Hello and thanks for any help on my video connection issue

     When I arm my DJI FPV rig, the video feed goes out shortly after I arm the quad.  When I disarm, the video transmission is restored.  I will post a video showing what is happening inside the DJI FPV goggles.  I am running the latest firmware on the Air Unit, DJI Radio and the goggles.  I have tried it with and without an SD card in the Air Unit and it behaves the same.  I've formatted the SD card inside the Air Unit as well.  I am running the MAMBA DJI F405 stack, 4S 1350mah, and FPVCrate Booster v2 2700 Kv motors with 5" props.  I have a 35v 1000mu Cap soldered to the battery leads. The air unit is being powered directly from the Mamba FC with its plug and play cables (no soldering). I have autorecord turned on in the goggles. Have any of you experienced this issue?  Please help me with any suggestions on errors I might be making in my build.  Thank you!

Hi Chris
I have the same issue with my caddx vista and a kakute f7 stack these days.
All the signal are normal since I armed the quad:
- the red error is displayed
- the connecting lines go away and the picture disappears

Can anyone help us? :-)

I thing I have the solution - don't go with betaflight 4.2.1

Switch to Betaflight 4.2.0 and it works for me!

its the same for me as well. when i arm screen freezes or goes half green and then it just cuts out. im plugged straight into kakute f7 fc. ive stripped quad and checked for short circuits. i noticed i have a short to negative and frame when camera is fixed to frame with m2 screws. this is the same on all my dji units and they are fine. i will disconnect camera from frame and try to arm next. i changed aerials to new ones and still not working. im flying bf 4.2 and have identical build and fc and is not happening on that. the only other thing i can think is to change cable between air unit and camera. it is routed under my esc as i have no choice due to cable length and was worried about emf from esc but again it has been fine for both builds until now. the only other variable i can think of was that i was tuning pids and it happened after a front flip so voltage spike for manoevre may have caused it. my build and air unit is only a couple months old and was flying great as i finalised pids. previous build is 6 months old and has been abused and crashed and repaired and is fine.

Usually a power issue. Where does the air unit get its power from? Also, check the capacitor, an exchange may help.

Problem SOLVED!  Thank you everyone for trying to help.  My problem was a grounding issue.  One of the screws that holds the right arm was too long and touched a motor pad on the ESC board which has pads on both top and bottom sides ( MAMBA F50 ESC ).  Once I installed the correct shorter screw it removed the grounding to the frame and issue immediately went away. So check your build for grounding errors like mine if you may also be experiencing this problem.  Now it flies and works like a champ everytime, no breakups, no short range issues either.     Thanks all!

  

jazzman1985 Posted at 8-2 01:11
its the same for me as well. when i arm screen freezes or goes half green and then it just cuts out. im plugged straight into kakute f7 fc. ive stripped quad and checked for short circuits. i noticed i have a short to negative and frame when camera is fixed to frame with m2 screws. this is the same on all my dji units and they are fine. i will disconnect camera from frame and try to arm next. i changed aerials to new ones and still not working. im flying bf 4.2 and have identical build and fc and is not happening on that. the only other thing i can think is to change cable between air unit and camera. it is routed under my esc as i have no choice due to cable length and was worried about emf from esc but again it has been fine for both builds until now. the only other variable i can think of was that i was tuning pids and it happened after a front flip so voltage spike for manoevre may have caused it. my build and air unit is only a couple months old and was flying great as i finalised pids. previous build is 6 months old and has been abused and crashed and repaired and is fine.

Yeah, it might not hurt to try a new cable.  If it's not the cable, you have a spare.  I had build Furadi's Hornet HD 3" with the caddx vista and one day I turned it on and I could see the OSD data but not the video, all black.  I changed the cable and the problem was solved, I had the video back.  Don't know how the first cable got damaged, maybe high heat from the Vista unit touching it? DK

Cris_Rock Posted at 8-2 13:58
Problem SOLVED!  Thank you everyone for trying to help.  My problem was a grounding issue.  One of the screws that holds the right arm was too long and touched a motor pad on the ESC board which has pads on both top and bottom sides ( MAMBA F50 ESC ).  Once I installed the correct shorter screw it removed the grounding to the frame and issue immediately went away. So check your build for grounding errors like mine if you may also be experiencing this problem.  Now it flies and works like a champ everytime, no breakups, no short range issues either.     Thanks all!

[view_image]  [view_image]

Glad you got it sorted

Fritz Wlan Posted at 8-2 03:13
Usually a power issue. Where does the air unit get its power from? Also, check the capacitor, an exchange may help.

Yeah.  I had thought the same initially.  So much so that I even tried rewiring the Air Unit’s power straight to the battery leads instead of its original plug and play cable feeding 9V from the Mamba DJI flight controller.  The problem didn’t go away. I also tried different capacitors on the battery leads but no change.  Then I found out that a screw from the frame was touching the ESC board.  Thanks for your reply.  

This seems to be a not so uncommon problem. I found a quite extensive topic about this in a German forum. I linked your post there. I am curious if it helps the guys there. Thanks for sharing. Could not imagine that this grounding issue could cause these problems.

@DJI Could mounting the camera with metal screws to the carbon also cause this kind of trouble? I suppose the camera housing is connected to the electronics the same as inside the full air unit.

A reply from someone with technical insight would be very much appreciated!

It is confirmed by other users also. If you mount the DJI FPV Camera to the frame with metal screws it gets electrical contact with the frame. EMR induce voltage into the frame and this causes freezes and horizontal lines. Electrically isolating the camera solves the issue. Use plastic/tpu camera mounts or nylon screws folks!

Drone worked perfectly fine. Did some reasembling and this problem occurred. After hours of investigating and rebuilding drone multiple times came to the conclusion that I just tightened camera screws too tight

EDIT:
Might not be the case since I also found out that video antenna cable was damaged.