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No WiFi signal, can't pair with DJI Go, no fan spin

mightypilot2000

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Hello,
My Mavic AIr crashed. Gimbal cable is torn (plug going to pan motor). Mavic has solid red rear light. It doesn't show up in WiFi, even after setting it to "WiFi only mode (button push and 2 beeps). I can communicate with it in newest DJI Assistant, all sensors are working ok, I can download flight logs etc. Even internal memory card is showing up on my computer. Debug version of DJI Assistant sees it as Mavic Pro "orange30" and it can't set correct airframe. I'm not sure about that but to me it looks like it is not compatible with Mavic Air since newest version is working fine. There is no water damage, no obviously broken components (checked under microscope). The fan is not spinning at all, after 2 minutes heatsink is hot to the touch.

Since there are no schematics for the Mavic Air I need your help. Have you ever seen such damage? Any ideas, help, anything?

Thanks in advance!
 

Thomas B

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Likely more damage than you mention. Recommend sending it to a company like DJI Drone Service for a free assessment and free shipping. They are also likely the lowest estimate you’ll get. If you have DJICare or are still in factory warranty contact DJI.
 

old man mavic

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it needs to be stripped by a qualified repairer and have any damaged parts replaced
 

mightypilot2000

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Yeah... you are kinda not helping. I know I can send it to the service shop... I just want to fix it myself. Thanks anyway. I'm looking for people who are specialized in board level repairs.
 

mightypilot2000

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Sorry guys, Maybe it was not clear I'm not looking into sending it to the repair centre. I want to fix it myself. I'm technical person. I'm looking for possibility to access the drone via ADB/ssh/telnet to possibly access system logs. I think there is an issue in the hardware after crashing but it's not visible on the mainboard. I've inspected it under the microscope.
 

hiflyer201

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You kinda don’t know how to get the proper help
 

Thomas B

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Sorry guys, Maybe it was not clear I'm not looking into sending it to the repair centre. I want to fix it myself. I'm technical person. I'm looking for possibility to access the drone via ADB/ssh/telnet to possibly access system logs. I think there is an issue in the hardware after crashing but it's not visible on the mainboard. I've inspected it under the microscope.
See post #2 above they won’t repair it unless you authorize that. They will ship it back after giving you the assessment and they have a great parts inventory.
 

Done

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Sorry guys, Maybe it was not clear I'm not looking into sending it to the repair centre. I want to fix it myself. I'm technical person. I'm looking for possibility to access the drone via ADB/ssh/telnet to possibly access system logs. I think there is an issue in the hardware after crashing but it's not visible on the mainboard. I've inspected it under the microscope.
Well you haven’t done your due diligence. It wouldn’t be hard to figure out how to get the flight logs if you took the time to do so.

There’s all sorts of how tos on YouTube that will show you how to disassemble and repair your aircraft.
 

mightypilot2000

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Once again - sorry, didn't want to sound mean. English is not my native language so it's hard sometimes to avoid misunderstandings. Anyway - thanks for your input. I live in Poland so I can't send it overseas to recommended service centre. Also I'd like to fix it myself if possible. I've already downloaded flight logs but they are not really helpful as those only provide information about location, altitude etc. Not really what I want. I need to access system logs to see why WiFi is failing to boot. I know it's possible to access shell via ADB on Mavic Pro and you are able to see system logs. I don't think Mavic Air has been rooted yet but I'm here to listen to more experienced people. Hope you understand me right now. And once again - sorry for my first post.

I also already disassembled the drone. I inspected all PCBs under microscope to see if there is any obvious damage - there is none. All boards seem to be fine. Maybe I'll try reflowing them if I'm out of ideas. Some BGA chips might lose connection during the crash.
 
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Detritalgeo

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Have you looked-up all the IC's to determine what they are and if datasheets are available?.. This may help to start tracking down any shorted caps or assess if any enable pins are missing voltage..

Have you looked over 'dji-firmware-tools' python library on Github for any good info?

Perhaps we can start to contribute to this: o-gs/dji-firmware-tools

I can try to start helping out with this... I have a spare that will also partially boot with access via USB-C and DJI Assistant but nothing else...
 

Manty

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. If that does not work try Searching Utube for Mavic Air-Teardown. Its in German but its a total dismantle
 

mightypilot2000

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I've narrowed down the issue - fan, WiFi and gimbal are not working. Since WiFi and gimbal are internally connected via USB I suppose what all of them have in common is 5V power rail. 5V line is shorted on the fan header. I will try to identify 5V power regulator and look around it for any shorted components. Since it's a total short I assume capacitor somewhere is shorting it to the ground.
 

Detritalgeo

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I am already ahead of you.

The mains 12V rail from the battery goes into the 10011B TI 788 chip which then provides a ~5V supply (5.2V in my case).

The red dots are pads with the 12V rail, if I were you i would first check the 4 big caps i show in the image just below the 2.2 coil.

I cannot cannot find datasheet for the 10011B TI 788 IC anywhere! so if you find it let me know.

the grungy image is my salt-water trashed mavic air so dont mind that... it has provided its body for science..lol

I hope this helps



5V_rail.JPG
 

mightypilot2000

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Thanks a lot. I think it will be pretty helpful in the future! My Mavic Air has been fixed :) I did a short circuit test on 5V rail by freezing the motherboard and found the shorted capacitor. After removing it WiFi and the fan came back to life. My drone is 99% working right now. I'm waiting for a new gimbal assembly and it will be almost like new since I've also swapped whole case from the dummy unit.
 

Detritalgeo

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Thanks a lot. I think it will be pretty helpful in the future! My Mavic Air has been fixed :) I did a short circuit test on 5V rail by freezing the motherboard and found the shorted capacitor. After removing it WiFi and the fan came back to life. My drone is 99% working right now. I'm waiting for a new gimbal assembly and it will be almost like new since I've also swapped whole case from the dummy unit.
Sounds good.

With the new gimbal, just run the DJI firmware tools command-line utility to complete the factory positioning calibration. If you have the original camera module and put it in the new gimbal housing you should be back to 100%. New camera modules tend to either request your drone to be 'Activated' or generate the 'Camera Error 3' notice.

I have gone through a spare old dead board and gathered info that could find.

If you use Inkscape I can pass along the file.
 
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mightypilot2000

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Dang, sensor on my camera board is scratched (don't ask how...). I will see how it works, I might just replace the IC on the camera board and it should act as my old one. Did you try to change only the daughter board on the camera board? I wonder where serial number is stored.
 
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Detritalgeo

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Well, you could try the new gimbal as-is and see what happens before moving forward.

In the past I have just switched out the whole module for the original but you could be correct.
 

mightypilot2000

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@Detritalgeo Turned out something is still broken on the motherboard. Gimbal is not moving at all after replacement. Camera is working and I get Camera Error 3 as expected. Do you know how gimbal is powered? Thanks in advance.
 

Detritalgeo

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@mightypilot2000,

In the image below i show the location of the 3 brush-less motor driver IC's for gimbal (one for each axis). From my investigation, they receive most power through the resistor/fuse marked 000 that the arrow is pointing to. From memory I believe this was supposed to be the ~12V rail. I have seen this 'fuse' break the connection in some drones when is should pass through without issue. This is where I would check first. It can be a little tricky to power-on the drone while probing this location though.

The 12V rail supply is on the right pad in the image and the left pad is what should have about 12V if the 'fuse' is still good.

Good luck.

1589904121183.png
 

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