Like any vintage item, 8mm projectors can be quite difficult to repair. If you don’t know how to repair it yourselves (and most of us wouldn’t), then you’ll be dependent on other people to repair it. However, because so few people use them, it’s very difficult to find someone who knows how to repair it. Further, even if someone does know how to repair it, there may not be sufficient replacement parts if something needs replacing.
However, all is not lost, as there are still a number of people who specialize in one of two types of repair. 8mm projectors can often be repaired either by those who specialize in vintage cameras, or by those who specialize in A/V repair. Many companies that specialize in cameras will also be able to do work with anything involving film (including projectors). On the other hand, 8mm projectors are still similar enough in their overall construction to other A/V items that people who specialize in fixing A/V items will often be able to repair them.
When looking for someone who can repair an 8mm projector, you’ll want to look for two things in particular:
Expertise: The first question is: can this person actually fix my projector? As is often the case with repairs, people may claim that they can fix something, but they actually cannot. One easy thing to do when looking for someone to repair your projector is to say what they think might be wrong given your description. At the end of the day, film projectors are not very complex instruments (though they are precise ones). There are only really a few things that can go wrong with them.
Access to Parts: Does the person to whom you are entrusting your projector have access to replacement parts if necessary? Some companies will have replacement parts on site, though this is unlikely except with the largest companies. You should ask the people you are speaking too where they get their replacement parts from, and how long it will take to get them. If they get them from a strange source, it could take months, while you could save all that time by working with someone else.