Repeating Image (Ghosting) with the HP LaserJet Printer (119446)

SYMPTOMS

When you print to a Hewlett-Packard (HP) LaserJet printer, an effect known as "ghosting" occurs. Ghosting refers to an object or letter that is repeated several times down the length of a page at even intervals. The repeated image appears as a light or dark area relative to the surrounding image.

CAUSE

Ghosting most often occurs when a large black pattern is followed by a fine gray scale. The condition is caused by residual electrical charges left on the surface of the electro-photographic (EP) drum or a lack of toner in the developer region. Ghosting is a condition experienced in one form or another by all devices that use the electro-photographic (EP) process. Both the developer and the EP-drum can produce dark or light ghosting.

Both light and dark types of ghosting can be caused by either the developer or the EP-drum. The circumference of the developer or EP-drum corresponds to the distance between the repeated images. Therefore, measuring this distance determines whether the EP-drum or the developer is the cause of the ghosting.

The most common form of ghosting results from a developer condition known as developer starvation, which occurs when so much toner has been required to print the first image that the developer does not have enough time to pick up enough new toner and charge it sufficiently. Developer starvation produces light ghosting.

Developer and EP-Drum Measurements

   EP                 Developer              OPC
   Cartridge          Circumference          Circumference
   -------------------------------------------------------

   EP-S (92292)          50mm                    94mm
   EP-L (92275)          50mm                    94mm
   EP-N (92291)          50mm                    94mm
   EP-E (92298)          50mm                    94mm
   EP-P (92274)          25mm                    76mm

RESOLUTION

To correct this problem, do the following:

Use a different pattern. Avoid patterns that use a 50-percent gray scale or a "dot-on-dot off" pattern.
Make changes to the layout of the page so that gray-scale patterns do not follow black areas. If possible, make dark patterns lighter and light patterns darker. Print the image in landscape.
Experiment with print density and resolution enhancement technology (RET) settings.
Print a completely black page immediately in front of the page that is experiencing the ghosting condition. This black page must be part of the same print job so that the printer's gear train does not pause between the pages.
Check humidity and temperature: Low temperature and humidity can exaggerate a ghosting condition. Make sure the printer's environment meets the requirements given in the printer's user's manual. Light or dark ghosting caused by the developer is HIGHLY affected by environmental conditions.
Print at 300 dots per inch (dpi).
In most cases of light ghosting, changing the toner cartridge does not improve the condition. Dark ghosting caused by the EP-drum may be corrected by replacing the toner cartridge because the EP-drum or charging roller may be damaged.
Because ghosting is mainly an issue with the EP process, switching LaserJet components and assemblies does not, in most cases, correct this condition.

REFERENCES

This information was obtained from the Hewlett-Packard fax system. The information is provided to HP customers upon request.

The HP products discussed here are manufactured HP, by a vendor independent of Microsoft; we make no warranty, implied or otherwise, regarding these products' performance or reliability.