Super User is a question and answer site for computer enthusiasts and power users. It's 100% free, no registration required.

Sign up
Here's how it works:
  1. Anybody can ask a question
  2. Anybody can answer
  3. The best answers are voted up and rise to the top

really part 2 of this question, but its a different issue than what i thought. I've been doing some testing, the screen seems to be non flickery if more than 1/4 of the screen is black, if i have any other colour taking up more than 3/4 of the screen there's flickering along the horizontal axis (only).

I've ruled out it being flickering due to frequency (i had that before), so.. what could the issue be?

Its an old CRT (a compal F708) if it matters, OS is windows 7 (i haven't been able to test it in anything else yet), running at 1024x768 at 80 hz

EDIT: further testing shows its worse when there's lots of red or green in the screen. blue is not as bad. flickering stops totally when i reduce the size of the non-black area. I've not tried other combinations of colours.

By flickering, a horizontal line looks flat, and a vertical one looks wavey

share|improve this question
And if you turn the brightness down? – Ignacio Vazquez-Abrams May 18 '11 at 1:49
... post that as an answer. that worked. But how? – Journeyman Geek May 18 '11 at 1:55
up vote 4 down vote accepted

The three beams that a CRT uses to project the image onto the phosphors have an electromagnetic charge (because, well, they're electron beams), and the charge on each beam affects the other two beams. The effect can be anything from a slight enlargement of the image to a disruption in the form of flickering. Reducing the brightness of the image reduces the strength of each beam, in turn reducing the disruption.

share|improve this answer

Have you tried degaussing the monitor?

I had an old monitor that would get that way. It likely is just the fact that it's aging. Magnets control the direction of the electron stream in CRT, and when there is a buildup of static charge, it affects the EM field lines, which can cause this, which degaussing can fix. However, if they are just aging and deteriorating, there may not be much you can do.

When you have so much white on your screen, there are a lot of electron streams being fired (for each pixel). Because they each have an EM field, they can interact with each other. That's why you would see picture warping in very bright images on CRT displays (including TVs), than images that are full of black areas.

share|improve this answer
first thing i tried, actually. – Journeyman Geek May 18 '11 at 1:54
or any other colour. It makes sense, but i think ignacio gave me the actual solution ;p – Journeyman Geek May 18 '11 at 1:58

Your Answer


By posting your answer, you agree to the privacy policy and terms of service.

Not the answer you're looking for? Browse other questions tagged or ask your own question.