The early 50mm f/2.0 Nikkor-H has a rather large overhanging f/stop ring which is probably snuggling up against your TC-200, preventing the aperture ring from moving easily. You can grind down the excess plastic quite easily, but before you do so, kindly make sure that what I am describing is actually the source of your problem. I have an early 50/2.0 Nikkor-H and I had a similar problem mounting it on a Nikon Digital body. Before I ground it down, I protected the rear glass with one of those cheap push-on white plastic Nikon rear caps.