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-   -   HELP! Spektrum DX7 radio failure? (https://www.wattflyer.com/forums/showthread.php?t=22015)

compflight 12-20-2009 05:47 PM

:silly:
The gentleman concerned was a very experienced F3a leccy flier and had decided to carry out a succession of snap rolls. Ironically, the final one on the downline turned in to more of a snap than he bargained for !
The seperate battery pack was more than ample, it would seem, for snaps with breaks between them but not it seems, consecutive.
Other members are now going over to Futaba, especially when they see the connection speed of my Futaba. Only one receiver to fit. No problems with binding. Ability to go down to less than 3volts. . . I could go on. Dont bother trying to sort out the DX7's just go and buy a Futaba. You wont regret it.

TDisaster 12-20-2009 05:59 PM


Originally Posted by compflight (Post 673739)
:silly:
The gentleman concerned was a very experienced F3a leccy flier and had decided to carry out a succession of snap rolls. Ironically, the final one on the downline turned in to more of a snap than he bargained for !
The seperate battery pack was more than ample, it would seem, for snaps with breaks between them but not it seems, consecutive.
Other members are now going over to Futaba, especially when they see the connection speed of my Futaba. Only one receiver to fit. No problems with binding. Ability to go down to less than 3volts. . . I could go on. Dont bother trying to sort out the DX7's just go and buy a Futaba. You wont regret it.

Same reasons I went Airtronics, except they're cheaper. ;)

But I liked my DX7, till my first brown out. Now I LOVE my SD-10G, and no brownouts. :D

Lieutenant Loughead 12-20-2009 06:03 PM

This is the first I've heard of an AR7000 receiver issue. I have two of them -- one in each of my two larger (40 sized) aircraft. I have not had any issues with my AR7000 receivers (even way back when I started this thread and had a bad DX7 transmitter, the AR7000's performed flawlessly).

Now, that doesn't mean that others haven't seen issues -- I'm just saying I'm surprised that the AR7000 may not be as "perfect" as I thought it was! :eek:

firemanbill 12-20-2009 06:55 PM


Originally Posted by Lieutenant Loughead (Post 673744)
This is the first I've heard of an AR7000 receiver issue. I have two of them -- one in each of my two larger (40 sized) aircraft. I have not had any issues with my AR7000 receivers (even way back when I started this thread and had a bad DX7 transmitter, the AR7000's performed flawlessly).

Now, that doesn't mean that others haven't seen issues -- I'm just saying I'm surprised that the AR7000 may not be as "perfect" as I thought it was! :eek:


I think is true for just about everything...

kyleservicetech 12-20-2009 06:56 PM

[QUOTE=compflight;673670]

Originally Posted by caltrop (Post 668524)

Still not sure if I fully trust the DX7...:confused:
QUOTE]

Precisly why I sold my JR gear and bought a Futaba. Never looked back.
Turn on and connection mS's later - now that inspires confidence. I see a clubs F3A bite the dust when it - on post crash investigation - browned out. It never recovered yet there were probably 2 or 3 seconds before it hit the ground. A Futaba system would have recovered and probably not lost contact in the begining.

That just proves a point. A fellow club member that has been flying RC since 1962 lost a jet turbine due to a verified failure of his top of the line line Futaba 2.4 Ghz radio. (The transmitter quit right in front of him.) He since has gone to the top of the line JR 2.4 Ghz radios, with absolutely no problems over the past 18 months.

Any radio can fail, no matter how much it costs. Just ask NASA.

So, those modelers that have had good success with Futaba will say that the Futaba radio system is the best out there. And the same goes for JR, Spektrum, Hitec, you name it.

But, from what I can tell, many of the modelers that have gone to 2.4 Ghz radios use the JR/Spektrum lines. The very last published issue of RCReport magazine did a pretty comprehensive study of the 2.4 Ghz radios, and found that the top of the line JR receiver with four slave receivers was pretty much bullet proof against any sort of interference.

As for me, I've got the Spektrum DX7 systems, with five AR 7000 receivers. All but one has functioned perfectly, the one that failed had a bad plated through hole in the circuit board that supplies positive voltage to the servos. That was a manufacturing defect, and I fixed it. (The model quit on the ground during taxi tests in my back yard.)

