Recovering from a crash... Need advice on gray wire, maybe more

[KHobbs5]

A couple of weeks ago I foolishly flew my P3S into a tree while doing a POI exercise. It fell from about 80 feet up but got hung in vines on the way down, thereby limiting the damage. See photo. The main problems I identified were the pulled out gray cable from the body to the gimbal, the little gray wire pulled out of the gimbal, and the setscrew loose on the gimbal arm. The gray cable was just a matter of plugging back in (I think), replacing the gray (antenna?) wire in its connector, and retightening the gimbal setscrew. I was surprised to see that the little antenna wire was actually a tiny shielded cable, so I tried to reinstall into in its plug just as I would a TV cable. I can't say for sure that the inner wire makes proper contact inside the plug, but I'm pretty sure the shield contacts the housing.

When I took the unit out to check it out, the camera just jerked around like it had a seizure, and then I discovered the loose setscrew. I fixed that, and the unit seemed to fly just fine in the little test I did. See Dropbox - WatchMeFly.avi.

Today I took it out for another spin, and it misbehaved. I never was able to start it by pulling the levers to the center; I only got it up with automatic takeoff. Once it was up, the levers were crazy. In general, it went the opposite ways that I was trying to make it go. I checked the lever settings, and they were set on Option 2, which I believe is standard.

I'm guessing that maybe the problem is the bad contact in the antenna wire I repaired. If that is true, what wire do I need to order to fix it?

Also, is there a better explanation for what I'm experiencing?

Thanks!

 

[SkyHog]

In your short flight, or with bench tests, did the video appear on you RC device correctly after you stuffed the grey cable into the connector?

It would be a very good stroke of luck if you can actually get the antenna cable working again just by pushing it back into the connector. I suppose the shield may be making contact, but it's hard to imagine the center conductor of that coax cable is making proper contact also. Others have tried stuffing the cable back into the connector but I am not aware of any successes with that. The usual repair in that situation is to replace the entire antenna/cable assembly and plug the new cable connector onto the gimbal board connector. The antenna/cable assembly isn't expensive, but it does require separating the body to install the new antenna and fish the cable back to the gimbal.

I'm not sure how or why that would affect your stick control though. That might be a separate problem.

 

[ServiceCall]

If a wire came out of a connector you cannot just push it back in. It has become broken from the crimp or solder point in that connector.

 

[DanMan32]

Not necessarily. It isn't uncommon for pins to pull out of the connector but be electrically sound and even to have the pin lock to still be OK.
The antenna wire may also be likely OK. Just look if the center pin is still intact and not bent. If bent you have nothing to lose to carefully straighten it. I doubt it is bad though as this would not affect how the stick responds.
The gray gimbal ribbon cable might still have a loose pin though and that might get stick control get misinterpreted.
Try toggling stick mode and do a stick calibration.

 

[robca]

You can't really "push back in" a thin coaxial cable working at 2.4GHz and hope it works I have said this on a few threads, but be careful about powering on a P3S when the antenna wires are not working properly. Those are Tx/Rx antennas. It's ok to use a receiver without an antenna, worst case you get no signal. On the other hand, you should never use a Tx without an antenna, because all the power generated in the power amplifier has nowhere to go, and more often than not damages the power amplifier. There are many examples of people burning their RC Radios and FPV Tx by forgetting to use an antenna while testing. Maybe the DJI power amplifier doesn't burn as easily, maybe not

If you have a problem with the grey or black coaxial cables, the only safe fix is to buy the complete antenna assembly (Part 97) and replace it

 

[ServiceCall]

Not necessarily. It isn't uncommon for pins to pull out of the connector but be electrically sound and even to have the pin lock to still be OK.
The antenna wire may also be likely OK. Just look if the center pin is still intact and not bent. If bent you have nothing to lose to carefully straighten it. I doubt it is bad though as this would not affect how the stick responds.
The gray gimbal ribbon cable might still have a loose pin though and that might get stick control get misinterpreted.
Try toggling stick mode and do a stick calibration.

True, if it is of the pin and sleeve connection. But then the pin has still been compromised.

 

[DanMan32]

Only if it is damaged. There's an excellent chance it only popped off like a clothing snap.

 

[KHobbs5]

In your short flight, or with bench tests, did the video appear on you RC device correctly after you stuffed the grey cable into the connector?

It would be a very good stroke of luck if you can actually get the antenna cable working again just by pushing it back into the connector. I suppose the shield may be making contact, but it's hard to imagine the center conductor of that coax cable is making proper contact also. Others have tried stuffing the cable back into the connector but I am not aware of any successes with that. The usual repair in that situation is to replace the entire antenna/cable assembly and plug the new cable connector onto the gimbal board connector. The antenna/cable assembly isn't expensive, but it does require separating the body to install the new antenna and fish the cable back to the gimbal.

