Laser printers usually manifest problems by creating poor output. One of the most important tests you can do on any printer--not just a laser printer--is called a diagnostic print page or an engine test page. You can print a test page by holding down the Online button as the printer is started or by selecting the menu option on the printer's operator panel. You can also select Start; Settings; Printers in Windows and issue the test page command from the printer's Properties dialogue box.

Here are a few common problems encountered with laser printers:

Blank Paper:
Blank sheets of paper usually mean the printer is out of toner. If the printer does have toner and nothing prints, print a diagnostic print page. If that's also blank, remove the toner cartridge and look at the imaging drum inside. If the image is still there, you know the transfer corona or the high-voltage power supply has failed. Check the per's maintenance guide to see how to zero in on the bad part and replace it.

Sometimes ghosts appear at regular intervals on the printed page. Either the imaging drum hasn't fully discharged and is picking up toner from a previous image, or a previous image has used up so much toner that their the supply of charged toner is insufficient or the toner hasn't been adequately charged.

Light Ghosting vs. Dark Ghosting:
A variety of problems can cause both light and dark ghosting, but the most common source of light ghosting is developer starvation. If you ask a printer to print an extremely dark or complex image, it can use up so much the toner cartridge won't be able to charge enough tone to print the next image. The proper solution is to use less toner by doing the following:

Low temperature and low humidity can aggravate ghosting problems. Check your users' manual for environmental recommendations.

Dark ghosting can sometimes be caused by a damaged drum. It can be fixed by replacing the toner cartridge. Light ghosting cannot be solved in this way. Switching other components usually won't fix ghosting problems because they're a side effect of the entire printing process.

Vertical White Lines:
Vertical white lines are usually caused by clogged toner. Clogs prevent the paper dispersion of toner on the drum. Try shaking the toner cartridge to dislodge the clog or, if that doesn't work, replacing the toner cartridge.

Blotchy Print:
This is most commonly because of uneven dispersion of toner. Be sure the printer is level. Finally, make sure the paper isn't wet in spots. If the blotches are in a regular order, check the fusing rollers and the photosensitive drum for foreign objects.

Spotty Print:
If spots appear at regular intervals on the printout, the printer's drum might be damaged or toner might be stuck to the fuser rollers. Dry off the fuser rollers. Check the drum for damage. If the drum is damaged, you must get a new toner cartridge.

Embossed Effect:
If your prints have an embossed effect (like putting a penny under a piece of paper and rubbing it with a pencil), a foreign object is almost certainly on a roller. Use regular water with a soft cloth to try to remove it. If the foreign object is on the photosensitive drum, you'll have to use a new toner cartridge.

Incomplete Characters:
Incompletely printed characters on laser-printed transparencies can sometimes be corrected by adjusting the print density. Remember to use only material approved for use in laser printers.

Creased Pages:
Laser printers have up to four rollers. In addition to the heat and pressure rollers of the fusing assembly, rollers are designed to move the paper from the source tray to the output tray. These rollers crease the paper to avoid curling, which would cause paper jams in the printer. If the creases are noticeable, try using a different paper type. Cotton bond paper is usually more susceptible to noticeable creasing than other bonds. You might also try sending the output to the face up tray, which eliminates one roller. No hardware solution exists to this problem. This is simply a side effect of the process.

Warped, Overprinted, or Poorly Formed Characters:
poorly formed characters can indicate either a problem with the paper (or other media) or a problem with the hardware.

Incorrect media causes a number of problems. Avoid too rough or too smooth paper. Paper that's too rough interferes with fusing of characters and their initial definition. If the paper is too smooth (like some coated papers, for example), it might feed improperly, causing distorted or overwritten characters. While you can purchase laser printer-specific paper, all laser printers will run acceptably on standard photocopy paper. Because paper picks up humidity from the air, don't open a ream of paper until you're ready to load it into the printer. Always fan the paper before loading it into the printer--especially if the paper has been left out for more than a few days.

The durability of a well-maintained laser printer makes hardware a rare source of character-printing problems, but it is a possibility. Fortunately, checking the hardware is easy. Most laser printers have a self-test function, often combined with a diagnostic printout, that's quite handy to verify those "is it the printer or is it the computer?" questions. Run the self-test to check for connectivity

  • Replace the toner cartridge, especially if you hear popping noises.
  • Check the cabling.
  • Replace the data cable, especially if bends or crimps exist, or objects are resting on the cable.
  • If you have a Front Men Panel, tun off Advanced Functions and High Speed Settings to determine if they aren't working properly or aren't supported by your current software configuration (check your manuals).

If these solutions don't work, the problem might not be user serviceable. Contact an authorized service center.

All of this info was given to me by the computer tech guy at the library I work at.