Auto chinon mcm 55mm 1,7 macro disassembly

!Karen · Joined: 20 Jul 2013 Posts: 837 Location: Belgium Baby

I have the chance to buy this lens but the aparture doesn't close, it has oil on it.
Anyone experienced with the disassembly of this lens, is it do-able?
Price is 65� but it comes with 4 other lenses and a chinon cm3 with motor drive.

mo · Expire: 2016-07-30

I can't help with the repair but I have the same lens with the same problem.It is a common issue with this lens and the blades....I have not had the money to get it repaired. Sad

!Karen · Joined: 20 Jul 2013 Posts: 837 Location: Belgium Baby

Does it look too difficult to do it yourself?
Anyone maybe have an optical diagram of this lens. Usually it is just take off mount and screw off rear element to get to the aparture. I just want to be sure first.

Found this but unfortunately no info on how he did it Sad

http://youtu.be/EFo3NWynq9Q

mo · Expire: 2016-07-30

For me yes it looks hard to fix. There is the rear glass that looks like it screws out by itself (there is a ring with two holes holding it), then there are 3 screws around the mount itself. I tried to remove just the glass elements but they are screwed in fairly tight.

sceptic · Joined: 01 Jun 2013 Posts: 255

Based on the images of the lens found at http://m42lens.com/m42-lens-database/319-chinon-mcm-macro-auto-55mm-f-1-7-16
I'd say it looks fairly easy to clean the aperture blades. I usually clean the blades while, if possible, still inside the lens (to avoid having to dis- and reassemble the mechanism). First, I remove all the optics and then I drip naphta/petroleum/lighter fuel onto the blades followed by drying with non-shedding paper and air blower.

The back elements seem to be held in place with a single retaining ring, accessible without having to remove the rear mount, which makes it easy to remove.
For the front elements to be removed, the name ring needs to come off (can be difficult without proper tools) and probably one or more retaining rings behind it.

A lens spanner is recommended, although a caliper can be used as an alternative:

Remove front ring by scepticswe, on Flickr
If the name ring lacks slots to fit the spanner/caliper, you can try using a sink cap or the back of a rear lens cap covered with a rubber glove for friction.