VTX sudden failure on Emax Hawk 5 (Resolved)

[Wr4ptr]

Need some help troubleshooting a VTX issue. I got my first BNF quad, an Emax Hawk 5. Great quad! As expected, despite putting in my hours on Liftoff simulater, I still crashed it a few times, finally resulting in a broken VTX card (would still transmit but only for a very short distance and button for changing power was broken off). So, I bought a replacement card (same card the Hawk 5 originally came with). It was difficult to get the old one off (3 pin solder) but I managed it and got the new one on. On power up, I got good pic and good transmission. Flew it for a couple of minutes when all of a sudden, I got complete loss of VTX signal (no warning, just went from good strong signal to snow-->crash). Posted on this board (without video) and someone suggested that it might be a loose antenna connection. I had already affixed it with liquid electrical tape, but, I thought, maybe. . .so I popped the top and really glued that sucker on with a generous dollop of liq elec tape. This time, not just over the connection, but also at a separate spot along the wire to really stabilize it. . .it was/is solid. So, took her out to fly again. Very gentle flight (no flips or anything). Flew for a few minutes, then, boom, same freaking thing. I went ahead and made a video this time. Full screen is the GoPro footage. PIP is the DVR from my goggles.

A bit of additional info for trouble shooting: I'm using Aomway Commander V1 goggles. I'm using new (matching) LHCP Pagoda antennas on both the quad and the goggles. I have a good quality patch antenna as well as I know the patch that those goggles come with is garbage (put the link to that antenna in case it could be the issue. . .I have the LHCP version of it). I have switched the position of the CP and Patch antennas on the goggles (this failure has happened with them in both positions, so no effect).

I would really appreciate any input as this I'm just going to have to ground this otherwise awesome quad. Thanks!

 

[tevek]

Well that sucks, I replied to your last post regarding the vtx with the ufl antenna connection. As an aside, I still wasn’t happy with just using the liquid electrical tape, I fitted a 3D antenna mount to secure the whole show in place. Reason being that if I tapped the antenna slightly, the reception in my goggles would start to break up suggesting that the ufl mount wasn’t exactly in place despite clicking it in. In your case, if the reception was fine with the old vtx fitted and not so now with the new one, it is leaning towards that rather than the goggles. If you have RSSI set up, you should see the reduction in signal as you walk away from the quad to at least prove that you have a signal in the first place. Are you using auto channel search or manual for your goggles and can you confirm you have 200mW selected (red dot on vtx). Alternatively, if you can access another quad, you can rule out the goggles and head back to your quad and maybe change out the antenna to the dipole unit they come shipped with.

 

[rtkDarling]

I would turn the quad on, leave it on a table in your house, then walk away down the street a bit with your goggles in your hand. If it never kicks off then it's likely a minor physical tweak (caused by how it's installed and movement of the quad). If it kicks off after a time, even though the quad hasn't moved, then it's more likely an electrical / heat issue. Cold solders come in many flavors I've found, some will work for a little while, or under smaller load, then fail to work under different circumstances.

 

[Wr4ptr]

Thanks for the replies, guys. I've got another quad that I recently built and I'm not having VTX issues with that one, so that rules out the goggles. When I got back after the issue the other night, I pulled the top off and re-did my soldiers, thinking it might be a cold solder or the like. Then, last night, I took the Hawk 5 out with me to test when I was going out to fly my other quad. I plugged the Hawk 5 in and goggles didn't pick up any signal. Figured the VTX card was fried. As I bent down to pick it up, I noticed a flicker in the goggles. . .when I got within about 3 feet of the quad, I picked up the signal faintly. When I got about 2 feet it was crystal clear. When I stood back up, static. Does that give any helpful clues? You think I made the soldiers worse?

Good trouble shooting step on plugging in and walking down the street. If I get it working better, I'll try that.

Tevek, on your other questions: I usually use auto channel search and, yes, 200 mW selected (red dot present).

 

[tevek]

Hmmm, I’d be leaning towards either the vtx or that shite ufl connection. If you are getting reception of sorts, then maybe your vtx hasn’t expired, I certainly noticed a tremendous amount of heat from the ufl connector where it connects to the board and again it wasn’t quite seated and pumping out 200 mW wasn’t helping. Have you swapped out the antenna lead for the dipole unit? It’s painful digging out the liquid electrical tape but it my need to be done.

 

[Wr4ptr]

Today I took off the top and powered it up (props off, of course). Put it in 20 mW mode. I got good, clean video. I wiggled the antenna lead and the connections (at the quad and at the SMA) around and go no adverse response whatsoever. About 2 min after I powered it up, boom, same exact thing as when I was flying it the other day. The video just died instantly. I waited a few minutes and did it again, this time with a timer. Right at about 1 min 50 sec, same thing, instant total drop. Also, since I had the top off, I could see that I still had power, not only to the FC, but also to the VTX (the LED on top was still displaying the channel info). It was just no longer transmitting (no matter how close I got my goggles to it). I couldn't connect on any channel. But it came back clean after I powered down and waited a few minutes. Also, the first time, the card did get a bit warm, so the second time, I put a fan on it. Both times (regardless of fan) VTX transmission ceased just before 2 min. The second time it was just barely warm to the touch. I'm wondering if I just got a bad card?

 

[tevek]

Today I took off the top and powered it up (props off, of course). Put it in 20 mW mode. I got good, clean video. I wiggled the antenna lead and the connections (at the quad and at the SMA) around and go no adverse response whatsoever. About 2 min after I powered it up, boom, same exact thing as when I was flying it the other day. The video just died instantly. I waited a few minutes and did it again, this time with a timer. Right at about 1 min 50 sec, same thing, instant total drop. Also, since I had the top off, I could see that I still had power, not only to the FC, but also to the VTX (the LED on top was still displaying the channel info). It was just no longer transmitting (no matter how close I got my goggles to it). I couldn't connect on any channel. But it came back clean after I powered down and waited a few minutes. Also, the first time, the card did get a bit warm, so the second time, I put a fan on it. Both times (regardless of fan) VTX transmission ceased just before 2 min. The second time it was just barely warm to the touch. I'm wondering if I just got a bad card?

Sounds like it may be just the card as it’s the only variable left. I would still confirm the ufl connection and swap it out for the dipole since you look like digging into the vtx to change it. If it still doesn’t fix the problem, maybe even look at upgrading the vtx for something with a mmcx connector and walk away from it. As I posted earlier my card got very warm until I managed to click the stupid connector into place and the ghosting/reception drop out stopped.

 

[Wr4ptr]

Just an update: I resolved the VTX card problem on the Hawk 5. Unfortunately, it was through the power of my wallet. . .LOL. I bought another VTX card. For those of you counting at home, that's number 3 (the one the Hawk 5 came with and that I damaged, the first replacement which would work for about 1 min and 40 sec then drop out, and now this second replacement).

The only tip that I can give is how I mounted the second replacement. These cards come pinned to the FC (rather than connected with wires). The first replacement, I trimmed the top of the pins holding the orignial VTX, then removed as much solder as possible and pulled it off (the only way I could figure to do it at the time). I used the residual pins to put the second card on. Perhaps I compromised the pin connections at the FC end or maybe just didn't get good connection at the VTX? But the problem was odd, so who knows. Anywhay, when I got the second replacement, I went to the trouble of pulling off the FC and completely removing those pin from it (in the process of removing the second VTX). Then I put new pins in the FC and mounted the third VTX to those pins.

Seems to be working at this point.