. So if you run 4.8v packs with Spektrum you still can get brownouts that will take about 1/2 second to reboot. If that happens at the bottom of a loop it will still cost you an airplane.
Everyone is entitled to their own opinions, but I'll never fly Spektrum or JR (the parent company) equipment. They released a product line with a major flaw and only admitted the issue after the complaints were too well known for them to ignore it. There was a big spike in complaints about the Dx8 radio having unexplained crashes too so apparently that's their business model. They either didn't do any product testing in the real world or they just ignored the issues in order to get into the market first. With systems that were reliable from the start from Airtronics and Hitec (Futaba had an issue with heat causing shutdowns which they promptly fixed) I don't see why we as a community haven't put Spektrum out of business.

BarracudaHockey

My Feedback: (11)

If you want to see actual testing, watch the 2.4 radio clinic put out by Radio Carbon Art. Its directed at gliders but 90 percent of the information in it is universal.

opjose

Eh, it's less than 3.2 volts not 4.

Equipment, particularly servos can produce momentary large drains that make it appear that the RX is rebooting at higher voltages, but what occurs is that the voltage drops too quickly for a lot of meters to register correctly.

Put everything on a scope and you can see all of this.

The same is true of Futabas and other brands so it is not endemic to any one make or brand.

The original problem with Spektrums was the longer reaquisition time which was cured long ago.

rcjetflyer0718-RCU

My Feedback: (1)

Spectrum and JR are 2 totally different companies. Spectrum licensed their 2.4 technology to JR. After Spectrum came out with the dx7 and people were having unexplained crashes and spectrums response 'we dont know what your talking about"; the car guys came out and they had that problem with their Spectrum radios 2 years before and Spectrum came out with a capacitor to connect between the battery and receiver to stop the brown outs. The car guys were only using up to 2 servos and were having that problem how do you think it was for someone flying a BVM F100 with leading edge slats, flaps, brakes and retracts at TOP GUN? I have friends who lost their plan, engine and radios because of Spectrums lies. why did spectrum sell their radios with digital servos and 4 cell reciever battery? That is why I will never buy a Spectrum radio.