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Pentax Auto Takumar 35mm F2.3 Loose barrel Fix
Posted By: Pedrodelta, 03-13-2019, 10:19 AM

I recently acquired a lovely old 35mm f2.3 Auto Tak but was dismayed to find that the rear of the lens felt quite loose and this was most pronounced when mounted to my camera. The lens appeared to work well enough but the amount of play in the bodywork was disconcerting and I felt it needed to be addressed. I searched the internet for advice yet whilst it became apparent that others had experienced the same issue, there was no information to be found on how to address the malady.
Undaunted therefore, I determined to tackle the problem myself and in doing so, I kept a record of my endeavours, that they might prove helpful to others in a similar situation.
The process turned out to be quite straight forward and I'm delighted to claim was 100% successful. The lens is now as firm as it was when it left the factory almost sixty years ago and with care should continue to provide enjoyment for many, many years to come.

Preliminary preparations.

1/ It's not a lengthy operation but even so, make sure you allow plenty of undisturbed time to concentrate fully and uninterrupted on the task in hand.
2/ A clean, well lit and tidy work area. A white sheet, paper or linen is good to work on as small parts or screws are easily seen against a white background. I like to use a large tray to contain all the various parts.
3/ A good quality set of jewellers screwdrivers is an absolute must. Some of the screws you will be dealing with are minute and their slot heads would be easily damaged with anything other than perfectly fitting drivers.
4/ If your eyesight is challenged by small items, then a good magnifying glass or glasses will prove invaluable.
5/ A small amount of grease, lithium or silicon.
6/ Paper towels, cotton buds and some cleaning fluid.
7/ Pen, paper and or camera to make reference notes and or photo's of your progress.

Disclaimer - Proceed at Your OWN Risk

Part One
Focus the lens out to infinity, make sure the aperture is not cocked and set the aperture ring to f22
Looking at the silver metal band around the middle of the lens, the one that denotes the aperture scale and has the red dot on it, you will find three very minute screws. They may be slightly recessed and their heads hidden with dirt from years of handling. These three screws when revealed need carefully unscrewing but not removing. Sequentially unscrew each of them a couple of turns at a time until it is loose enough to slide up beneath the trailing skirt of the large focus ring. This can be acheived by using your thumb nails, pushing them into the tiny gap between the silver aperture scale ring and the black aperture adjusting ring below it and then gently and evenly applying forward pressure until it's pushed as a far up as it will go. This action will then reveal three more and larger screws on the barrel below it.

The small screws I referred to are shown by the green arrows. When sufficiently loose the sliver metal ring can be pushed/slid up in the direction of the red arrows until it's mostly hidden under the skirt of the focus ring. (See the first photo below)

Part Two

The three screws you have just revealed will probably be found to be loose. This is part of the problem but not the whole of the problem. The fact that they are loose though is at this stage an aid as they need to be removed. Again, sequentially and a bit at a time, unscrew all three, remove and put safely aside.
The lower barrel of the lens can now be seperated from the upper barrel by carefully easing them apart from each other. By firmly gripping the upper barrel with one hand and the lower barrel with your other hand to pull them apart, applying a very, very slight side to side twisting motion if necessary.
Once apart, the upper barrel can be set safely to one side as it will only be the lower barrel portion that requires more work. I'm sure at this stage too, you will be glad to learn that no helicoids are involved at any stage. (See photo's 2,3 & 4 below)

Part Three

From this remaining section the next stage is to remove the black plastic aperture adjusting ring. This is acheived by gently sliding/pulling it forwards and off. Whilst doing so, it will be prudent to keep the f22 part uppermost, as located below this point is a tiny metal barrel bearing seated in a little recess. It is this bearing that provides the click when altering the aperture. Remove this, wipe it clean and set it safely aside. The black aperture ring can also be cleaned on its inside by removing any old compacted dust and grease and again setting safely aside for the pending rebuild of the lens.
The removal of the aperture ring will have revealed yet another four screws which may be initially hidden by more old and dirty compacted dust and grease. Once this has been cleaned away, the four screws should now be prominent and will also found to be quite loose. It's the looseness of these screws which is the crux of the problem. These screws hold a two parts of the lower barrel housing together, the bottom being the metal outer barrel and the plastic being the inner barrel. These two parts need to be pushed tightly together and the four screws then firmly tightened up to re-establish the integrity of the lower part of the lens. I would suggest that they are tightened up sequentialy a bit at a time until all are firmly seated and none stand proud of the barrel. (See photo 5 below)

