Care and Safety of Overhead Projectors

This posting covers occupational health and safety issues concerning overhead projectors. It is important in the care of overhead projectors to:

• Avoid direct sunlight, as the heat may warp the Fresnel lens
• Avoid carrying the projector by the arm or post
• Keep the display as bright as possible by cleaning all the components in the light path, using a lint-free cloth and window cleaner
• Replace damaged parts, e.g. a scratched lens
• Make sure the main lamp works
• Keep a spare lamp with the projector if that is your organisation's policy
• Do not touch lamps with your bare hands, as this can shorten the lamp life

Ensure that the Fresnel lens is not warped or otherwise damaged and that it is installed the right way up. If it is not, the light will be concentrated through the centre of the image, and you will see projected a bright circle on a dark background.

If nothing is happening, you need to:

• Make sure the projector is plugged into the power point, that the power is turned on, and that the 'on' switch is in the proper position.
• Check if the lamp is burned out and needs replacing, and if the lamp-changing switch is positioned to the spare which is missing.
• Close the lid properly, as the safety cut-out switch may be operating.

If a bright circle shows up on a dark background, you need to ensure that the Fresnel lens is installed the right way up.

If the picture is not showing up clearly, you need to clean any dirty component in the light path, e.g. stage, lenses, and check the Fresnel lens to see if it is warped.

If the whole image is blurred, you need to check the Fresnel lens to see if it is warped, if the projection arm is out of alignment or broken, and make sure the focus knob is operating correctly.

If no light is showing, you need to clean the Fresnel lens or top glass and replace old and darkened lamp.

By following these safety procedures, there should be no further problems.