You are most probably right figuring it is the rubber belt that is the problem. But a rubber band will not work. Even though it seems to be spinning the disk it does not spin it correctly due to the elasticity of a rubber band. I had the same problem and tried it myself but without success. I eventually fixed it by finding a rubber VCR belt that fitted, then everything was good. Try a VCR repair store that may have some belts around or dead VCRs that have a suitable belt. You just need to find one that fits OK thats all.