I'm not sure how or why that would affect your stick control though. That might be a separate problem.

The video on my phone screen was correct when I was doing my original test flight. It still seems OK, even when it is flying crazy.

 

[SkyHog]

The video on my phone screen was correct when I was doing my original test flight. It still seems OK, even when it is flying crazy.

Okay, thanks. I was curious because I suspected the video would work with or without the grey cable, if the black cable was still functional. The black and grey cables are presumably supporting MIMO processing within the bird. If just one cable is functional, you should still see video, though you may get much less link range and much less link stability. I would not assume everything is okay if you are getting video in a short range test. That doesn't mean your grey cable is working. Your link range could be significantly compromised.

 

[nightspy]

My crashed two maybe we can help each other

 

[Techcop50]

In regard to the directional confusion, is the compass damaged? Are you getting any compass errors?

 

[KHobbs5]

OK. I've now torn down the copter and installed new pa rt 97 antennae, and while it was open I replaced the gray ribbon cable for good measure . I took it out and tried it, and there's no improvement.
The gimbel/camera initializes properly. The DJI GO app connects. It asks for compass calibration, which goes fine. It tells me it's ready to fly. I pull the levers to the center to start the propellers, and nothing happens. I tell it to take off automatically, and it does.

 

[KHobbs5]

I try to fly it, and the it totally confuses the stick commands. It is in Mode 2 but does not behave like it.
I've heard of a transmitter circuit burning out. How would that make it behave?
Would reinstalling the firmware help?
Note: When I run this on the simulator app, it behaves the same crazy way.
Any ideas?

 

[KHobbs5]

In regard to the directional confusion, is the compass damaged? Are you getting any compass errors?

I haven't observed any problems with the compass.

Okay, thanks. I was curious because I suspected the video would work with or without the grey cable, if the black cable was still functional. The black and grey cables are presumably supporting MIMO processing within the bird. If just one cable is functional, you should still see video, though you may get much less link range and much less link stability. I would not assume everything is okay if you are getting video in a short range test. That doesn't mean your grey cable is working. Your link range could be significantly compromised.

 

[SkyHog]

Not necessarily. It isn't uncommon for pins to pull out of the connector but be electrically sound and even to have the pin lock to still be OK.
The antenna wire may also be likely OK. Just look if the center pin is still intact and not bent. If bent you have nothing to lose to carefully straighten it. I doubt it is bad though as this would not affect how the stick responds.
The gray gimbal ribbon cable might still have a loose pin though and that might get stick control get misinterpreted.
Try toggling stick mode and do a stick calibration.

If the grey cable was ripped out of its gold connector, there is very little chance that this can be fixed by stuffing the cable coax back into its gold connector at the end of the cable. On the other hand, if the grey cable and its gold connector are still intact, but the connector is just unsnapped from the mating gold connector on the board, it could be as simple as you said. Just snap them back together.

I think the confusion here may be that you are assuming the OP meant that the connectors just became separated (antenna cable gold connector unplugged from its mating gold connector on the board). While I was assuming that the OP meant that the antenna grey cable became separated from its own gold connector, leaving both gold connectors still snapped together and attached at the board, but without any grey cable attached at all.

 

[KHobbs5]

If the grey cable was ripped out of its gold connector, there is very little chance that this can be fixed by stuffing the cable coax back into its gold connector at the end of the cable. On the other hand, if the grey cable and its gold connector are still intact, but the connector is just unsnapped from the mating gold connector on the board, it could be as simple as you said. Just snap them back together.

I think the confusion here may be that you are assuming the OP meant that the connectors just became separated (antenna cable gold connector unplugged from its mating gold connector on the board). While I was assuming that the OP meant that the antenna grey cable became separated from its own gold connector, leaving both gold connectors still snapped together and attached at the board, but without any grey cable attached at all.

I've now installed new Part 97 antennas (the black and gray cables), along with a new gray 8-conductor ribbon cable on it, and it didn't help. So the grey antenna cable issue no longer exists.

The crash pulled the gray ribbon cable out of the gimbal assembly, so maybe that damaged the socket in the gimbal? Would that cause the drone to confuse the commands from the control and cause it to fly erratically?

What's still interesting is that it actually flew properly for a brief time before goofing up again. (See video above.) This might indicate a loose connection of some kind, maybe in the ribbon cable?

When I try to run this in the DJI GO simulation, the simulated drone behaves erratically, just like the real one.

I did try changing to a different control mode and then switch back to defauld Mode 2. Didn't help.

I haven't tried reinstalling the firmware because I can't imagine this being a software problem. I'm not opposed to it, though, if you think it might help.

Thanks!

