[P]

I have an iMac G5 with the mini-VGA port. I also have a video-out adapter that I use to connect the Mac to the TV via an S-video cable. Usually, when I plug it in, the Mac senses that it's a video adapter and sets up the signal to be video out. In System Preferences -> Displays, the external monitor is identified as "NTSC/PAL".

Now, however, this autodetection seems to be failing. The picture on the TV is just rolling lines, and in System Preferences it says "VGA-monitor". It seems to be sending a regular VGA signal instead of the video-out signal. Rebooting doesn't help, and I don't think I've done anything special to the setup recently, so I don't understand what's wrong. Does anyone have an idea?

[macaddict0001]

You have to set the refresh rate to either ntsc or pal, I believe ntsc is default, but in many parts of europe pal is the universal standard, try changing that.

[P]

Right. The problem is that neither NTSC nor PAL show up as alternatives. In fact, when watching the NTSC picture on my TV, it all works except that the picture is gemoetrically distorted. Now it's just rolling lines with no color at all. I think the problem starts with the fact that the iMac won't recognize that it's a video adapter at all - usually I can only select either NTSC or PAL and 2 resolutions, now I can select anything except those.

Checking the web shows that others seem to have had the same problem I've had, but noone seems to know the solution. For some reason, the adapter autodetection has failed, and it thinks I have a VGA adapter in the mini-VGA port. I just want to convince it to either rescan, or just overriding the autodetection and forcing TV out.