KP wrote:
On Apr 22, 3:09 am, Michael J. Mahon <mjma...@aol.com> wrote:KP <kjpm...@gmail.com> wrote:Help! I noticed that there seem to be two tiny bands running up the screen of my AppleColor RGB. They are very, very tiny, but they are consistently present. Seem to be much more obvious when the brightness is turned way up.Is that normal? Is my RGB hitting its final days?Could you be more specific? What is the orientation of the bands? Their size and location? Fixed or moving, and if moving at what speed? What color? This could be something easy...or not. -michael - NadaNet 3.1: http://home.comcast.net/~mjmahonThey are 2 horizonal lines. They slide up the screen until they hit the top of the screen and then they go back to the bottom of the screen. The lines are probably spaced about equidistant apart. If the background color is dark blue, then the lines probably appear what you might call light blue. Sort of as though they are moving over each band of the display. Thoughts?
The lines you see are noise at a 60Hz repetition rate (AC line frequency) getting into the video. The lack of phase lock between the computer's video refresh rate (60Hz) and the AC mains causes the lines to drift at constant speed relative to the computer- synchronized raster. You mentioned that you just noticed them. Have they recently appeared, or is it possible they've been there for some time? I ask, because if you have recently changed the position of the monitor or some electrical device around it, that change may be responsible for the problem. If so, try changing things back to see if you can isolate the problem. If that doesn't do it, check the connectors on both ends of the video cable. A poor ground or shield connection could cause interference from, say, a light dimmer, to get into the video causing the lines. Let us know if any of this resolves the problem or *changes* it. -michael NadaNet 3.1 for Apple II parallel computing! Home page: http://home.comcast.net/~mjmahon/ "The wastebasket is our most important design tool--and it's seriously underused."