Clean the projector's exterior. This often remedies most problems because the projectors are typically very old and stocked for a very long time. Wipe away dirt and grime with a damp, lint-free cloth or towel. To clean areas that are hard to reach, use a Q-tip. Spray a dry lubricant or oil on the mechanical joints, then wipe off any excess.
Check the projector's wires. You may need to cover exposed wire on the power cord with electrical tape or replace the cord.
Plug in the cord and run film on the projector. To avoid risking important footage, use a dummy reel or test reel. As the projector is a mechanical device, with motors and sprockets to move the film, it may have stocked up parts, or the parts have accumulated too much dirt and dust. Stop the projector if problems develop, such as irregular speed, scratching or tearing of the film, problematic light or unlikely sounds.
Put more oil or lubricant on the projector's joints and replace the take-up and feed reels if necessary. Try running the projector again. If the problem persists, you will have to check the other parts of the projector.
Unplug the projector and secure it on a flat work area. Place cleaning materials nearby.
Remove the screws and optical parts of the projector, including the lens and mirrors. Clean these by wiping them in a circular motion with a fresh lens cleaning cloth. Make sure that these parts have no dust, hair or finger smudges and place them somewhere safe from accidental bumping. These parts are fragile.
Open the bulb housing and unscrew the bulb. Remove dust from the bulb compartment and the bulb itself with the brush. Replace the bulb, or install a new bulb if the old one is malfunctioning.
Remove any hair or dust from the film gate with the orangewood stick. Take care not to scratch any part of the projector, most especially the optical parts. Remove any dust with the brush.
Reattach the optical parts and make sure that all parts are secured. Thread the test film and turn on the projector. Look at the image to see whether the optical parts are free from dirt and dust and the motor and other parts are moving smoothly and not scratching or snagging the film. If problems continue, have the projector serviced by a professional.