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VTX issues

outthayr

Active member
#1
I put together a rough assembly and tested everything, TBS nano signal was coming through strong - perfect clear video, even when leaving the room. As I finished up and added an RX and was starting to setup Betaflight I tried the video again - it was going static, or black bars, or just cutting out. Swapped to a new battery with same results. I realized the ground to the VTX was loose, thought that would fix. Then I realized my small monitor antenna was almost broken off - so the next day got the ground to the VTX and opened my monitor and hit with some solder. I figured that would fix it. Nope.

Thinking maybe the monitor has seen better days I tried my goggles, same result. So, I swapped out for another VTX... and same thing. Static and loss of signal if I move a few feet away. Went over all my connections, tested voltage, twisted signal wire with ground, wired ground for cam and vtx together, added capacitor, powered cam from vtx... nothing working.

So, perhaps during fiddling I did some damage to the PCB itself? I'm not the best at soldering but I'm getting better and have only burned out one pad long ago in the past. I don't have another board so I cannot rule that out just yet. At a loss for now...

Have gone over this and some similar reading https://oscarliang.com/connect-vtx-fpv-camera/
micro--lux-v3-diagram.jpg
 
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outthayr

Active member
#3
Try connecting the signal wires from the cam and VTx directly together without the FC. If that works, you know the problem is in the FC.
Tried this and I get clear video, but if I move a few feet away it goes static. Have tried with two different RX (monitor and goggles), and have tried 2 different antennas - always the same result.
 
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ElectriSean

Eternal Student
Mentor
#4
Check that your antenna connections are good, and if using CP antennae, that the polarization matches. Also make sure that the channels match perfectly, sometimes an adjacent channel will come in at close range but drop out quickly.
 

outthayr

Active member
#5
All checked. Just checked two working quads and signal comes through on monitor and goggles no problem. My meter shows steady 5.15v from the pads. VTX is 5v in.
 

outthayr

Active member
#6
Re-wired with another VTX and having better results. The TBS Nano had small pads so maybe I had a bad power/ground attached? I'll save the nano in my just-in-case box, but prolly won't be messing with it again. I reckon it may have been solder - possibly not getting a clean ground. My solder game is sloooowly improving. Thanks for the tips above.
 

outthayr

Active member
#11
Wired up a little 5v pololu stepdown to feed the cam and vtx from a battery, crystal clear feed. I suppose it was the FC filtering power in a weird way.
 

outthayr

Active member
#13
Now troubleshooting a different build. VTX OSD shakes, and sometimes becomes totally unusable.

Vbat to VTX
5v vtx to cam (Runcam says best input is 9v or 12v - will install a 12v stepdown later)
Cam and vtx shared ground
*vtx out ground was just a trial - seems slightly better with than without.

EC453CDB-AE7B-4F68-9DB3-DE9E131616D9.jpeg
 
#14
you state your under powering the VTX with 5v instead of the recommended 9-12V.......

I have a vtx that behaves the same way when the battery is running out of power.
I deliberately ran down a set of batteries really LOW, from the VTX , VRX and a monitor to see at what point I will loose my video signal and thats when I experienced the poor feed beginning to develop and got worse as the voltage continued to drop
 

outthayr

Active member
#15
you state your under powering the VTX with 5v instead of the recommended 9-12V.......
Board specs are DC 5-20V. Recommended by RunCam 9v or 12v. Have a 9v stepdown coming, will see if that helps. Run 3 other setups with 5v input to the RunCam without a problem. RunCam OSD is clear - just the VTX OSD that shakes.

https://shop.runcam.com/runcam-hybrid/

My batteries are at more of a storage level, I can see what happens on a full charge.
 
#16
Board specs are DC 5-20V. Recommended by RunCam 9v or 12v
well thats a diff story then and it shouldn't be low voltage unless something else in your system is defective drawing too much power, maybe break out the multi meter and start checking the power consumers, servos etc to see if there is a power problem at least to eliminate the possibility of a power issue
 

outthayr

Active member
#17
Never really fully fixed this issue, just fiddled around and ended up removing the ground for CAM coming from the VTX and the 5V and just powering/grounding to/from the board. It still shakes but not too bad - holds long enough to enter settings and exit. Turned off VTX OSD as the slight shake is not fun to see while flying.
 

PsyBorg

Wake up! Time to fly!
#18
I just caught up on this thread...

You need to work on wire routing. Parallel run lines over or near anything that pulses like an oscillator or a crystal or anything with alternating current will inject signals into every wire that is in line with the field it produces.

When doing a build ALWAYS use the shortest wire lengths needed to make the connection allowing just enough extra there is no stress on any of the joints. IF wires have to cross try your best to make sure they do so at 90 degrees to each other. side by side =BAD.

90% of what we use has three wires.. power, ground and signal. I braid all my wire sets for two reasons. Mainly because the ground wire will sink induced signals better and it acts like a spring and takes up stress and strain on the wires.

Also understand if you are working in an area with florescent lights like a shop or a garage that too will make your video goofy and all twitchy.

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