I've got some technical problems with my P4P and I need an advice. I use my multicopter alot and when something goes wrong I repare my bird myself. This winter there was very bad crash and looks like it's time when hidden damages show up. I want to ask this questions to make a list of spare parts to replace.The crash. It was in the winter. My tab has got frosen and gone black. I pressed RTH and duaring climbing to the RTH altitude the copter has got in to electric wires. So it fell down on frosen ground from about 15 meters. Thank you DJI drone's shell is designed to save as much as possible. The shell was broken to pieses and the yaw motor cable was teared. Nothing serious - there was only one warning: gimbal motor. So I've replaced the shell and to get back faster replaced the gimbal yaw motor instead of waiting for the cable for it.

After repairing there were no problems for several months. Then I noticed that two propeller mounts are broken. I've replaced them and that was an epic fail - I've bought fake mounts. Hell is waiting for the seller - one of this mounts has crumbled in the air so there was another accident. Not a real crash - the MC has done emergency landing from 60 meters down to a box with sand. I was shooting a building process ang there were a lot of bare concrete, but that day I was lucky. After a good clean I've foud genuine mounts and the MC is in the air again.

Four months later I've got this problems.
1. Left rear optical sensor communication error. In the Assistant 2 left rear camera is blank. I'm going to replace the sensor. Is it a sensor problem or it may be a control board?
Maybe I'd better swap sensors and watch the overall status?

2. The gimbal behavior is like it does not get the copter's IMU information. I know how the gimbal works when it is powered on whith no MC connected - it does stabilise, but when it's been tunerned, it's motors move very slowly. And this is what I observe now. The camera works good, I can move the gimbal up down and it does move left/right when I move the yaw stick. But it does not change it's behavior when I toggle FPV/Follow in the DJI GO. All the simptoms say that the gimbal does not get the IMU information. I'm happy that  this months I take photos, not video. Each time I turn the copter, I wait till the gimbal gets its roll axis stabilised. It does, but it takes about 3-5 seconds. Also the gimbal has no idea where is the copter's heading so the yaw motor is moving slowly too. The gimbal is just like a sloth - it's slow, but it does work. I've used the C-Fixer on both compasses - did not help (but I'm happy I did). I've calibrated IMU on a perfectly aligned surface - did not help. And as the copter's behavior is just perfect now (even better than before the crash), I started to look deeper and I think the gimbal does not get the IMU information. Can you help me? I'm going to disassemble my bird again and observe all the flex cables. I hope the problem can be solved by reconnection, but not sure.

1. It is more often than not the actual sensor that requires replacing and not the board, It's best to actually look at the sensors and the board though, you have had several crashes so you may even actually see the damage visually, like a cut ribbon cable or something, this would help you confirm if you are in doubt, but you should know it's not impossible for it to be the board.

2. I don't know about your gimbal getting no I.M.U information as i believe if that was the case you would get an error in the app and the gimbal may not start at all. Have you tried calibrating the gimbal and refreshing the firmware, you might have already done these, but you would be surprised at how often they fix issues. Isn't the gimbal motor speed a setting in the gimbal settings or am i miss-remembering ? Are all motors equal or is one of the motors moving slowly and the others are fine ?(Pitch motor is slow and yaw/roll are normal for example). You definitely have a strange fault though.

Ben Mason, thank you for the answer!
1. OK. I'll buy the sensor before disassembling. Hope replacement will help.

2. I've tried calibrating everything and installed the latest firmware. Did not help.
When I move the MC, all the motors are moving fast, but wrong - they hold the camera in place but not where the MC is heading. If I take the MC in hands and move it without turning, motors move fast and camera is oriented horizontally. If I turn around, the gimbal tries to compensate moving, the camera floats, the roll motor moves slowly and when I stop turning it takes some time for the gimbal to stabilize.
It's right what happens when the gimbal is disconnected and powered on without a MC. When the MC is hovering or on the ground, motors are moving equally slow to set the camera horizontally.
I've looked EXIF - there is the GPS information. As far as I know, the GPS information is in the same long package with accelerometers and compass. That means that the gimbal to MC cable is OK and the problem is in the gimbal. Not motors and not the MC.

Aloha Alexander,

     Ben has some good ideas about your problems and from your post, you are doing a good job under the circumstances.  Ben does bring up an interesting point.  The gimbal response speeds are determined by DJI GO 4 settings, so that may be related to your problem.  If you have done any firmware updates as part of your repairs, the settings may have been changed by the update.  Below is a link to DJI Grace's Guide to the DJI GO 4 App;

https://forum.dji.com/thread-118397-1-1.html

     Grace's Manual has been very helpful for me.  Even though it is based on the Mavic platforms, there is still a lot in common with our Phantoms.  Mostly, I like being able to look at each of the settings and advanced settings without wasting battery time.  Keeping track of my settings by writing them down and noting the changes I make help me understand what works better.

     I am glad to see that you have got your bird up and running well.  It was fun swapping out the skin for my P3 Pro a few years ago (upside down crash).  My P3 Pro is still my favorite.  But my P4 Pro does have some really nice capabilities that were not available on the P3s.  What you said was interesting that the temperature was so cold that the shell cracked into "pieces".  You make me like living over hear in the warm weather even better.

     Hope this helps!

Aloha and Drone On!

Alexander Trotsenko Posted at 8-12 01:36
Ben Mason, thank you for the answer!
1. OK. I'll buy the sensor before disassembling. Hope replacement will help.

Hmm, I've not really seen that issue, it's hard for me to visualise it from your description, perhaps you can upload a video to give me a better idea, for example turn on the drone on a flat surface, then tilt the drone in each direction right before the cut off angle(on a normal drone this would be the angle where the camera no longer centres but instead angles itself with the drone). Then show it with the controller movements.

You can also check your I.M.U/Compass readings in the advanced settings/sensors page and the overall status screen for errors, just in case as some of the rarer errors show up there but do not inform you on the main screen.

Hello and good day Alexander Trotsenko. I am sorry to read what happened to your DJI Phantom 4 Pro. Since there was a crash that had happened, some of the internal components of the said drone might have acquired some damage that is why you are experiencing these issues. I would recommend you contact our DJI support team to start up a ticket for the said drone at https://www.dji.com/support?site=brandsite&from=nav . We have the professional team who would do their best to fix the said damaged drone. In addition DJI do not recommend doing a DIY in fixing the said drone. To avoid further damaging the said unit. Thank for your understanding and for your support.

Cetacean, thank you! Yes, I did try to do adjustments with the DJI GO. But it makes no difference.
Ben Mason, you are right. I'll post a video today.

Stephen, thank you for the reply! First of all I contacted the DJI support. I live in Russia and that appeared to be a problem.
I understand that DJI staff can not recommend DIY repearing but for me this is the only way to do. I'm happy to say that DJI makes the best multicopters! And they are as reliable as Kalashnikov AK-47. My first DJI drone was the Phantom 3 Standard and I still fly it time to time just for fun. I think that it's not a problem to replace some parts at home if they are not fake ones. And I have to do so because there is no DJI service in our region and I doubt there is one official in Russia. That's why I ask other pilots here - this forum does help!