Part Four

The re-build can now commence and this is done in reverse order with one slight difference and that is; the black aperture ring is returned to the barrel before the little metal bearing that provides the click stops. Before replacing the aperture ring, smear a thin film of grease around the barrel where the aperture ring will sit, line up the aperture ring (there is a slot on the inside of the ring to accomodate the screw which drives the aperture blades (See photo six)) and push firmly home. Once satisfied that it is correctly seated, turn the aperture ring the full extent of its travel to the f2.3 end and then back one stop to f2.8, then looking inside the barrel underneath where the f2.8 mark is, the sharp eyed will see a small rectangular piece of spring steel secured at one end by a small screw. (See photo seven It is this spring steel plate that provides the pressure on the bearing that defines the aperture clicks and beneath it is the recess that houses the click bearing. By carefully loosening the screw, this plate can with the aid of a small screwdriver or other implement, be lifted at the opposing end sufficiantly enough to relocate the bearing. This again can be acheived by the use of a small screwdriver with a little dab of grease on the tip to pick up the bearing and then deftly manouvre it into place. Then, making sure it's covered by the piece of spring steel, re-tighten the screw and aperture clicks will have been restored. (Try not to remove the screw whilst attempting this as it's a pain to relocate it. Replacing this bearing was the single most difficult part of the whole rebuild) Now turn the aperture ring back to it's f22 position, being mindful to ensure you don't detach it once more from the barrel and the rebuild can continue. (If you like to use your lens for video work and would prefer to have a variable fluid type aperture, then this last step can be omitted)

Part Five

Continuing with the reassembly, the two parts of the lens can now be re-united. Clean as necessary, line up the bottom half of the lens with the upper part and they can be gently pushed together, a slight jiggle of the two may be required to ensure correct location of the aperture guide. Push firmly home and ensure the screw holes marry up in both barrels and the three securing screws can now be replaced. Tighten sequentialy a couple of turns at a time until all are tight, ensuring that none are standing proud of the barrel. The silver ring can now be drawn down again, ensure it lines up exactly and secured in the same manner with its three screws. Voila! You have now successfully repaired your 35mm f2.3 Auto Tak. Mount on camera, test and enjoy!!!

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07-11-2020, 06:14 PM - 2 Likes   #16
sjp
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Hello,

Here is a brief guide for partial CLA of the 2.3/35 Auto-Takumar that I put together based on the advice from forum members ‘Kozlok’and ‘niceshot’ and my own experience. Perhaps it will prove useful for others.

Step 0: Tools needed. I used a set of vacuum pads and a TD-55 JIS screwdriver set (shown in the photo), and a needle-nose soldering iron, a rocket air blower and lens cleaning supplies (not shown in the photo). Four of the screws needed repeated heat cycles with the soldering iron before I was able to unscrew them.

Step 1: Unscrew the front element (the left most part in the attached photo). This step is straightforward, and I used the largest vacuum pad.

Step 2: Remove the truncated cone front part that now looks like a large lens hood (the second part from the left in the photo). It is important to mark its position before moving it in either direction, because it can be used to fine-tune infinity focus.
Inside the cone, there is a single retaining screw (the hole for it is visible in the photo towards the bottom near the silver thread) Before attempting to unscrew the cone part , I removed the retaining screw completely to make sure that it had made an imprint (a small metallic dot) and that I could see this imprint with the cone still in place. Once I verified that the imprint was present and visible, I unscrewed the cone and removed it.

Step 3: Remove the focusing ring (bottom center part in the photo). There are three screws at the top that attach the ring to the inner part of the focusing helicoid (the brass ring at the top of assembly shown in the top center). Once these are unscrewed, the ring can be simply removed.

If the lens mount has already been removed, as shown in the original post by ‘Petrodelta’, what is left is the assembly shown at the center top in the attached photo.

This assembly is very similar to focusing mechanisms found in other manual focus lenses. There is the brass focusing ring; a limiting screw that restricts the helicoid movement between infinity and MFD; two guide rails, each held in place by two screws; and an outer barrel that attaches the helicoid to the lens mount.

Because the 3-in-1 oil had started to react with the grease in the helicoid (as I was afraid would happen), I had to take the helicoid apart to clean it completely before relubing. This step might not be necessary, though, and partially unscrewing the helicoid (just take care to not turn too far) and applying fresh grease to the exposed portions of the threads might be sufficient. However, there was no oil on the aperture blades or the inner lens elements, so I did not have to take the lens completely apart.

My lens had been serviced before, and I could rely on the existing markings while reassembling it. There are many good tutorials online (albeit for different lenses) that provide some guidance as to what should be marked before taking the helicoid apart.

I removed the two guide rails (the two screws holding one of the rails are visible in the photo under the 95 mark) to remove the outer barrel and clean the oil that had made its way there. Then I took the helicoid apart and cleaned it in lighter fluid. The barrel and the helicoid had already been marked, so I just had to keep track of the marks while taking the pieces apart.

After cleaning and relubing, I followed these steps in reverse to reassemble the lens.

