Super Takumar 50mm f1.4 repair??

So, I lucked out and recently bought a Spotmatic SP (broken), Super Takumar SMC 28mm f3.5 with lens hood (near mint) a well used 50mm f1.4 Super Tak. and a fungal Tamron 300mm f5.6 in a charity shop for 12 quid. Woohoo!

 

The glass looks great in the 50 and 28, but the aperture ring is pretty sticky (intermittently) in one direction on the 50, and has the usual yellowed glass that is well documented on the net, and which I have it on the windowsill for. Anyone out there know how difficult it might be to remedy the stiff aperture ring? I am loath to 'go in' unless it is straightforward, having lost the detent ball on a Tamron 90 recently in the same manner. I can probably live with it, but I'd rather it was smoother.

 

TIA

The sunlight, if it works at all, has to be direct, not filtered through other glass. I'd just use the yellow tint as a slight "warming" effect. Call it a "Pratt filter" if you feel like it.

 

It's surprising how fungused up a lens can be and still work (see my post at LINK) but cleaning is very difficult to impossible. Just don't let it mingle "unprotected" with your other lenses.

I cleared my Super Tak a few years ago in the following manner. Put aluminum foil on the rear of the lens and around the lens (this is to keep it cool in the sunlight) - held on by rubber bands. The rear piece is to reflect sunlight back out of the lens, doubling the effectiveness. Tie or band the whole thing on your tripod in bright sunlight and aim it at the sun...you may have to reposition it 2-3 times/day. Next day reverse the end you put the foil over and repeat the above procedure. Keep switching things around for a couple of weeks and you should have a crystal clear lens. Sorry I can't help with the aperture ring....they are tricky.