Hi.
I have a small portable monitor which is composite in, however I can't get either my 6d or 550d to output to it. It occasionally shows the "sensor cleaning" message when I shut down the camera but nothing else.
Can you do live output on these cams using the av out cable or is it HDMI only?
Thanks
I've got a home made EVF that runs on composite and I sometimes have the same issue (on the 550d)
Booting directly into video live view seems to be the issue, I believe its canons issue. try connecting the monitor and turning your mode dial somewhere else. Then trying to go into movie mode. That's seems to fix mine. Connecting to the AV jack with the camera booted up also seems to cause this issue.
It does work, but yes i've seen this happen.
Edit: I've also just remembered sometimes connecting the audio jack fixes it, I've wondered if its an issue with a common ground. So try that too.