Auto Takumar question

<p>Hi all<br /> I hope this is the correct forum/place to ask this question.<br /> I've recently acquired a Pentax S1 with an Auto Takumar 55mm f/2.2 lens. The camera seems just about perfect, but the lens aperture wouldn't stop down with the aperture ring. I dismantled the lens and found there is a broken spring which is the cause of the problem. That's fine and I can workout how I can replace that. The problem is there are also some issues with the aperture blades - some of them were not correctly positioned and started to buckle as the aperture arm on the back of the lens was moved.<br /> Because of the danger of the blades becoming damaged, and because one of them fell out of the front of the lens during disassembly, I've removed all the blades with fine tweezers (and fortunately they are all fine and undamaged). What I can't work out however is how to do the final part of the disassembly to get the the aperture plate and refit the blades. I have the focus helicoid assembly, with the aperture adjust ring still fitted and can't find any obvious screws. There is a set of notches on the back for a ring spanner but I can't get it to turn (and I don't want to exert too much force unless I know it should open).<br>

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<br /> Does anyone have any experience of this lens and if so could advise me ?</p><div></div>

<p>the ring is most likely sealed with thread locker. the commonly used product will dissolve with nail polish remover. use a cotton swab and put a generous amount around the top inner edge of the ring and allow to sit 5 to 15 minutes. The threads may have seized from corrosion and may be stuck. hold the lens barrel with a rubber strap wrench or jar opening aid while trying to unscrew.</p>

<p>Normal installation for aperture blades is pick a starting point on the fixed ring then insert the blades in a counter clockwise direction then sit the movable ring onto the blades with the blades at wide open.</p>

<p>Extra fine powdered graphite can be used on the blades and their pivots as can DuPont Dry teflon.</p>

 

<p>Thanks for that advice Charles - yes a small amount of acetone on the thread left for 15min got the bottom of the helicoid unscrewed and I can now reassemble the blades. Thanks again</p>

<p>You are a braver man than I am! I hope you get the lens working. If your S1 or lens needs servcie I would consider Eric Hendrickson. He is the person I send my Takumar lenses to for service. He's great.</p>

<p>www.pentaxs.com</p>

<p>Thanks Anthony - I did get it fixed! I posted a description of the procedure on my site if you are interested. http://simonhawketts.com/2016/02/22/strip-down-clean-lubricate-auto-takumar-55mm-f2-2-lens/ </p>