Crash Repair (Ongoing)

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Hello, all. New member here.

There's certainly no small number of "crash" threads here on PhantomPilots, but I thought I'd add my own story from a different perspective: I'm starting off as someone who found a crashed P3P on Facebook Marketplace and felt the challenge to make it fly again for as cheaply as possible (much of my life has been spent toying with electronics and working as a system administrator, so I find a lot of enjoyment in solving computer problems and working with electronics and tools). In going through the motions of learning about this unit, the culture surrounding it, and DJI's philosophies, I've learned a good deal which might be useful for other enthusiasts who come across damaged or otherwise unresponsive equipment.

It began on a Monday afternoon; I took a 2-hour backroads country drive to Kansas City and bought the still-unsold Professional for $60 from an up-and-coming cinematographer. The gentleman wasn't able to provide much backstory on the unit as he had purchased it for parts off someone else. The evidence was unmistakable, however, that this unit fell fast and hard. Here are a few photos from his original ad posting:

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Initial Examination & Drone Repair

At this point, I knew nothing about the Phantom 3 Professional other than it still serves as the "gold standard" of private quadcopter-format drones, but some online research quickly helped reveal how the various parts of this device operate. Before doing anything, a visual inspection had to take place and unfortunately I don't have those early photos accessible at the moment. It's pretty clear from the above photos that:
  • The camera gimbal is mangled
  • The camera base is shattered
  • The lens debris glass cover is shattered
  • An antenna mount is knocked loose
But there were other obvious external issues as well, such as:
  • A cracked landing leg
  • A cracked screw post behind one motor
  • Two surface mount cable sockets were ripped off
  • One of the camera's rubber absorbers was ripped
I should point out that this unit came with nothing more than itself a 3 propellers, meaning repairs would initially be underway without the aid of a battery or controller. This would mean attempting to run the unit off of a suitable bench power supply and not knowing if anything could even talk to it.

And there-in was my first mistake--not a fatal one, but certainly in practice. Never attempt to run power to a damaged device until AFTER you've inspected it thoroughly. There's too much of a risk that something might short out or cause further damage, possibly even a fire. Other than removing the entire camera and gimbal assembly due to its erratic state, I didn't think the situation through and powered the unit off of 12VDC only to receive a loud and steady stream of prolonged beeps. I got lucky nothing was further damaged and you'll see why shortly, but let's first look at some photos of the unpowered camera's condition:

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and inside...

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You can't really see it in these small photos, but the CNC aluminum parts and motors absorbed much of the fall after the landing gear cracked. At least half need replacement. Worse though, is that the main logic board still took a sharp blow from the yaw arm's elbow when the motor post bent. In the first of the above three photos, an SMD capacitor was pressed into plastic cover and was ripped off the PCB. In the second, you might be able to see where it belonged, but another spot is vacant and a few pieces have shifted the traces from the immense pressure. In the third photo, that's the shattered BGA on the opposite side of the PCB (look for the three cracks leading out from the center). I've never seen that kind of damage before.

After the original powered test, I opened the main shell up to find much more substantial damage to the drone. From the markings on case edges, it's clear I wasn't the first one to peer inside. Though almost everything appeared okay to the eye, one piece was clearly out of place: The main controller. The center piece is soldered in place and sits on a very shallow and thin plastic ledge, one of the worst design decisions I've ever seen. The main drone PCB also is supposed to attach to four floating screw mounts which absorb some of vibration from landing, but in a case like this they simply cracked their mounts and the main controller tore free of every single solder point. I don't have that early photo handy, but here's how the device looked after substantial resoldering and wire runs (where the pads were torn off one side or the other):

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I made liberal use of hot glue for vibration damping on wires and to better hold the center core in place from any future shock. While performing this sort of surgery, I also took advantage of the opportunity to make a raw backup of the SD card firmware in case any log data was sitting on it. Here's the process used on my Mac:
  • Backup:
    • Plug card into Mac
    • df -h to see which device the card is mounted as
    • diskutil unmountDisk /dev/disk9 (ex)
    • sudo dd if=/dev/disk9 of=~/Desktop/BACKUP.dimg
  • Restore:
    • Plug card into Mac
    • df -h to see which device the card is mounted as
    • diskutil unmountDisk /dev/disk9 (ex)
    • sudo dd if=~/Desktop/BACKUP.img of=/dev/disk9
  • Use a partition application to grow the partition as necessary.
The above process is especially useful for the inevitable day when the SD card will fail. As I understand it, the controller also uses an SD card for its firmware storage and both have micro USB ports to directly interface the cards, though I believe you need special software to do so.

