If there has been a noticeable degradation in the quality of the projected image, and the image is speckled or blotchy, it is possible that your projector needs to be cleaned. If the image is dim, try another lamp. If there is no change, your projector may need to be cleaned.
If you have an LCD projector, please consult article 1298 for more information about arranging an optical clean. If you have a DLP projector, please contact Promethean Technical Customer Support.