|Flickering is usually caused by an old (or very cold) inverter and CCFL tube. If it's just cold, it should stabilize after a few minutes.|
However, what you may be seeing is pixel jitter, which has nothing to do with the backlight. If the monitor only "flickers" when it displays a certain image or pattern, then it's pixel jitter. As far as I know, jitter only affects analog (VGA) panels; I've never seen a jittering digital panel. It can sometimes be prevented by using a better VGA cable, if DVI/HDMI/DP is unavailable.
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