Quote:
Originally Posted by drh4683
Interesting. I'll have to keep checking around. If I turn down the brightness control, the contrast and turn all the screens and background controls fully CCW, the raster is still present, a drab green image is what appears, slightly below average viewing brightness.
I worked on a CTC-19 a couple years ago that had little control of brightness that I couldn't cut off as well. That set turned out to have a completely hacked up B-boost circuit with parts that didn't reflect any schematics. I changed it all back to factory and it worked perfect again.
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This sounds like a problem with the grid voltages going to the crt. OR you may be right about the screen voltage being to high
Snoop around the 12AT7's and check voltages,Caps, Resistors and the coils.
The green gun seems to be the brightest color on the 21axp crt for some reason so that may be why you see the green stand out with everything cut off.
Still, The drab green image may be a clue as to what is going on too.
My favorite hack job is when they would turn the high voltage all the way up when the set had a weak crt or there was not enough horz width.
Of course I would see there kids watching the dam thing to boot
The next thing would be when they put in a 10 amp fuse in a circuit that takes a 1 amp fuse.
. Man , Techs did some strange things back then.
Ed