HobbyKing.com New Products Flash Sale
Reply
Thread Tools
Old Jun 16, 2010, 05:42 PM
Registered User
chriscat's Avatar
United States, KS, Wichita
Joined Feb 2010
67 Posts
Discussion
DX7 issues? Brown out?

Yesterday I was flying my Super Cub LP all stock, no upgrades, in level flight using my DX7 tx, no real inputs on servos, when all of a sudden it went to down elavator straight into the ground, I had zero controll. Luckily I was flying over a wheat field that hasn't been cut, so there was no damage.

Next, I flew my Trojan t28d, with a ar6110e rx I installed after adding flaps to plane,same scenario, level flight, no real inputs on servos, when it decided to take a nose dive with a aieleron roll added to it, some damage but cushioned by the wheat field for the most part.

I've never had a single problem in the past until then.
Did I have a brown out, I never looked to see if light was blinking on esc's or not, never thought about it. I did notice the tx volt reading was at 10.8v. r did something go wrong with the tx for a few seconds.

I have seached through the forums & everything seems point needing a battery pack for the rx, but that doesn't make sense to me as I was only maybe 5 minutes into each flight at max & should have had plenty of juice left in them as I don't fly at full throttle, aslike nice easy flying.
So, could this have possibly been the tx sending weird signal to plane?

I bought the DX7 used from this form about 3 mo back, & it may be an earlier version by looking at the box compared to what the boxe looks like now.

I'm opened for any suggestions.

I hope I have explained this enough in detail, & sorry for the length.

Chris
chriscat is offline Find More Posts by chriscat
Reply With Quote
Sign up now
to remove ads between posts
Old Jun 16, 2010, 05:58 PM
60 years of RC flying
Daedalus66's Avatar
Canada, ON, Ottawa
Joined Feb 2006
16,760 Posts
You could have a transmitter issue, but it isn't the battery if it's up over 10v as you say. The DX7 will work right down to 9 volts or so, though you should probably recharge at about 10.0 to be on the safe side. Older and newer DX7s are essentially identical.

Have you done a proper ground range check? You should do one every time you go out flying. With bind button pressed you should get full control at 25m. If you have that, then you should have plenty of range for normal flying.

You do NOT need a receiver pack to fly an ordinary electric model. You just need a decent ESC with adequate internal BEC. Since both planes have been operating well for some time, there's no reason to think the stock ESCs they are using are inadequate.

So where does that leave things? The failure of two different models in quick succession with the same transmitter seems to suggest a transmitter fault (such as an intermittent connection). Or something in the environment (interference). Are you flying close to strong 2.4 GHz transmitters like WiFi (from the reference to wheat fields, I'm guessing not)?

I presume you are using 3s LiPo batteries. They should give plenty of voltage for the BEC to reduce to 5v.

Don't reject the idea that two failures in succession could indicate two different causes. While it's likely they are connected, it's by no means certain.

I'm running out of ideas. Do some more testing and see if anything turns up.
Daedalus66 is offline Find More Posts by Daedalus66
Reply With Quote
Old Jun 16, 2010, 06:20 PM
Registered User
chriscat's Avatar
United States, KS, Wichita
Joined Feb 2010
67 Posts
Quote:
Originally Posted by Daedalus66 View Post
You could have a transmitter issue, but it isn't the battery if it's up over 10v as you say. The DX7 will work right down to 9 volts or so, though you should probably recharge at about 10.0 to be on the safe side. Older and newer DX7s are essentially identical.

Have you done a proper ground range check? You should do one every time you go out flying. With bind button pressed you should get full control at 25m. If you have that, then you should have plenty of range for normal flying.

You do NOT need a receiver pack to fly an ordinary electric model. You just need a decent ESC with adequate internal BEC. Since both planes have been operating well for some time, there's no reason to think the stock ESCs they are using are inadequate.

So where does that leave things? The failure of two different models in quick succession with the same transmitter seems to suggest a transmitter fault (such as an intermittent connection). Or something in the environment (interference). Are you flying close to strong 2.4 GHz transmitters like WiFi (from the reference to wheat fields, I'm guessing not)?

I presume you are using 3s LiPo batteries. They should give plenty of voltage for the BEC to reduce to 5v.

Don't reject the idea that two failures in succession could indicate two different causes. While it's likely they are connected, it's by no means certain.

I'm running out of ideas. Do some more testing and see if anything turns up.
I charge the tx after I return home, it normaly starts out at 11.1 or so.

I didn't do a range check this time but have in the past with no problems, but I don't fly that far away, to hard to see for me. Each instance I'm guessing 3 to 500' away.

I agree, stock esc's on 3s should be fine, no need for rx packs.

There is a building at the back of fieid that has wifi, but I've never had a problem in past (not ruling it out). The only thing that has changed with building is a booster for verizon phones were installed to receive a signal inside.

