Pentax-A SMC 50mm f2 Disassembly

Disassembly and reassembly of a SMC Pentax-A 50mm f2 lens.
Lens is disassembled to access the aperture blades, mechanical components, and most of the body sections individually.
This lens is harder to take apart because it uses cheap materials and a cheaper design. A lot can go wrong with the mechanical parts internally, and I had to apply grease to the internal mechanisms to get the lens working properly.
Complete time of video was around an hour.
photography.mat...

[@davestubularvideos9046]

Thanks for the video. I’d looked on the Pentax Len’s repair forum where a member directed me to this, but there is one point of difference that caused me trouble when I followed you. It’s the small angled plate under the bullet shaped ball, spring and bracket. I tucked it down the slot as you showed followed by the bullet, spring and bracket but on testing found the bullet ball, when switched to A was no longer emerging through the hole in the bayonet plate. Cleaned up the hole but no improvement. The first little plate actually needs to be fitted with the narrow angled part vertical, upright, nearer the lens elements rather than the aperture ring. That way, like on the forum, it won’t bind against the bullet and spring, and the electrical contact will be picked up on certain Pentax cameras to show the aperture is set on A. Thanks for making me brave enough to attempt the task!

[@OUoht14l]

I second this! I just repaired my lens too; the thinner arm of the L-shaped plate has to be facing up. Otherwise great disassembly :)

[@jamasters62]

It is now Sept., 2021, and I received one of these lenses yesterday. Fungus just beginning on edges of two inner lens elements. The focusing action was super stiff due to the helicoid grease hardening. I found your video on this Pentax lens and watched it twice. This video helped me most of the way to a total teardown. I cleaned each optical element with hydrogen peroxide and cleaned the three pieces of the helicoids and regreased them. Got it all back together just fine. Now this lens is like new with clear glass and buttery smooth mechanical operation. THANKS SO MUCH FOR YOUR HELP!

[@alfredbassDoP]

what grease do you use bro?

[@markcrooks3669]

Thank you very, very much for this video and all the others you have done. They have added a new dimension to my vintage lens photography. The satisfaction of finding and repairing a problem on a lens would never ever be possible for me, and others I'm sure, without your guidance.

[@jdutch1011]

Just wanted to say thanks for a great tear-down. I have done a few things over the span of my life; fixed my iPhone 4 logic board by basically removing everything, and jamming/tucking a piece of plastic under a heat shield to make the connection underneath it more secure... but I've never done a lens. I was able to figure out your tutorial (though my problem was actually that the focus ring was stuck and had actually jumped a step, and I had to sort that out on my own) and put my dang lens back together and IT WORKS! Much appreciated!

[@theolich4384]

I would have sent my Pentax A 50/2.8 Macro off to a technician...if not for your video that explains how the "A" aperture index pin works. It's a little different on my lens, but the idea is the same. Lesson learnt: never fumble with aperture mechanism without prior knowledge - and thank you very much!

[@LuigiBarbano]

great video, thanks. BTW the little annoying to assemble piece that goes out on the lens base is the contact to let know the camera that the leans is in A(uto) position so the camera has the control of the aperture.

[@OUoht14l]

!!! There is one tiny mistake in the reassembly: The part being placed at 15:35 is facing the wrong way. The thinner arm of the L-shaped piece has to be facing upwards and towards the center of the lens (not in hole). Otherwise great instructions :)

[@anphiibian5013]

Very usefull video, just finished cleaning my 50mm f2. Thanks man

[@bartwaggoner2000]

This video has convinced me to stick with SMC Pentax-M lenses!

[@dukenukem5768]

I think they are very much the same. Try an autofocus lens though, with lots of little sprung connectors!

[@michaelraven8764]

Thanks, great video. I have the f1.7 version and I was surprised and the number of small differences inside when compared with this. The problem with mine was that one of the sprung metal ratchet pieces inside the aperture ring was coming loose where it attaches to the lens body. Nearly lost the ball bearing too...

[@dukenukem5768]

@5:50 Clean the diaphragm assembly by submerging it. Submerge it in what?

[@Deivid_C]

too bad you didn't disassemble the focus ring mechanism. That is where I am having problem since it is not coming in and out.

[@pdtech4524]

I have the SMC Pentax-A 50mm 1.7 lens, so it's slightly different, trying to find a disassembly of this lens. The issue I have is the aperture ring won't close past 9.5 it jams up like something is blocking it, the A button won't pish in at all and the aperture adjustment around 2.8 to 1.7 gets very rough whil on the camera but taken off it's smooth there! One thing I've noticed already is the ball bearing you can see on your mounting plate is just an empty hole on mine! Any ideas?