Later on during the winter season, I returned all of my receivers to Horizon for software updates. Horizon updated all of them no charge, and replaced that circuit board with the bad plated through hole, even though it was nearly a year after I had repaired the circuit board.

Gohmer 12-20-2009 08:54 PM

More OT Stuff
 

Originally Posted by compflight (Post 673739)
:silly:
The gentleman concerned was a very experienced F3a leccy flier and had decided to carry out a succession of snap rolls. Ironically, the final one on the downline turned in to more of a snap than he bargained for !
The seperate battery pack was more than ample, it would seem, for snaps with breaks between them but not it seems, consecutive.
Other members are now going over to Futaba, especially when they see the connection speed of my Futaba. Only one receiver to fit. No problems with binding. Ability to go down to less than 3volts. . . I could go on. Dont bother trying to sort out the DX7's just go and buy a Futaba. You wont regret it.

Your speedy futaba transmitter will instantly hook up with any model bound to it. This isnít such a good feature if you try to fly a different airplane than the model memory your transmitter is on.

kyleservicetech 12-21-2009 06:30 PM


Originally Posted by compflight (Post 673739)
:silly:
Other members are now going over to Futaba, especially when they see the connection speed of my Futaba. Only one receiver to fit. No problems with binding. Ability to go down to less than 3volts. . . I could go on. Dont bother trying to sort out the DX7's just go and buy a Futaba. You wont regret it.

I've checked all five of my AR7000 Spektrum receivers on my variable DC supply. All five work down to 3.2 volts, plus or minus a few percent. And, all five "reboot" in a split second after your battery recovers. (All five have had the "quick reboot" firmware upgrade installed)

If your battery ever drops to 3.2 volts at any time during your flight, you've got inadequate batteries in your model. If your battery should ever drop to low during a flight, Spektrum programmed the (upgraded) software in their receiver's LED to flash on and off, letting you know what happened. (It's simple to check this feature. Power up your transmitter/receiver, then switch your receiver off, then on. Your receiver LED's will start flashing.)

And, those 2400 Milliampere Hour "AA" size batteries on the market might have the milliampere hour capacity, but their internal impedance is far to high for high drain digital servos. I caught one of my club members using a single 2400 MaH "AA" sized Nih five cell receiver battery pack on his 25 pound gas model this past summer. Convinced him to go to a dual primary/backup "Sub C" pack before the first flight.

If you've got big airplanes, high powered servos, or similar, you need receiver batteries to match, such as the 2400 Mah Sub C NiH cells, or 2300 Milliampere Hour A123 battery packs. And that applies, whether you've got Spektrum, JR, Futaba, Hitech, or what ever brand radio you use. Just about every name brand radio works well. (Until they don't! And a certain percentage of every brand of radio will quit. These radios do not have zero failure rates.)

Nice thing about the A123 cells, their voltage immediately after charging is slightly LESS than a five cell Nih cell that has just been quick charged. So, if your airborne radio works with a five cell Nih battery pack, it will also work with a two cell A123 pack.

Lipo's are another option, but they usually require voltage regulators. And, the Internet has a lot of warnings that suggest these Lipo batteries should not be charged while inside your model airplane.

caltrop 12-21-2009 06:40 PM

Futaba vs DX7
 
Yes that is one drawback to Futaba is that it will work with any model bound to it. Just like 72MHz you need to verify the correct model before flight. You should always preflight your aircraft before getting it in the air regardless what radio you use. I think the binding issue is irrelevant compared to the DX7 failure issues. I would rather have a reliable radio over one that differentiates models.

Since my DX7 is back for the fourth time and Horizon looks like they will never fix the problems I am looking at other systems. Hitec has a nice 2.4GHz system that has modules like JR. Hitec is also coming out with a dedicate 2.4GHz in about a year. With Hitec just swapping out an affordable module gives you 72MHz. I also like the touch screen Hitec has.