With all the obvious repairs made to the main unit, minus the camera and gimbal, I was able to power it up again. This time around, it went through its self-test and registered as a valid DJI USB device on my Mac. Here's a video of that startup and obnoxious beeping:


The above progress was motivating enough that I started buying cheap accessories off eBay:

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A few quick notes: The lens cover screw in place and resolved the issue of the broken glass; the controller was marked lower than most broken controllers thanks to someone painting it; the case is in great shape for the cost; the stickers are terrible...they curl up and rip because they're paper-based; the charger, extra parts, and propellers was a great save as opposed to buying each chunk separately.

At this point I was awaiting the parts in full, but to my luck the controller shipped and was delivered within 72 hours. Up next is my experience with the DJI Go app and syncing, both fairly horrific experiences with a happy ending...and a clue regarding the original owner!
 
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One thing I didn't mention in the timespan above: Just a day after buying this unit and bringing it to my office to inspect, our university building had a huge fire. The water and smoke damage throughout the (very large) building was so substantial that it was weeks before I could go back in and claim it. You can imagine the anxiety I had not knowing the conditions it might have been in and not being able to put time in on the repair so close to purchase. I'm certain this beast will fly again despite all the adversity its seen.
 
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Just a great write up!!! I wish you all the luck in the world as this is not an easy task. Keep a clear head and take your time. You will get this done. It is a shame due to mass production and to lower consumer costs what the engineers will do to meet their goals. Some designs make sense while logic is lacking in others.
 
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One thing I didn't mention in the timespan above: Just a day after buying this unit and bringing it to my office to inspect, our university building had a huge fire. ... I'm certain this beast will fly again despite all the adversity its seen.

I, too, brought back to life a P3P. However, similarities in our experiences stop right there. When the owner asked me if I was interested in this "messed up drone", I said sure why not. Perhaps I could use it for parts.

This bird had a lot of mud, 3 broken props and a muddy battery (with a low charge count). The camera and gimbal were hanging by the main 8 pin cable which had been "liberated" from its pin connector, the gimbal vibration plate's 4th arm was severed completely but still hanging by the rubber shock absorber; and one of the legs was ripped from the shell bottom.

The fix cost $0.00. I super-glued the dampening plate back together and rotated it 90 degrees (the rubber shock was now in an un-repaired part of the dampener), I used a slightly larger self tapping screw to convince the leg to its near default position, carefully set the wire leads of the camera back into the row of contacts (this required magnification); 4 new props and a good spit shine and she flies and films as good as new.

The couple that "donated" this machine to me described it as a complete loss and went out and bought a P4. They also gave me the original controller (still trying to get original charger as I'm sure it is of no use to them and will offer them a pittance for it as the rest was totally free).

Ironically, I had reason to film THEM at work recently, and asked the wife if she recognized this UAV. She said, "hmmm, no. Wait ... REALLY?"

Not sure why I let THAT cat out of the bag - I was being childish I suppose.
 
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unit338 and Avocet: Thanks for the encouragement and story! There are plenty who say repair isn't practical, can be equally expensive as buying reconditioned or used, and that the units will never be 100%. All that's probably true, but the joy is in the journey otherwise you wouldn't have so many people restoring vehicles and other items of eras long since passed. One learns a LOT through the reconditioning and repair of devices and that knowledge is transferrable to similar equipment as well as other devices of the time. It also opens the door for buying used equipment that someone else has written off which can then be manipulated or repaired for pennies. There's also a strong sense of ownership in something you discover all the dimensions of. I've always been a firm believer of "built, not bought" whenever possible and hope to add some fancy features, such as sudden-drop recovery and various IoT/Single-Board-Computer experiments. There are also other fun approaches one can take with devices that follow GPS and sensor readings (in very specific environments), such as autonomous and automated movement.

There's also a lot of talk and fear regarding aftermarket batteries on here which I plan to somewhat address later with this rebuild. You rarely go wrong dealing with OEM and warranty-tied batteries, you can definitely go wrong with aftermarket, but you can also make some compromises and do just fine. The trick is to stay informed and working with a wrecked drone makes those compromises easier to explore.
 
