On the LaserWriter Select 300, LaserWriter Select 310, and LaserWriter Select 360 printers this problem can occur when there is a build-up of toner on the glass inside the printer.
The laser beam passes through a window in the printer chassis before striking the photosensitive drum within the toner cartridge. The window is in a long narrow slit directly behind the toner cartridge. If toner build-up occurs on this window, printouts exhibit a faded inconsistent look, similar to the appearance of a toner cartridge at the end of its life. The faded appearance is often more pronounced on the left side of the page.
How to Correct Image Fading
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1. Remove the toner cartridge.
2. Wipe the front surface of the glass with a lint free cloth.
3. Replace the toner cartridge.
4. Print a startup page. (If the print quality does not change, the problem is not with the window.)
5. Replace the toner cartridge with a known good cartridge.
If the problem does not go away, your printer needs to be examined by an Apple service technician.