Learn how to troubleshoot and repair laser printers

 Learn how to troubleshoot and repair laser printers

Computer technicians, help desk professionals, and administrators can spend an inordinate amount of time dealing with laser printer problems. If you'd like to streamline the amount of time you spend with laser printers, then you should master some of the maintenance, troubleshooting, and repair techniques in this article.

Understand laser printers

In a previous article, we examined the inner workings of a laser printer. If you read that article first, then you will be able to better understand and implement the tips in this article.

Cleaning

Cleaning can go a long way towards keeping a laser printer running smoothly. The exterior of the printer can be cleaned with a water-dampened cloth or a cleaner rated for electronics. The interior can be cleaned with a small vacuum or with compressed air. If you are using compressed air, remove the fuser assembly to allow a path for dirt and debris to exit the printer. The interior can be further cleaned with a dry, lint-free cloth.

Troubleshooting

The first step in troubleshooting is determining the nature of the problem and then concentrating on a specific area. Many laser printers contain a status message area that displays the printer's current state. If an error occurs, the printer will almost always display a message or an error code. For example, the HP 2100 laser printer communicates status and problems to the user via three status LED's located on the printer's control panel. The latest model, the 2300, has a front-panel status display for communicating to the user. Status information is also conveyed to the user by the printer's queue software.

Errors are often also written to a status log. The status log can usually be viewed by printing a self-test/configuration page. Of course, if the problem is keeping the printer from printing, then the configuration page will not be available. In this case, troubleshooting can be performed by connecting the printer to a PC via a parallel cable or network connection and running diagnostic tests.

More severe errors may indicate a problem with the electronics. The service manual usually details each error and the corrective action needed. Error codes and their meaning can also be researched on the vendor's Web site (e.g., the HP Web site). Although problems with the printer's electronics do occur, the bulk of the problems are mechanical. The mechanical issues usually occur in two common forms: paper jams and image problems.

Paper jams

By far, the most common complaint is the paper jam. If there is a paper jam, determine the area where the jam is occurring and examine the area. Most jams occur due to a paper path blockage or a worn roller. I have been called to repair a paper jam and, often, find the cause to be a small piece of paper that was not removed from a previous jam. Many times, the paper itself is the cause of the jam. Poorly installed paper, or paper that has been stored improperly and allowed to curl prior to installing it in the paper tray, can lead to paper jams.

If the paper jam is at the paper tray, suspect the pick-up roller. A worn pick-up roller will not grab the paper correctly and will result in the paper being partially removed from the tray. When you open the tray, the leading edge of the paper will be slightly out of the tray. If the printer is pulling in multiple sheets of paper, suspect the separation pad at the front of the tray. I usually replace the separation pad and pick-up roller (Figure A) as a set. If one is worn, the other probably needs to be replaced as well.

If the paper makes it inside the printer and stops, look for paper debris or other material that may be blocking the paper's path. Also, examine any associated rollers for wear. Internal jams are typically caused by a blockage. A small vacuum, or compressed air, can be used to remove debris from inside the printer. When looking for the culprit of an internal jam, remove the top cover, fuser, and laser-scanning assembly to get an unobstructed view of the internal components (Figure B).

If the paper jams at the fuser, suspect a blockage in one of the fuser rollers. The fuser is typically a field replaceable assembly and is usually easy to remove. Remove the fuser to examine it for paper debris, worn gears, or other mechanical problems. Remove the screws securing the fuser and any electrical connections (Figure C).

If the fuser appears to be working properly, examine the entrance and exit paths to the fuser. Also inspect the exit rollers for missing or damaged components. Every component in the paper path must be clean and smooth for the paper to travel through without problems.

Image problems

Any deterioration in the quality of the image is directly related to one of the components in the image subsystem. The first step in image troubleshooting is to examine the toner cartridge. The toner cartridge contains the drum and developing rollers. If either of these components becomes damaged, it will result in an image problem. Inspect the drum for marks or debris. The drum can be inspected by pulling back the plastic shutter that protects it when it is removed from the printer (but, remember that the drum is sensitive to light; so, do not expose it to bright light for long periods of time).

The most common problems are scratches or lines around the drum (Figure D). These lines will transfer to the image. If the complaint is a solid or partial line on the image, inspect the drum for a matching set of lines. Replace the toner cartridge if the drum appears damaged or if you suspect the drum to be the cause of the image problem. If you replace the toner cartridge and the lines remain, then there's a good chance that the problem is with the drum.

The fuser can also be the source of image deterioration. Scratches or damaged areas of the fuser can result in missing or smudged areas on the printout. Remove the fuser, and examine it closely for damage or deterioration (Figure E).

HP has recommended intervals for replacing the fuser, typically around 150,000 printed pages. For most models of its printers, HP sells a maintenance kit, which includes the fuser and other replaceable rollers and belts. Most printers can print a configuration or test page that lists the number of pages printed. This can be used as a general guide; but, you should also examine the print quality by printing a test page. If you see smudged or missing lines, replace the fuser. If the fuser is bad, then you should also replace the rest of the recommended parts as part of an "overhaul."

If the image appears blurred or distorted and you have ruled out the toner cartridge and fuser, check the transfer roller and laser-scanning assembly. A worn transfer roller can cause a "faded" image symptom. The transfer roller cannot be cleaned; it must be replaced. Also, dirt or debris on a lens or mirror of the laser-scanning assembly can distort the beam and cause image problems. Remove the screws securing the top, and examine the interior. Carefully examine and clean the reflecting mirror and lenses (Figure F). Typically, the laser assembly can easily be removed for cleaning or replacement. In the HP 2100, four screws secure it to the interior of the printer chassis.

Figure F

Obtaining parts and service information

The best source of information on HP laser printers is, of course, the HP Web site. Access to parts and servicing information can be handled through a tool known as "PartSurfer." PartSurfer provides online exploded-view diagrams for identifying all parts and part numbers in all HP products (not just laser printers). PartSurfer allows you to search by equipment type, model number, part number, keyword, and description. Parts can then be ordered directly from HP. In addition to PartSurfer, a Service Parts Information CD-ROM is also available for purchase from HP. The CD-ROM contains the same information as the PartSurfer Web site. The CD-ROM can be ordered individually or as a quarterly subscription, which keeps the information up to date.

End sum

Many of us have heard about the coming of the "paperless office" for years. The reality is that the average office still needs paper copies of many documents. Thus, you should take advantage of the insights and tips in this article to better troubleshoot the laser printers that you manage, because they probably won't be phased out any time soon