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Discussion Starter · #1 ·
I just purchased a Marquee 8500. When I picked up the unit, I checked the tubes and there was no wear at all on the phosphors and the unit powered up fine. I have the unit home now and I cannot get it to project a picture on the wall. I can see the set up screens inside the tubes without a problem. I don't have a source connected as yet so I selected an internal frequency using the utilities menu. Still nothing. I hope this is something simple and I'll feel really dumb afterwards. Does anyone have an answer?


Thanks, Colin
 

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Are you saying the setup screen are so dim you can see them on the tube face yet they will not project on the wall?


If so, I would suspect a filament voltage that has crept up due to a bad power supply, causing the cathodes to fail. I just had 2 out of 3 tubes do this on an 8500 myself with very high hours on it.


There's a mod that Tim Martin or Mike Parker can do if you're not a tech to prevent this in the future. If this is the case, you'll nuke the new tubes in a very short period of time.


Other things is that the contrast/brightness are turned way down, or the G2 voltage is too low.


Curt
 

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Discussion Starter · #3 ·
Thanks for the reply Curt. Actually, I can only see the setup screen when I look into the tubes and see it on the back. It is not being projected outwards at all. (ie. there is no light coming out of the tubes)
 

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Guys


If the tubes have sufficient output then looking into the lens at a test pattern, with contrast and brightness at 45, should require sunglasses. If not, you have weak tubes or gray scale needs setup for correct drive and G2 values.
 

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Discussion Starter · #5 ·
Thank you both for the help. I adjusted the brightness and contrast up and that seemed to solve my problem. They were both set around 30.
 

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Say King


This might prove helpful also:


For gray scale setup for a Marquee projector, try this, this is done in a darkened room:


a) Warm up the projector for 30 minutes. Input a signal of 31khz or higher, or push UTIL, 1, 6, 2 for an internally generated signal of 31khz


b) Set Contrast to 45 and Brightness to 50


c) Go into Service Menu, push UTIL, 9, 0901, 1 (color temp), 2 (6500^) Note existing Drive and G2 values on a pad of paper before changing the values!


d) Set Red Drive to 35, Red G2 to 60. Push Enter to continue


e) Set Green Drive to 90, Green G2 to 60


f) Set Blue Drive to 50, Blue G2 to 60


These are typical Drive and G2 (background) levels as found in new projectors. Using the # button, bring up the test pattern of different intensity gray blocks, also known as the Stairstep

pattern.


g) Look at Stairstep for each color; raise or lower G2 for each color until the second darkest square is just lit, but the darkest square is not lit (lower left corner)


h) Push Enter until all three colors are on. Instead of Enter, if you push Tint you can adjust each color while all three colors are on. Raise or lower Drive for each color until peak whites look okay (bright squares of the Stairstep pattern. The Drive adjustment interacts some with G2, so repeat step g) as needed.


i) Inability to see the second darkest square with G2 below 75 for any color indicates a worn or damaged tube. The need to set Red Drive above 60, or Blue Drive above 75 also indicates weak tubes.


j) If you have a digital voltmeter, take the top gray covers off and try to measure the filament voltage across the connector P14, it should not exceed 6.45 volts dc when the unit is powered up. P14 is on the mother board just below the cover for the blue neck board. Filament voltage above 6.45 for a few hundred hours will destroy the cathodes in the CRT electron guns. Most people are not aware of this potential problem, if the tubes are still okay I can fix the voltage problem by having you send me the low voltage power supply for rework, it is the module that the power cord plugs into and is easily removeable.
 
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