Laser printer print defects - Vertical white lines

Problem	Possible Cause	Solution
Vertical white lines	Failing toner cartridge	Very common -- Try gently shaking the cartridge to redistribute the toner. If the problem continues, replace the toner cartridge.
Vertical white lines	Contamination in the laser path	Somewhat common -- 1. Clean the laser scanner mirrors and lens. 2. Replace the laser / scanner assembly.