If the motor on your GAF 2788Z works but the light won't turn on, you probably have a dead lamp on your hands. Age and damage from misuse and mishandling can lead a lamp to blow out prematurely. Replacement lamps for GAF projectors can be difficult to find. Call your local photo supply company or search through Web classifieds. Ask point-blank if the lamps for sale are new, as some lamps advertised as "new" are merely vintage lamps that have never been used. If you can't get your GAF projector to start at all, it may have a blown fuse. Unless you have extensive experience with electrical repair, a trip to your local appliance repair shop is in order.
If your attempts at projecting home movies result in slow-moving reels or a variable-speed mess, your GAF projector may need lubrication. After years of storage in a basement or attic without adequate temperature regulation, the decades-old lubricant in your projector may have dried out. Similarly, an un-boxed projector stored in a dusty space can suffer gummed-up bearings. Open up the projector and blow it out with compressed air. Then clean all of the bearings with a lint-free cloth soak in alcohol. Once you've restored the sheen to your GAF's metallic insides, re-lubricate it by apply sewing machine oil to all moving parts.
The transport mechanism of many GAF dual-8 projectors features no less than seven rubber belts. If you've cleaned and lubricated your projector and still have problems, one of these belts -- which can dry out or crack with extreme temperature changes -- may be to blame. If you don't have the original manual or schematic for your GAF projector, take a reference photograph before removing any belts so you won't forget where each one goes. If you find that any of the belts have cracked, snapped or melted, you will need to replace them. Rather than trying to track down expensive, specialized replacement parts, consider updating your projector with modern cloth-based belts.
One of the most terrifying problems to the novice projectionist is the dreaded projector jam, which occurs when the film folds in on itself and stops the transport mechanism completely. Thankfully, projector jams and threading issues are often a problem with the film and not the projector itself. Take off the cover and carefully remove the jammed film from the projector. Smooth out any creases, then inspect the length of the film for broken sprocket holes and sloppy splices. Snip hanging pieces of any broken sprocket holes and reinforce them with a clean piece of splicing tape. Remove the tape from sloppy splices, clean the underlying frames with alcohol, then remake the original splice with a clean piece of tape.