I used Andy Brown's tutorial as a guide. Andy recommended dunking the whole aperture assembly in soap water, I prefer to clean the individual blade. I would advice you to try Andy’s advice first, because this lens aperture assembly is more complicated than other lenses that I’ve worked on.
Optically this is a very good lens, but mechanically this lens is not on par with Takumars. There are some plastic parts inside, and it is not possible to fine tune the focusing mechanism. In my copy, it is possible to focus a bit past infinity.
For cleaning the blade, I prefer naphta, as some aperture blade corrode easily when exposed to water. For cleaning helicoid, I use water and laundry detergent.
Remove the 3 screws (A). Then just pull the back casing.
Remove the outer element and shroud (A). You could remove it later on, but I prefer to work with as little lens element as possible.
Remove the 4 screws holding the focus rod (B). Remove the rod right away.
Remove the focus adjustment screw (C)
Unscrew the end of the casing.
Pull the lens hood (A) and unscrew it. Some might have a small screw, mine doesn’t.
To remove the aperture assembly, unscrew the 3 screws and pull the assembly.
The A/M lever(C) is connected to a spring (B). Unhook the spring from the post (A). Then remove the A, C and D.
Unhook the aperture spring (D) first. I use a needle to do it.
Remove the outer collar (A), use a spanner for this. Then remove the inner collar (C)
Remove the aperture rod screws (B)
Remove the inner collar (C) . It is not screwed, you just need to pull it out. Installing it is a bit tricky, because the spring need to be attached first. I use a bit of gue to attach the spring, before installing the inner collar.
Installing the aperture blade is a bit tricky. Install all the items in picture 5.
Position the inner & outer disk so the lever is in this posotion.
Put the inner collar, it has a slot, so it will only goes in in this position. Make sure the outer disk is centered.
Attach the spring to the inner disk’s lever.
Pull the inner disk lever as far as possible to the right. Adjust the outer disk, so the aperture opening match the inner disk’s.
Remove the inner collar, and install the aperture rod.
Then install the inner & outer collar. You might want to install the aperture rod first,but I find it difficult to position the disks with the aperture rod & ring installed.