Power error & motor resistance rotating

[marty78]

Hi all,

I flew my mini yesterday and possibly due to wind it didn't seem to want to come back and ended up crashing somewhere and found it upside down on tarmac.
A couple of propellers were broken so have replaced those but now getting a hardware power error. I read about replacing the ECU chip but also that it could be a motor? I found the motor with the broken propellers is a bit more stiff compared to the others. I took the propellers off it and it then started a few times fine but then the error again.
Could it be just the motor maybe, is it easy to fix?
What I can also see is there is barely any gap under the motor compared to the gap under the others.

Many thanks in advance

 

[Yorkshire_Pud]

Could it be just the motor maybe, is it easy to fix?

How easy you consider it to be depends on how 'handy' you are and what tools you have available. To do the job properly you would need a soldering iron.
I rebuilt/reshelled a wrecked mini 2 (for the purposes of this thread its the same drone) and found it easy.

I have seen some suggest that one could literally replace just the motor, I wouldn't like to try that, there's probably VERY little slack in the wiring at the motor and soldering would, I think, be difficult. If it's a front arm then you are also working/soldering near the wiring for the antennae.
Personally I would replace the arm and motor and do the soldering at the ESC board.

Could it be the ESC board, possibly, but I wouldn't fancy trying to replace a chip, I'd replace the entire board. The problem is that DJI do not sell parts to the public so you are going to be buying either second hand parts or pattern parts and hoping they are good and that you are replacing the actual damaged component. If you think the motor is stiff I'd replace it.

Also check the shell closely for cracks or loose arms especially around the rear arms, the rear pivots butt mount onto the middle shell and are clamped to the shell by 3 screws, those screws can pull out and or the shell crack around them, either would IMO scrap the middle shell.

Watch multiple dismantling/teardown youtubes, some are better than others.
If the motor is a front motor and assuming you replace the arm and motor, set the arm to the tipping point between spring-open and spring-shut when you are trying to remove and refit the arm's pivot, it takes the pressure off the pair and the pivot comes out and goes back in easily.

If you not going to fit a replacement front arm immediately I would twist the pivot so that it springs to either the open position or the closed position and takes the pressure off the internal spring.

 

[marty78]

Many thanks, much appreciated.
I did try trying to gently lever the motor up a little to get a slight amount of clearance from the arm like the others as I thought the outer metal of the motor had been impacted.

After a few restarts it then again came up working ok but haven't tried flying it. I can't see any damage other than a slight amount of scuffing on top. The gimbal seems ok and when it starts up it makes the clicking noises but often not the tone it makes when ready.
It's a front arm that's affected yes.

I did find a DJI approved specialist repairer not far from me if it comes to it.

If it was the ESC would it have the error intermittently and seem to work now and again or would it be more likely to permanently show that error every time?

I can't see any other damage and the arms all fold in and out fine. The damage seemed to be the propellers and the screws otherwise.

Another thing I found was difficulty screwing the propellers in. I had to screw and unscrew a few times but also I noticed when screwed in as tight as the others the propellers wouldn't move, I had to loosen the screws a little to allow the propellers to move so thought that would be the case if the metal motor casing had buckled?

 

[Yorkshire_Pud]

I think an ESC would either work or not work and not alternate between the two states. Though the programming may be 'clever enough' to shut it down before it cooks. The Phantom 3 could cook an ESC if it was trying to drive a stuck motor but things may have improved since then.

With regards to the screws, you MUST BE VERY CAREFUL getting them square, so that they do not go in cross threaded.
What I do is put the screw in the blade then hold the blade with the base of its hub FLAT AGAINST the top of the motor. I then LIGHTLY press the screw into the screw hole and turn the screw BACKWARDS, as if trying to undo it.
Paying attention to what I feel, I can feel the screw drop into the start of the female thread in the motor. I then screw the screw in, no great force should be required.Unfortunately "no great force" is subjective and is complicated by the resistance of the Loctite on the screw thread. If a screw tightens up before it is 'home' I undo it until I feel it drop into the female thread again etc. etc.. But with these screws there should be only one start point for both the male and female threads so there should be ONLY ONE location where the screw "drops in".

If your screws are clamping the blades then I would ask, are you using genuine DJI blades and screws? I would only use genuine blades and replace BOTH blades using BOTH blades from a pack, they are weight balanced/matched.
If you are using genuine blades then I fear you have cross threaded the screws and tey are leaning slightly but I would check the blade and screw for any "mould flash" or dirt etc.. If you have cross threaded then I fear the motor is scrap, the threads are so tiny I wouldn't trust a damaged thread, there is no safe way to repair the female thread in the motor.

With regards to getting someone else to repair the drone, I would be inclined to go straight to DJI. They have the reputation for being quite reasonable with regards to cost but I think you can ask for a quote once they have recieved the drone. I believe you effectively get a new drone back, so remove the memory card. The only problem is that you MUST complete all the customs paperwork, the drone will probably go to Holland and thanks to Brexit if the paperwork is not completed duty may be levied and the carrier may charge a fee for collecting that duty.

 

[marty78]

That's great, thanks. The screws and propellers went in really nicely on the other arm with damaged propellers. This arm they screw in ok now easily and was careful to make sure it was going in level etc. One of the propellers on that arm seemed to not move anyway before I took it off, it seemed to be stuck. Definitely seems something amiss with this arm as it was tricky screwing in and out initially and have to leave slightly loose for them to move.
The replacements are the ones that came with my drone and used all new screws as well.

Shame as my Refresh+ ended (2 years) last July and never to use Refresh at all (always the way).

If it's just the motor on that arm as it sounds like, do you know how much that might cost?

Apparently the repair place near me is an authorised DJI repairer but if cheaper to send away to DJI could go with that.

 

[Yorkshire_Pud]

do you know how much that might cost?

No idea sorry, ebay is probably your best bet for second hand bits.
I have used two sellers for bits (so that I had spares if I ever need them) djisales_5 & jdrones_67 and they have been "dead on". I don't know if they are still selling bits.
DO NOT be tempted to use an arm and more especially a motor from a Mini 2 or Mini SE, I do not know if the arm will fit properly but the motor is different and Mavic Mini props will not fit.

 

[marty78]

Great, thanks very much. I've done lots of small repairs to things and work in IT so used to disassembling computers etc. So if it might be an at home repair with just the parts cost with a YouTube vid thinking it might save a fair bit over sending it in for repair. Will be wary of the antennas though if the front arms are a risk.
I'll check out those sellers. I did also wonder about getting parts (bit of a wait of course) from Aliexpress thinking they could be original of DJI is a Chinese company?

 

[marty78]

I've been quoted £115 to replace the arm including return postage but a bit pricey for me. If I can get a front arm or motor for around £20 or so and it just involves some unscrewing and a little bit of soldering I like the idea of having a go at it or using connections that could locally. Having seen a YouTube vid on it it doesn't seem too tricky.

The thing is if the arm seems fine in itself and it's the motor that seems buckled somehow from the impact is it still better to change the whole arm or just the motor?
I'm thinking there's just the few screws for the motor and running the wires through the braided piece into the main body?