bendavis2
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Jun 13, 2007, 12:38 PM
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Phillips Magnavox 51 RPTV - Blue Gun has serious lens flare, or out of focus??
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I just acquired a very cheap 51" rear projection TV. (Phillips Magnavox 51mp392h).
The problem it has is that anytime there are strong white images on a dark background, there is lots of blue that "bleeds" off the white into the black or dark background. It seems far worse than what I would expect for acceptable lens flare, and only happens with Blue.
I got a DVD with some test signals, and opened up the TV to see if I could isolate the problem.
When viewing a "Dot Hatch" pattern (a predominantly black field, with criss-cross white lines, and white dots), I can cover up two of the guns/lenses to get a look at what is going on with each individual gun.
With only the red, OR only the green gun showing this pattern by themselves, the black background is very black, the red/green lines are sharp and distinct. But when I leave just the blue gun showing, the pattern is visible and pretty sharp, but the black background is flooded with a mild blue. Not pure black, like it should be.
I can manually adjust the physical lens focus, which allows me to bring the lines in and out of focus, but the background never approaches pure black. I can use the focus knob, with the same results. I can also adjust the screen knob, which adjusts the overall fill of blue in the background, but the only way to use this control to make the background pure black results in the lines and dots being nearly invisible. (ie, so little light that none of the blue picture is showing correctly.)
I performed both a simple and 'manual' convergence using the basic user menu, with no help. This doesn't seem to be a convergence issue.
I have also cleaned the surfaces of the lenses, the mirror, and the inside and outisde of the screens.
[Another problem, which I suspect to be linked, is that when viewing a completely white screen, the sides of the screen become progressively more yellow the further from the center of the picture. I'm hoping that "focusing" the blue gun, the blue light will compensate this yellowness, but I could be way off]
I'm not at all uncomfortable with trying to replace boards or circuitry, or opening up the lens if it seems to just be a cleaning issue, but I don't have the service manual.
Any help is greatly appreciated.
(This post was edited by bendavis2 on Jun 13, 2007, 1:30 PM)
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