Black band near top of page HP LaserJet 4250 4350 4240
If your printer often prints a black band of toner at the top of pages -- usually the band is 2 to 3 inches tall and stretches the entire width of the page -- on the LaserJet 4250 , 4350, or 4240 series printers this is a sign of a failing high voltage power supply.
Failing power supplies become more of a common problem as these printers age. Replacing the power supply is considered an advanced procedure; we do have installation instructions available. If you are doing the repair yourself you can plan on 1 hour to 1.5 hours install time.