Regards,





Last edited by sjp; 07-12-2020 at 07:17 AM. Reason: Removed redundant images.
07-14-2020, 09:39 PM   #17
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QuoteOriginally posted by sjp Quote
. . .

Regards,

Thanks for the helpful info, sjp.
07-18-2020, 07:04 PM   #18
sjp
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QuoteOriginally posted by .a.t. Quote
Thanks for the helpful info, sjp.
You are welcome, .a.t.. I wasn't planning to do the work myself, but with Covid-19 restrictions and the focus helicoid starting to seize up, I figured I did not have much choice. After getting some useful advice from PF members and completing the work, it made sense to post my notes. I think it's only a matter of time before somebody else ends up in a similar spot, and there is not much information about this lens on line.
07-22-2020, 02:53 PM   #19
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Original Poster
QuoteOriginally posted by sjp Quote
Hello,

Here is a brief guide for partial CLA of the 2.3/35 Auto-Takumar that I put together based on the advice from forum members ‘Kozlok’and ‘niceshot’ and my own experience. Perhaps it will prove useful for others.
......

Grateful thanks to you SJP with your successful CLA and for posting your valuable input to this thread, which in turn may hopefully inspire others with the confidence to tackle their own maintenance of this beautiful if somewhat irksome piece of Pentax engineering.

Best regards, P.D.

07-26-2020, 01:30 PM   #20
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I'm just finishing one and about to start another. The testing so far has proven well worth the effort. I created my own lubricant composition since I feel the throw on the len's focus ring is short. Specific dampening that's suited to me was important. To that end I followed an impulse to introduce some things I've had prior success with that would not have been typically available for this kind of use during the time this lens was manufactured. This's no normal maintenance run & done, because in what's popular regarding vintage lenses, so much that's related to this lens's design bucked convention. It was more a restoration that ran stem to stern. The problems? Dust and debris inside, corroded fasteners, a lot of oil on the aperture blades, the focus ring just about seized (sometimes more so than at others), and intermittent double-vision often most noticeable at infinity. Also, Pedrodelta I had your loose barrel. Thank you for your post. It assisted in maintaining a needed "well OK then why not?" attitude. If there is any way I can help anyone with questions about doing this I'd be more than happy to assist.

Last edited by Raymond Johnson; 07-31-2020 at 02:46 AM.
07-26-2020, 05:48 PM   #21
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QuoteOriginally posted by .a.t. Quote
Thanks, niceshot. It's good to know your guide is available. But for now, I think I'll just leave well enough alone.
Some tools (the better you have, the better your result and nerve endings); and you may not need them all since with some things you can improvise to good effect, but then with others not so much. Along with some patience, fairly good light and some time. I think that between "Pedrodelta" and "niceshot" here with what they've offered and the support they've provided I'm certain you'd end up with exactly what you're looking for. I might be able to help as well.

Last edited by Raymond Johnson; 07-31-2020 at 02:49 AM.
07-26-2020, 10:20 PM   #22
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QuoteOriginally posted by Raymond Johnson Quote
. . .
I think that between "Pedrodelta" and "niceshot" here with what they've offered and the support they've provided I'm certain you'd end up with exactly what you're looking for. I might by able to help as well.

Welcome and thanks for the encouragement and offer, Raymond. I have the necessary tools and some experience with simple repairs. But I've bungled enough lens "fixes" that I'm reluctant to tackle a classic such as my 35 f/2.3.

The only problem my lens has is a stiff focus ring, so it's still fully usable. And I know I have all the help I could need right here on Pentax Forums if I do decide to try a re-lube.


Tim
07-27-2020, 02:11 AM   #23
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QuoteOriginally posted by .a.t. Quote
Welcome and thanks for the encouragement and offer, Raymond. I have the necessary tools and some experience with simple repairs. But I've bungled enough lens "fixes" that I'm reluctant to tackle a classic such as my 35 f/2.3.

The only problem my lens has is a stiff focus ring, so it's still fully usable. And I know I have all the help I could need right here on Pentax Forums if I do decide to try a re-lube.


Tim
just a quick note to all, they used rubber cement as locktite so use alcohol to break it down.

07-27-2020, 08:18 AM   #24
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QuoteOriginally posted by niceshot Quote
just a quick note to all, they used rubber cement as locktite so use alcohol to break it down.

Thanks, niceshot.
07-27-2020, 06:45 PM   #25
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QuoteOriginally posted by .a.t. Quote
Welcome and thanks for the encouragement and offer, Raymond. I have the necessary tools and some experience with simple repairs. But I've bungled enough lens "fixes" that I'm reluctant to tackle a classic such as my 35 f/2.3.

The only problem my lens has is a stiff focus ring, so it's still fully usable. And I know I have all the help I could need right here on Pentax Forums if I do decide to try a re-lube.


Tim
Any time a.t., any time.
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