Solid Line Across Screen

BAD OPTIC UNIT BLOCK

It is usually caused by the drum. The lines are vertical? perhaps the drum was scratched and needs to be replaced.

If you replaced the toner before the lines appears, the printer needs to be cleaned.

Try cleaning the contacts on the connectors going into and out of the Tcon board, if that doesn't fix it replace the board, here is the manual if that helps.
Samsung HL S4266W Owner Instructions Manual

try moving the small blue slider on top of the drum cartridge side to side 10 times.

Do you happen to have a cable box? (reset cable box also by unpluging it). is that line also showing on dvd player on different input?

WHEN YOU HAVE A SOLID BLUE LINE THAT DOES NOT MOVE...YOU HAVE A DEFECTIVE PANEL...LIVE WITH IT OR REPLACE PANEL..NOT COST EFFECTIVE TO REPLACE PANE....JOE ACE

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Your comp's video card refresh rate (in Hertz, abbreviated Hz) may not be totally compatible with the monitor. Check the properties of your video card, and change the refresh rate (you may have to look around for it) to 60 Hz. This is a pretty standard refresh rate that works with just about every monitor. If it's already there, I'm afraid someone else will have to try and help!

Hope this helps, and please rate my answer, good OR bad.

Good luck!

hi there, you do have a vertical section problem and at the power supply section problem. do some test, check for some cold solder at the power supply section, test some electrolytic capacitor at the vertical section. ty

Inverter board is bad or video cable loose either behind LCD panel or near video adapter.