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What does a bad ESC look like?

Discussion in 'General Discussion' started by dptcalvin, Feb 11, 2015.

  1. dptcalvin

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    Took my P2 v2 (non-Vision) out for a flight today and noticed one of the motors wasn't spinning upon startup. This was with a (fully charged) Limefuel 6000 battery. Tried it twice more, no luck. Stuck an OEM battery in and it all four motors spun. I even flew 15 minutes successfully.

    Took the bird home, put in the Limefuel battery and tried to reproduce the problem and couldn't. All was well.

    Opened up the shell and looked at all four ESCs and they all look the same. None of them look different from each other. None look burnt.

    Here is a picture of the ESC from the motor that wasn't spinning. Does it look okay to you?

    [​IMG]
     
  2. dptcalvin

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    Here is a picture of each of the four ESCs.

    [​IMG]

    [​IMG]

    [​IMG]

    [​IMG]
     
  3. PhantomFanatic

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    The photo, that you submitted, looks like cold solder joints. A good solder joint should be shinny.

    I just took my new P2 apart tonight and although I feel I could have made better looking joints, but they looked good enough to work.

    I recommend that you should solder suck the joints go to the motor wires. If you know how to solder, resolder them. I can send pictures tomorrow if needed. :)
     
  4. Narrator

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    I saw a video on replacing ESC's and the guy showed three or four. But as he said, you couldn't tell just from looking at them that one or more of the chips had failed.
     
  5. dptcalvin

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    Well, I think the MOSFETs are showing signs of heat/wear as demonstrated by the white discoloration on them. There's at least one MOSFET on each ESC showing this white discoloration.
     
  6. Green_Phantom

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    Solder job in that first picture looks like garbage. Could be an intermittent connection due to that soldering. Suck up all the old solder, clean everything nicely, get some good quality solder and redo all of them since none of them look very promising IMO.
     
  7. Narrator

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    I also seem to recall the guy in the video saying they're cheap enough to just replace and not bother trying to fix.
     
  8. dptcalvin

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    They're about $19 a piece. If I replace one, I'd likely replace them all (since I have 2.0 and I would want 2.1).

    From what I understand, DJI will not replace ESCs if they aren't yet faulty...then again, do I really want to wait until one faults? Guess I should just suck it up and pay $80 now rather than deal with a possible (and likely) broken gimbal, GoPro, etc. if an ESC fails during flight...

    Ugh. :(
     
  9. Narrator

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    Gives you some spares... send one my way. :p
     
  10. Hughie

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    The MOSFETs are meant to get hot, so sometime they can look as if they have been sweating a bit - this does not necessarily mean they are on their way out.

    I agree with other posters who question the integrity of the solder joints. If you are not brilliant at soldering, dont worry too much, but you must at least reflow the existing joints. However, ideally you should be removing all the solder and applying new. If that ESC has bad joints it is worth checking the others too.

    Finally note, that if you have stalled a prop (say in a tip over or a crash) you may have weakened the MOSFETs and their life may be shortened. However since this mode of failure is intermittent I would expect this to be down to bad joints.

    In case you had not seen an ESC with a blown MOSFET, here is one. Caused by a tipover.
     

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  11. N017RW

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    (emphasis added)

    That's not likely anything other than some type of internal marking during manufacturing or assembly to indicate some level of inspection or testing. Heat stress will cause the epoxy to bubble, pit, or similar.
     
  12. Prophecies

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    Wow, I'm fairly new to flying bigger drones (have a ton of experience flying small nano drones and the Hubsan X4) and I've been learning a lot lately. But this is the first I've heard of being able to blow your ESC by tipping over or a light crash. What exactly are the "symptoms" one should be looking for, so that I can prepare in case something blows mid flight? Is there a way to test the ESC pre-flight? It seems weird to me that something as minor as a tipover could blow your ESC/MOSFET.
     
  13. Hughie

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    Since you asked, have a read:
    http://forum.dji.com/forum.php?mod=view ... es&lang=en
     
  14. RichWest

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    I believe the white you are seeing on the mosfets is the conformal coating, possibly an indication of the coating failure. Can't tell by the pictures, but if the surface seems "bubbled up" it would indicate high heat IMHO.

    The solder joints depicted could be from a non-lead based solder, which will appear dull. But yes they do appear to be cold joints based on the irregular surfaces. I would respect CapnBob's opinion, if he cared to chime in further...
     
  15. dptcalvin

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    Thanks for the replies, everyone. Fortunately, no bubbling.

    I've done a tone of searching and have only found 2 other people (that have posted) with similar white markings on their MOSFETs. As mine, their's only had white markings on one MOSFET on each ESC.

    I know the principles of soldering, but don't have much actual experience. Debating what to do next.

    Again, thanks for the replies!
     
  16. Prophecies

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    Thanks for the links and information guys. I had a crash where one/two of my props hit a tree at very low speed, but the force of the impact almost jammed one of the propellers by having the motor screw the prop too tight when it hit (and two props broke) This was before I knew about busted ESC's, and I've flown it a few times since. No issues whatsoever. Still flies wonderfully (after replacing the broken props). One thing is, it was cold. Very cold. I was flying in -25 to -30°C weather (around -13 to -23°F) and I'm wondering if that level of cold saved my ESC from frying.

    I'm sorry, I don't mean to hijack the thread. Back on topic, I hope you don't have any issues flying, dptcalvin!
    Thanks again for the wealth of information everyone, it's been a good learning process.
     
  17. dptcalvin

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    No worries, it's all relevant and I'm learning, too.

    I guess I'll look into fixing the soldering, whether it be myself or someone else with more experience, and just keep an eye for any more odd behavior. I'll keep an eye on the MOSFETs, too.
     
  18. jason

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    I agree that the solder joints do look cold. When I changed all the motors on mine all the joints were nice an shinny. You mentioned changing all the ESC at one point. Who would be doing the soldering? You most likely. When I did mine I removed all the boards which was more work then necessary. What I would suggest is take the motors and ESC's loose and place a piece of cardboard under the boards that way you won't damage the frame while soldering.