Canon Lens Repair Manual 70-200
You probably shouldn’t read this article unless you’ve at least skimmed through. To summarize, we had a that had been dropped and no longer would focus. We tore it down both to see if we could repair it and to see what-all was up inside there. In the first part, we did the initial disassembly of the major components and a complete disassembly of the back (mount) half of the lens.
We found a few surprises and some different ways of doing things. But we didn’t find the problem with the lens. The Rest of the TeardownSo after a snack break and some more caffeine, we tackled dissecting the front half of the lens. You can see the ring on top, with the black plastic zoom-link ring right underneath it (you can see a metal zoom key peaking out above it on the side away from Aaron’s hand). Lensrentals.com, 2017Two holes on the opposite side were bent upward slightly. This plate is attaching two heavy lens-halves, and it’s fairly thin aluminum (or aluminium, if you have a non-U.
The picture below shows the thickness of the plate through one of the screw holes; we measured it as 1.2mm. That might be thick enough if it was stainless steel or titanium (I’m no materials engineer) but this is aluminum; we could bend it with our hands. If the screw holes were bent, we had to assume the rim of the plate was also.
Lensrentals.com, 2016Some engineer with way more math than me obviously calculated that this plate was thick enough to hold the mass of the two lens-halves together. But I’m damn sure he didn’t consider the part about force and velocity squared and all, because this plate, the one I can bend in my hands, is not going to resist much force. At all.While the plate did hold the lens together just fine despite these bends, we’re obviously concerned that the bent plate could affect the lens optically. There are strong elements on either side of that connection and a tilt of a few microns could cause some significant optical disturbance.Anyway, while we aren’t happy about the plate, it certainly wasn’t preventing the lens from focusing, so we continued on with our disassembly after getting the parts department to order a replacement plate.With the connecting ring out of the way, we can access the keys to remove the inner ring linking the zoom barrel you turn to the zoom mechanism inside the lens.
Lensrentals.com, 2017After that we spent 4 or 5 minutes colorfully discussing the parentage of the lens’ mechanical designer who saw fit to make the stacking of the ring USM an integral part of the disassembly. In a nice lens, designed with the thought that someone might actually repair it some day, you take out a couple of screws and take off the ring motor assembly.
In this lens we (I’m using the Royal “We” here; Aaron does all the hard stuff) have to take the USM apart piece by piece to get further into the lens.So after carefully marking the alignment, Aaron started counting turns to remove the pressure plate (because it has to go back to exactly the same point). Lensrentals.com, 2017Oh, Yeah. About that Focusing ProblemAt this point we we had one piece left – the front group barrel assembly you can see in the picture above. This contained some zoom elements in the smaller part of the barrel, and the front focusing group in the larger part. Reaching through the slots with forceps we could tell that the focusing group was still grinding when we moved it up and down, with a lot of resistance.
We could also see it was slightly tilted. This usually means a roller or cam was broken or bent.We removed all 6 rollers, which by the way are some really robust, ball bearing containing, pieces of engineering. They were all working fine and even with them out of place the focusing groups was still scraping when we tried to move it. Lensrentals.com, 2017We decided to put the lens back together, bite the bullet and see if the service center could repair it. But being a suspicious person by nature I did some checking first and found out, in typical Sony fashion, this entire assembly was considered a single part. So if we sent it in they would replace this entire assembly at a repair cost of slightly more than half the price of a new lens. Needless to say, we switched into nothing-to-lose mode and went back to looking for a way into this assembly.We could have removed the zoom groups from the small end, but that wasn’t going to give us access to the larger focusing area.
Canon 70 200 Comparison
The only way in appeared to be by removing the second group, which was held in place with both a spanner ring and also with adjustable collars through the side of the lens. Lensrentals.com, 2017I won’t bore you with reassembly, except to add that we discovered that the spanner ring over the ball-bearings is like that for a good reason. Tightening the spanner compresses this bottom spring and you can ‘dial in’ the proper amount of tension for the focusing element. Too loose and it rattles around a bit. Too tight and it gets a little resistance to sliding up and down. It’s an interesting arrangement.But if this spring comes out of position with any regularity the repair is going to be a royal PIA.
This is just one dropped lens so let’s not run screaming about what may or may not happen again. We may never see this again.
Only time, and a few more dropped lenses, will tell.Usually I end these posts by saying we’ve got the lens reassembled and it’s back in stock now. In this case we’ll wait for a new connecting plate, and then optically test and adjust the lens after final assembly, and really, really carefully check it before putting it back in stock. But we did reassemble it with the old connection plate to make sure the autofocus system worked properly. So What Did We Learn Today?Well, first and foremost, that lens repair is a miserable way to make a living.
