Sellam, IIRC, it is possible to have the brightness adjusted so that you can see the raster, but the contrast adjusted so that you cannot see the text. If the contrast is the knob that is frozen or broken...then that might be the problem. Strange, these pots tend to get a little dirty over time, but I've never seen one get that bad off. Maybe they were exposed to some kind of contaminant. I've got 3 Model III's, and the worst problem I've had was a bad VRAM chip. Also, if you do have a scope, I remember there was a decent test point where the video data can be tapped on it's way to the video circuitry. That way you can tell if it's a computer problem or a video problem. Good luck, -Frank