Try this before you pull the aperture apart in your lens. It may be a simpler fix in the mount. This is not a guarantee but a quick check. If you see oil on the blades then you will have to pull the aperture. However this might be a simple fix.
This Nikon 50mm f/1.8 Series E is a fantastic little lens which people give away as body caps and can be found on tons of film SLR bodies. This incredibly small lens is a great pocket lens to carry and works perfectly on Nikon’s DSLR’s and other DSLR’s brands with Ebay adapters!
The Pentax Super Takumar 50mm f/1.4 Asahi is another amazing example of a really well built M42 Manual Focus lens which Pentax is famous for. If you don’t mind manual focus then this little lens is great for even today’s digital cameras with M42 adapters.
Being extremely well built and with great ergonomics, this Leica R Summicron-R 50mm f/2.0 Leitz is a great lens. Plus it is built in Canada! Woo Hoo!! However I am not fully convinced it is worth the money they are fetching for today.