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

[justin00]

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

Nah that is "cooler master" brand thermal paste.
They are advising to use Artic silver. If you look on the PC over clocking forums they also say artic silver is the best..
Need to be careful with thermal paste as some are just useless/crap.

This is what you want http://www.scorptec.com.au/product/Cool ... vAodgZMA8Q

I'd say most local PC shops should stock it as its very very popular.

*edit* you won't need a 12 gram tube like in link I provded.. You can get diff sizes.. I think I got a 5gram tube for $15 AUD and it is small but provides more than enough to do everything mentioned in this thread.

*edit 2* i've ran the booster app for a week, then switched to "utility pro" which does the data logging to (maybe it depends which app) and have done around 40 flights, thats using 2 batteries.. so you could say 80 flights.. then I permanently edited the settings in Camera and RE so its permanently higher wifi for another 20-30 flights, again using 2 batteries.. 40-60 flights and all good so far.

that would be good information. Any correlation to booster app?

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

 

[nhoover]

This is very interesting. I've been running the booster app on most of my flights - probably have used it on over 80 flights now without problems. From now on I'll only do it on long range flights and will monitor take a look at mine next time I open her up. Thanks!

 

[burlbark]

I thought it would be best to bump this back up to the top and show a second unit that was showing some signs of heat stress, along with the fix I came up with. Its running great and the final amplifiers in the circuit like to run cold, down to -45c. There is no reason to let them get hot.

 

[plasmo]

Good job Burlbark. Was that mine that you dissected

 

[burlbark]

Good job Burlbark. Was that mine that you dissected

It sure is, I havent yet tried to reflow it. I can see one chip that is warped and lifted on one end. I will end up putting a stack of quarters on it and heating it back up with a hot air station. Time for lunch. Thanks for helping bring a fix to this easily fixable issue.

Using a hair dryer allows the wifi unit to pull right off the mother/main board.

 

[Mako79]

A while ago, I was looking into getting a small 12v CPU fan to bolt on top of the wifi unit.
I never got around to it.
I may look into this now considering that my theory was true...
They suggest anything transmitting over 200mW should use a heatsink and fan.
viewtopic.php?t=20037&p=186345

 

[justin00]

The RE shielding component also gets incredibly hot after 3-4 mins of usage. I had the lid off and was doing some antenna testing and noticed it... Anything we can do to increase cooling ?
or its not to important seems it sits on the R/C unit... Even if we had the lid off (where the battery sits) there wouldn't be to much air cooling seems the R/C doesn't move much... and not at any speeds as it does on the Phantom.. .but yeah thought I'd mention it.

 

[burlbark]

The RE shielding component also gets incredibly hot after 3-4 mins of usage. I had the lid off and was doing some antenna testing and noticed it... Anything we can do to increase cooling ?
or its not to important seems it sits on the R/C unit... Even if we had the lid off (where the battery sits) there wouldn't be to much air cooling seems the R/C doesn't move much... and not at any speeds as it does on the Phantom.. .but yeah thought I'd mention it.

I am a little confused as to what component you are talking about. "The RE shielding" I assume you are talking about the metal case around the wifi unit, or a whole other quad in general?

 

[justin00]

Nah on the range extender on the R/C.. when you take the lid off.. it has this metal cover that covers 1/3 or so of the board. This metal component gets very hot after a few minutes of use.
If you go to page 1, and look at the second picture.. you'll see a metal cover which has been taken off.. that is what I am talking about... but that metal cover? heatstink?? is also on the range extender... I'm not talking about the wifi module in the Phantom.

 

[CityZen]

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

Here you can see the final amplifiers are not making any contact with the heat sink emf shielding, no attempt was made at placing thermal compound.

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.

I've thought about this some more, and one issue that I didn't consider is that the Phantom is not your typical wifi usage case: it's often operating at the limits of wifi range, where RF power needs to be at its maximum, with continuous usage for minutes at a time. This is in contrast to stationary wifi APs, which don't usually have such usage.

 

[burlbark]

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

Here you can see the final amplifiers are not making any contact with the heat sink emf shielding, no attempt was made at placing thermal compound.

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.

I've thought about this some more, and one issue that I didn't consider is that the Phantom is not your typical wifi usage case: it's often operating at the limits of wifi range, where RF power needs to be at its maximum, with continuous usage for minutes at a time. This is in contrast to stationary wifi APs, which don't usually have such usage.

