Dissasembly and Repair of Minolta Maxxum AF 50mm f/1.7 and f/1.4 Lenses Photo Gallery by Pete Ganzel at pbase.com

Dissasembly and Repair of Minolta Maxxum AF 50mm f/1.7 and f/1.4 Lenses

1.7 and 1.4 50mm lenses as well as the 35 and 28mm f/2.8 have nearly identical construction and these photos can be used as a guide for all.

The Minolta AF 50mm "normal" lenses are classic double Gauss designs and are similar to their MD/MC counterparts optically.

Advances in manufacturing allowed simplified more or less "sealed" plastic lens cells.

Cover.jpg	Pg1 Parts.jpg	Pg2 Parts.jpg	Rear Trim Plate.jpg	Lens Mount.jpg
Rear Element Group.jpg	Crutch Tip.jpg	Front Ring.jpg	Front Trim Ring.jpg	2nd Ring.jpg
FrontElement Group.jpg	Snap Ring Tool.jpg	Snap Ring.jpg	Iris Removal.jpg	Iris.jpg
Bad Solder.jpg	Plastic Front Element Group.jpg	Plastic Rear Element Group.jpg	Minolta 50mm ROM.jpg	ApertureSpring2486.jpg
GroundSpring2891.jpg	Toothpick Spring 2905.jpg	cover 1.4	50-1.4 3.jpg	50-1.4 5.jpg
50-1.4 9r	50-1.4 10r	50-1.4 12r	14 rear cell 1066.jpg	14 rear cell 1067.jpg
Hood Assembly 1069.jpg	Front retainer 1065.jpg	14 Front group 1070.jpg	14 Oily Iris 1071.jpg	Ultrasonic0012.jpg
14 mark 1074.jpg	14 Helicoid 1081.jpg	gallery: Maxxum 50mm Front Cell Disassembly	Iris Assembly 2850.jpg	Moving Plate 2857.jpg
Iris Tool 2858.jpg	Iris on Tool 2860.jpg	Inserting Iris 2862.jpg	Minolta AF 50s.GIF	Stop Screw 3451.jpg
Stop Screw 3457.jpg	Stop Screw.jpg	Ring Actuator 0009.jpg	Front Cell Compare 05.jpg	Rear Cell Compare 0010.jpg

post a comment

Chris		19-Dec-2009 20:16
This was pretty straight forward, thanks for the write-up. I would suggest taking the front trim ring off in the first step since it gave me a little trouble. Having the rear of the lens open and trying to get the ring out made me nervous.

Pete Ganzel		04-Nov-2009 06:45
Michael: The first section of the gallery shows assembly of the iris with the rear of the lens removed and just as you say with a cylindrical tool with the iris fully open. This is my preferred method. As for the ground spring, it is necessary for glitch free operation. A short piece of copper wire cut slightly long will substitute if you lost yours. No further adjustment should be necessary if you put everything back the way it was and did not disassemble the focus helicoid. If you did not mark the iris plate some adjustment may be necessary for the iris opening. Pete

Michael		03-Nov-2009 09:14
OK i finally fixed it. My solution was opening the iris blades up so it was fully open, sticking a cylindical object through (in my case a stick of glue). I also wasnt making sure the iris holder was sitting in its seat properly at first. I lost my ground spring... does this make any difference? If so where can i get another? Also how do i test that all is ok with the camera...are there any tests to do? Many thanks for the guide!

michael		02-Nov-2009 13:36
Please help. Im really struggling. All has gone fantastic until it has come to putting the iris back into the lens fitting. I am not using the tool suggested, i am using the crutch foot to rest the iris casing on, whiclt lowering the lens casing over it. I turn it over keeping pressure applied, remove the crutch foot so i have acces to be able to put the circular pin back in place...but everytime i have carried out this proceedur, the irs blades seem to get knocked out of the iris casing, causing the blades to come out of their 'rails' meaning i have to start over again. Its happening everytime, so wondering where i am going wrong?! How does the iris with the sticky tape have an adnatage over what i am doing? as i cant see how it can?