Besides the bldg, its a 180 acres of wheat with a almost 1/2 mile paved road through middle. No houses, cars,trafic, people, poles, or hi wires in the way, perfect for me being new.
chriscat is offline Find More Posts by chriscat
Reply With Quote
Old Jun 16, 2010, 08:03 PM
Registered User
USA, TX, Diboll
Joined Aug 2007
224 Posts
Dx7 is what I use also and have never had any issues "knock on wood". Did both issues take place while flying in the same area? This could point to a possible interference in that area.

Double check all your connections and make sure all are secure.

If each instance was with a different receiver then the problem points more to either outside interference or the radio.
Chestum is offline Find More Posts by Chestum
Reply With Quote
Old Jun 16, 2010, 08:33 PM
60 years of RC flying
Daedalus66's Avatar
Canada, ON, Ottawa
Joined Feb 2006
16,760 Posts
What can we rule out? Please disagree if I get it wrong.

Doesn't sound like a brown out, for three reasons. First loss of power or low voltage generally leaves the controls where they are -- you say there was a distinct down-elevator event in each case. Second, the ESC setup ought to be adequate and had not given problems before (but next time do try to check for flashing receiver before unplugging -- I know it's easy to forget). Third, big coincidence for it to happen with two different models in quick succession (but not impossible).

Doesn't sound like receiver or servo problems as it would be a big coincidence.

Doesn't sound like Tx battery given the voltage readings.

Could be interference. How close are you to the Verizon booster? I'd be inclined to walk over fairly close and do a careful ground range check.

Could be a transmitter fault. I would take the back off and have a good look around. I would also poke and prod (non-conductive probe) with the receiver working to see if you can induce loss of connection.

Final option is to ship the Tx to Horizon for a check up.
Daedalus66 is offline Find More Posts by Daedalus66
Reply With Quote
Old Jun 16, 2010, 09:12 PM
Registered User
chriscat's Avatar
United States, KS, Wichita
Joined Feb 2010
67 Posts
Quote:
Originally Posted by Chestum View Post
Dx7 is what I use also and have never had any issues "knock on wood". Did both issues take place while flying in the same area? This could point to a possible interference in that area.

Double check all your connections and make sure all are secure.

If each instance was with a different receiver then the problem points more to either outside interference or the radio.
Chestum
Each instance is with a different rx, stock sc, & 6110e for the trojan, but with same tx.
As stated before straight & level flight then all of a sudden down elavator. With the trojan It added a aeirlon roll to make it look better I guess
chriscat is offline Find More Posts by chriscat
Reply With Quote
Old Jun 16, 2010, 09:18 PM
Registered User
chriscat's Avatar
United States, KS, Wichita
Joined Feb 2010
67 Posts
Quote:
Originally Posted by Daedalus66 View Post
What can we rule out? Please disagree if I get it wrong.

Doesn't sound like a brown out, for three reasons. First loss of power or low voltage generally leaves the controls where they are -- you say there was a distinct down-elevator event in each case. Second, the ESC setup ought to be adequate and had not given problems before (but next time do try to check for flashing receiver before unplugging -- I know it's easy to forget). Third, big coincidence for it to happen with two different models in quick succession (but not impossible).

Doesn't sound like receiver or servo problems as it would be a big coincidence.

Doesn't sound like Tx battery given the voltage readings.

Could be interference. How close are you to the Verizon booster? I'd be inclined to walk over fairly close and do a careful ground range check.

Could be a transmitter fault. I would take the back off and have a good look around. I would also poke and prod (non-conductive probe) with the receiver working to see if you can induce loss of connection.

Final option is to ship the Tx to Horizon for a check up.
I don't think brown out either as the angle they went down,
about 60 degrees, as if I flew them down.

I will check to see if I can re-inact the situation, but I think ultimately it needs to go back to Horizon.

Thanks to both of you for your input. Maybe someone else will chime in, but don't stop now if you think of something else please post.

I will check & see if cell phone booster will recreate problem on the ground. I don't think it will as it was mounted on roof for obvious reasons.
chriscat is offline Find More Posts by chriscat
Reply With Quote
Old Jun 16, 2010, 11:22 PM
60 years of RC flying
Daedalus66's Avatar
Canada, ON, Ottawa
Joined Feb 2006
16,760 Posts
Quote:
Originally Posted by chriscat View Post
I will check & see if cell phone booster will recreate problem on the ground. I don't think it will as it was mounted on roof for obvious reasons.
Ah, now I understand what it is.