The thing I will miss about Spektrum is all the micro stuff they're coming out with but the other companies will most likely be doing the same shortly. But like I said I would prefer a reliable system over NEAT STUFF. It does not matter what radio you have if it does not work right.

I've given Horizon several chances to make good on my DX7 and it has not happened. So it's they're loss that some of us will be using other systems. I've lost enough money, not to mention the sress watching an out of controll aircraft slam into the ground, to Horizon and it will STOP now!

jasmine2501 12-22-2009 03:20 AM

I gotta say, this is very surprising. Spektrum doesn't have a notably high failure rate, and Horizon has very good customer service. It sounds like you got a lemon, which is possible with any mass-produced product. So, by switching to Futaba, you would actually be hurting yourself in the long run, against the option of simply getting another DX7 or JR. Since the problem is with your individual unit, and not with the brand as a whole, you wouldn't really be mitigating any risk by switching to another brand, and you would have to convert your existing equipment to use the new radio, overall, coming out behind.

These issues with brown-out are not unique to Spektrum, and not unique to 2.4GHz either. The brown-out occurs with all receivers, if they are subjected to low input voltages - and any receiver, whether 2.4 or 72, will take a while to re-boot if it is a computerized receiver. Futaba's initial connect is fast because it doesn't have ModelMatch, but it's no faster than Spektrum's quick reconnect, in the case of an in-flight re-boot. Both systems require the input voltage to come back up before the re-boot can happen anyway. In my experience, that is the real problem, and not the receiver connection speed. If you brown-out, and it takes 5 minutes for the ESC/BEC to cool down and get back up to operating voltage, then it doesn't matter if you're using Futaba or Spektrum or whatever - it's gonna take 5 minutes to come back online, period. If you're overheating your BEC, then it's not the fault of the reciever, and it's going to be a problem regardless of the system you're using.

spad 12-22-2009 03:42 AM


Originally Posted by jasmine2501 (Post 674241)
I gotta say, this is very surprising. Spektrum doesn't have a notably high failure rate, and Horizon has very good customer service. It sounds like you got a lemon, which is possible with any mass-produced product. So, by switching to Futaba, you would actually be hurting yourself in the long run, against the option of simply getting another DX7 or JR. Since the problem is with your individual unit, and not with the brand as a whole, you wouldn't really be mitigating any risk by switching to another brand, and you would have to convert your existing equipment to use the new radio, overall, coming out behind.

These issues with brown-out are not unique to Spektrum, and not unique to 2.4GHz either. The brown-out occurs with all receivers, if they are subjected to low input voltages - and any receiver, whether 2.4 or 72, will take a while to re-boot if it is a computerized receiver. Futaba's initial connect is fast because it doesn't have ModelMatch, but it's no faster than Spektrum's quick reconnect, in the case of an in-flight re-boot. Both systems require the input voltage to come back up before the re-boot can happen anyway. In my experience, that is the real problem, and not the receiver connection speed. If you brown-out, and it takes 5 minutes for the ESC/BEC to cool down and get back up to operating voltage, then it doesn't matter if you're using Futaba or Spektrum or whatever - it's gonna take 5 minutes to come back online, period. If you're overheating your BEC, then it's not the fault of the reciever, and it's going to be a problem regardless of the system you're using.


Lots of conclusions, here, with no factual bases or few bases stated-now, I use a DX-7 and JR X9303, mind you, but I'm just saying....

jasmine2501 12-22-2009 07:41 AM

Well, break it down to the facts then...

1. Brown-out is caused by a low voltage condition
2. Low voltage condition number 1 cause is overheated BEC
3. Overheated BEC needs to cool down before it starts working again
4. Receivers need to start up and connect after the low voltage condition and they can't do that until the power comes back - connection time, in my experience, is negligible compared to the time it takes for the BEC to come back online - I've had times when it took 5 minutes, and it doesn't matter what equipment you're using - 5 minutes without sufficient power is going to bring you down. Even 5 seconds is too long - heck, even one second is too long with a heli, usually.

