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Electronics Repair (sci.electronics.repair) Discussion of repairing electronic equipment. Topics include requests for assistance, where to obtain servicing information and parts, techniques for diagnosis and repair, and annecdotes about success, failures and problems. |
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#1
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Folk,
A photo of a small portion of the screen of a Philips Brilliance 17A CRT computer monitor is here. http://members.shaw.ca/peasthope/PhilipsVideo.jpg Notice the green ghost to the right of any dark area. Also, the generally poor focus. I've tried each of the two focus adjustments and found little improvement. Can anyone explain the greenness? Is adjustment or repair of this old monitor advisable? Scrap it? Thanks, ... Peter E. |
#2
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Peter Easthope wrote:
Folk, A photo of a small portion of the screen of a Philips Brilliance 17A CRT computer monitor is here. http://members.shaw.ca/peasthope/PhilipsVideo.jpg Notice the green ghost to the right of any dark area. Also, the generally poor focus. I've tried each of the two focus adjustments and found little improvement. Can anyone explain the greenness? Is adjustment or repair of this old monitor advisable? Scrap it? Thanks, ... Peter E. This may be a bad video cable. It could be reflections on the cable bouncing back and creating the ghost. It could also be a failed termination resistor in the monitor, or a bad contact or broken solder joint at the video connector. Jon |
#3
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On Dec 19, 12:37*pm, Jon Elson wrote:
This may be a bad video cable. *It could be reflections on the cable bouncing back and creating the ghost. *It could also be a failed termination resistor in the monitor, or a bad contact or broken solder joint at the video connector. Thanks Jon, after Xmas I'll swap the video cable for one from a working system and report, ... Peter E. |
#4
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Yes it could be the cable, but I think it would be a pretty rare
failure mode, maybe even a freak. I looked twice to make sure - this IS a CRT monitor. In that case if the chassis has a floating filament supply this could be an HK short in the green gun. The trailing positive that makes the white after black green also makes the black after white on some of the text magenta, which is minus green. The frequency response of the green is limited, too much capacitance. A standing wave anywhere in the green path could also be at fault as someone already pointed out, but lots of CRTs short out this way. If so, if I have a print of the vid finals, the CRT soicket board, I can maybe figure out how to EQ the vid output. I have done this more that once. However I did that on NTSC units and I didn't worry about FCC part 15 or anything. Those things only have about five Mhz video bandwidth, this might be different. There is a way to do this on almost any CRT based monitor, but the question is whether it is worth it or not. The focus isn't really all that bad but it ain't that good either. You have to differentiate that from the smear in the green though, if the green was sharper it would look sharper overall. Without the print of the CRT socket board, ar at least a sheet on the IC(s) on it, it's about impossible to do anything. In fact that's true even if it's not an HK short. J |
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