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The backpack, charger, propellers, and small OEM accessories all arrived yesterday. Can't believe how fast these these parts shipped. They're in both new & near-new condition and cost less than items in much worse shape.
 
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DJI Go & Controller Sync

I have to commend the person who sold me their 2nd-hand controller. It arrived fast and fully charged, something that worked out well considering my lack of power supply at the time.

My initial experience with the DJI Go app for iOS was not positive. The app was stuck at the "How to connect" message, refused to acknowledge that anything had been plugged in, and consequently wouldn't detect the drone. In a situation like this where that's a critical milestone, I wasn't thrilled. Apparently many other people have experienced the same issue in both iOS and Android, something that seems entirely irresponsible of DJI considering the it-works-or-it-doesn't result. It's possible that most of the people selling controllers on eBay that say, "Can't connect with DJI Go app" might be having a similar experience as I did, one that was a problem with the app itself. The one positive was that when I plugged my phone into the controller, it would blip the iPhone briefly to show the presence of external power, but then disable charging, presumably intentionally to avoid draining the controller battery. That shows a certain logic taking place between the two devices.

I assumed there must be a manual way to sync a new remote with a P3P without the DJI Go app and apparently there is:


This worked out great for me. Once the two devices were paired, the DJI Go app simply picked up the P3P despite the previous failed attempts.

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Of course, after hitting Camera I was bombarded by all of this:

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The good news here is that I live in a Class D area, so that was reporting correctly. The "Motor Overloaded" message might very well have been from the device's last circumstances. I'll have to verify that the motors function correctly once I can get my hands on a battery (more later on this). The "Strong wireless interference" is correct as well since the power supply I used to power the drone is extremely noisy and was alligator-clipped right beside it (you can actually hear the consequences of that on my video in the main post).

I also saw errors like these:

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The "Data Recording Error" I need to investigate as the only SD card that's not available is the one that the now-disconnected camera provided. I'm somewhat fearful that I might have cut a trace when removing the silicone sealant on the internal SD card for the drone itself.

The compass error was strictly an issue with the power supply being so close and interfering. EFI will really mess up the compass operation, so anyone else working with an external power source or in a room full of WiFi or whatnot should consider that.

I'm also not quite sure what was up with the IMU, but it certainly updated correctly this afternoon:

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So there are a few things to look at, but much of it I suspect is the way things are rigged up right now. I'd like to say that I was able to test the motors, but the firmware on both the P3P and controller are DJI's latest, so they refuse to start the motors until a proper battery is detected. The battery will be the next big adventure.

Some general comments on used controllers: I've found that many working P3P controllers still sell over $120 on eBay while damaged controllers, in any form, tend to sell between $75-90. I'm really lucky to have bought the one I did, a visually marred up working one, for less than the price of a broken controller. Up until that point, I had been considering what type of broken controller to buy and attempt to fix. They seem to be available in these categories:
  • DJI Go app won't connect with the controller
  • The USB port won't power device
  • The USB port doesn't work at all
  • The controller doesn't turn on at all
  • The controller won't connect with the drone
  • The controller won't charge
  • The latest firmware update broke my controller and it won't connect
  • The latest firmware update makes my controller lights flash and it won't respond
Some of these overlap and there are known USB problems with some models, but there are also some really good tips online that explain how to overcome many problems. If I had to rewrite those common complaints into a more realistic list, I'd do so as:

An unexpected perk of getting a controller and the DJI app working is that I was able to see the existing config settings, such as the drone's name:

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Anyone by the name "Gabe" here sell off a P3P for parts? :)
 
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Internal SD Card (Flight recorder data)

As mentioned earlier, one of the errors I'm seeing is "Data Recording Error". I had thought this was crash-related, but am confident it's related to a dead SD card stored in the Phantom, internally, just above the battery compartment. This SD card, silicone glued in place, is used to gather flight data and can be accessed indirectly through drone's front-facing USB port.