Matt Craig		29-Oct-2009 04:08
Thank you for the guide. While my experience was a little different, this really helped me a lot in taking apart, cleaning (oily iris), and reassembling my old Minolta 50mm f/1.4. It's great to have it working well. For the longest time I simply thought the old lens was incompatible with the new Sony DSLRs. By the way, I found pulling the blades off the iris and cleaning them individually to work well, and reassembly was easy. The Iris Assembly slide was very useful for this. I believe that tiny contact spring was what caused the most consternation. I didn't lose it, but it wasn't too keen to stay in place while putting the rear trim plate back on.

philipp		23-Oct-2009 21:13
Thanks a lot for your guide!

Wolfram		28-Jun-2009 11:58
Attempt with AF 50/1.7 RS Last night I tried to fix the oily blades of an AF 50/1.7 RS, thus the newer and "restyled" version. Unfortunatly, I did not succeed for two reasons. This first reason was up to my inability and lack of the right tools to remove the snap ring. Someone here suggested to use a safety pen instead of the depicted dental tool, but I am hesitant to sacrifice one of those at the moment. Thus, I could not remove the iris assembly completely, and I decided to clean the the whole inner helicoid as others did successfully according to their reports here. However, now the changed design of the RS version came into play. To clean the inner helicoid, one has to open the lens from the rear and to remove the rear lens assembly. According to the drawings and pictures here, the rear lens element is attached with three screws to the inner helicoid. But not in the RS version. Here, the rear lens assembly and the inner helicoid form one single plastic part. According to this finding, one really has to remove the snap ring in the RS version to get full access to the iris from both sides, and the shortcut of cleaning the whole inner helicoid incl. the still attached iris (but without the rear lens element) does not work any longer... :-( And one comment to the reassembly of the rear lens part: One really has to be careful to reassemble the lens in the right way such that the focus still works over the whole distance range (incl. its ADI interpretation by modern camera bodies). For this purpose, one has to insert the inner helicoid into the outer helicoid in exactly the right orientation before screwing it in again. Nevertheless, thank you very much for this detailed documentation. Maybe I will find the right tool to remove the snap ring. Wolfram

Brad		20-Apr-2009 13:51
I used this to repair the oily blades on my 50mm f1.7. I couldn't get the snap ring out, so I just put the whole tube with the iris and helicoid still in it into warm soapy water. I jiggled the iris open and shut quickly, and gently brushed it with an old lens brush when it was shut. Then I did the same thing in clean water to rinse it, then did it again in alcohol to dissolve the water and evaporate quickly. Then I used a hair drier on low to dry everything. I figured that at worst I would also strip the grease off the helicoid threads and have to re-grease that somehow, but because I didn't move it or scrub it with a brush doing what I did, the grease was still there. I figure that what I did may have actually removed a bit of the "excess" grease that caused the problem to begin with, if it removed any of the helicoil grease at all. I could see a definite film of grease on the threads before I reassembled, and the operation was smooth. If the focus stiffens up, I'll just take it back apart and re-grease the threads, but I don't think it will. It's been over a week now, and it still works perfectly. Thank you for the guide. It helped a lot. Darren and anyone else wondering about the screw size.... go to the hardware store and get a set of "jeweler's" screwdrivers. Use the largest one that will fit into the screw head and you shouldn't have any problem. None of the screws seem to be tight enough for you to destroy the head. The most likely things to destroy a screw head in my experience is cheap screws (the ones in this lens seem pretty good), a screw frozen in place by corrosion (not likely in properly cared for lenses... if it's there, you'd likely have other problems than just the iris), and using screwdrivers that are too small for the screw (they don't get the proper grip). Press down hard when you are turning hard to make sure the driver doesn't slip up in the slot. If it stays firmly in the bottom of the slot, you won't damage the screw.

