Ghosting description

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. This condition 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 developed 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. See Figure 1 for an example of ghosting.

Determining the type of ghosting

As mentioned above in the ghosting description, there are two types of ghosting: light and dark. Both types of ghosting can be caused by either the developer or the EP drum. The circumference of the developer or EP drum will correspond to the distance between the repeated images. Therefore, measuring this distance will determine whether the EP drum or the developer is causing the ghosting.

The most common form of ghosting results from a developer condition known as developer starvation. Developer starvation 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 will produce light ghosting.

Corrective actions to minimize image ghosting

• Check power source. Plug directly into a wall outlet and bypass any surge protector for testing purposes. Try a different circuit.
• Use a different pattern. Avoid patterns that use a 50% gray scale or a "dot-on-dot-off" pattern.
• Make changes to the layout of the page so that grayscale 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 HP LaserJet printer's gear train does not pause between the pages.
• Check humidity and temperature: Low temperature and humidity can exaggerate a ghosting condition. Make certain that the HP LaserJet printer's environment meets the requirements given in the User's Manual. Light or dark ghosting caused by the developer is highly affected by environmental conditions.
• Print at 300 dots-per-inch (dpi).

Important items to remember

• In most cases of light ghosting, changing the print cartridge will not help the condition. Dark ghosting caused by the EP-drum may be corrected by replacing the print cartridge, since the EP Drum or charging roller may be damaged.
• Since ghosting is mainly an issue with the EP process, switching HP LaserJet printer components and assemblies will not, in most cases, correct this condition.