 

[SkyHog]

I've now installed new Part 97 antennas (the black and gray cables), along with a new gray 8-conductor ribbon cable on it, and it didn't help. So the grey antenna cable issue no longer exists.
The crash pulled the gray ribbon cable out of the gimbal assembly, so maybe that damaged the socket in the gimbal? Would that cause the drone to confuse the commands from the control and cause it to fly erratically?
What's still interesting is that it actually flew properly for a brief time before goofing up again. (See video above.) This might indicate a loose connection of some kind, maybe in the ribbon cable?
When I try to run this in the DJI GO simulation, the simulated drone behaves erratically, just like the real one.
I did try changing to a different control mode and then switch back to defauld Mode 2. Didn't help.
I haven't tried reinstalling the firmware because I can't imagine this being a software problem. I'm not opposed to it, though, if you think it might help.Thanks!

Okay, good to hear the video antennas are working well. Out of curiosity, was the grey wire separated from its connector or did it just unsnap its connector from the mating connector on the board?

As for the erratic flying behavior, I wouldn't think the gimbal connection has much to do with it. Have you tested the ability of the gimbal to maintain pointing? If you turn on the drone, leaving motors off, handhold the bird and tilt it up/down right/left, does the gimbal try to keep the camera aimed on a point in space as it should? Without the motors running, can you take pictures, switch to video, change the camera settings? I assume you can you see the camera video on you control device. If all those tests are normal, then I'd assume you got the grey ribbon cable wires and video antennas all connected and working properly. And I don't see how any of that could cause the bird to fly erratically anyway.

I'd suspect there is an entirely different failure that is still lurking from the crash. If you are seeing erratic flying behavior after recalibrating the controller, and using the controller in the simulation mode and still getting erratic flying behavior, that seems consistent with a hardware failure. Since the simulation mode requires the bird to be connected and in the loop, there is no way to separate the bird from the RC to isolate the problem. Likely, the bird is the culprit, since these problems began after the crash.

How do you characterize the erratic flying behavior? Will it maintain a steady hover at all? Does the control input seem backward when you operate the sticks, or is it more like a delay between stick operation and bird response? Does the bird fly erratically without any input at all? Not sure where to go from here without more clues. Unfortunately, this one might need to go to DJI.

 

[KHobbs5]

Okay, good to hear the video antennas are working well. Out of curiosity, was the grey wire separated from its connector or did it just unsnap its connector from the mating connector on the board?

As for the erratic flying behavior, I wouldn't think the gimbal connection has much to do with it. Have you tested the ability of the gimbal to maintain pointing? If you turn on the drone, leaving motors off, handhold the bird and tilt it up/down right/left, does the gimbal try to keep the camera aimed on a point in space as it should? Without the motors running, can you take pictures, switch to video, change the camera settings? I assume you can you see the camera video on you control device. If all those tests are normal, then I'd assume you got the grey ribbon cable wires and video antennas all connected and working properly. And I don't see how any of that could cause the bird to fly erratically anyway.

I'd suspect there is an entirely different failure that is still lurking from the crash. If you are seeing erratic flying behavior after recalibrating the controller, and using the controller in the simulation mode and still getting erratic flying behavior, that seems consistent with a hardware failure. Since the simulation mode requires the bird to be connected and in the loop, there is no way to separate the bird from the RC to isolate the problem. Likely, the bird is the culprit, since these problems began after the crash.

How do you characterize the erratic flying behavior? Will it maintain a steady hover at all? Does the control input seem backward when you operate the sticks, or is it more like a delay between stick operation and bird response? Does the bird fly erratically without any input at all? Not sure where to go from here without more clues. Unfortunately, this one might need to go to DJI.

 

[KHobbs5]

It seems to be OK now. Before I explain, let me answer your questions:

The gray antenna wire was pulled out of the gold connector, which was still connected to the gimbal board. In the video above, the copter was flying properly with the "repaired" connection.

I started the unit up and checked the camera positioning. It held its orientation just as it should.

It did successfully take both still shots and videos even before I put the propellers on and "flew" it.

When I flew the unit, it held its position, even when I manually pushed it around. When I used the controller, it jerked and misbehaved just as it had been doing. I brought it back down.

I'm ashamed to admit that I had apparently not recalibrated the control sticks. When I did, I discovered that the "left" and "back" directions were not working at all. I did this calibration, and the copter worked fine. I even flew it away and let it return-to-home. It did it perfectly.

I'm still mystified as to what caused the controls to lose their calibration after the above video was taken. I'm going to carefully watch the stick calibration in the future to see if it ever happens again and, if so, what caused it.

Thanks for all your help, guys!

 

[SkyHog]

Glad to hear it is back in the air and behaving correctly. Don't know why an RC calibration would have been necessary, but it's good to know that it worked. Happy Flying.