Once the ouput fets and the processors are properly heatsinked the likely hood of burning them up with the onboard regulated voltage becomes almost zero. I doubt there is an app that can change the onboard voltage....

I have 2 more being shipped to me for heat sinking. Its an easy fix that takes less than an hour and can save $200 and a fly away. Its a no brainer.

I need more range and may have to do some investigating. I cant justify buying $4 antennas for $50, the package deal makes it easy though. I may have to break out the spektrum analyzer and start testing. $250 dollar packages that should be selling for $75 is to much mark up for me. I will have to provide something for the community. I buy the bulk cables and connector and they run me less than a dollar each.

 

[RichWest]

Burlbark aka J - followup to our conversation... I placed two temp recorders on and under the wifi module, I never exceeded 60C. The underside was about 30C.

I have a question about thermal grease, based on what I've read so far on the material and understanding within other applications. My unit had full coverage of whatever type of heatsink paste off the top cover, actually excessive. But I don't think thicker is better for this material. Shouldn't this just be a very thin layer rather than a glop like depicted in your photos or like my first hand example? It would seem the thermal grease would create a thermal bridge when gapping a large gap of say .01".

I'm leaning towards an alternative to gap the two thermal contacts (chip(s) and cover) within the WiFi module. There are solid materials, possibly silicon, that conducts heat and would gap the two surfaces. I've seen them in an old CD drive I tore apart recently and from limited google'n last night found sources for a variety based on application. Just need to determine thickness for the needs.

Further, I read that even though the AS5 is non-conductive, it does have the ability to electrically bridge and act link a capacitor. Could this be the source of DJI's problems with deteriorating FPV? The thermal compound is flowing onto contacts as the unit heats up, then causing an electrical bridge to drop FPV further over time... Just thinking out loud...

 

[burlbark]

Burlbark aka J - followup to our conversation... I placed two temp recorders on and under the wifi module, I never exceeded 60C. The underside was about 30C.

I have a question about thermal grease, based on what I've read so far on the material and understanding within other applications. My unit had full coverage of whatever type of heatsink paste off the top cover, actually excessive. But I don't think thicker is better for this material. Shouldn't this just be a very thin layer rather than a glop like depicted in your photos or like my first hand example? It would seem the thermal grease would create a thermal bridge when gapping a large gap of say .01".

I'm leaning towards an alternative to gap the two thermal contacts (chip(s) and cover) within the WiFi module. There are solid materials, possibly silicon, that conducts heat and would gap the two surfaces. I've seen them in an old CD drive I tore apart recently and from limited google'n last night found sources for a variety based on application. Just need to determine thickness for the needs.

Further, I read that even though the AS5 is non-conductive, it does have the ability to electrically bridge and act link a capacitor. Could this be the source of DJI's problems with deteriorating FPV? The thermal compound is flowing onto contacts as the unit heats up, then causing an electrical bridge to drop FPV further over time... Just thinking out loud...

1. While placing a temp sensor under/over the wifi reveals some data it does not tell you what operating temp of the actual components are. If you are seeing 60c on the case or even inside the case you can rest assured something is getting to the edge of thermal runaway. The surface area of that case is huge compared to the component that are operating at temperature. This alone is cause for alarm. If you have been to my facebook page or my website you will see that I have FLIR thermography equipment. I can map the component temperatures in real time. I dont need to even use it, the thermal stress signs are visible to the naked eye on failed units.

"Thermal bridging" is preferred, thermal insulating is not. Electrical bridging is what we avoid... unless I am stacking mosfets

2. While I do not know the specs on the stock thermal compound we can be certain that the thicker the compound the less heat transfer we will see. This is why I recommended shimming and arctic silver and that is the procedure I showed in the pictures. Be aware that you should leave some room for expansion and contraction. This is one reason why I went with multiple layers. The elasticity of the AS5 is pretty good from my experience at least with in the first 200-300 hours.

3. The capacitive effects of the thermal paste has been noted. Thats why you limit it to the top of the component and dont allow bridging. Arctic silver hardens somewhat into flexible putty and will eventually harden firm. It does not tend to flow after a couple heat cycles. The stock thermal compound does not appear to do the same. Here is the PDF on Arctic silver 5.
http://www.arcticsilver.com/PDF/appmeth ... d_v1.2.pdf

While the ideal situation would be to have the heat sink spring mounted for expansion and contraction, I currently have to work within the design limitations given to us by DJI. Because of variations in depth setting of components, case dimensions, stand off height and screw tension, we must do the best with what we have. If there are additional problems by DJI gooping on thermal paste I would not be surprised. Rather than proving that with my RF analyzer I will just remedy it by removing it and applying it correctly.

