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Discussion Starter · #1 ·
I've just finished setting up my home theatre in its final configuration and am now having trouble with the Green Tube on my Sony 1292 .

Even when "cut-off" the green crt there is still a green light emitting from it. The other tubes cut off no problem. When running all 3 tubes the green seems quite dull . Do I have an internal short somewhere ? Any help/advice greatly appreciated !
 

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Hey,


The green tube in my Sony 1271 glows for a time even after the power is turned off. This is normal. If you green tube illuminates the screen when you don't have a source hooked up then maybe you have a problem. The persistance of the phospher used in green tubes cause them to have an afterglow which is normal.


Anyone whom can confirm or deny this should do so as I love to learn about this stuff.


Good Luck,


Brian
 

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Discussion Starter · #4 ·
thanks for the 2 replies so far . I've checked the gain and bias settings and they are not the problem.

The green crt stays on at about 20% light level all the time even when crt has been cut-off. It doesn't get to full brightness when displaying a picture and the area's that should be "white" in a picture remain a washed out "red" . i.e. lack of green.

I hope i have been a bit more specific this time.

Any more thought/views would be appreciated.
 

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In many cases, the correct G2 set-up for the correct color and grey-scale causes one or more tubes to light-up always, even when the image is totally black, at a normal birghtness level.


For example, the G2/cathode level for the Barco 8 inches, in the most of the cases causes the three tube slightly turned on, the the contrast is set to zero and the birghtness to 50%...


just try to lower the brightness and check it out if and when the green tube turns completely off.



ciao

Romano
 

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Discussion Starter · #7 ·
thanks for thr replys so far , however the problem isn't with "contrast/brightness" "bias/gain" .

Do crt's have "shutters ? " . It's just that some green is always coming through washing out the black and killing the whites.

just turned the projector off again (after trying the bias/gain) and for at least 5 mins afterwards , looking into the green tube , i could still see the green screen in there. the other tubes were black in a few seconds ...anyone ?
 

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You need to have a qualified tech look at it. All CRT's should cut off when a signal is not present. As you noted, it will be impossible to get a proper grayscale if it doesn't.


Armed with a schematic, it should be easy to determine the problem. Worst case is, an internal short in the CRT. It's more likely that a resister that has change value and not supplying proper voltage to the CRT.


Good luck
 
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