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Vision 2+ wifi units fix and why they are dying.

Discussion in 'Phantom 2 Vision + Discussion' started by burlbark, Oct 23, 2014.

  1. burlbark

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    I bought a wifi unit from a forum member here. It was toasted and would no longer output video. I opened the unit and this is what I found. None of components requiring heatsinks where touching the large heat sinking case. These components are secured to the board by "balling". Because of thermal expansion and excessive trapped heat in the component the balling would melt and the component lifts no longer doing its job.

    If you have a vision 2+ and you want to save the wifi unit and make it last a long time, purchase some Arctic Silver and some copper shims and make sure your components are heat sinking properly.

    I am going to try and reflow this unit and see if it can be brought back. More than likely it is fine and will be back in service, however its life span will be diminished from the excessive heat cycling.


    I took a second wifi unit apart that has not yet failed and found a little better quality control. They used more thermal compound.

    However once again I did not find any thermal compound on the final stage amplifiers. They are not supposed to exceed 85C but I found heat discoloration on the shielding above them. I usually only see this coloring when temps get above 400F. I decided that I would run additional heat sinking on these components also.

    I tried different shim material and I wanted to find something conforming but did not want to use thermal foam. I ended up putting a bead of Arctic Silver thermal paste on aluminum foil and folding it to the right dimensions and thicknesses and then mounted it with paste on the components requiring it. I then added more grey Arctic Silver to the components that had minimal paste and applied better coverage and aluminum heat sinking material.

    Of course while I had it open what better time to fix the GPS drop issue with more shielding. I dont think the GPS drop issue starts until the wifi begins to fail. I have caught mine in time. If you dont want your wifi module burning up you better do something about it.



    Jeremy James
     

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  2. justin00

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    Re: Vision 2+ wif units fix and why they are dying.

    Would be great if you posted up a how-to please :)

    Btw.. I've heard the term "reflow" a few times... whats it mean exactly? Recondition/fix?
     
  3. DBS

    DBS

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    Re: Vision 2+ wif units fix and why they are dying.

    [youtube]http://www.youtube.com/watch?v=eOUf59iut3s[/youtube]
     
  4. CityZen

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    Re: Vision 2+ wif units fix and why they are dying.

    It looks like just tapping down the circuit board mounting studs a bit should bring the components closer to the case for proper heatsinking. That is, hitting the studs gently with a hammer and a punch tool or other suitable tool for transferring the force.

    The unit shown on page 2 of the "HOW TO: Removing/Replacing your WiFi Module" thread also seems like one of its components wasn't making good contact with the case.
     
  5. burlbark

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    Re: Vision 2+ wif units fix and why they are dying.

    I will hopefully post a how to. When a board is being built they use an oven to flow/melt all the solder paste and seat the components onto the board. When a component gets really hot the solder melts and the component can lift from the thermal expansion of the remaining solder. Reflowing allows the component to settle back down, as it sees uniform temperature again.

    Finally pics friendly...
     

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  6. Idbird

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    Re: Vision 2+ wif units fix and why they are dying.

    :D that would be good information. Any correlation to booster app?
     
  7. CityZen

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    Re: Vision 2+ wif units fix and why they are dying.

    Hmm, the data sheet for this part (AWL6153) doesn't mention anything about special thermal treatment, and in various other applications I don't see it being heatsinked.
    Also, if this part went out, you'd lose the entire signal, not just the video. I'm not suggesting it's not a good idea to heatsink it, but rather that this particular part doesn't
    seem to be the failure root cause.
     
  8. justin00

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    Re: Vision 2+ wif units fix and why they are dying.

    So everything with the arrow needs heatsink paste/shims or just paste?

    Thanks for pics :)
     
  9. burlbark

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    Re: Vision 2+ wif units fix and why they are dying.

    I have just pulled the data sheet on this component and all I can tell you at this time is that component shows sings of thermal stress. I have briefly glanced over the specs and I see 85c max operating temp. It should be heatsinked if the temps exceed that or approach that.

