DX7 Crashed Two Planes
 

I finally got my World Models Cap 232 all together and took it out for the maiden flight. I had all the trims right and range tested my DX7 and everything seemed to work great. I warmed up the engine and took it off. As soon as the plane got airborne, it started rolling to the right and never responded to any controls. After it "landed" upside down, I took it back home and fixed the wing. Just for the sake of me screwing something up, I swapped the RX and TX over to my never let me down Thunder Tiger 40. I took it back to the field and same thing. Plane rolled right with no response. Unfortunately, it didn't fare up as well as the Cap. I have since tried flying the Cap again with the same thing happening. I just got done reading several negative posts about the DX7. I flew the Thunder Tiger not three days before along with my Arrow 40 using my DX5 and both planes worked flawlessly. Is there something I am missing with the DX7? I spent a full day going through and setting it up to my Cap thinking that I got everything. Any help would be greatly appreciated. I would love to finally fly my Cap.

RE: DX7 Crashed Two Planes
 

I am sorry for your loss. No one enjoys a crash and especially one where all systems were checked before the flight.

Did you do a range check using the procedures outlined in the manual? If so, did you notice any unusual response from the control surfaces on the aircraft during the range check?
Was the battery fully charged?
What type of chemistry battery? NiCad, NiMh, LiPo, A123, Eneloop? What voltage?
Did you check all the connectors that were common to both aircraft to see if there was a loose pin?
What about the Tx battery?
Did you perform one last Bind after the Tx Model Memory was set up?

We have many fellow club members who have DX7's and none have failed over the last few years, but that does not mean that you did not receive a defective one.

The only thing I do not like about the DX7 is the Big Fat Bind Button, the Throttle Inhibit feature, and the location of the Trainer Switch.

RE: DX7 Crashed Two Planes
 

Hello bradfordalston

I am not sure I should respond to your posting but the situation intrigues me.

Here follows some thinking and wondering in my mind.

Sincethe Cap 232was on its maiden flight I would have to assume that it was checked properly for lateral balance. One of the intrigues is that you had no control response after doing a normal range check as if the transmitter was suddenly not transmitting or was emitting very low abnormal power level.

You may have had enough power for a normal range check but not enough for any further distance. How about if your transmitter battery was nearly dead ?
Or perhaps the receiver battery.

It just appears to me that the reason is a weak radio signal since you had flown the Tiger 40 without problems with the DX5.

Of course it is possible that your DX7 might be defective but that is not yet proven.

Which receiver was in use ?
Was the range check (in both case, both models) made with the antenna pointing at the model ?

You say thatyou hadall the trims right. I wonder how you can say that ?
I just do not know how I could set the trims right before a maiden flight. I make sure the model is laterally balanced and the CG is within range (preferably near the center of the range) and then adjust any required trimming while flying.

What if one of your trim was inadvertently and unnoticed way out such as the aileron or rudder trim ?

I am hoping that the negative comments you have read or heard about the DX7 are not influencing your good judgment and making you jump on a wrong conclusion.

There are very many DX7 in service and operating without problems.

I would think that more work is needed to resolve this situation.

I will be very curious to read comments from other users.

Wishing you a prompt recovery with you DX7 and it associated receiver.

Regards deZor.

RE: DX7 Crashed Two Planes
 

Sorry for not reading your post more slowly. I see that you did Range Test the radio. That is imperative before a maiden flight or at least at the beginning of each flying day.

The rest of the questions I posted are always asked when someone has a crash that appears to be radio related. You will see these questions in many threads on RCU and other forums.

RE: DX7 Crashed Two Planes
 

bradfordalston . . . and all readers,

You may have some reaction as you finish reading this posting.

I may have to join you and the group of many fliers who have complained about the DX7 system.

Please read what happened to me this evening.

I am building a Spectra sailplane and have just finished installing all the controls. Three servos operating the rudder, elevator and an On and OFF switch for the electric motor / prop.

