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Clay1905
Tinkerer
Username: Clay1905
Post Number: 1
Registered: 03-2007
Rating: N/A
Votes: 0 (Vote!) | | Posted on Wednesday, March 28, 2007 - 08:00 pm: | 
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Hi all,
I have a Yashica Mat with a sticky shutter.
The symptoms are these: The shutter refuses to release when the release lever is depressed. Wetting the mechanism with solvent causes the shutter to work until the solvent dries.
There are two little levers that share a common stud, that engage with the release lever at the top left (as viewed from the front). If I "assist" the lower of these levers, the time control train runs, but the shutter blades don't open.
I have removed the shutter mechanism from the front board, and taken the bridge off the shutter release train. The pivots for all the wheels and quadrant are cleaned and polished.
None of this helps with the problem, although this cleaning was likely needed anyway.
My questions: It appears that the problem is gummy lubricant, and is in the rear section of the shutter. Do I really have to disassemble this side of the shutter? (I'm supposing so) I'm a bit nervous of the iris leaves. Any helpful tips or advice for working in this area?
What is a suitable lubricant? Obviously greasy stuff will slow the motion, but clock oil doesn't seem suitable either as that's intended for slow moving trains. Light mineral oil would seem to be problematic too, as it may evaporate and leave a film in the internal optical surfaces.
What is considered good lubrication practice? Just pivots of wheels and levers? Is it right to lubricate gear teeth? What about the shutter blades, should they be lubricated too?
Any advice for messing about in this area would be greatly appreciated.
Thanks in advance,
Clay. |
Rick_oleson
Tinkerer
Username: Rick_oleson
Post Number: 216
Registered: 07-2006
Rating: N/A
Votes: 0 (Vote!) | | Posted on Thursday, March 29, 2007 - 09:11 pm: |
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It sounds like your leaves might be sticking together. The best way to clean them is to remove them from the shutter and clean them individually, but this is a hassle as it involves removing the entire shutter chassis from the shell. You might be able to clean it by removing the glass and giving it a REALLY good flooding in solvent. If you go this route, I would not spare the solvent - immerse the shutter in it and operate it numerous times while submerged to work the solvent into the hidden spaces. Dissolving the oils does little to clean the shutter unless you also REMOVE the oils.... this is why just getting things wet does no good, when the solvent evaporates the oil is still there. If you have a large enough volume of solvent for a long enough time, you can flush the oils out and replace them with clean solvent which leaves the shutter dry when it evaporates. For solvents, an electronics cleaner is good (make sure it has NO lubricant blended into it), and the old standby of naphtha (cigarette lighter fuel) is probably safest.
The best practice for lubrication is none at all, of any kind. Certainly never on the blades. If, once you have the shutter perfectly clean and dry, you find that it hesitates at the slow speeds or on the self timer, you can apply a small drop of thin oil to the spindles of the pallet and star wheel, and to the teeth of th star wheel. Possibly to the spindle of the first gear in the train, the one that is engaged to the star wheel. It should not be necessary to go farther up the train than that, and too much oil is always worse than not enough. You will never use enough to cause any visible vapors to reach the glass, if you do you've gone way too far with it. Watch oil will be fine, or the finest grade of hobby oil, gun oil, or the clear liquid skimmed off of a small bottle of WD-40 after you let the solids all settle out to the bottom. |
Clay1905
Tinkerer
Username: Clay1905
Post Number: 2
Registered: 03-2007
Rating: N/A
Votes: 0 (Vote!) | | Posted on Thursday, March 29, 2007 - 10:54 pm: |
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Thanks for the words of advice Rick.
I have an old parts washer for small clock and watch work. I'll put the shutter back into that for a much longer soaking. I'm using what is locally sold as shellite, or white spirit. It's pretty good for disolving old oil. Obviously it needs a lot longer to do it's magic.
I have some 10 weight acid free mineral oil. I think I'll plan on applying small drop onto the escapement to be sure. I use a broken needle for this, so the amount will be miniscule.
Thanks again,
Clay. |
Clay1905
Tinkerer
Username: Clay1905
Post Number: 3
Registered: 03-2007
Rating: N/A
Votes: 0 (Vote!) | | Posted on Monday, April 02, 2007 - 06:52 pm: |
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OK,
I gave the shutter a long soaking, with repeated operation at intervals whilst wet. After about five hours, I let the shutter dry thoroughly, lightly lubricated the escapement and re-assembled.
Viola! All is working. The lowest speeds seem to me to be running a bit slow, but that's not a scientific opinion by any means. I'm presently running a roll of film through, trying shots at various speeds to see how things look, as that's probably the best measure I can do without some diagnostic tools. (Here's hoping the light meter is calibrated within cooee.)
Thanks again, now I feel up to attacking the Rollei. I was a bit timid, but with the Yashica for a practice run, I'm feeling a lot more confident.
Clay. |
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