[@kiss4luna]

my lens is very strange. it has the outer chase of the M model, but inside it's the A model. I'm confused.

[@seanconnors9912]

I lost the ball bearing and the small spring. Am I screwed or can I purchase those?

[@richardong7029]

Lots of parts, you did a great job!

[@gvfo]

A thousand thank! I was able to fix my lens thanks to your video. :)

[@alfredbassDoP]

nice, dont know if any other ask this, but my lens focus ring at the middle of rotation it gets hard to move, how can i fix that? have you fixed somthing like that? thanks bro

[@christianhaslett]

Thanks to you I fixed my lens! I do have a complication though. I seem to have reassembled the lens incorrectly because my lens will screw apart if I continue to twist the focal ring. I disassembled various times and could not figure out what I did wrong. Any ideas? What stops the focal part of the lens from screwing completely off?

[@engage3668]

That was a great instructional video. I have been considering buying a SMC Pentax-A telephoto lens but someone had removed the K-mount and replaced it with a different mount which I think is a Arri Pl mount. Do you think that this could be converted back without too much trouble?

[@xwingfighter999]

Very helpful, thanks for sharing!

[@BUBBENVAN]

very clear delivery

[@djuydoiu2627]

i have a Pentax 67 - 55-100mm f/4.5 on the front there is no plastic ring, screws, no 2 slits, i tryed some rubber but nothing moved you might have a idea ?

[@seunghan9078]

Thank you for sharing these tutorials. If you want to declick this lens would you remove the ball bearing on the side as well as the one on top? Thanks

[@25Lipee]

the plastic top ring on mine simply does not move, what can I do to twist it?

[@edcanola]

Same for mine... I feel like I will need to pry it out using the 2 tiny little openings near the plastic ring that should give access underneath

[@cevoner]

@@edcanola Yes, I have the 28mm A and that ring does not budge like it is glued. Any special rubber tool to loosen it. I see you did yours by hand.

[@bigpardner]

I've noticed that some Pentax lenses, such as here at the beginning, 0{20 etc., you see the small ends of the aperture leaves sticking out toward the front, when usually they are in the rear. Also, to me, going through the aperture click stops on the A lenses seems hard and rough compared to the older M and K. Now that I look at then closer I wonder if the aperture ring is actually plastic. I never cared for Pentax putting so many click stops in there anyway. One at each f stop is enough. A click stop at every in between point makes it harder, for me anyway, to fine tune a match needle or diode setting.

[@amanisaking]

bigpardner the ring is plastic.

[@MrCulldog]

I have a SMC Pentax-A f2 with a jammed focus ring, The inner aluminum ring on which the focus ring rides is not parallel with the rest of the assembly and is jamming the focus ring. How do you properly align this. It doesn't seem to want to budge

[@Mattbierner]

Yeah this lens is pretty finicky. Which piece do you mean specifically? The helicoids? Or when looking down at the front of the lens, that silver ring you see directly inside the focusing ring itself perhaps?

[@JeffDvrx]

www.dpreview.com/forums/thread/2724605 some guy explained it really well in this forum thread, i just fixed mine following his instructions. screwing the focus ring back in place was a real bitch though

[@amanisaking]

Thanks for this video. I cleaned and lubricated my lens using this. But i have a problem. When i put the lens back, the last piece that is the shiny ring which makes the aperture open with the outer aperture ring. It has play in it and barely opens the aperture when turned to f2. The little protruding on the ring doesnt seem to push the aperture mechanism far enough to open the aperture fully. I cant make out what the problem is. I can upload a video too if needed. Can you help?

[@Mattbierner]

You can able to adjust how the aperture opens and closes by adjusting where it is locked down: see 23:00. This should let you adjust how far open it is when the lens is set a f2. Let me know if that helps or if I misunderstood the issue

[@Gringle_]

That ball bearing.

[@grubbybuggy]

My 50mm f/1.7 aperture ring stops between f/8 and f/11 and doesn't close further. I followed this, put everything back, and still it doesn't turn beyond that point. Really annoying

[@stonehenges5722]

Just bought a Pentax with 1.7 and funny enough.. Aperture ring is very rough and stucks also between 8 and 12. Could you repair with help from this video? Is there a big difference between 2.0 and 1.7 lenses?

[@stonehenges5722]

Typo: not 12 but 11..

[@tentarangoding4783]

can you disassembly yashica ml 50mm f2 ? thanks

[@tomasdantones2469]

Te amo

[@thangasivam]

Very Helpful.