I just finished soldering the two leads on the motor and installed the prop. I decide to test the system and secure the fuselage so it would not move and have plenty of clearance for the prop.

I turn the transmitter on and look at the voltage. It reads 10.0 volts on the Xmtr screen. It is a 9.6 volts system so that is good. The receiving system battery read 4.8 volts. again that is good.

I turn the plane system on (receiver) and I get a binding within just about one second. Two steady red lights (main rcvr and satellite rcvr).

BUT __surprise __the servos are NOT responding to Xtr control. None of the three are working.
Servos are absolutely dead.

Turn off rcvr __turn off Xtr. Wait 10 seconds ___ Turn Xtr on __turn rcvr on. Got two steady red lights.
Servos are working fine.

Sincethe problem was all three servos not working it seem the cause would be the 4.8 v supply to all three servos. So I play with the suppy connectors from battery to switch and switch to rcvr.
No difference and servos keep working.

Turn system off.

Thinking ___(no magic answer) ___

Turn the system back on. Have two solid red lights ___and no servo response. All three are dead for the second time.
Put the voltmeter on the battery connection at the receiver. That cause the two red lights to start blinking. Is this not suppose to be due to a momentary lack of voltage (power) at the receiver?

The servos are still dead.
Disconnect the connector from the battery (from the switch) to the receiver and inspect. All three pins on the receiver are solid (fiddling with tweezers) .
Put the connector back on. It is a little stiff to push in ___looks like good connections.
No servos are responding.

Turn the system all OFF.

About ten minutes later I turn the sytem on. I have two solid red lights on the receivers and the servos are working fine (normal as expected).

Turn system OFF and ON many times in the following 20 minutes (or so) without any failure.

Conclusion ___
No real conclusion can be drawn at this time but it nearly look as if the transmitter had failed twice to have any modulation.
I have great doubts that I have a poor connection. When I have no servo response and all I do is turn the recvr switch off , then Xtr switch off. Wait a few seconds and turn Xtr back on and Rcvr back on and all works fine. It sure does not appear to be a connector or an intermittent circuit.

More research will be done >>>>>>>
We just cannot risk flyingin these conditions.

An unreliable system is useless and just money thrown in the gutter.

More to follow.

Zor

RE: DX7 Crashed Two Planes
 

You say that you checked the rx voltage and it read 4.8 volts. I'll assume you are using a 4 cell Nimh or Nicad and if that's the case, then that would be the nominal voltage not the fully charged voltage in which case, that isn't good and may very well have lead to your results. It was simply too low of a voltage for your rx.

If it were me, I would start with at least a 6 volt battery system on the rx. Spectrum, in my opinion should not be run with a 4.8 system as that will lead to a typical brown out, especially if you started out with a 4.8 battery that may not have been fully charged.

Try using a higher voltage battery. Just my thoughts.

RE: DX7 Crashed Two Planes
 

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5.4pt;mso-para-margin-top:0cm;mso-para-margin-right:0cm;mso-para-margin-bottom:10.0pt;mso-para-margin-left:0cm;line-height:115%;mso-pagination:widow-orphan;font-size:11.0pt;font-family:"Calibri","sans-serif";mso-ascii-font-family:Calibri;mso-ascii-theme-font:minor-latin;mso-hansi-font-family:Calibri;mso-hansi-theme-font:minor-latin;mso-bidi-font-family:"Times New Roman";mso-bidi-theme-font:minor-bidi;mso-fareast-language:EN-US;}</style><![endif]><p class="MsoNormal"><span lang="EN-US" style="">This also happens now and then with my DX7. It is very irritating but seems to be one of its characteristics. I don&acute;t think it is due to a low battery voltage it just does not connect every time. So it is important to check that you have control before you fly not just checking the LED:s because they do not always tell the whole truth.</span></p><p class="MsoNormal"><span lang="EN-US" style="">The manual also describes it on page 15.</span></p><p class="MsoNormal"><span lang="EN-US" style="">If possible use a 5 cell battery with DX7 otherwise the battery will always be suspected if you have an issue. Sometimes the battery is the reason but there ar other curious things with the DX7.
</span></p>

RE: DX7 Crashed Two Planes
 

Hello pdm52956 and thanks for your response.

