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Help! Frying VTXs!!!

#1
Hello friends! New poster looking for help. I am also relatively new to FPV so forgive my assumptions and anything obvious I am forgetting. I have a Tinyhawk S that I lost video signal on. Assumed it was VTX since I have no signal at all. Figured if only camera was bad I would still get OSD in goggles. I decided to upgrade camera and vtx anyway cause I really like my tinyhawk. Now have the Runcam nano 3 and Rush Tiny Tank installed. Everything was going well for the first few batteries...then nothing! Upon doing some test I found that if I held the vtx antenna within an inch or less of the video antenna I could get a picture ( although bad). Also if I pinch the antenna connection to the vtx I can get a picture but only out to about foot from video receiver. Also sometimes when I boot up for testing the vtx will be scorching, unplug, replug normal. So assumption number two...I have another fried vtx. Now the question, could the flight controller be frying the VTXs? I have check the voltage going to the vtx and it is 4.8 volts. Any thoughts or ideas would be greatly appreciated!

~Cheers
 

FDS

Well-known member
#2
VTX’s normally cook because they are being run too high output or the antenna comes off, or the input voltage is wrong. I just use the cheap diamond VTX’s on my nanos, none have blown.
Check the antenna is plugged securely into the board, I hold my VTX antenna in place on the canopy by shrink wrapping it to a zip tie, this stops the micro connector being pulled off.
If you are running it at 200mw+ then you may shorten its life, generally Rush VTX’s are good quality but a tiny VTX at high power output under a small canopy with minimal airflow is not going to last long.
A better camera is a good investment, lots of nano’s ship with relatively poor ones. Yours should be fine. If you get a black screen with OSD then it’s the camera, if you get snow only then it’s the VTX that is dead.
 
#3
FDS, thanks for the info! I went with the Rush because they do seem to have good products. I don't need the 200 mw, actually didn't even get a chance to use it. I did try 100 mw just to see the difference. But that was only for about a minute flight.

I am worried that I may have an issue with my FC since this will be the second vtx that has failed. Don't know if FC can even cause that, but maybe I am just having bad luck...third time's a charm?!?

~Cheers
 

FDS

Well-known member
#4
If the voltage regulator is not working or there is a short in the wiring tail to the VTX that can cause a voltage spike that could damage the VTX. Otherwise it’s only a video line and 5v/ground going to it. Smartaudio cannot damage a VTX unless you hook it up to a power source by mistake.
It doesn’t sound like it overheated.
I would also check that the antenna was firmly connected, running a VTX without the antenna can burn them out.