There are differing philosophies about the card's presence and DJI's use of glue. Quite a few people write this off as data that only DJI can read, that they'll use to verify proper operation against warranty repairs, and that the glue is to keep people from tampering with it. I'm sure that's a big part of it, but not the only part. The glue is used elsewhere in the drone for dealing with vibration and it makes absolute sense to keep the SD card bracket and card in place so they don't come loose or so the SD card contacts don't skip upon bumps or landing. That's a common practice in anything that can suffer shock and has SD cards tucked away. The flight data is also readily available, as mentioned, through the USB port and open source readers exist (such as the software found here).

During my repair, I presumed this card held the firmware on a proprietary filesystem, so I cloned the card as it wasn't readable by my Mac and then hot glued it back in place. I realize through further testing that the card is dead and needs to be replaced, something that will be harder now that I've used the hot glue and resealed the drone. Pretty much any SD card will do, my preference being SanDisk since they're so prolific, cheap, and the most common go-to by manufacturers. It shouldn't matter if you go with another brand, but you never really know.

So to explain "further testing", I simply mean I entered Flight Data Mode and used the USB port to try to format the card. As people say in the following links, when using Windows you can format as Fat32, but avoid "quick format" so more checks and balances take place.

Helpful links:

On a Mac, you can format DOS FAT or exFat (a format of Microsoft FAT used on many SD cards). I have a Mac, but used a Windows laptop to also access my card. A healthy card will register like a flash drive and just mount on your computer. A corrupt card might ask you to format it. A dead card will fail format and repartitioning attempts. Since I couldn't access myself card just by plugging the drone in via USB to my Mac and a Windows laptop, I attempted to format so new data could populate it and the annoying "Data Recording Error" would go away, but with no success. These cards get a lot of data written to them and it's possible to see IO errors over time, so it wouldn't surprise me if the card was dead well prior to the crash (the only way I can see the crash even affecting it and not the sensitive circuitry is if there was some sort of electrical disturbance that it was sensitive to while the circuitry was designed for overload or static protection).

If you want to access this card through USB and have never done so before, the trick is to open the DJI Go app, enter Flight Data Mode, hook the front-facing USB port (unit the rubber cap) to a computer, and then the card will show up.

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You can then copy data off of the internal SD card and access your flight data. When you're done, unmount the card data and reboot or shut off the craft (note that Flight Data Mode is sort of perpetual and the drive will keep remounting if you don't act quickly).

All this having been said, my next step is to replace this SD card while exploring a long-term battery solution.

Edit: Here's a close-up of the SD card that I just ripped out.

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Regarding drone repair...

I posted this in another thread, but am repeating it here for those who are considering their own repairs:

Much of the camera can be replaced fairly cheaply outside of the primary logic board. When you find damage on that level--and you might not through visual inspection alone--that's where the big money comes in and you should consider all options, such as professional repair or buying a refurbished unit.

Pretty much everything else can be bought through eBay: Shells, motors, landing gear, and internal components. My repair is about moving forward as cheaply as possible. It's a very impractical decision though, so unless you're a masochist with spare time...

Before you make a decision either way, look at repair as a two-part strategy: Flight-worthiness & camera. Drone repair is one thing, but the gimbal & camera are entirely different (for now, I've removed mine and just intend to get the drone flying). I suggest you at least open the main shell to inspect the internals. Hard crashes can have devastating effects on the way DJI designed the P3 mainboard. Also, be honest with yourself about what you're able to do on your own as repair can get pretty involved and touch-and-go.
 
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Since I just took the craft apart again to get the SD Card, here's a photo of my poor approach at shock dampening, a solution that works fine even if not ideal:

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Those foam pieces are all held in place with a single dab of hot glue. They get compressed when the top goes back on and hold the board in place, but provide some give should the craft take a jolt. This was necessary since the four mounts that loosely hold the board in place had snapped and I didn't want the PCB moving around too freely. With this approach, the circuit board still somewhat sits on those four posts which provide some upward push, but the compression of the foam keeps movement minimal in any other direction and holds the board down.
 
