Please help, my VTx isnt powering up

[Redbeard]

Hello, I need some help as I'm starting to lose interest in this hobby. This is my first build.
So I've finished my first build:
Armattan Gecko 3" frame
HGLRC 1407 3600kv motors
HGLRC F428 Stack
TBS Unify Pro32 Nano VTx
FrSky R9mm Rx

Heres the problem. The build was fairly simple. I flew it a few times with no problems. On my last flight my video dropped in midst of a power loop, and when I recovered the quad my antenna had detached from the VTx. I dont know if this was from impact or not, but my VTx smelled fried and it was powerless. So I bought a new one and it is not powering on either. Everything is wired the same as it was the 1st time.
I used a multimeter to test for power on the VTx leads and I'm getting all 15.5 volts co.i g through. Is that supposed to happen? Or am I only supposed to be pulling 5v? Would that suggest a bad FC even though it's getting power? Bad VTx out of the box? Please help. Man, I got this thing built and the day I finished it, it started raining for 2 weeks straight. Now the weather is so nice and this is driving me nuts, a little depressed actually....lol. Thanx in advance

 

[Dugdog47]

Pics help I'm dyslexic lol!

 

[Redbeard]

At work now, bit I will post tomorrow. I'm getting 5v output on my camera pads and 3v output on my Rx pads. But when I test the vtx pads, they're putting out 15.5v. That can't be right, right?

 

[RENOV8R]

yes, we need pics of your wiring. Which vtx pads are you referring to that are measuring 15.5v? Because the Unify Nano can only take 5v

 

[Redbeard]

Quad is taken apart at the moment. CAM is pulling 5.5v. Rx is pulling 5.5v. VTx is pulling all 15.5 of my lipo.

 

[RENOV8R]

At work now, bit I will post tomorrow. I'm getting 5v output on my camera pads and 3v output on my Rx pads. But when I test the vtx pads, they're putting out 15.5v. That can't be right, right?

Yes that's right, most flight controllers that have a pad for vtx power are going to provide full battery power. Your Unify Nano can only handle 5 volts

 

[Redbeard]

That's not what I wanted to hear...lol. I already ordered a new FC. So now back to having no clue why it's not working. Bad VTx out of the box?

 

[Redbeard]

So basically I fried my new vtx the second I lit it up? Makes sense. My dumbass is learning the hard and expensive way, haha. So, order another vtx and hook it up to a 5v pad this time? I wonder now why it work for a few flights to begin with though.

 

[RENOV8R]

Yes, sort of curious. When your antenna detached, that's what probably killed it. Anyhow, I'll throw another wrench in your gears and this is why I don't use the Unify 5 volt vtx. Most flight controller 5 volt supply is 1 amp at the most and isn't really intended to be used for powering a vtx as they draw quite a bit of power. I think the Unify Nano itself uses 500 or 600 mah, so combined with also powering the camera, you could overload the flight controller. Best thing to do is connect the Nano directly to your lipo with a 5v volt dropdown regulator

 

[Dugdog47]

I like you use a vtx that is powered off the battery power usually work great hooked up to a 9v pad on the flight controller.

 

[wafflejock]

Think Reno was just meaning that the VTX should only have 4.5-5.5V input so was probably supplied with too high a voltage and so is fried, why the first one didn't fry immediately is an anamoly not the normal case, typically if any voltage regulator or IC in general is hooked to a voltage potential greater than what it's rated for is likely to have high current flow through it causing it to heat up more quickly than it can dissipate heat. Long story short always check voltage supply output and max input for components before hooking voltage supply to the input.

Many vtx can be powered directly off battery voltage but those have a built in regulator to drop the voltage to something the ICs can work with (typically ICs operate at 5V or 3.3V). The TBS nano specs say it needs 5V though.

 

[Redbeard]

Thanks for the responses guys. I've ordered another vtx and have learned an expensive lesson