Needing to replace the rear lens on a TLR.

[waynecrider]

I was given a YashicaMat 124G with a bad rear lens. Luckily I have a replacement on a YashicaMat 124 camera with a bad shutter, both Yashinon lenses. By the time I buy a spanner wrench and lens sucker I'll still need to replace the seals which I have material for. The big question is whether I can run into problems with needing shimming or such for collimation? If I repair it myself I get new tools; If I send it out the camera repair will probably be the same price. What do you think.

[Jeff L]

Send it out. I say this not knowing what your repair skill level is.
If it was me- I'd send it out.
If it's just a bad shutter in the one, can you not just replace the shutter from the one with the scratched lens?
I'd be inclined to keep the complete good lens no matter what body it comes from or goes into, and change the shutter.
I have a 124G and find it very good.
Jeff

[John Jarosz]

I'm not familiar with that camera, but can you replace both cells from the unit with the bad shutter into the one you want to save? The mechanical tolerances on the physical mounting of the lens cells is probably the same.(you could probably verify this by taking some measurements with a micrometer, if there is room) On the off-chance that the cells are a matched set, replacing both cells may be a better idea.

John

[John Koehrer]

Not having one of those lying around to look at, some of the tlr's have a light shield around the rear elements & you might have to remove that also.
If not, there's no need to buy spanners. Take a pair of needlenose pliers & grind the tips to fit the spanner notches. If your thinking of swapping the entire shutter you'll need to remove the rear element anyway since the mounting flange for the shutter is under the element.

[greybeard]

The big question is whether I can run into problems with needing shimming or such for collimation?

I am under the impression that the viewing and taking lenses for TLRs have to be matched in focal length, since normal manufacturing tolerances aren't good enough to allow complete interchangeability. This is probably only important for close-up work (i.e.--portraits in dim light) once the two lenses are positioned for infinity focus. It would seem that the best bet would be to use all the glass from the body with the bad shutter, and look closely for an adjustment (probably on the viewing lens mount) where the infinity adjustment is made.

[ic-racer]

I believe it should unscrew. The shims (if any) help with flatness of field and should not affect collimation. The front and rear elements of a Rolleicord I recently acquired came off easily for cleaning.

http://www.apug.org/forums/forum51/4...-mat-124g.html

[waynecrider]

Gee what happened to this thread. I can't read the responses without scrolling off into the wild blue yonder. Is this a problem on the APUG end?

Good point John J; I may need to do that but I think I'll try just the rear element for now.

JK, it does indeed have the light shield around the lens and it can't be removed.

My skills are good and I need to pull apart a Rollei 35 to see whats up with the film wind crank so I'm going to buy the tools. Besides the new camera seems to have a nice shutter in it an not needing service.

P.S, ic-racer, can you send me a link or PDF on that diagram? It's sized like a 30x40 inch print on my 15 inch computer screen. Thanks.

[ic-racer]

Here is the site with the Yashica assembly diagrams. Hope it helps, good luck!

http://www-unix.oit.umass.edu/%7Ecor...a/ymchttc.html

[paul ron]

Is the replacement lens the same as the old lens?

The rear cell should just unscrew out n the new one put in it's place. Once you have it back together, there is a locking screw that keeps the viewing lens from turning in it's mount. It's just under teh top left side under the mounting plate. Loosen it. Now set up the camera on a tripod n aim it at a subject that will focus at infinity.

Mount a GG on the film plane of the open backed camera. Be sure it sits nicely on the film rails n tape it in place. Focus the camera, as if taking a pic, on the GG to that infinity sunject using a loupe to be sure it is razor sharp.

Now look into the WLF n see if it focuses properly? If not turn the viewing lens till it comes in nice n sharp. Set the locking screw n you are ready to fly. Oh be sure to check the close up focusing at min distance to be sure all is well.

Another site to look at with nice pics of the camera as it is being repaired... http://davidrichert.com/Yashica%2012...ashica_124.htm


A yahicamat is about the same shutter mounting...

http://davidrichert.com/yashica-mat.htm

[Ed Sukach]

From many moons of lens testing, I'll say that elements are NOT interchangeable, Replacing one will degrade the overall performance of the system (read this as having a confidence level of 95%). It is POSSIBLE to "luck out" and improve things (in re-reading, 5% seem too optimistic), but I would NOT bet the farm on improvement.

Lens manufacturing tolerances necessary to insure element interchangeability would have to be fantastically "tight"; net result, one unreasonably expensive lens.