Phantom 2 Vision Crash - Problem Identified

[lowthian]

I'm writing this in case anyone else has a similar experience.

I bought my P2V on Nov. 7 and have flown it probably 30 times without problems. That's not to say that I didn't have hard landings in the beginning where I chipped props and had to replace them, but nothing catastrophic. At least not until 2 days ago.

I have installed all the firmware upgrades that DJI has issued and have installed a Flytrex core.

Here's what happened.

I had been flying for a little over 12 minutes and had 48 % battery left according to the DJI app on my phone. I was ending the flight because I live in Michigan and my hands were to cold to continue. I was flying in Attitude mode. I brought the Vision down to about 20 feet of altitude over my front yard and it was hovering. Without warning it fell to the ground like a rock. Luckily, I have about 8 inches of snow in my yard so the impact was somewhat cushioned by the snow. The only visible damage was two chipped props. I shut everything down and brought the Vision in the house to get the snow off of it.

Since I still had plenty of battery left, I powered up the flight battery. The battery came on, but there was nothing happening on the vision. No noise, no flashing lights, nothing.

I shut down the battery and removed it. Then I powered it back up to check the voltage output. It read 12.1 volts so I knew the battery was working. In order to check the voltage to the controller board, I had to take the vision apart, just like when I installed the Flytrex core. When the top cover is removed the controller board is visible. I put the battery back in the vision and powered it up. I checked the voltage on the board at the point where the wires from the battery connect to it. It was zero.

So I started checking the wires that run from the battery terminal to the circuit board. There I found the problem. The black wire had disconnect from the battery terminal at the solder joint. If I touched the black wire against the solder joint where it belonged, the vision fired up as it normally does.

So now my task is to take out the controller board and re-solder the joint. I suspect it was a cold joint when originally built. The difficulty in doing this is the battery terminal is buried under the controller board so I know it will require a lot of dis-assembly to get at it.

Wish me luck and I'll let you all know how I make out.

 

[urgno]

seem that QC at DJI in these days was not enough :roll:

 

[Nvr2fst]

Pictures

 

[iDrone]

Pictures

Agreed, absolutely! :ugeek: Please post close-up pics of the problem showing the wire & NG solder joint, esp if there's a gap. (BTW RoHS compliant solder will have a dull finish, so don't let that mislead you)

Nice find.
iDrone

 

[Migmon]

Pictures

yes please document this with pictures so we can do it too.

 

[lowthian]

I must apologize to everyone because right after I posted the original msg I tore into the Vision in an attempt to repair it and never thought about taking photos along the way. I should have thought of it because I know how valuable photos are, but I didn't. I guess my mind was focused on the fix.

Anyway, I did repair the solder joint and it was difficult to get at because of being buried under the controller board. But after about 90 minutes I had it repaired and back together. I inserted the flight battery and powered it up. The vision beeped and blinked just like it was supposed to. The next step was out to the front yard to see if it would fly. It took off normally and I hovered it at about 6 feet off the ground for 5 minutes in GPS mode to make sure it was going to stay in the air. It did.

So then I got my courage back and flew for another 15 minutes (staying pretty close to home) without incident. I even achieved a personal high ascent of 506 feet according to Flytrex.

Once again, I apologize for not taking pics of the teardown.

 

[Nvr2fst]

Once again, I apologize for not taking pics of the teardown.[/quote]

Ok just don't do it again. Just kidding. But if what you say is true, it really needs to be documented so as people don't start tearing their Phantoms apart on a whim wondering about theirs having this problem. If I saw pictures I would tear mine down in a minute to check it.

 

[TexomaEV]

When you finally got to the solder pad where the wire was supposed to be, did it look like there were any wires still soldered on the board (IE: frayed ends of wire strands sticking out) I'm wondering if over time vibration/movement of the wire caused stress fractures at the solder joint and the wire broke loose. It's sorta the argument of soldered connectors -vs- crimped only, which is best for longevity/durability especially in something that is constantly moving, vibrating, jarred around, etc......

I guess I'm asking if you feel a person should maybe apply some hot glue on some of the wiring to keep it from fracturing at the solder joints, by limiting the harness ability to move.

 

[garygid]

Good find, and thanks for the description.

If one removes the battery and inserts a right angle dental inspection mirror,
can one see the wire and the solder joint in question?

 

[Shrimpfarmer]

Thanks for reporting this find. It could turn out to be the missing link. Anyone suffering such a failure will 100% certain see their bird fall like a brick.

Thanks also for the tip that an inexpensive dental mirror, available from most pharmacies can allow you to visibly inspect the suspect joint. I am going to have a look at mine and if possible take a photo for reference.

I would welcome any other thoughts about what people can do thats fairly simple to strengthen that joint?

 

[Shrimpfarmer]

I took this of my phantom which has not suffered the problem so far. Unfortunately my mirror is not 90 deg otherwise I could have got a better view. But perhaps the OP would be able to comment if the fault area is shown in this picture please?

I was unable to view the connection at the other end of the wires from inside the phantom battery bay.

 

[lowthian]

I took this of my phantom which has not suffered the problem so far. Unfortunately my mirror is not 90 deg otherwise I could have got a better view. But perhaps the OP would be able to comment if the fault area is shown in this picture please?

I was unable to view the connection at the other end of the wires from inside the phantom battery bay.

The problem area is visible in your photo using the mirror. It was the black wire, which is attached to the lug that feeds the bottom blade. When I got things apart and could inspect the solder joint more closely, there was no place on the joint where I could see that the wire had previously been attached. Just a nice shiny ball of solder with no holes in it where the wire pulled loose. The wire was stranded copper and there was a small area at the very tip where solder had bled into the wire.

FYI, I had the bird up again last night without incident.

 

[garygid]

... mirror MIGHT allow inspection.
Please report if it works, since I have not yet tried it.
The contacts might not be visible, even with a mirror.
Cheers, Gary

 

[Shrimpfarmer]

OK

I think that anyone reporting a bird just falling from the sky now needs to report if the craft powers up again after recovery. If this fault is present then the battery should show as charged but nothing should operate or sound on the drone.

If the drone does not power up then go on to check the wires as shown.

If the bird powers on however then we can discount a broken solder joint ?

 

[garygid]

If the bird powers on again after the crash, the "broken" wire connection might
simply be touching again. And, it is probably a minor miracle in any case.

Also, in my opinion, do not wait for a dangerous fall from the sky event to
examine your P2V. When one airliner falls from the sky because of a
worn or broken cable or wire, they (should) inspect all the other aircraft
that are constructed in the same (or similar) manner.

It is your choice, and it us a pain to deal with, but I intend to
check mine, and try to examine all the wires and connections,
if I am able to do so. Perhaps if you are rich enough that losing
your bird does not matter, then consider that, in falling out of the
sky, it might kill someone that you love.

 

[Shrimpfarmer]

I agree that the wire should be checked.

However my soldering skills are not that good. Can anyone who is good at soldering these types of thing give any tips on what we are supposed to be looking for ? Clearly if the wire is loose then that should be easy to spot but I am not sure I could recognise a bad joint from a good one.

If anyone attempts a repair to this then please try and post a video how to.

 

[Firestat]

Glad you found the problem. Like so many other posts on this forum, it will help short cut some fixes.