Mark		10-Feb-2009 00:38
This this repair for an oily lens last night. What great information. My old 1.7 50mm lens works perfectly now! I used a safety pen adn bent the tip instead of using a dental tool. Worked with no problems at all!

Aaron		09-Nov-2008 22:45
I performed this repair (oily iris & oil drops on interior lens) on a Minolta 28mm 2.8f. It was almost identical with the following exceptions: the lens assemblies are screwed in and no retainer ring. Took me about 2 hours, most of which was reassembling the iris and getting it back in. One thing, to remove the front trim ring, I used two rubber bands under each thumb, pushing in opposite directions. Made my $40 ebay purchase a good-as-new lens. Thanks a bunch. Thanks, thanks, thanks.

Aaron		30-Oct-2008 16:02
I was curious, are any of you concerned about or taking any anti-dust measures?

Matt Staben		18-Sep-2008 07:32
Thank you Pete for your instructions, I was able to restore to perfect working condition a the f1.7 50mm. I have three suggestions: 1) use a ball of rubber bands for the crutch. If you collect (or save as it were) a set of rubber band balls, you will have different sized crutches. 2) Use fingernail polish to mark the position of the iris assembly retainer, it will stick around even if you clean out the inside of the barrel. 3) A plastic film canister with mailing tape wrapped around it backwards works well for holding the iris assembly as it is pushed up into the barrel. The film canister is small enough so that you will have room to hold in the iris assembly as the retaining ring is replaced.

darren		05-Aug-2008 15:20
great tutorial. could you give me an idea of the sizes of screwdriver required for a project like this, i dont want to fail at the first destroyed screwhead!! thanks.

Serban		30-Jun-2008 05:48
Excellent guide, wonderful website. My 50mm f/1.7 works better than ever after it had the aperture blades cleaned. Thank you!

Bob		01-Mar-2008 08:21
Pete Really useful site. I have a Maxxum 50mm f/1.7 which I ahve stripped as per your help. I now find that the middle helicoid has sufffered damage and needs replacing. Do you know of any suppliers who can provide spare parts? I'm in the UK but would appreciate names of any supplier worldwide. Regards Bob

Bob		01-Mar-2008 08:20
Pete Really useful site. I have a Maxxum 50mm f/1.7 which I ahve stripped as per your help. I now find that the middle helicoid has sufffered damage and needs replacing. Do you know of any suppliers who can provide spare parts? I'm in the UK but would appreciate names of any supplier worldwide. Regards Bob

Bob		01-Mar-2008 08:19
Pete Really useful site. I have a Maxxum 50mm f/1.7 which I ahve stripped as per your help. I now find that the middle helicoid has sufffered damage and needs replacing. Do you know of any suppliers who can provide spare parts? I'm in the UK but would appreciate names of any supplier worldwide. Regards Bob

Pete Ganzel		16-Feb-2008 18:22
John: My bet is you haven't really cleaned off all the oil from the blades. Alcohol will dissolve a bit but in my experience you need to emulsify with detergent and rinse with water...lots of it. The blades are steel and they can be magnetized by tools that are magnetized and they will also stick together a little for this reason. Pete

John Askham		15-Feb-2008 22:07
I have been through this process a couple of times now using alcohol to "de-grease" the blades. I'm not convinced it is oil that is stopping them but possibly water. I have noticed a couple of times after going from the cold outside to inside and not using the lens for a day has allowed the iris to stick. But on warming up the blades have freed themselves. Not saying that the original problem isn't oil/grease but if it gums up again I don't see where it has come from. Anyway these are just thoughts as I have no objective evidence to back these thoughts up.

Malcolm Turner		23-Sep-2007 23:34
Pete, many thanks for this very detailed guide. It seems to be such a common problem with this lens (50mm 1.7). Just like Reiner, I couldn't move the snap ring so removed the two guides and unscrewed the whole unit. Cleaned and dried it with a hairdryer and appears perfect. On a very quick test, focus seems o.k. and exposures seem consistent. It's the first time I've stripped down something this small and some of the smaller screws were great fun with my varifocal glasses!