<span style="color: #ff0000">Please see the red inserts which I find more convenient that the quote and unquote brackets.
</span>
Thanks for your quick and kind response.
I will post results of my further research.

Zor
Spelling not verified.

RE: DX7 Crashed Two Planes
 

A DVM will NOT catch a short voltage drop. The update rate of the DVM is too slow and it averages the voltage. To see a glitch like this you'd need an Oscope.

Tim

RE: DX7 Crashed Two Planes
 

Zor, I hope you figure out what's causing your issue with the rx and tx. I'd be interested to know what you find out. I started with the DX6i and have a different thought process when it comes to rx voltage. I've upgraded to the 9503, but I'll continue to fly with higher voltage rx packs that I feel feel more comfortable with.

I for one would NEVER run a 4.8 battery on a Spectrum rx. Been there done that. Doesn't mean your problem is the same as the one I had, I just won't take that chance.

I've seen brown out conditions during bench tests at times that you would think it should NOT have happened. Now I'm no electrical geru by any means, but the use of a higher voltage battery possibly being the difference between bringing one home in a bag or on it's wheels tied down in my trailer, I choose the battery every time.

I'll be following this thread with interest to see what you come up with. Good luck and happy flying!

RE: DX7 Crashed Two Planes
 

Hey - Zor!! I have not talked with you in a while.

As I read your post, you do not mention putting your batteries under a load when measuring the voltage. A No-Load voltage reading is not very useful as the voltage can drop significantly with just a .5a load for NiCad or NiMh.

I think there is enough evidence circulating around to indicate that running Spektrum receivers with less than 6v batteries is not wise. If the servos are not compatible with 6v you can use a voltage regulator to drop the voltage, but you are still less likely to have a Brownout than if you were using 4.8v Rx batteries. It is also important to have batteries with more than enough capacity.

I use 2cell 2500mah LiPos in all my aircraft. I use either a 5v or 6v regulator depending upon the servos I use. These batteries are inexpensive to buy, easy to charge quickly, and the charge lasts for a long time.

I have an 84" Katana running a 10S 5000mah pack for the motor and a 3cell 2200mah pack for the Rx, using a separate CC Bec. I have been using 2cell 2500mah LiPos in both of my JR XP9303 Tx's (with Spektrum RF Modules) for several years, without issue.

I have two FMA 10S chargers. I connect them to a Pyramid 40a Power Supply in my home or to two 6v Golf Cart batteries (in series) in the back of my van. Some of my fellow club members have Honda 1000w generators and use the generators and power supplies at the field. Recharging is fast and easy.

After many years of NiCad/NiMh, I no longer use them. I also have Eneloop and A123cells, as well.

RE: DX7 Crashed Two Planes
 

Further to my post #8 ___

Reading again the DX7 manual for the upteen time, I notice on page 24 that the minimum Rx voltage is quoted as 3.5 volts while on page 16 it was quoted as 3.2 volts.

Also on page 24 it says
quote
The voltage should remain above 4.8 volts even when all servos are heavily loaded.
unquote.

When I read these discrepancies, I really wonder what one can believe and trust.

Does the receiver stop functioning below 4.8 v or 3.5 v or 3.2 v ___???

As I said, i will try (as soon as I have a chance) a source of variable DC voltage with high current capability and see what is happening.

We need observation of facts and some data we can trust.

I do not find that reliable info in the manual or in the forum.

Many fellows have circumnavigated the problem by going to 6 volts and that is a helpful solution but I am keen at trying the best I can in finding what really is going on (happening).

For me it is part of this hobby.

