Something strange happened to me when I watched a reel one of North by Northwest. The audio was gone when I played it again. I rewinded a couple of times, switched the button for optical/magnetic up and down, and the mono/stereo with no luck. I switched to another reel and the audio was there. I switched back to reel one of North by Northwest, and still no audio. I started to panic but rewinded a bit and tried again, and then the audio was there again loud and clear!

I talked to Vidar when we used his ST 1200 and he suggested I had not made sure the button for the threading had been released. The audio is gone until that has happened. On the ST 1200 it is a button you can press at the back, but on the GS 1200 you can just pull the film just a hint at the back and the button on the top front is released (and the fan speeds up). This sounded like a good explanation and I thought that was it. But now I started to think again: Doesn't the picture go quite black until this button is released on the GS 1200 (it does not on the ST 1200)? I thought it did (but the projector is not at home at the moment so I can't check at the moment). I saw the picture very well and it was not dark as far as I can remember.

Has anyone of you experienced something like this? Maybe I am just starting to get senile and I don't remember it correctly and Vidar was right about the threading release :-) I have to check how dark the picture is while the threading button is down as soon as I get to the cabin this weekend. Maybe it isn't as dark as I thought.

Could happen if the sound stripe is not in full contact with the sound head, and if there is no sound on the stripe itself. You have said that once you re run the reel it came back, so it will be non contact of film to sound head. Maybe the spring loaded pressers which keep this area in contact when the threading has finished are sticking up. There is quite a lot of little levers and springs in that area, but make sure you are in the correct forward sound mode and not forward silent mode. You can get build up of deposits from the film in this area too, give it a clean with the little brush and cotton buds with suitable cleaner.

Thanks, Paul! This sounds plausible. I must check the mechanism. I didn't know there were movable parts around the audio head.