Reiner from Switzerland		04-Jul-2007 22:28
Many thanks to Pete for this superb gallery. Took me 2 hours for my 50/1.4, I guess 30 mins will be sufficient for the next lens of this type. I think the job is less scary than it looks from the pictures. I tried a simplified, home-grown version of cleaning the iris: I did not go through the tricky step of removing the iris assembly from the inner tube (14 Mark 1074 and Snap Ring) but removed the two brackets that guide the inner tube (visible on 14 Helicoid 1081 and on Iris Removal). The aluminium tube with the iris installed may be screwed out to the front of the lens now. I cleaned the tube with the iris installed in a bath of dish liquid then clean water then drying with a hairdryer. Actuating the iris some minutes when bathing and drying did the job. Using alcohol will be even better. I'm wondering if this sub-perfect cleaning method will be a permanent solution or if the blades get stuck again or take on some rust... but the pictures of the removed iris didn't convince me the iris is easier to clean or to dry when removed from the tube. It would be fun doing it a second time anyway and I'm looking forward to the next challenge: an oily 24-85 !

Evil EMT		11-Apr-2007 03:27
I knew that flea-bay deal was too good to be true: "clean and oil free" indeed! My 50/1.7 now has a functioning iris finally. 2.5 hours start to finish - never even thought about what makes a lense work before; I'm handy but a complete novice. Thanks for the wonderful guide! May I suggest a few pictures showing the suggested markings for ease of reassembly? Now if I could just find some info on how to stop a Maxxum AF 100-200 f/4.5 from creeping out towards 200mm all the time thanks to gravity...

David Cram		01-Apr-2007 11:46
Thanks again for this guide. Just saved myself $100 on sending my KM 50mm f/1.4 off to get oily iris blades cleaned!

D Timoce		08-Feb-2007 23:37
Well, i've cleaned the oily blades of a 50mm 1.7 too, and thanks to your detailed step-by-step description of the process all went well. As for placing the iris in place, i've used a film box; works quite well. Thank you

Alexander Schrab		07-Feb-2007 06:00
Thanks for a good visual guide. I did manage to break my ground spring, but I am crossing my fingers it won't cause problems. Anyhow, a small tip would be posting detailed close ups on the correct rotation of the aperature blade ring and the actuator. The ring is not quite rotational symmetrical and the correct assembly could be shown with pictures.

Erik Pronske, M.D.		01-Feb-2007 03:43
Thank you for posting this information. I have a twenty year old 50mm 1.7 that I bought with my Maxxum 7000 in 1987. The aperture blades wouldn't close down properly. The camera repair store said it would have to be sent to Sony to get it fixed and would cost over $200 (for a lens that isn't worth that much). I took it apart according to these instructions, cleaned the aperture blades and it is now functioning as good as new! I really like this lens and now I have it back. Thanks, Erik

Jeff		28-Dec-2006 03:11
Thanks for the great instructions, I fixed the oily blades on my 50 1.7. It turned a bad ebay deal into a great lens.

Markus		20-Dec-2006 02:37
Thanks! After finding this guide online I was encouraged to clean the aperture blades on a Minolta 35mm f/2.8 MC Rokkor HG that somebody sold me on ebay without mentioning the oily aperture blades. It took me about 4 hours to take the lens apart, clean the aperture blades and the rest of the lens, and put it back together. The hardest part was to get it to focus correctly again, but you can adjust that without disassembling the front of the lens again. Also, putting the spring that makes the aperture ring click back in was a major pain. The trick is focusing the lens at a short distance, and then putting the back of the lens on at a slight angle to squish the spring (when you take such a lens apart you'll know what I am talking about). I would definitely do this again!

briseyw		07-Aug-2006 13:00
Thanks Pete Although I wasn't brave enough to takle it myself, a very good friend followed your instructions to the letter and now my 'oily iris' is working perfectly.