So that's why I say, regardless of which brand of receivers you're using, it's not the problem. It is the inadequate power system which is the problem, and this problem is still going to exist if you change receivers.

spad 12-22-2009 02:27 PM

Well, while I accept these comments, they are still opinions, and may not sway others. What we need is "objective data" to counter the claims that Spektrum is "the" issue.

rcers 12-22-2009 02:44 PM


Originally Posted by spad (Post 674372)
Well, while I accept these comments, they are still opinions, and may not sway others. What we need is "objective data" to counter the claims that Spektrum is "the" issue.

Easy to find. People vote with their wallet and fly with equipment they trust.

Go to three events this year:
- Joe Nall (won't allow 72MHz this BTW)
- IRCHA Heli event (national heli event worlds largest)
- SEFF (largest electric event)

This gives a nice mix of types of events. Electric/Heli/Scale IMAC

Count how many systems you see and what brand they are. That will show you what folks buy with their own hard earned cash. There is one clear leader in the pack by the way. :) (And it is NOT Futaba BTW).

Mike

flypaper 2 12-22-2009 02:48 PM

Had the same thing happen that Jasmine was talking about. Piled in the little bipe in my avatar when everything went dead. Of course I thought it was the radio. Took it home and tested it on my work bench. Plugged everything together and rotated the sticks to see if I could get it to act up. The ESC kept getting hotter and hotter till I couldn't touch it then it shut off completely, no control at all. After about 8 seconds, everything turned back on when the ESC cooled down. My own fault, which is not unusual,???? After rereading the CC ESC instructions, it said, only use 3 servos on a 3 cell batt. Took off the servo operating the upper ails. and put pushrods from bottom to top ails. and had no trouble since. At the time I was sure it was the radio. I imagine ths happens more often then not. Without the test it would have been the radio's fault.

Gord.

spad 12-22-2009 03:38 PM


Originally Posted by rcers (Post 674378)
Easy to find. People vote with their wallet and fly with equipment they trust.

Go to three events this year:
- Joe Nall (won't allow 72MHz this BTW)
- IRCHA Heli event (national heli event worlds largest)
- SEFF (largest electric event)

This gives a nice mix of types of events. Electric/Heli/Scale IMAC

Count how many systems you see and what brand they are. That will show you what folks buy with their own hard earned cash. There is one clear leader in the pack by the way. :) (And it is NOT Futaba BTW).

Mike


I'm a "die hard" Spektrum guy, but there are several, equally likely explanations here, and marketing is chief among them.

My only experience is with Spektrum so I have no basis on which to offer opinions regarding the others.

My only brownout came when I designed a power system badly (pre-Watts-up days!) and, tah, dah, the bec overheated.

For me, and for most others, "objective data" means something empirical, not something subjective like, "I bought this radio because my friend said so...the ads say so....."

Just my two cents-anyway, I love my DX-7 and JR X9303.

rcers 12-22-2009 03:47 PM

Marketing did not get 25 year+ Futaba guys buying Spektrum. :) Technology did. So did the fact that they were first (by a large margin).

While being first is good they would not have taken over control of the RC radio market (and they have) with an ad. They did it by building an excellent system that works.

I have used all the major 2.4GHz systems (Hitec Aurora coming now!) and all of it works and works well.

Anyway it is fun to speculate but at the end of the day people bought Spektrum because it works - and word of mouth is a powerful thing. So perhaps you are right. Marketing! :)

Mike

Lieutenant Loughead 12-22-2009 04:32 PM

I was a "die hard" Hitec guy, but bought a DX7 for the technology. After getting rid of my lemon, I am now a "die hard" Spektrum guy. :)

I agree with Jasmine -- you've got a lemon. Get Spektrum to replace it (or even buy another one), and you will be very happy.

spad 12-22-2009 04:47 PM


Originally Posted by Lieutenant Loughead (Post 674410)
I was a "die hard" Hitec guy, but bought a DX7 for the technology. After getting rid of my lemon, I am now a "die hard" Spektrum guy. :)

I agree with Jasmine -- you've got a lemon. Get Spektrum to replace it (or even buy another one), and you will be very happy.

And, this from the fellow who once thought the design was flawed-no better recommendation, I'd say.