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New internal SD card installation

I added the new SD card, wedged my hot glue gun tip between the case, PCB, and wire arrays to add a thick drop to hold the card and bracket in place, then tested the arrangement out via Flight Data Mode. Interestingly, on my Mac, the volume wouldn't mount, but did show up in Disk Utility as ~3GB, but wouldn't let me mount it (the option was greyed out). I switched to my Windows laptop and the card mounted immediately as a 2.8GB FAT32 volume under the name "DJI FLY LOG". That name is particularly interesting since the card used to be called "DJI FLIGHT LOG" with an unknown partition type. I originally named the new, unnamed, SD card "FLIGHT LOG" before inserting it into the drone and with its full 16GB partition, so it looks like some automatic card prep was done by the Drone's firmware. It's also possible that the drone only see's a hardcoded partition size and is behaving funky, which would explain the confusion on the Mac (which holds to standards fairly strictly). Dunno. Whatever the case, I'm not touching it at this point and will rely on how DJI is handling the card given that the name change was automatic and size is fairly specific.

Just be aware, folks, that despite the larger card, it's only seeing what the original 4GB SD card would have presented, so don't waste money on anything more than what a $9 "Best Buy special" will get you.

And yes, the "Data Recording Error" went away and a file was automatically populated on the card.

Old and new:

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How Windows Vista (don't judge me, it was a free laptop) saw the default card arrangement via Flight Data Mode:

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Batteries

During this repair, one form of trauma I noticed is within the rear battery bay. As the weight of the craft shifted during crash, the battery end took out a strut which attempted to protect the central core of the main craft PCB. As mentioned in my first post, the central core completely detached and the main PBC also broke its four mount posts. I believe all of this was part of one action.

To move forward with testing, I need a power source which the latest DJI firmware will trust and allow for the operation of the four motors. That almost exclusively means a DJI-official battery. Let's discuss options, however...

  • Some folks have had luck with rebranding and "grey market" sales where DJI batteries are sold under another company name by the true manufacturer (one of several known companies) or simply under the manufacturer's name itself.
  • Others have had success with factory discards being resold inappropriately usually with a cell or two that didn't pass balanced-recharge quality control.
  • And then there are assembled battery packs which use cells not rated for rapid discharge and thermal build.
In all three cases, the one thing I never hear about is the "smart" feature set and firmware. For batteries to be compatible with the DJI Go app, the companies would either have to reverse engineer the dialogue between the smart appliance and the drone or, more likely than not, clone DJI's PCB and steal their firmware. At that point, the vendor can then do just about anything, such as man-in-the-middle rewrites of the data to suggest false cell charge statistics, provide fake serial numbers, etc. This seems to even be the case for some people who have had multiple batteries reporting to be the same and register all the recharges to one unit instead of several. When DJI catches on to these practices, then they block out those hacks with firmware updates.

While I firmly believe aftermarket batteries can work out, these categories are important to consider with the Phantom drone scene. Stealing DJI's firmware and designs can make non-DJI products work well, but I can fully see why DJI would not want these sorts of devices gaining financial traction, sometimes for the sale of substandard parts, and then building up the reputation that Phantom-official batteries and drones are poor quality, will fall out of the sky, and that the DJI Go app was reading correctly (or, conversely, that the application sucks and is providing bad feedback because a battery is misleading the user).

At the same time, I'm pretty sure DJI has no issues with adding to the sense of fear surrounding knock-off batteries both to reduce sales and to remain in the dark about design flaws. There are many reports of people who have had drones behave erratically or abruptly fail who swear that their battery is a genuine DJI. Many people are quick to claim these problems are related to 3rd party batteries, but having seen the kinds of odd RF holes that can appear due to all sorts of external reasons--trees, concrete, power signaling, line-of-sight communications, antenna design, and crosstalk from other sources--I wouldn't be surprised if normal operations means that there are plenty of issues that aren't or even can't be resolved by DJI.

Regarding general info on LiPo batteries, I find these pages to be especially helpful:


Have said all of the above, what I hope to eventually complete is a divorce between the smart circuitry and the LiPo pack. The smart PCB and wiring appears to mostly consist of a high-amp positive and negative, a thermistor sensor, and some independent battery cell monitoring. The original Phantoms had an independent pack and I believe a 3D-printed caddy can be produced to hold the smart circuitry and be used to add and remove an appropriate LiPO cell pack. This might be somewhat pointless, but it would be nice to have a P3 for years to come even when the proprietary batteries become scarce. Issues will remain regarding recharges and serial numbering, but there is likely a "fix" which can be applied for customizing the serial number and there-by resetting statistics. This is all speculation though and I don't want to jump into it too much since it might be fall under the forum's "firmware hacking" rules, and I certainly wouldn't recommend this approach to anyone using equipment with an active warranty.
 

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