I've just bought a Soligor 28mm f2.8 in really lovely condition. It's Tokina made and is like new and came with it's Soligor case, also in good nick. It's my first FD-mount lens. I think it's the earlier breechlock type. I've bought a cheap Fotga adapter and after a bit of googling and fiddling I've worked out how to mount it, but it's not stopping down. The aperture ring does nothing. This seems to be a quite common problem, and I hope it's something to do with the adapter or the way I've fitted it, rather than the lens having stuck aperture blades. Anyone got any advice or tips?