But, I'm biased, having two Spektrum radios, gobs of their receivers and no experience with any other system but 72 mghz!

kyleservicetech 12-22-2009 05:19 PM


Originally Posted by jasmine2501 (Post 674321)
Well, break it down to the facts then...

1. Brown-out is caused by a low voltage condition
2. Low voltage condition number 1 cause is overheated BEC
3. Overheated BEC needs to cool down before it starts working again
4. Receivers need to start up and connect after the low voltage condition and they can't do that until the power comes back - connection time, in my experience, is negligible compared to the time it takes for the BEC to come back online - I've had times when it took 5 minutes, and it doesn't matter what equipment you're using - 5 minutes without sufficient power is going to bring you down. Even 5 seconds is too long - heck, even one second is too long with a heli, usually.

So that's why I say, regardless of which brand of receivers you're using, it's not the problem. It is the inadequate power system which is the problem, and this problem is still going to exist if you change receivers.

And add to this, if your model uses internal receiver batteries, make danged certain that your receiver batteries can handle the load. Other threads have indicated that quickly moving a servo from clockwise to counter clockwise can draw a real slug of current, something I've personally verified.

And if your receiver batteries have to high of internal impedance, that slug of current by the servos is going to cause a very momentary voltage drop to your receiver. If your receiver drops below 3.2 volts (for Spektrum), you're going to have a reboot of its microcontroller.

By the way, the supplied Spektrum receiver battery is not really adequate to run a 25 pound gas model with digital servos. These types of models require heavy duty receiver batteries set up as primary/backup battery systems.

*rider 12-23-2009 02:29 AM

Yes for a big model with high-current draw servos you'd likely need a decent power bus w/voltage regulation for a high-capacity lipo (or two for redundancy). Just cycling 2 of the 6 JR DS821's (not high-end @ $30 each) in my .50 size was enough to make the voltage dip significantly when testing on the bench with a JR 1500mah 6v ni-mh. I couldn't get the receiver to brownout but it wasn't very confidence inspiring. Right now it has a CC BEC with 6v output but I'm considering other options to drive the servos and RX JIC I have a problem between ESC --> parallel lipos. Maybe a voltage regulator and a good lipo.

kyleservicetech 12-23-2009 03:11 AM


Originally Posted by *rider (Post 674612)
Yes for a big model with high-current draw servos you'd likely need a decent power bus w/voltage regulation for a high-capacity lipo (or two for redundancy). Just cycling 2 of the 6 JR DS821's (not high-end @ $30 each) in my .50 size was enough to make the voltage dip significantly when testing on the bench with a JR 1500mah 6v ni-mh. I couldn't get the receiver to brownout but it wasn't very confidence inspiring. Right now it has a CC BEC with 6v output but I'm considering other options to drive the servos and RX JIC I have a problem between ESC --> parallel lipos. Maybe a voltage regulator and a good lipo.

Yeah, as I recall, my Spektrum DX7 servos drew a peak current something over an ampere each when rapidly cycled back and forth, as measured on my Tektronix 2236 oscilloscope. And, if you do acrobatics where the servo's get loaded by aerodynamic loads, you could get into trouble with an inadequate receiver battery. :(

I did check my CC uBEC with a 10 Ampere rating, with a 10 ampere load. That thing put out 6 VDC, whether it had zero load, or 10 Amps load. And, I simply switched that 10 Ampere load on and off with a toggle switch, worst condition. :tc: Only thing I didn't like about the CC unit was the high frequency ripple voltage on its 6 VDC output. ???? The CC unit's switching regulator voltage ripple feeds directly on its DC output.

