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Question about Philips Magnavox 51MP392H Rear Projection Television

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Blue out of focus; casting blue "glow"

I have a 51" rear projection TV. (Phillips Magnavox 51mp392h) 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 to get a look at what is going on. With only the red, OR only the green gun showing this pattern by themselves, the black background is very black, the lines are sharp and distinct. But when I leave just the blue gun showing, the pattern is visible and fairly 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 button, 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. I performed both a simple and 'manual' convergence using the basic user menu, with no change. [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. I'm hoping that "focusing" the blue gun, the blue light will compensate this yellowness, but I could be way off]

Posted by Ben Davis on

  • Ben Davis Jun 12, 2007

    After further research elsewhere, it seems as though this problem may be due to bacteria growth in the coolant inside the blue CRT. I will replace the fluid and report the results.

    Here is a link to much detail on the subject of replacing coolant fluid in CRTs for Rear Projection TVs:
    http://www.tv-forums.com/forum/TV_Equipm...

  • Ben Davis Jul 09, 2007

    I replaced the coolant using the tips found at the link above. I was careful about leaks during the procedure, and monitoring the CRT afterwards. The picture, though good before, became about 1000% better. The colors are now totally uniform. The TV looks just like brand-new. The coolant I removed looked about like runny applesauce. The stuff I put back in was crystal clear. What a Difference!

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Anonymous

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Be very carefull replacing the fluid as leaks will short stuff out and are messy.

Posted on Jul 06, 2007

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