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Alex
Rating: N/A
Votes: 0 (Vote!) | | Posted on Saturday, June 04, 2005 - 11:06 am: | 
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Quite a few M42 lenses, when mounted on my Yashica TL-Electro, show an odd phenomenon. Pressing the shutter release stops down the lens, then it sticks, the shutter doesn't fire, and the mirror stays in the up position. Easing the lens to unscrew then lets the shutter fire and the iris opens back up.
What seems to be happening is that on some lenses, when the kicker plate strikes the diaphragm stop-down pin, there's enough resistance to stop the kicker plate in its tracks. When I simulate this with the lens off, using my fingernail to inhibit the kicker plate, I get the same phenomenon - mirror lifts, but shutter won't trip till I let go. So I reckoned that perhaps the stop-down pin was a fraction of a millimetre too long, catching the kicker plate early in its travel, and offering enough resistance to stop it.
When I first noticed this, on a fairly cheap Hoya lens, I gently filed down a little off the end of the stop-down pin, until the iris stopped down correctly and didn't need the lens unscrewing to let it open again.
Of the six M42 lenses I have tried (two Yashicas, four CZ Jenas), four have exhibited this phenomenon (one Yashica, three CZJ), and in each case, filing down the stop-down pin has cured it. However, I can't help thinking that there might be some adjustment that could be made to the kicker plate instead, but I don't know how I'd set about that. But I'd rather try that avenue that have to take a grinding tool to the pin each time I buy a new screw-fit lens.
I'd be grateful, as always, for any pointers or suggestions.
Alex |
Glenn Middleton
Rating: N/A
Votes: 0 (Vote!) | | Posted on Saturday, June 04, 2005 - 05:41 pm: |
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I do not know anything about the workings of your Yashica,but I am not surprised about the problem.I have made a number of adapters to mount M42 wide angle lenses on FED/Zorki bodies.It has proved impossible to hold the iris pin in the stopped down position by a simple turned in situ stop.Each make of lens that I have used has different length operating strokes,the at rest length of the pins vary also.The adapter has to have an adjustable stop,set up for each lens.(Lenses with auto/manual switches tend to be too bulky)
If you find that the Yashica has an adjustment on the 'kicker plate',make sure that you adjust to factory limits.You could feasibly end up with the camera not able to stop down certain lenses.
I find it a bit of a puzzle that a Yashica lens gave problems.Usually a manufacturer ensures that specifications and tolerances are such that his own kit always works.This might suggest that some part of the camera linkage is loose or seized. |
Alex
Rating: N/A
Votes: 0 (Vote!) | | Posted on Sunday, June 05, 2005 - 03:45 am: |
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Thank you for the quick response. I must confess it surprised me too that a Yashica lens should exhibit the same problem. The 50mm Yashinon is fine, but the 200mm Yashinon stuck. This was the first one I filed. I'd notice that gently unscrewing the lens by just a small fraction of a turn was enough to free it up. A 50mm Tessar, 26mm Hoya, and a 29mm Pentacon, all stick, and all are release with varying degrees of slightly unscrewing. The Tessar and Hoya are now filed down and work. On purely visual inspection, the kicker plate looks like it's working OK - snaps out as far as it can (before butting on to the lens mount), and releases to rest position later. The camera itself was an Ebay rescue camera, and other than needing light seals and mirror damper replaced, seemed fine. Obviously I don't mind doing the filing on cheaper lenses, but as you can imagine, I'm more reluctant to have to do this to rather more expensive examples! |
Glenn Middleton
Rating: N/A
Votes: 0 (Vote!) | | Posted on Sunday, June 05, 2005 - 04:39 pm: |
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Alex,
Whilst checking specifications of M42 mounts, I came across a Japanese patent? report which illustrated various operating linkages.I seem to recall that a couple seemed to have a spring loaded arm which allowed movement of rest of mechanism,even when lens had stopped down and 'kicker'was unable to move forward anymore.Does the Yashica have something similar or is it like the original Praktica;just a simple mechanical linkage?
Another explanation could be that the release button is not tripping the mirror and shutter at the correct point in the release cycle.If there is no adjustment on the 'kicker'perhaps it is some where on the actual release mechanism.
Surely some one has stripped one of these down or are they one of those that's built like the proverbial, so rarely fail?
I do know that M42 lenses made specifically for Edixa slr do not align correctly when fitted to Pentax slr and obviously vice/versa.I had always taken this to be due to the orientation of the thread start position.Perhaps there is more to it than that.No doubt somebody out there will know the full details.
Glenn |
Gary Turner
Rating: N/A
Votes: 0 (Vote!) | | Posted on Sunday, June 05, 2005 - 06:21 pm: |
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I have a similar if not same problem with 2 Ricoh Singlex II cameras. They wind & fire then hang up the mirrors with almost every M42 lens I place on them with the exception of a few Yashica M42 lenses! Must have something to do with friction between the pins and the aperture blades?? Actually the Ricohs work well with all lenses but only if triggered upside down. I can only suppose the problem is related to the mirror box and the friction created with its many intricate springs and pivots. Maybe lube dried out but I'd think these would not require lubrication. Spring tensions might have been lost over the decades? If I knew for sure I'd be tempted to peel the leatherettes back from the camera fronts, and remove the lens mount plates to expose the mirror box assemblies. Maybe that area can be cleaned? |
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