Two weeks ago I sent my 28-105 f3.5-4.5 to Canon NJ for repair. It gives an f-stop of f 0.0 when attached to my cameras. This problem started a good 7 years ago, about a year or two after I bought it new. It was rarely used, maybe 10-20 rolls of film, total. Due to the fact I stick with primes as my main lenses, I had never sent it in for repair. Recently, though, I thought it would be good to get it fixed and put it into service again as a spare camera system to leave at work.
The lens was returned to me today, from Canon repair in NJ, saying that it was not repaired due to fact that there are not parts available. This lens is a USM from about 2000 or so, I think a series 1. I can't believe they wouldn't have parts. They didn't specify that they looked at it or what parts were needed. They did say that they could give me names of authorized service centers I could try! Before I sent it, I had called them and they said to send it in----they could have told me then that they wouldn't have parts if parts were needed.
Oh, well, it may go up for sale, and cheap!!