That ripple voltage has zero effect on my Spektrum AR 7000 receivers, but I'd be a little concerned about that ripple noise on a 72 Mhz radio.

jasmine2501 12-23-2009 07:11 AM

That is very interesting, Kyle - it's not the kind of thing you would notice on a regular ammeter, but it's very possible that an exceedingly brief moment of low voltage could send the receiver into a reboot. It is possible to build a receiver that attenuates that a little bit, but I would bet that manufacturers are saying "we'll leave it up to the user to provide a reliable power supply" and there's only so much you can do while still giving people what they want - reliable, small, light units that work in their planes.

caltrop 12-23-2009 07:30 PM

I Don't Think So
 
After three tries with Horizon I am not going back to them. I don't trust their radios. Why should I buy a new DX7 when the one I have (well, Horizon has it right now) does not work and Horizon will not replace or fix it. Horizon does not know what's going on with these bad systems anyway. I agree that we that have the BAD radios are a small minority but... I've got a really bad Spektrum taste in my mouth right now.

I'm also not having BEC issues since this problem is occurring with more than one model and some of those are BNF's. I also had problems on the bench with no servo's operating. The AR6100e just would not link properly until everything was cycled several times.

As far as receiver brown outs the Spektrum stuff was originally advertised to work down to 3 volts but we all know how that worked. That same bench test I just did I dropped the voltage down to a single fully charged LiPo and the AR6100e failed to work properly. That was a minimum of 4 volts and it failed! It kept browning out everytime I moved a servo but it did recover quickly but I would not want to be flying womething like this.

I might hook up the Tektronix Scope and Fluke Meter to see what the peak currents are just so I know. It's still hard to see rapid spikes on the oscillascope and my meter only has 100ms detection but that should be good enough to see how high things get with four HS-45 servo's.

rcers 12-23-2009 09:11 PM


Originally Posted by caltrop (Post 674854)
After three tries with Horizon I am not going back to them. I don't trust their radios. Why should I buy a new DX7 when the one I have (well, Horizon has it right now) does not work and Horizon will not replace or fix it. Horizon does not know what's going on with these bad systems anyway. I agree that we that have the BAD radios are a small minority but... I've got a really bad Spektrum taste in my mouth right now.

Fully agree - you should not use a system you do not trust.

So rather than continue to beat the dead horse - what system are you going to replace it with?

Mike

kyleservicetech 12-23-2009 09:50 PM


Originally Posted by caltrop (Post 674854)
After three tries with Horizon I am not going back to them. I don't trust their radios. Why should I buy a new DX7 when the one I have (well, Horizon has it right now) does not work and Horizon will not replace or fix it. Horizon does not know what's going on with these bad systems anyway. I agree that we that have the BAD radios are a small minority but... I've got a really bad Spektrum taste in my mouth right now.

I'm also not having BEC issues since this problem is occurring with more than one model and some of those are BNF's. I also had problems on the bench with no servo's operating. The AR6100e just would not link properly until everything was cycled several times.

As far as receiver brown outs the Spektrum stuff was originally advertised to work down to 3 volts but we all know how that worked. That same bench test I just did I dropped the voltage down to a single fully charged LiPo and the AR6100e failed to work properly. That was a minimum of 4 volts and it failed! It kept browning out everytime I moved a servo but it did recover quickly but I would not want to be flying womething like this.

I might hook up the Tektronix Scope and Fluke Meter to see what the peak currents are just so I know. It's still hard to see rapid spikes on the oscillascope and my meter only has 100ms detection but that should be good enough to see how high things get with four HS-45 servo's.

Just a note, all microcontrollers will "Brown out" when they hit their "Minimum Voltage" limit. And they will brown out in microseconds. What Spektrum did early on was put a large capacitor across the battery input to "Knock off" those instantaneous voltage sags that could come from sudden high current surges from overloaded batteries and heavy duty servos.

As I've indicated, Spektrum is not by any means perfect. I had one of my Spektrum AR7000 receivers quit dead while taxing around in my driveway. (That's what's called an infantile failure)

But, the last issue of RCR (Radio Control Report) magazine had a very well detailed test routines for Spektrum/JR, Futaba, and one or two other brand radios. Spektrum/JR came out on top, Futaba was a very very close second, and the other brand radio was so bad, they quit testing it in the middle of their test procedure.

Admittedly, RCR's radio interference test was about as severe as you could make it, but it does give a clue on what is going on. If they had conducted that same test on any of the 72 Mhz radios, they would have had just about every radio system cause a crash.

Good luck with your Futaba radios! And Happy Holidays!


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