Fixing the Canon EF 24-70mm f2.8L II from water damage (Updated with pictures of the icebergs)

I was shooting some images of the icebergs on the black sand beach by the Jokulsarlon Glaicer Lagoon, Iceland with a rental EF 24-70mm F2.8L II. Iceland is notorious for being windy, and while I was shooting there was blowing winds carrying ocean spray and water splashes all over me and my camera + lens. Unfortunately, it seemed that sea water got into the lens either from the autofocus switch, the "weather seal", or the extended barrel when you zoom out. After a short while, the lens stopped autofocusing and i got errors about connecting to the camera.

My worst fear happened, i could see the lens soaked with water. I was so focused on composing that i forgot to check the equipment conditions. I immediately disconnected it and let it dry. After a full day of drying, the autofocus failed but i could still use the lens on manual focus. The iris was working fine and i could take a photo no problem.

I explained my case to the shop when i returned the rental but unfortunately a few weeks later after they sent it for repairs (they send it to Canon), Canon replied back that the lens was damaged beyond repair due to sea water and nothing can be done, they will dispose of it and send it to recycling and i would have to pay the full price. I agreed as it was in my possesion anyways but i asked that the lens be returned. So i paid the full price (well luckily it had $500 off promo) and took the lens home. I didnt really mind it as i already had plans on purchasing this lens but what bugged me was how could water damage the lens to the point where it was beyond repair.

I opened the lens and found that the parts affected were only the PCB (later i found some salt stains i the USM motor). I went on ebay and found an original new OEM PCB assembly for this lens for $36 so i grabbed it. Then i got a new USM focusing unit as well on ebay for $90, total with shipping: $140. To my surprise i was able to fully fix it and it works perfectly fine. So i wrote this step by step visual guide on how to fix this lens for any kind of water/focusing damage or just as a general repair guide for this lens. The weather sealing is rather piss-poor, they use gaskets... but if i didnt ask for the lens, this would have been a perfectly salvageable lens gone to recycling and i would pay full price for no lens in return. So i hope this guide will help you fix your lens one day or even show you how to replace critical components.


Step 1 (Instructions for each steps are listed below each image)

Firstly, wash your hands. Next, be calm and patient. These devices are precision devices and you need to be patient. Please ensure you have the required tools as shown above. You dont need to desolder anything. And please for the love of photography and DIY, use magnetic screws. If one screw slips and falls inside the lens assemble, it will be a nightmare to find it. Secondly, PLEASE be very gentle and careful, if something (except Step 5 might require some strength) doesnt come out easily then you are doing something wrong, check all screws were removed or try turning the barrels to a position so it will come off. I apologize i dont know the number for these screwdrivers, its not printed, they come from a set i had a while back. I put a Canadian 10 cent coin to show the sizes you will need.

Step 2

This is what a new autofocus unit looks like. (I forgot to take a photo of the PCB before assembling this guide but you will see it below in other pics).

Step 3

Remove the rubber ring by sliding the flat head screwdriver and pull it off.

Step 4

Remove this screw that holds the position encoder. This is hidden under some tape.

Step 5

The only part that might be fiddly, insert the screwdriver between the contact PCB and this plastic cover, then lever it up gently.

Step 6

Remove that peasant cover that uses no screws... grrrr!

Step 7

Using the smallest phillips screwdriver, remove these two tiny screws first.

Step 8

Remove the 4 screws as shown above.

Step 9

Gently lift off the metal ring, note the "weather seal" gasket will come off as well. Store safely.

Step 10

Gently lift off this plastic cover.

Step 11

This is the PCB board exposed. Dont remove the screw yet!

Step 12

This is nightmare mode and the trickiest part, GENTLY remove these princess ribbon cables. Don't use squeezing tools, you might break it (happened to me in the past) I use this screwdriver trick and gently pull it out perpendicular to the socket. You can use twizzers but make sure the tips are rubber coated.

Step 13

Then remove this screw. Had you removed it first, you could have damaged the princess ribbons since the whole assembly will start moving.

Step 14

Pull out this mofo gently to avoid breaking the princess ribbon cables. (fuck ribbon cables, seriously!)

Step 15

This is where the water got in... Damage is visible, it probably shorted the board's chip. Chuck this piece away. Funny enough, i couldnt find any other places with the salt water, maybe some stains on the USM motor, but i wonder if i really had to change that part.. (Really Canon? This is what you call beyond repairs??!)

Step 16

Once the board is removed, you will find 12 screws in a ring, remove all of them.

Step 17

Gently pull out the top cover barrel, thats where the autofocus switch is. You might have to zoom out completely so it comes off. Leave the part with the metal dip.

Step 18

The USM autofocus unit is exposed. These two screws hold the focusing plate, remove these 2 screws and the plate and install them in the same location on your new autofocus unit.

Step 19

GENTLY pull out the USM autofocus kit. Then chuck it away. (Well, one day i will test it with the new PCB, i have a feeling this part is ok but i wanted to make this lens as new as possible so i thought i would put in a new USM motor and explore this lens for the purpose of this guide. The problem with electronics is that if the motor unit is shorted, it could short the new PCB so i took no risks and changed both.)

Step 20

Put in the new autofocus part. Please pay attention to the metal bar in the autofocus unit and make sure it is to the left-most position in its groove as shown above. When you insert it, it needs to align with the hole in the lens unit as shown above. The autofocus works by moving this bar, which once in the hole, moves the inner lens element to allow for focusing. Simple!

Step 21

This is what it will look like once you assemble teh new USM autofocus unit. Take care of the princess ribbon cables.

Step 22

In case you forgot, please make sure you put the focusing plates back on, else you will have to repeat all above steps again.

Step 23

Put back the top barrel cover, the part that has the autofocus switch. Be careful of hurting the princess ribbon cables.

Step 24

Put the position encoder back in its place and dont forget to put back the tape over it.

Step 25

BEFORE putting the princess ribbon cables back, put the screw in first, this will make sure everything is held securely first.

Step 26

Nightmare mode part 2 - Princess Ribbon insertion. Most of these cables have an extruded part behind the contacts, you can use a screwdriver tip to push each one in one side at a time or use twizzers to push both sides in at the same time.

Step 27

Put back the plastic cover, make sure the line aligns with 24mm.

Step 28

Put the "weather seal" gasket back on.

Step 29

Insert the 4 screws first before the 2 tiny ones.

Step 30

Insert the tiny screws and make sure they are securing the contact board to the metal ring.

Step Finale

Put back the peasant plastic cover and test the lens! Phew! We are done and we have a perfectly (electronically new) revived EF24-70mm f2.8L II :)

Testing autofocus gif

Gif showing my tests after changing the parts. Hope you this guide and find it useful! Leave me a note if you have a question.

Here is a link to a RAW file i took today after fixing this lens. No optical errors found, as we didnt go into the optics, which were fine and pretty well protected. Position encoder wroked fine, lens is recognised, exif is stored. Mission successful! