Canon 100-300mm f5.6 Macro Autofocus Repair

[@robinlee5744]

I wish i was brave enough to open a lens. Even though I've been in IT all my life and have built many computers from the ground up. I do like your video and I found it because I have a USM 100-300mm EF zoom canon who's AF does not work. Takes beautiful pics but. It makes no noise at all. And you said at the end of your tutorial hit you up in the comments and maybe I can send it to you.

[@UltimatePostman]

I would say no noise at all is great, as long as the AF does work. I can give you some info to send it my way, but I make no guarantee that I'll be able to get it back up and running. If it needs parts, you'll have to pay or them, play any shipping costs. If it's the same issue mine had - which was more than likely caused by a drop, should be an easy fix. However, if the internal cables or board is bad, that's another story.

[@robbrown3543]

Hi did you have any luck figuring out how to clean the rear elements? Thanks @@UltimatePostman

[@UltimatePostman]

@@robbrown3543 Althought I have had the lens sitting on my desk the last several months, it has not been on my priority list to clean (and my lens does need to be cleaned). I don't really use this lens much, But as soon as I do a breakdown I will post it. Not sure when though.

[@phatdad7247]

Thank you for the in depth tutorial, I need to repair my 70-210 with the same problem. I purchase the trio, 35-105mm, 70-210 and 100-300mm for my canon 5d mk3

[@UltimatePostman]

Glad to help, and good luck!

[@phatdad7247]

@@UltimatePostmanAll repaired now! Thank you. The only difference with the 70-210 lens, it has 3 screws under the rubber cover but everything else seemed to be the same. 😊👍

[@philip851]

Help me Postman. I have this lens and it works great. However the front element group has fungus. I unscrewed the front circlip and removed the 3 little side screws on the barrel. However the group won't come out. How do I remove the front element?

[@philip851]

Okay managed to take the front element group out, cleaned every surface free of fungus. Now....second group managed to twist off the plastic ring but there are no screws underneath to release the middle element. Which is the one with most fungus on. What is holding it in? How do I proceed?

[@UltimatePostman]

Good to hear with the first cleaning. I still haven't gotten aroudn to pulling it apart yet - it hasn't been a priority since I don't really use the lens, but it'sstill sitting on my desk and is on my list of videos to make.

[@philip851]

@@UltimatePostman That's good to hear..I very much look forward to it as I'm stuck.

[@luluke5403]

Thanks so much for sharing this, which is very helpful. I've tried very hard to find a way to disassemble my 100-300mm f/5.6L lens. The rear group of the lens has got some fungus inside, in that I have no clues of cleaning it. I know the 100-300 and 100-300 L lens share the same optical structure, so you might have an idea of how to disassemble the rear group. Any ideas would be more than welcome.

[@UltimatePostman]

Let me see if I can figure out how to do that. Going from the rear was my initial thought, but then I figured out how to go from the front.

[@zaren2245]

@@UltimatePostman I also have the same problem cleaning the rear lens. Cannot find a good way to open up the rear as it has something connected in the middle. Haha. Seems like this kind of lens is really rare.

[@UltimatePostman]

@@zaren2245 Not sure if it's really a rare lens, or not many people are selling theirs. I definitely don't use it like I thought I would. So if you need assistance trying to open up the real, I can see if I can produce a video on it.

[@mdiazvega]

I got the same problem, my 100-300 L has fungus on the middle and rear groups, I have already take apart almost at the same level than your video, but can't figure how to take the elements out to proper clean

[@philip851]

My beard has grown 6 inches waiting for you.