| Author |
Message |
    
Will
Rating: N/A
Votes: 0 (Vote!) | | Posted on Thursday, September 09, 2004 - 09:39 pm: | 
|
Hi all,
I'm working on a Yashica Mat TLR with a Copal MXV shutter. The shutter was malfunctioning due to a sticking/bent selftimer mechanism. I now have this problem corrected and the shutter fires at all speeds correctly. But I now have a problem I didn't have before. The aperature blades bind and bunch up when they are stopped down. When I hose some Ronsonal on them, they work very smoothly. Once dry they become very tight to operate and revert back to bunching up when stopping down. I tried oiling them lightly, but by the time the excess oil is removed they bind again. What happened? What's the fix?
Thanks in advance,
Will |
Jim Brokaw
Rating: N/A
Votes: 0 (Vote!) | | Posted on Thursday, September 09, 2004 - 11:33 pm: |
|
No oil. Aperture blades are mostly made to work dry, though its not so important when they are not SLR 'instant-return' apertures. The many thin leafs of rigid steel overlap quite a bit, and even a small amount of oil creates a tremendous amount of 'stiction' between the leafs (relatively speaking...) This stiction can easily cause the leafs to bind against each other and then shear off the little pins upon which they pivot. If that happens you can only replace the leaf, which is a very intricate and delicate job.
Sometimes a thin coating of very fine powdered graphite is recommended to help lubricate the leafs overlaps, but in most instances I've found this is not necessary.
What IS necessary is to completely and thoroughly clean out all the oil from both the visible area of the leafs and the rotating and pivoting pins and base area of the leafs... this can require disassembly and separation of the aperture mechanism from the shutter mechanism. In many cases you remove the 'guts' of the shutter which then reveals the leafs and associated rings which manipulate them to open and close the aperture. Soak the leafs and pivot areas and rings with naptha (Ronsonol) and dry with bits of tissue or canned air. Make sure you get ALL the oil and crud out. This is easiest to do if the shutter mechanism is separated, but IMO you don't generally need to disassemble down to the individual leafs unless there is evidence of rust or corrosion on the leafs. I've had success polishing leafs smooth and removing rust with a pencil eraser, applied carefully to the individual leafs against a slightly padded backing of paper towel...
The iris aperture is really a quite clever design, but can be tricky, and even more of a hassle to deal with when the leafs are not flat but domed as they were in an old Leica lens I disassembled...
If you do this carefully and if there is no mechanical binding in the linkages and pivoting areas you should be rewarded with a smooth working light touch aperture. Take your time and study the way it goes together when you get in there, its sometimes not obvious how the leafs overlap (sometimes there are 'left-way' and 'right-way' leafs that alternate, for instance. Most SLR apertures are simple with few blades, but the old lenses with 11, 13, 15, or even more leafs can be a real pain to deal with. Search the archive for my story of how I got that Leica lens back together... which is how its going to stay! |
Winfried
Rating: N/A
Votes: 0 (Vote!) | | Posted on Friday, September 10, 2004 - 04:05 am: |
|
Iris apertures of modern shutters (i.e. most shutters with a linear aperture scale) are not as difficult as older ones. On old lenses, you sometimes count 12 or more aperture blades, most shutters from the early 60s and later have just 5 or 6 blades. These arrangements are not too hard to disassemble and to reassemble - reassembling a 12-blade aperture is a real pain.
Biggest problem might be separting the iris mechanism from the shutter. On some shutters there are screws from inside the shutter assembly, and sometimes hairsprings run against the 'wall' of the shutter housing which is an extension of the iris mechanism housing and will come off together with it - and if you did not disassemble the shutter from the front more or less sometimes they are hard to locate.
You can refer to the repair article about the Yashica Lynx5000 for a typical shutter/iris aperture arrangement of that era. |
Will
Rating: N/A
Votes: 0 (Vote!) | | Posted on Friday, September 10, 2004 - 08:03 pm: |
|
Thanks Jim and Winfried. I spent a few hours flushing (and flushing..)and working the aperature blades with Ronsonol - and they FINALLY responded to the treatment and work freely now (no oil). I didn't have to disassemble, but for awhile I thought I would have to. They were quite resistant to the cleaning. Thanks again for the help!
Will |
Jon Flanders
Rating: N/A
Votes: 0 (Vote!) | | Posted on Thursday, September 16, 2004 - 01:23 pm: |
|
Iv'e cleaned a couple of shutters now, and it seems to take about three days of naptha and q-tips to get all the old oil out. I tried carb cleaner the last time, it might have speeded things up, I don't know.
Its very cool when all of a sudden things start working right.
Jon Flanders |
Jim Brokaw
Rating: N/A
Votes: 0 (Vote!) | | Posted on Thursday, September 16, 2004 - 10:39 pm: |
|
I find that 'brake cleaner' works well, dissolves most kinds of grease and leaves clean no-residue behind.
Cautions:
Wear safe 'rubber' gloves. Latex gloves may not protect, you need special gloves that are chemical resistant. This is because some components of brake cleaner and carb cleaner (and probably naptha as well) can be absorbed through the skin. Once in your body they can affect nerve and muscle functioning until flushed out at, no doubt, a heavy cost to your liver and kidneys. Plus, the long term consequences of exposure to these chemicals may be bad e.g. cancer, palsy, etc. Better to take proper precautions in the first place.
Secondly, avoid breathing the fumes, and avoid using indoors or near source of spark or flame, the vapors may be explosive in concentration as well as medically hazardous.
Thirdly, make sure that any parts you are flushing are not affected. Some kinds of plastic are dissolved or turned brittle by chemicals found in carb cleaners and brake cleaners. Best to avoid any contact with plastic parts, which means you need to carefully inspect the mechanism you are cleaning before spraying.
I find naptha (Ronsonol) is safe for most plastics, and isopropanol alcohol 91% or 99% seems to be but I recommend testing first. Acetone is very dangerous to most plastics, as well as being very volatile and explosive if fumes build up. Don't even -think- about using gasoline... it is a known cancer-causing agent... as is benzene a major former component in gasoline (perhaps not as commonly used now, though). Xylene, toulene, lacquer thinner, etc. all seem to attack many plastics... and have medical and flammability consequences as well.
Be very cautious about using all chemicals! |
|