How To Clean Canon 70 200 Lens
And lens repair on this lens will be miserabler than most.Second, we learned that dropping your lens is bad, so don’t do that.Third, 1mm thick aluminum plates maybe shouldn’t be used to hold two halves of a heavy lens together. And yes, Fanboy, I know the Sony engineers are smarter than I am. They designed 962 really great parts that I couldn’t have designed. But it doesn’t take massive engineering knowledge to figure out that the thinnest piece of soft metal shouldn’t hold the two biggest pieces together.And finally, we learned there’s some really elegant and complex engineering in the. There’s also some engineering that just seems complex. It may be far more awesome than I realize and I’m just missing the point. Or not.I’ll repeat what I say all the time: Sony is trying a lot of new things; that’s how you advance. I completely admire the risk taking and efforts to try new things when most manufacturers are just fine-tuning what already is.
Some of these new things turn out to be awesome, some don’t. It’s just as important to identify which new things are not better, or not even adequate, as it is to identify when the new thing is a dramatic improvement.Roger Cicala and Aaron CloszLensrentals.comMarch, 2017. I dropped my 70-200 F2.8, mounted to my A9 from hip-height onto a grass playing field.I missed the holster as I swapped between 70-200 and 24-70.The lens mount on the 70-200 bent enough that it would not attach to my A7r III very easily.On closer inspection, the mount was clearly deformed at two of the mount screws.The cost to repair?$700!Sorry, but a Canon or Nikon 70-200 F2.8 is a professional grade lens. The Sony is not.The lens mount is 1.2mm aluminum as Roger found and this could be bent by hand pressure. I grew up on a farm and in the 60s we had a pair of government surplus Cat D6s bought in the 1950s. We would only shut them off to change the oil because they were such a pain to start.
Canon 70-200 Zoom Ring Stuck
Start the pony engine with a rope then use that to start the D6, hate those pony engines. You could rebuild them in the field, in a tent on a tarp of course. Totally unkillable tractors, we kept using them until 2000 or so when we sold them with the farm. On the other hand just Google Caterpillar C13 and C15 to see how far the mighty have fallen. Mercedes Benz in the 1960s and 1970s was the same way, We drove ours for 700,000 miles until a tree fell on it. Now they realize that making things to last forever is bad business. If you want machinery that will just keep running until, well whatever wipes humanity from the face of the earth, the old two cylinder John Deers are what you want.
If someone made cameras like that, well back then lots of companies made cameras like that notably Leica, Nikon, Linhoff, and Graflex before that sewing machine company bought them. Zeiss notably epoxied their cameras together to prevent them from being serviced. Roger you seem to have quite high confidence in the claim of customer that he dropped this lens from a height of only two feet.This leads you to a criticism of sony engineers that the the lens is not robustly designed against general rough handling that it might see in practice. Yet is there any evidence that the customer was being honest about how the damage was sustained? Is it less likely that the team of engineers who successfully design this complex mechanical assembly did not think of a seemingly obvious parameter when specifying the plate thickness?Who would you give the benefit of doubt in this scenario – a random customer who damaged the lens or a team of specialised engineers responsible for complex design scenarios?
You seem to think the engineers made some obvious oversights based on the word of this customer.To me as mechanical engineer the internal assembly looks like it is possibly intentionally designed to localise plastic deformation upon overloading to that aluminium plate. If you overload the lens assembly sufficiently (such as due to large load on account of a fall) some material will eventually plastically deform and result in permanent deformation; if the lens assembly is uniformly stiff it will be difficult to localise that deformation to a predictable location (where a deformed part of the assembly could be easily replaced). However, If a section of the assembly in the load path is markedly less stiff, then the deformation will be predictably localised to that location.i.e. In a replaceable component. The fact that a lot of glue is also used to seal lens elements also suggest robustness against possibly decentering.Whether this a concentrated failure point design is the best approach for such a telephoto zoom lens I am not sure.
But it seems somewhat arrogant of you to imply the engineers do not know what they are doing and did not think of this detail. To me it seems they did think of it when specifying the design.If the plate is in fact the aluminium plate is not stiff enough to avoid deformation under general rough handling, replacing it with stainless steel with the same geometry would make it about 3 times stiffer so is an easy design correction. Well, Sony are not alone to not consider heavy mechanical shock in lens design. I had my Tamron 24-70/2.8 break right through in the middle after taking a fall of around 2.5m inside the photo bag, mounted to the camera.
And I think they’re right. As a lens maker you can rightfully assume that photographic equipment is well cared for and protected from mechanical harm. And you’ll admit that the little aluminium ring is a good indicator for a repair mechanic about what has happened to a lens. I’ll even venture saying that little piece is the “canary bird” of this lens.
Had it been any sturdier, the lens would have been broken just as good with much less indication as to what has happened. “I think that one key difference is that people who buy serious construction equipment tend to be much more knowledgeable about what they’re getting than photographers”Hahahaha. Just snorted coffee thru my nose. Most construction types have no idea and abuse their equipment until if fails.
I know, I ran a cstr biz for 20+ years. The good news is good equipment is built with that sort of ignorance in mind – so companies (like CAT) tend to overdesign things. In the good old days, Terex (owned by GM at the time) used to produce the lamest junk you’d ever see.