Pete Ganzel		02-Jun-2006 02:46
Hello "guest" The only place that lubrication is used on the lens is on the helicoid and on the focus drive gear train. I wouldn't use lubrication of any kind on the aperture mechanism. Likely the spring is deformed or the little "arch" that it fits in is binding. You might try to bend that sheet metal a little. The "aperture spring 2486" photo shows this guide on the inside edge of the spring. Pete

Bj�rn Simonson		01-Jun-2006 19:11
Thanks for a great guide, it helped fix my 50/1.7. Now I might have a 50/1.4 RS with oily blades coming in, any difference picking that apart compared to the non-RS versions? Best Regards!

guest		01-Jun-2006 14:13
HI, thanks for the tutorial. I have a problem though, I think the aperture spring assembly is a bit jerky. Would it be an idea to spray some silicon spray in there??

Sam		13-May-2006 15:33
Many thanks for this guide. I managed to (just about) fix an oily 28mm f2.8 lens using these instructions. I think the iris could still be a bit snappier than it is and I did lose the ground spring, but at least it works! I got into a bit of a tangle with the focussing as I hadn't been careful enough about marking where things matched up. A bit of tinkering and it seems OK now. Cheers! Sam

Bob		13-May-2006 15:33
Had "the pleasure" to try this method because somebody sold me an oily 50 F/1.7 on ebay without mentioning it was an "out of order" one... Thank you to have taken time to post pictures and explain the "tricks" Do not be afraid to unmount the iris and take the blades apart. It is really easy to mount it again, do not worry... As I do not have a ultrasonic cleaner, I simply used 96% alcool and let the blades "take a bath" for about 15 minutes. Now I am looking forward to take some pictures with this nice lens !

Mal		01-May-2006 03:17
Absolutely the most informative site on Minolta lenses. I had tried to get to the iris but could not get the trim ring out. The crutch tip worked so well I couldn't believe it. With your guidance I removed the iris mechanism and placed it in a small plastic jar of alcohol. I closed its top and placed the whole jar into an ultrasonic cleaner. In that way the water in the ultrasinic fluid would not get to the steel blades of the iris - possibly resulting in rust at a later time. Then I also used Q tips to clean the oil that was all over the place. Thanks again for your devotion to detail.

Ruud v. Veen		02-Mar-2006 21:47
Thanks, Your wonderful description made it possible to succesfully clean the oily iris. You�ve made a stressful day in a beautiful one. :) Thanks

George		04-Jan-2006 20:04
Hey!Thanks big time! Glad you took the time to post this in such detail. I Just did my Minolta 28mm F2.8. The Iris was sticking loaded up with grease and the lens was useless. I did lose the iris blades and it did take some time to get them back in there place the right way but it was well worth it.All and all it was much easer then the 50mm 1.7 to do much less to have to take apart. If anyone out there has a 28mm F:2.8 they need to do all I can say is just do it! Also I found after doing it if you use two way tape on the end of a round spool the right size there is no need to take the back of the lens apart.Jus make sure you turn the lens over before you remove the iris. But what ever way you decide to do it it's easy.I also decided to place the lenses in the camera bag with the back face down this may buy a bit more time with keeping the iris grease free. Thanks Again! George in New Hampshire

Gene Nichols		13-Nov-2005 19:16
Awesome! I have a sticky aperture on my 50/2.8 macro. Using your instructions I'm going to give it a shot. Any major differences in the 50 and 50 macro? Thanks! Gene

Rich		15-Jun-2005 19:50
Great site! I was able to disassemble my Maxxum 28mm f/2.8 using the 50mm as a guide. Quite similar internally. I had an oily aperture that is now quite snappy. Thanks!

click on thumbnails for full image