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9500LC: Green "spot" on shutdown -- already swapped neck boards and checked heater voltage.

post #1 of 3
7/19/12 at 3:31pm
Thread Starter 
My PJ is showing a green "spot" when it shuts down. I think of a spot as not not moving, so I'm not sure the term really applies here -- the "spot" moves as it fades away. G2 wire is connected, and I double checked the connection point. I purchased another neckboard and swapped it out, but nothing changed. I also checked the heater voltage -- 6.3v. I've been turning down the contrast to turn off the PJ (lower than 30), and so far it doesn't seem to be damaging the tube any.

The image dies the moment the PJ clicks off, and I'm guessing that's the spot kill circuitry kicking in as the retrace stops. Why does the green tube come back on a moment later? Mystery.

Here's what it looks like:

http://www.youtube.com/watch?v=uY6hcPlA66A

Any idea what might be causing this?

edit: Any possibility this is secondary (cold) emission?
Edited by cwm9 - 7/20/12 at 4:36pm
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post #2 of 3
7/21/12 at 8:10am
yes that's cold emission. It's basically Carbon contamination on the electron gun which is holding and electrical charge, like a capacitor, after the main voltage to the tube is switched off. It won't hurt anything AFAIK, to get rid of it tap the tube neck with something non-metallic like a wooden dowel rod.
Usually the tube needs to be out and siting upright, skinny end pointing up
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post #3 of 3
7/21/12 at 12:18pm
Thread Starter 
Thanks, draganm.
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AVS › AVS Forum › Display Devices › CRT Projectors › 9500LC: Green "spot" on shutdown -- already swapped neck boards and checked heater voltage.