I am having the same problem with both the controllers for the Phantom 3 Pro and my Phantom 4. Both controllers have been updated with the HDMI board. I can use both successfully with my HeadPlay goggles in HDMI mode (using the cable) with simultaneous display on both the tablet and the goggles. But, if I plug in my TX-5D transmitter or use a HDMI to Composite converter (on either controller) there is no video output. However, if I plug the TX-5D transmitter into the HDMI output jack of my Parrot SkyController (Bebop), I have beautiful HDMI video. The same holds true if I plug the HDMI to Composite converter into the SkyController. Any ideas why the DJI HDMI board will not work with these devices? The attempt is to allow my HeadPlay to be "wireless" as well as provide others with a portable receiver display by using the TX-5D to transmit a picture.