Extreme Video Lag

[jbrown630]

Like many others on this forum and elsewhere my formerly perfect and almost brand new P3A started to develop a 2-4 second lag in the video on the tablet vs the aircraft movements and position. This made flying FPV for shooting video and positioning for stills VERY difficult. Alot of my flying is around buildings under construction which requires FPV flight to position for the video and stills.

After Googling and reading everything I could find, it does appear for whatever reason that the ARM2 chip on the gimbal board was getting too hot and causing the delay. Whether this was a result of additional processing strain on the ARM2 chip due to a firmware update or not, it was fine when I got it and I never crashed it. Same tablet always used to fly. After cracking open the gimbal assembly I, as many others have discovered, found a lack of a thermal transfer pad to transfer the heat from the ARM2 chip to the heatsink . I ordered some thermal pads on amazon but I got impatient. It seemed to me that since the heatsink was milled with contact pads in the heatsink that thermal paste should do the job ( Although the repair directions I found said it won't work). I went to Best Buy and bought some TG-7 from Thermal Take. I put a healthy blob of the TG-7 thermal paste on the ARM2 chip and left the existing thermal pad for the other chips in place. Closed her back up and all is well! No more lag.

I'm still at a loss as to why the lag began in the first place. Unless a firmware update put more strain on the ARM2 chip, there's no reason the lack of a thermal pad or paste shouldn't have created this problem from day 1.

 

[3rdof5]

Just out of curiosity, do you have the video settings in the app to cache video locally?

 

[jbrown630]

Not certain and I packed up the drone. Never changed that setting so not sure why it would start now. And if your hypothesis involves local caching as a potential fix, why would the heat sink pasting fix the lag? I can imagine maybe that would load up the ARM2 maybe, but i never changed caching in the first place

 

[3rdof5]

Not certain and I packed up the drone. Never changed that setting so not sure why it would start now. And if your hypothesis involves local caching as a potential fix, why would the heat sink pasting fix the lag? I can imagine maybe that would load up the ARM2 maybe, but i never changed caching in the first place

I'm pretty sure local video caching in on by default, but to clarify, that only affects the performance of your tablet/phone, slower devices get better FPV with it off as it stresses the devices cpu less. It would have no affect on the AC itself as its transmitting that video always anyway. So ya maybe it is FW update that changes the stress on arm processor. Glad the new heatsink solved it tho.

 

[jbrown630]

Appreciate the attempted assist anyways! Yeah it's on a beefy 8 core CPU tablet so I doubt that's the cause. Whatever the reason glad it is behaving now!

 

[hblink93]

jbrown630--

Your advice was PERFECT. I was experiencing a 2-4 second video lag. My first troubleshooting step was to wipe my tablet and reauthorize it with a new email account (I did this so all of the baggage--emails, apps, etc.--wouldn't automatically download and bog my tablet down again.) Although the tablet worked a lot quicker, the lag was still present.

I took your advice and took my gimbal apart. After removing the existing weird pink stuff, I used heat transfer paste (the kind you use between a CPU and a heatsink on a PC build) and smeared it on the chips in on the gimbal board that looked like they mated up with the heat sink. I put a little too much at first, so I spent some time with toothpicks, Q-tips, and electronic contact cleaner to fix my mess. Once the chips were well (and neatly) covered, I put everything back together again--lag reduced to about .4sec. As good as new.
Thank you for sharing...Thumbs up from me.
--H

 

[happydays]

I had the same issue - but unplugging and replugging in the cables on the gimbal cured it. Perhaps you unplugging the gimbal to do the heat seal fix did the same thing?

 

[Lar1Man]

So was it a lag or the intermittent green and black screen. Just wondering before I crack open my bird
Thanks in advance

 

[happydays]

Mine was pure lag. Around 7 seconds.

 

[Solar B]

I had great success eliminating bad video lag. Remove both ribbon cables between the drone body and the gimbal. Use a magniying glass you will likely see the very small pins on those connectors are black. This is oxidation. Use a very tiny sharp point to gently scrape the pins and you will see some metal shine come through. This does require some patience and dexterity. Now re assemble with these cleaned up ribbons and let us know.