Good luck.
Daedalus66 is offline Find More Posts by Daedalus66
Reply With Quote
Old Jun 18, 2010, 10:06 PM
Registered User
chriscat's Avatar
United States, KS, Wichita
Joined Feb 2010
67 Posts
I was just thinking, what's with the dsm2 technology isn't that suppose to stop interference, or is that just for RC?
chriscat is offline Find More Posts by chriscat
Reply With Quote
Old Jun 18, 2010, 10:10 PM
Registered User
chriscat's Avatar
United States, KS, Wichita
Joined Feb 2010
67 Posts
I couldn' recreate problem next to bldg.....Naturally
chriscat is offline Find More Posts by chriscat
Reply With Quote
Old Jun 18, 2010, 10:15 PM
In love with aviation
flying-things's Avatar
Joined Apr 2010
387 Posts
yes, dsm2 is supposed to be bullet proof, however every system has it's limitations, and the older spektrum technology is the weaker of the major brands unfortunately.
Quote:
Originally Posted by chriscat View Post
I was just thinking, what's with the dsm2 technology isn't that suppose to stop interference, or is that just for RC?
flying-things is offline Find More Posts by flying-things
Reply With Quote
Old Jun 18, 2010, 10:31 PM
Registered User
chriscat's Avatar
United States, KS, Wichita
Joined Feb 2010
67 Posts
Quote:
Originally Posted by flying-things View Post
yes, dsm2 is supposed to be bullet proof, however every system has it's limitations, and the older spektrum technology is the weaker of the major brands unfortunately.
Please educate me. Is what I'm using "older technology" & what are the major brands as I thought spektrum was one of them but obviously wrong. I'm just trying to figure it out so it doesn't happen again.
chriscat is offline Find More Posts by chriscat
Last edited by chriscat; Jun 18, 2010 at 11:02 PM.
Reply With Quote
Old Jun 19, 2010, 12:12 AM
60 years of RC flying
Daedalus66's Avatar
Canada, ON, Ottawa
Joined Feb 2006
16,760 Posts
Spektrum is the major brand in terms of market share. DSM2 was the first of the mainstream 2.4 protocols (after the relatively brief reign of DSM) and is still one of the best. I have had three years of excellent service with no problems except with a particular type of receiver. Your problem is not a general one of Spektrum, it's a specific one that needs to be tracked down.

The only real criticism of the DSM2 approach is that it uses two frequencies that are more or less randomly allocated in the band (and change every time you turn on). On rare occasions, these two frequencies will be close enough together that a single broad source of 2.4 signal (like a video transmitter) can hit both of them. But such interference is relatively rare at most fields.

It is very unlikely that all this has anything to do with your problem as it would require:
1. a close and strong source of interference that is fairly broad.
2. a 1-in-100 (or whatever) occurence in which the two frequencies of you transmitter happen to be close together and coincide with the interference.
3. a second instance of the same thing that causes your other crash.

Forget my earlier reference to interference -- I think now it was misleading.

Focus on the common element -- the transmitter. Send it to Horizon (along with the receivers) and explain what happened.
Daedalus66 is offline Find More Posts by Daedalus66
Reply With Quote
Old Jun 19, 2010, 08:10 AM
In love with aviation
flying-things's Avatar
Joined Apr 2010
387 Posts
Sorry to cut you off deadalus66,
I just thought I'd mention http://rcmodelreviews.com/
Lots of great info about spektrum radios.
flying-things is offline Find More Posts by flying-things
Reply With Quote
Old Jun 19, 2010, 01:50 PM
60 years of RC flying
Daedalus66's Avatar
Canada, ON, Ottawa
Joined Feb 2006
16,760 Posts
Quote:
Originally Posted by flying-things View Post
Sorry to cut you off deadalus66,
I just thought I'd mention http://rcmodelreviews.com/
Lots of great info about spektrum radios.
I'm well aware of those reviews. Good source of information on the relative merits of various radios. Nothing I said is inconsistent with what's found there.

For example:
As stated in the review, the DSM2 system is generally quite good. It uses two separate parts of the band and has a good degree of "spread" for each of its chosen frequencies, thus ensuring that under normal conditions, DSM2 provides a robust and resilient link between transmitter and model.

My point was that to have the kind of double failure experienced by chriscat would take some highly unusual conditions and/or a very big coincidence. There is no reason to believe that the failures are the result of a Spektrum design issue. Rather chriscat should be looking to specific problems in the transmitter as the likely cause.
Daedalus66 is offline Find More Posts by Daedalus66
Reply With Quote
Reply


Thread Tools

Similar Threads
Category Thread Thread Starter Forum Replies Last Post
Help! Need help trying to track down a power/brown out problem Zeta30 Electric Heli Talk 59 Jun 06, 2010 10:37 PM
Help! Brown Out - Motor, ESC, Rx...or what?? MrRetro Mini Helis 11 Apr 04, 2010 12:55 PM
Help! Does this look like a "brown out" to you??? omster Mini Helis 6 Mar 10, 2010 09:19 AM
Discussion Will mine brown out????? ty_horn Radios 0 Nov 06, 2009 08:46 PM
Off Site Will mine brown out????? ty_horn Aircraft - General - Radio Equipment (FS/W) 0 Nov 06, 2009 08:45 PM