Obviously by making sure you have adequate thermal compound, even if it is a thick layer, or shimming it with aluminum are measure that will reduce the temperature of the components in question. Convection is not proper heat sinking as you know all to well.

 

[CityZen]

Seems like the easiest solution is just to get some "thermal conductive pad", perhaps 0.5mm thick, maybe 1mm, and use this on the RF amplifiers and other components to bridge all the gaps to the casing.

 

[burlbark]

Seems like the easiest solution is just to get some "thermal conductive pad", perhaps 0.5mm thick, maybe 1mm, and use this on the RF amplifiers and other components to bridge all the gaps to the casing.

Thats a good idea however, I havent had any good luck with the pads. I have had many processors fail using the foam pads. Maybe there are some better pads out there?

 

[burlbark]

There has been some concern as to the capacitance of Arctic Silver 5 thermal paste. I just put a bb sized ball on a scrap of paper and checked the capacitance with my Capacitor tester. Rest assured..... .5-1.2 pico farads. The leads of my test probes resting in my lap detect that much capacitance if they are crossed or there is a loop in them. I dont think we have a real issue unless it is a gross amount.

 

[RichWest]

I'll admit I am no expert on the subject. You've shown you have the tools and knowledge, I envy this. But my understanding about manufactures, Chinese at that, they'll cut corners when they can. I just questioned its use (thermal grease) and that it "could be" the source of failure, based on what I've read so far. Thermal pads are likely more expensive, why was there one against the bottom housing and not everywhere else? And we're not talking about precision made hardware like you'd expect in a human aircraft.

Before I replace a $189 component, that didn't last me more than 12 weeks, I'll question DJI's abilities until I'm satisfied with the answer. Commercially this would not be an acceptable repeat failure. In my industry, more than a .1% failure rate gets everyone involved. Why shouldn't I expect the same from DJI, oh that's right I'm just one person...with one P2V+.

Sorry, rant off. Wasn't intended towards you BurlBark. You showed me the way, your Aces in my book. I feel like I just bought an iPhone off Alibaba and with a little use I now need to fix it myself...crap.

:lol:

 

[CityZen]

Seems like the easiest solution is just to get some "thermal conductive pad", perhaps 0.5mm thick, maybe 1mm, and use this on the RF amplifiers and other components to bridge all the gaps to the casing.

Thats a good idea however, I havent had any good luck with the pads. I have had many processors fail using the foam pads. Maybe there are some better pads out there?

Well, I think you have to put it in perspective. The processors probably should have been using something better. But a pad would certainly conduct much better than an air gap in this case!

 

[burlbark]

Seems like the easiest solution is just to get some "thermal conductive pad", perhaps 0.5mm thick, maybe 1mm, and use this on the RF amplifiers and other components to bridge all the gaps to the casing.

Thats a good idea however, I havent had any good luck with the pads. I have had many processors fail using the foam pads. Maybe there are some better pads out there?

Well, I think you have to put it in perspective. The processors probably should have been using something better. But a pad would certainly conduct much better than an air gap in this case!

Now if owners would just do the mod and save their wifi units. I think if a person starts to have a drop issue and starts losing range, if they just catch it quick enough they will be okay and not have to buy another hoping the under paid assembler was having a good day.

 

[RichWest]

Seems like the easiest solution is just to get some "thermal conductive pad", perhaps 0.5mm thick, maybe 1mm, and use this on the RF amplifiers and other components to bridge all the gaps to the casing.

Well, I think you have to put it in perspective. The processors probably should have been using something better. But a pad would certainly conduct much better than an air gap in this case!

Now if owners would just do the mod and save their wifi units. I think if a person starts to have a drop issue and starts losing range, if they just catch it quick enough they will be okay and not have to buy another hoping the under paid assembler was having a good day.

Great advice! I'm going the thermal conductive pad route for the original unit to test performance. Wish I had your Flir. As you pointed out several heat producing chips have no thermal material at all. So I can only improve how the heat escapes, hopefully I won't be creating another issue... If all goes well, regarding heat, I'll mod the new unit and then fly till it dies. Will reply with my results as time permits.

So does anyone have a suggestion for thermal conductive pads? Brands, materials or otherwise?