It would “look” like a CAT, but run like and last like it was a Yugo. The deformed aluminum piece may have been a ‘sacrifice’ design, to prevent other parts from impact failure.it may have been a specification error, as aluminum alloys comes in varying types as well, some softer, some a tad more rigid, even brittle.all that silicone?, seems like a curing process was used as most silicone takes a good day or so to become fixed, maybe some cute new light curing stuff that polymerizes in a few seconds?as for the little springy thing that came out of place? Shame shame shame on sony!know any good shops that do mirror refurbishing? Ive got a few cat’s that have seen too much moisture over the years. It is funny reading all comments below that people is expecting for a lens being made mainly from glass and ligthweigth materials to be working normally after a drop of 2-3 feet When lenses are heavy (Zeiss, new Sigma 85mm Art) everyone is complaining about the size, weigth and bla, bla, bla when manufacturers use ligther metals (eg: Aluminum) people complains about it bending under pressure. HumAgain, lenses are not meant to be dropped. If they do, things will brake.
I am a Nikon user but I believe Sony´s engineers weren`t using a “crash test” approach when designing this lens. Can someone please explain exactly how the damage to the aluminium plate was caused.“When we looked at the attachment plate above more carefully, it became apparent that two of the screw holes on one side of the lens were bent downward slightly.”Actually the bending you showed in the photo was upward ie towards the screw heads. I know it’s mentioned that on the the holes opposite the bending is in the opposite direction, I am aware that the lens has been reassembled but i would’ve like to see the other holes to understand the forces involved.The aluminium plate was screwed flash against the lens with a shim between the two surface. In the assembled state the forces that bent the plate would have had to go through the shim. Also any forces, due to the front part of the lens being knocked against something, would be taken up by to 4 outer screws and not the inner 8 screws. I am no lens specialist, but a 1.2mm ring made out of aluminium seems to be a design error – and/or Sony have had missed the material stress into here, in terms of a 2ft drop.
Stainless steel would have been also being cheaper perhaps then alu, i’d guess. It’ll be better for Sony to design this part out of steel then. Again, thanks a lot for this way interesting Lens Tear-down, Roger.For instance, i’ve dropped last december my (way old) EOS 20D, whileas taking pictures. The attached Lens was thankfully a cheap one, and got a stuck, defective zoom mechanism, but still took pictures, as a fixed “prime” now being stuck at around 35mm setting. Whileas the Canon Body only had a small scratch at the left corner, barely noticeable, it wasn’t a drop from 2 ft, but when i was standing and taking pictures at the lake here, i’ve slipped onto the mud, and felt backwards, whileas having the DSLR touching the ground with the bottom and not that heavy, the DSLR and lens came horizontal to the ground with my arm, and the 20D still shoots very well. But something into the Lens then prevented the Zoom mechanism from functioning, and when i slightly shake the setup, something is rattling inside the Lensthis is the 1st ever lens i’ve broken since 1987 for real, whileas being physical from apperance intact.
Hello everybody! I recently bought the old very old Canon 70-200 2.8 non is L, used and damaged, falling was it's problem.
Both rings were stuck because the lens did bend a little and the index barrel (I believed is it's name, the one in the middle of both rings) did crack and stuck them hard. I tested the lens before opening to check for AF, it worked but the focus seemed out of range, could be because something was loose inside I though. To repair it's visible problems I glued the the cracked barrel and sand down to live the rings rotate freely. It worked and all mechanisms work OK because the bend did not affect enough to stuck the insides.
After all this, the assemble went well, but, it keeps focusing, out of range, as it try to focus, the AF does its course, from 1,5m to infinity, but it looks like if it came a little bit more, it would focus. It's not focusing Macro either. So I believe something was bad assembled before it arrived to my hands as I did the exact same steps reversed to disassemble.
I think it can be some lens on backwards (weird but it happened to me one time on an old lens maintenance and the diagnostic was the same), some lens missing (one of the lens groups misses one lens, I don't even know if it is possible) or anything else. I have now this brick on my desk!
Did anyone ever passed something like this? Does anyone know something that I can be possibly missing? Please help if you have any ideas!
Sorry for my bad English and good 2019! Regards, Nuno Rodrigues. Fsong00, hello!
It all works! The rings turn, the autofocus does the all path from 1.5m to infinity, and the camera completely works with the lens. The issue, seems to be the range of the focus. I bet on some hypothesis, lens on backwards, or the previous owner who tried to fix it, did replace some lens group for some compatible but not the right one! I tried to mount all the groups of lenses on various positions, but it only assembles on the right one I guess, it's impossible to mount it wrong? What do you think? From what you described:' To repair it's visible problems I glued the the cracked barrel and sand down to live the rings rotate freely.
It worked and all mechanisms work OK because the bend did not affect enough to stuck the insides.' It looks to me the previous owner did not try to fix it. Or not try to replace the backward lens groups with some compatible version.What you got should be all the original.
Usually, the lens track for focus groups to be on track with the middle barrel; then the middle barrel on track with the outside zoom barrel should be unique and no ambiguous. You never know what the previous owner did with the lens to cause those out of track problem. I am very happy to hear by adjusting the mechanical track and you fixed the problem.