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Simple Steps To Isolating Printer Image Defects And Free Printable Tools

Updated: Nov 15, 2019


Anyone using a laser printer––whether new or remanufactured––knows that familiar, disappointed feeling of discovering one or multiple image defects on a fresh printout.


Signified by poor quality like flaws, streaks and spots, image defects are caused by numerous external and internal factors.


Some of the most common culprits are faulty toner cartridges, the scanner assembly, controller board, high voltage power supply, fuser, transfer roller/wire and reflective mirrors. Like a team working to sabotage success, these printer parts malfunction to create havoc on the printed page.


Examining the defect closely may lead you to a conclusion about why the defect is occurring. However, you can not truly understand why the defect exists without simulating your customer’s workgroup.


Find out what kinds of materials they’re printing, what type of paper they use, and how often they send jobs to the printer. Three of the most common types of defects are black/white printouts, poor quality prints and repetitive spots and lines.


You’ll know when you have a black/white printout because the paper emerges either totally black or white. If your paper is all black, you should examine your high voltage power supply and connection.


A faulty toner cartridge, controller board, high-voltage power supply, or a poorly seated transfer roller/wire usually causes a white page printout. In addition, the scanner often proves to be a culprit in these cases. You won’t have any problem determining if the scanner is at fault because most printers display an error message when the scanner isn’t working correctly.


Other Helpful Resources

Paper Jam Solutions For Laserjet Printers

Printer Service And Parts Glossary

Printer Service Error Codes


A faulty toner cartridge, dirty mirror, scanner, controller board, or poor connection from the high voltage power supply or transfer roller/wire can lead to poor image quality. I’ve prepared the following self-test to help you isolate continuous spots or lines.


1. Determine when the defect begins by performing a printer self-test.

2. Isolate each function. As the paper goes through the printer, stop the printer before the paper reaches the fuser. Now, check the image on the paper. Is the defect present? If so, then rule the fuser out as a possible cause.

3. Next, check the toner cartridge. Is the cartridge refurbished? Unfortunately, many refurbished toner cartridges don’t always comply with manufacturer’s specifications. The photosensitive drum may be of a lower grade, thus causing inferior quality printouts. The toner itself may be lower grade, or have a different consistency from the OEM toner, all which leads to clotting and premature wear of the fuser roller. For instance, if the toner is too fine, the wiper blade may not be able to clean the drum efficiently during each print cycle.

4. Is the defect on the photosensitive drum? If so, the defect may be caused by the scanner or the drum itself. You can conclude that if the photosensitive drum has a defect on it, then the imperfection will be visible if you rotate the drum manually. Remember: Touch the ends of the drum, not the photoconductive material. You don’t want to create more defects!

5. Check the scanner for an error signal. A solid white line down the length of the printout usually comes from something blocking the scanner’s beam.

6. One quick way to figure out if the roller is at fault when you have repetitive defects: Take the defective printout and roll it up in the shape of a cylinder so that the defects are aligned. This will show you the size of the roller that is causing the defect. Find that size roller in the machine and you have found your problem.

After following all of these steps, it’s possible that the printer will continue experiencing defects. Too often we get so concerned with the “guts” of a machine that we forget to look more closely at the exterior.


Now, check the printer for any damage, however slight, that may have occurred during handling. Replace every assembly in the printer that may cause the defect. Also, clean the reflective mirror and check all cables and connection devices.


From what we’ve seen in our shop, most defects prove relatively easy to isolate once you familiarize yourself with the components that cause them.


Educating the end user on preventative maintenance issues is always a good idea, and worth the extra few minutes it takes to show them how to clean toner spills and paper dust promptly and replace fuser cleaning wands.


These are just some of the simple end user tasks that will prolong a printer’s functionality.


Metrofuser is a leading global innovator, manufacturer of printer parts, equipment, diagnostics, repair information and systems solutions for professional users performing critical tasks. Products and services include hp printer parts, printers and printer repair training. Parts include hp printer parts such as printer fusers, printer maintenance kits and other hp printer replacement parts. The company's, customers include office equipment dealerships, online retailers, repair centers and MPS service providers nationwide. Metrofuser has been named to Inc. Magazine’s fastest growing companies five consecutive years.