Lens Repair Question - Aperture return and problems with condensed alcohol on glass

[Lamar]

I have disassembled a lens for the first time. The Konica Hexanon 50mm f/1.7 I bought at KEH had a sticky aperture that would not close to the correct setting before the shutter would release. Luckily I discovered this before ruining any film and KEH replaced if for free and allowed me to keep the lens with the sticky aperture as well. Since it was a freebie I decided that I had nothing to lose in performing surgery to determine the cause of the sticky aperture and attempt a repair. The partial disassembly required to expose the parts causing the problem was easier than expected. What I found was that a previous owner/user of this lens most likely attempted to lubricate the aperture mechanism. This did nothing but gum up the whole works over time by collecting grime and causing it to move very slowly . I used alcohol to clean it up and the aperture works fine now. The one problem I had was that some of the alcohol (I probably used more than I should have) made its way into the lens barrel and looks as if it has condensed on and spotted the inside of the lens elements. This may be temporary but it’s been there for about 12 hours now. Has anyone had experience with this before? Suggestions? If it doesn’t go away I’m considering taking out all the glass and cleaning it.

 

[steven_e007]

The previous owner probably committed the unforgivable sin - squirting something like WD-40 into the iris assembly. Pure alcohol should just evaporate. Try gentle heat from a hair dryer. The trouble is that the spots on your lens may be diluted WD-40 solution, that is they contain oil, rather than just alcohol. In this case you'll maybe have to dismantle the lens to clean the glass - but try and dismantle as little as you can get away with, more chance of having a working lens at the end of the exercise!

If you were able to get at the iris, can you reach through with a cotton bud to get to the spattered lens surface?

If so, use some pure cotton wool, roll your own cotton bud by pulling a small tuft off with a damp wooden stick (cocktail sticks are good) and rolling into a bud against the plastic bag. Don't touch with your fingers. Dip in pure alcohol and, starting at the centre of the lens, work gently in a spiral to the edge. Discard the cotton and roll another. Repeat as many times as you need too (maybe a dozen). Washing a lens like this is much safer and more effective than rubbing with a cloth...

 

[John Koehrer]

What steve_e said, but with any luck it's on the inner, accessible surface.
If not, it's no big deal to remove the front elements using a rubber bung and maybe spanner.

 

[John Hermanson]

Moving parts in the diaphragm are probably oily, that's why they move in slow motion or not at all. Those parts must be bone dry to slide over each other properly. Everything would probably have to be completely disassemble, degreased with the proper solvent, then rebuilt. The migrating oil is probably caused by old focus grease that is separating. That should also be removed, parts degreased and relubed. No WD-40, in the blade mechanism as that has wax in it. John

 

[Lamar]

Thanks for all the replies. The spots inside the lens went away over a few days but the slow aperture return is back. I think for a free lens I will give it up for the time being. To delve any deeper would require some more specialized tools and they would most likely exceeded the cost of the lens.

 

[michaelbsc]

Try using Varnish Maker's and Printer's Naptha to clean. In my local store it's labeled VM&P and sold as paint thinner.

It evaporates totally, and since it is petroleum based it dissolves grease wonderfully.

Careful though. It is extremely flammable and the vapors will overcome you. It's basically highly refined light raw gasoline without the automotive additives.

I wouldn't let it pour into the lens body. See if you can disassemble it.