CRT Brighteners...

modessitt

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Any problems taking one OFF of a chassis that has one? I have a strange brightness issue with a K7000 med-res that has one installed. The game is not a shooter, so it's really not needed, and I'd like to pull it off to see if it is the cause.

Basically - I installed a new flyback, have a good picture. If I turn up the brightness on the flyback, the screen gets washed out and I get raster lines as expected. but if I turn the brightness DOWN the picture gets really bright for a bit and all the colors bleed and then a little later the brightness goes down to black as I continue turning the pot down.

I'm sure it's not the flyback, and would like to remove the brightener to see if it is causing it....
 
When you say "brightener", what do you mean? Are you referring to a filament booster that plugs between the picture tube and the neckboard? Or, are you referring to that black "block" that bolts to the frame of some K7000's and is wired into the anode cup?

In either case, you can ditch it. The devices that plug in between the tube and neckboard are just stopgap solutions to boost a dim picture from a worn out tube. The black "block" is, from what I can tell, a capacitor, designed to help prevent sag when the screen flashes. You can ditch that safely too.

If you're getting retrace lines in the picture with the screen control all the way down, then you probably have a short in the picture tube.

-Ian
 
No short in the tube, as we are using a good working game to test this chassis in, and the other chassis (that does not have the brightener) doesn't do this.

The brightener in question is a white rectangular piece about the size of a deck of cards. The wire from the flyback goes to this, then to the neckboard socket. Apparently it was installed to help brighten the picture for shooting games that had problems with the light guns registering. They apparently increase the heater voltage to make the filaments run hotter. I'm going to take it out and see what happens...
 
Yeah. Take that out. It's not needed.

This same kind of "brightener" was commonly used many years ago on television sets, as the picture tubes wore out. By boosting filament voltage you get better brightness out of aging guns. It has the side effect of giving the image a bit of a "haze", but it made it bright enough to watch.

-Ian
 
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