One of my mottos "NEVER GIVE UP"

CUall later.

Zor

RE: DX7 Crashed Two Planes
 

Bradfordalston,

Please let us know if you have objections that we contimue discussing this topic in the thread you initiated.

It was all brought about by the mishap you had and you reported in your first posting.

Regards de Zor

RE: DX7 Crashed Two Planes
 

I haven't found an RC radio manual, yet, that seemed to be written by anyone who actually used the radio or flew RC aircraft.

I have fellow club members who are sponsored JR pilots. They know what problems have arisen and the correct way to set up systems to avoid or correct the problems. I trust them implicitly. I find this information more useful than any manual or public posting

RE: DX7 Crashed Two Planes
 

<span style="color: #ff0000">Text in red inserted by Zor as a response.
</span>
More soon as I find time. Leisure times only as this is a hobby.

Best regards always,

Zor

RE: DX7 Crashed Two Planes
 

Hi Mastertech,

Nice to have a "master" in here.
Yes I know about digital voltmeters needing scan times and not picking up a proper reading if the DC is not steady.
I hate digital voltmeters.
I still have some good old reliable VTVM as well as ordinary analog voltmeters.

Please read the last paragraph in red in post #15.

Zor

RE: DX7 Crashed Two Planes
 

<span style="color: #ff0000">Inserted text in red is by Zor as a response.
</span>
I think there is nothing wrong using NiCd or NiMH.
I just hope to find time soon enough to carry on further experiments; this time using my DC responding oscilloscope.

Thanks for your posting.

<span style="color: #ff0000">Season's Greetings.</span>

Zor

RE: DX7 Crashed Two Planes
 

Every problem I have seen with the Spektrum stuff could be traced back to failures in battery or/and regulators
All but one - and that was a rx which quit on the bench-permanently
- and was replaced on warranty
Any pack which reads 4.8 volts is already too low.
If you really have access to A123 - balance charge two cells (1100 or 2300), these will read 7.2 v and operate at a nominal 6.6
I ran a number of DX7 setup and various power setup and use it for rx and servos Jr stuf does well on these.
On electric powered models I always used the EFlite ESC with internal SWITCHING type BEC on anything larger than a 5 oz foamy
A 4.8 v battery will work just fine with the Spektrums providing you have cells which will actually fully charge and operate at designed capacities -
Even in a 35% 3D model - seen it over n over but personally I preferred the A123 setups
Voltage needed is voltage under operating load - some cells collapse in tiny spikes and caause problems but they are easily checked using a quality in line meter.
The Spektrum stuf is as good as it gets .

RE: DX7 Crashed Two Planes
 

Hello rmh,

What are you making (thinking about) the voltage values mentioned on page 16 and 24 of the manual ?

Thanks for your comments on that question.

<span style="color: #ff0000">Season's Greetings,</span>

Zor

RE: DX7 Crashed Two Planes
 

I'm a Certified Master Automotive Tech, hence the nickname.

I was pointing out to anyone reading this thread to understand a DVM isn't the proper tool to find these voltage drops.

I might bring home my DSO (Digital Storage Oscope) and do some testing and post the results here. I need to find out if the program I use will allow a me to post a capture here so others can see it.

Tim

RE: DX7 Crashed Two Planes
 

I think the wording could have been better - Frankly the Spektrum 7 manual was not very good and in some cases misinterpreted. Real world: The Spektrum rx operatee down to about 3.2 volts

This means that there must NEVER be voltage spikes which drop to THAT reading!
Again cells which will not hold voltage levels or regs which heat n collapse (and there were plenty of bad ones on the market) were ALWAYS the culprits
Iam accepting that the user has properly soldered and properly sized wiring through out

RE: DX7 Crashed Two Planes
 

I agree that there is nothing wrong with NiCad or NiMh, however, it is the fact that they Self-Discharge as they sit idle and take so much longer to charge than LiPos or A123 cells. If you inadvertently leave a switch on and you arrive at the field with dead batteries, you are done for the day. My experience with NiMh is that if they do not have the right level of Internal Impedance, they will False Peak the charger unless you keep the charge level very low, which translates to hours of charging. Eneloop is the closest I want to get to NiMh.

