thought the back for my rb67 was broken, it jammed and then the film winder would swing freely. I heard it was really hard to work on and much cheaper to buy another. Just being curious (and broke) I decided to take it apart. I found a copy of the service manual for another model, but they were relatively similar. I got it apart, was able to find the problem (ratchet slipped off gear when I forced it a little after I thought it jammed), got it all back together, and it works. Took a few shots, trying to finish off the roll tomorrow after class