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Request fr info/advice for repair Takumar 28mm f3.5 58mm dia
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PostPosted: Sun Nov 12, 2017 9:59 pm    Post subject: Request fr info/advice for repair Takumar 28mm f3.5 58mm dia Reply with quote


I wonder if anyone can help me.

I'm looking for good info on the disassembling and infinity focus correction on a version I Takumar 28mm f3.5 late build, M42 (ie the one with 58mm filter diameter, the max at f16 and "7m" as the last marking before reaching infinity.
There are no tutorials about the structural disassembly of this lens. The whole front lens group seems to be kept in place by a large gasket held in place with the name ring. There is only a primitive schematic of the lens elements (which I have) but that is all.

I bought this lens but it happened to be a lemon ie it has a spot on the last lens element which I tried to clean but it may be irreversibly damaged (classic soft last lens on some vintage lenses?). The thing that I want to correct is infinity focus, instead of just throwing it away. (as the seller suggested after a refund)
I think that the front portion of the lens has been disassembled for cleaning (the flaslight test reveals some light scratches on the second lens element for which I doubt that it should be there) but IMHO it has been badly reassembled or "adjusted" to focus to infinity on a poor adapter. I see no other reason for this focus problem as I have 5 other M42 lenses and 3 different M42 adapters and all my lenses nicely can focus just beyond infinity except for this Tak.
I want to see if I can correct it for this lens in terms of enhancing my repair skills. BTW I also searched the whole archive of this forum ... but maybe I missed something.
I spend days searching google and I have found some directives for Takumar 28mm but they all speak of the later 49mm types and these all have one consealed front lens elements block that can be unscrewed from the helicoid. This one doesn't have such a unit.I have the procedure explained by IndianaDinos at http://k10dpentax.blogspot.be/2008/05/fixing-infinite-focus-on-super-takumar.html but once again it is for a lens with contained lens block.
I opened mine by removing the name ring and gasket then I see classic screws, not the expected JIS cross head screws ...

Any advice or just bin it ?

PostPosted: Sun Nov 26, 2017 10:45 pm    Post subject: Reply with quote

Maybe ask over at pentaxforums

PostPosted: Mon Nov 27, 2017 11:27 am    Post subject: Reply with quote

Thanks, but on closer inspection it seems that the last lens element is completely corroded at the outside ... I'm undertaking a pathetic attempt to polish it, just for the fun of seeing what will happen.

PostPosted: Mon Nov 27, 2017 3:11 pm    Post subject: Reply with quote

Best wishes!

PostPosted: Mon Nov 27, 2017 9:29 pm    Post subject: Reply with quote

Thanks will keep you posted Wink