    From the discoloring occurring on the emf shield it is easy to say that it is exceeding this temp. DJI plastered heat sink compound all over the shielding but there is nothing contacting that shielding. I have a FLIR thermographer and could test it but its plainly overheating. In fact the part number is browned out and I may have to replace this component. I will check to see if its gates are still holding and run some continuity test on it. I am calling quits for the night. I got allot of repairs done today.

    Jeremy James
     
  10. burlbark

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    Re: Vision 2+ wif units fix and why they are dying.

    A good paste like Arctic Silver could probably fill that gap/void. I would recommend doing every component with an arrow. You can buy hobby aluminum in different thicknesses that would easily work. You however dont want aluminum slipping off and shorting out the board. Arctic Silver hardens a bit and acts like a glue after a couple heat cycles. So you want the aluminum wedged in there a bit with thermal paste on both sided of it.

    God be willing I will wake in the morning and pick back up on this by afternoon after shipping repairs.

    Jeremy James
     
  11. justin00

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    Thanks heaps for this.
    I've upped the power of the wifi so I'm guessing mine is probably running hotter than normal (but hope airflow is doing something to cool).

    In your first pic... there is the metal cover that covers half the board..Why does that have paste on it ? It looks like that metal piece just touches the metal lid ???

    *edit* I'll follow this guide to remove it and hopefully all comes apart when undo 4 screws viewtopic.php?f=27&t=20006
     
  12. justin00

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    Ok just did this.. Just have one question... in the first post.. second picture... how do you remove that board from the casing.. ?? I'm not sure if its safe to nudge off with a screw driver ?
    Also the tape that goes around it... I saved it, but its just to kind of hold it together right (or perhaps show DJI we have been fidling) ??

    Anyways put it all back together as I couldn't get that other piece out I mentioned.. plus I was curious if video still worked lol.. it did :p
    Once I can figure out how to remove the bottom piece I'll apply the arctic paste.

    thanks again :)
     
  13. burlbark

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    You need to take a flat bladed screwdriver and unscrew the standoffs. The small shielding on the pcb needs to have the metal tabs bent up to remove it.
     
  14. justin00

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    Are the standoff things the 4 posts that the screws to hold it all together go in? Couldnt work out how they come off??

    Yeah I got the shielding thing off.. wasnt to hard..putting it back was little harder.

    Got bored and put the paste on all the components except the ones on tge bored I couldnt remove. I put a bit to much on and know its gonna squirt out every where... That wont cause issues will it? The paste isnt conductive right?

    Anyways I put it all back together..
    Is putting the paste on the components on the board I couldnt remove vital?? I know was silly to put back together..but here we are.. Atleast now it will be easier to take apart.. The sticky thing holding wifi module is pretty sticky!!

    IGotto say Im quited pleased with my effort...I didnt break anything and it didnt end in tears like it normally does?

    Whats the copperish tape holding it together for.

    Thanke again so much!!
     
  15. Dirty Bird

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    This depends on what kind of thermal product you used. Some silver or copper-based thermal compounds are electrically conductive. Others, like Arctic Silver, are not. Though not electrically conductive, Arctic Silver is slightly capacitive, and they recommend NOT getting it on pins, traces, or leads. You never really want to use too much.
     
  16. justin00

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    Btw... if we want to reduce heat wouldnt it be better if we left the top of the casing off?

    It appears the top is also meant to act as heatsink judging but your arrows.. but ya wouldnt the increased airflor be better??
     
  17. justin00

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    ya mine was artic.. hmm wo dering if I should take apart and clean it abit..hmm it all works so maybe wasnt to bad hmm
     
  18. burlbark

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    No increased airflor is not the answer. :D You need to have it all encased to keep the wifi from interfering with the GPS.
     
  19. CityZen

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    Generally speaking, standoffs are posts that keep circuit boards away from the case or other circuit boards.
    The tape provides additional RF shielding to prevent interference with the GPS.
     
  20. rbhamilton

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    Re: Vision 2+ wif units fix and why they are dying.

    Yep. I ran that darn app just once in maybe 3 months and sure enough that very flight my WiFi module fried. I totally blame the booster App. Replaced my WiFi module and deleted the booster. It's been all good since then but couldn't hurt to grab some of that Arctic stuff...

    So is this the right stuff?

    http://www.tigerdirect.ca/applications/ ... &CatId=503