Help,,two jets,,two days,,,destroyed!

[elkmaster01]

OK,,,the two jets did the exact same thing,,,,,,30 seconds into flight they just went dead,,,motor/flight controls,,,dead. BUT,,they both powered back up about 3 or 4 seconds later,,,,,,too late to save them. When I got to them,,the Rxs(both AR7000) had solid lights and everything on the jets worked fine.

The first one(F-4E) I figured was an ESC brownout,,,but then the next day the second jet (twin SU-34) did the same thing,,it has two ESCs.

I have rebuilt the F-4E with all the same electronics and bench-ran it full throttle for 4 minutes,,,twice,,,no issues.


Whats the chances I have a radio problem?(DX7)


Another problem,,,,,,my F-16 has trouble arming(ESC). It will arm if I plug in a 2S or 3S battery,,,OR,,,if I drain a 4S to about 16.4 volts it will arm. On a full 4S battery I just get a constant double beep from it. This jet just started doing this,,I have been flying it for months. ESC going bad?? Ideas?

Thx!!

Randy

[Gabe]

I hate to ask the stupid question, but is the Dx7 reading over 4.8V on the charge?

[19000rpm]

The clue here is that the Rx was not flashing meaning that the brownouts happened on the motor side of the plane rather than on the power supply to the Rx.

I've had this happen at least 5 times: It was either the ESC or a connector at the ESC or motor.

I've also had a at least 4 cases where, I believe, it was radio interference. I'm not sure what the source is, but it's powerful enough to interrupt the 2.4 signal. No other cause could be found.

I guess there is a possibility that the TX is also responsible or maybe just the antenna. Check the plug and wire internally where it connects to the printed circuit board.

[elkmaster01]

Aug 17, 2010 0:37:47 GMT -6 Gabe said:

I hate to ask the stupid question, but is the Dx7 reading over 4.8V on the charge?

I'm using lipos in my DX7s,,,,charged to 12V,,,,I recharge at 11.5v,,,,charges are about a month apart,LOL.

[elkmaster01]

Aug 17, 2010 6:41:11 GMT -6 19000rpm said:

The clue here is that the Rx was not flashing meaning that the brownouts happened on the motor side of the plane rather than on the power supply to the Rx.

I've had this happen at least 5 times: It was either the ESC or a connector at the ESC or motor.

I've also had a at least 4 cases where, I believe, it was radio interference. I'm not sure what the source is, but it's powerful enough to interrupt the 2.4 signal. No other cause could be found.

I guess there is a possibility that the TX is also responsible or maybe just the antenna. Check the plug and wire internally where it connects to the printed circuit board.

The AR7000 won't show a signal loss will it? It just blinks on a power brown-out yes?

I'm having a hard time believing it's an ESC or motor,,,two jets,,,three ESCs/motors.

You may have something with the antenna,,,,I replaced the antenna on this DX7 several months ago. Spektrum does not market replacement antennas,,I think this was a e-flight antenna. I'll pull the Tx apart and take a look see.

[19000rpm]

The Rx just shows electrical brownouts not signal loss.

Although it may be coincidental, it all happening in such a short period of time, you could also have more than one problem.

Odds would have it that it's Tx related. Hope it's something simple like the antenna. Call Horizon and they'll probably send you a new one, they did that for Ray, or send the unit in for a full check.

[akent]

One other thing to look at is that when using a Lipo on these, the reason Spektrum/JR do not recommend that is because these use a linear regulator in the transmitter. These convert the internally used voltage difference from the battery into heat.

The internal voltage of the DX7 is 3.3v at somewhere around 150ma. I think they may use a little more, but that's a good example. Anyway, 12v (really should be 12.6v on a fresh charge) from a lipo - 3.3v used by the transmitter = 8.7v difference. Since a linear regulator drops the voltage with HEAT, here is the result.
3.3v at 150ma = 0.495 watts of power needed to run the transmitter.
12v at 150ma = 1.8 watts from the battery.
8.7v of difference = 1.3 watts burned up as heat!

That doesn't sound like much until you realize that this heat is being generated by a small chip in the transmitter without a heatsink.

I mention this as your regulator chip might be failing.

BTW, I'm also running a Lipo in my DX7, but I run it only at the storage voltage of the Lipo, which is closer to the stock battery voltage. I need to install a diode with a 0.7v drop so it will be fine with a full charge. Better yet, if my regulator fails, I'll just install a switching regulator there...No issues then with up to 30v of battery!!

Anyway, the Spektrum receivers DO tell you if you had a signal loss. I know the AR6110's do. These have the orange LED and if you have a brownout or three, there is a red led in there that flashes the number of signal losses you had.
I have never had one with the AR7000, but I would surely assume it has this capability or more.

That is a real shame, Elk, to have radio problems cause crashes. That said, my Evader EDF crashed on it's maiden from some kind of similar failure. I have not been able to track it down. I'm running the receiver out of it in my Uber fast Funjet (AR6110). No glitches there. I do suspect the ESC. I also had an Eflite ESC that would just stop all outputs, BEC included, if it got hot. What a POS. That crashed my Ultimate biplane. Ugh.

Best of luck figuring it out.
Kent

[akent]

At least with the AR6110, an orange flashing light was a power brownout. The red LED flashes the number of times the signal was lost.
I'll try that with my AR6200's and AR7000's tomorrow, if noone else has by then.
Kent

[akent]

Oh, and have you done a range check using the bind button, Elk? Might be wise to with a few of your toys.

[elkmaster01]

Yea,,I did a range check,,it'sd ok. You may havbe something there Kent with heat in the TX. Both days it was extremely hot and humid out.

Here's the rest of the story. The F-4E that I crashed was by far my favorite,,it flew so nice and never gave me any trouble,,,I have well over 200 flights on it. So I was upset when it crashed. But I had another airframe and rebuilt it. The wind was blowing for 3 days so I took the time and really detailed it,,,made it perfect in every way. I when thru the programming and flight control rigging at least 4 times. I also ran it on the bench 3 times for the whole pack. It was perfect!

Last night the wind died down to nothing 2 hours before sunset, time to maiden it.

It flew for about 3 seconds and crashed. It took off and rolled to the right and I couldn't stop the roll. I was really pissed now. Got it home and figured it out quickly; I had the aileron channel reversed!!ARRRG!!

I'm an IDIOT!

[19000rpm]

Man that's terrible. Looking more like a Tx issue.

[akent]

I've done that more than once, Elk!!!

At least you admitted it! One fellow at the Austin field did exactly that, too, when he replaced his aileron servos. They happened to be reversed and he didn't check it.

I have done that TWICE on new foamie builds. Ugh.

BUMMER when that happens!
Kent

[19000rpm]

Me too. The Tx issue being the human behind the sticks.