I realise that LiPo's do not recover well from inadvertent over discharge, so I disconnect them from the Switch Harness at the end of each day. When I check the voltage of a LiPo pack at the end of the day, it reads the same a week later. The newer technology LiPo packs can be charged at 3S to 6S if you have the right charger and power source.

I have never had any bad experiences. I can use my Transmitter for a week or two without recharging.

RE: DX7 Crashed Two Planes
 

Soon all new radio systems will be Lipo based, no more nicads or mhims at all. The servos are the weak point now but JR is building all new High voltage servos.

The wave of the future.

Tim

RE: DX7 Crashed Two Planes
 

Thanks for your reply "rmh".

I suppose you meant "
there must NEVER be voltage spikes which drop (to THAT reading!) <span style="color: #ff0000">below that voltage reading.

</span><span style="color: #000080">My interpretation is that the receiver should operate normally down to 3.2 volts and I agree that any spike below that would nearly instantly create a brownout.

Now we also have to interpret a spike which would be a drop below 3.2 volts for a certain lenght of time. I accept that a spike lastng even only a milisecond or even shorter might trigger the brownout.

</span>I am anxious to put my oscilloscoope on the battery supply. This oscilloscope is good up to 10 megahertz and the persistence of the phosphor and my eyes should be able to detect any spikes.
I am also hoping to be able to see the signal from the receiver to the servos.

No use speculating at this time. Let us wait and see what I can see.

<span style="color: #ff0000">Season's Greetings.</span>

Zor

P.S.: <span style="color: #ff0000">NOTE HOWEVER THAT AS THE SWITCHES WERE ACTUATED, Xtr FIRST THEN Rx THE BINDING WAS TAKING PLACE AS SHOWN BY BOTH RED LED COMING ON STEADY AND THERE WAS NO RESPONSE FROM ANY OF THE THREE SERVOS AND THE LED DID NOT SWITCH TO BLINKING AS IF THERE HAD BEEN A BROWNOUT OR A LACK OF Rx VOLTAGE FOR ANY LENGHT OF TIME.

IT IS JUST AS IF THERE WAS NO MODULATION OUT OF THE TRANSMITTER.A SUPPOSITONI WROTE PREVIOUSLY.


</span>

RE: DX7 Crashed Two Planes
 

Being a great believer in" the easy way first" - I once had a similiar experience and found out I was spinning my wheels
The reason being I had plugged in the servos backward
The next time I ran into "what's going on here" situation with the then new 2.4 Spektrum, I got another tx and tried comparison tests
Any Spektrum tx which is DSM2 compatible, binds up in th same fashion

1- insert bind plug
2 - add rx power

3 turn on tx with bind activator engaged -these button/switches roller-may differ but the sequence remains the same .

Onc the rx makes friends with the tx, the lights go solid - then the servos are coupled up. The tx and the RX do talk together and a determination is made -within the tx - as to what type rx is being bound.
No exceptions- this interplay insures any rx being connected gets THE CORRECT INFO
At this point realease bind on the tx - remove bind plug from rx and from THAT time on , the bind stays engaged unless you activate the bind button at the wrong time and kill the relationship
This happens is if you activate bind on the tx BEFORE the rx is turned on again-
This happened to some people who set their tx against a backstop which rested against the bind button- or to others who simply dumb thumbed the bind switch before bind was complete.

So save yourself anguish - borrow a TX (DSM2) and see if you get different results
You don't need a scope to operate these radios - really - just make meaningful simple tests . And -also- do a review on inf about how batteries work under load - this is a oftimes misunderstood thing which has caught quite a few .
Try one of the reviews by battery pack supplier ( No BS etc..)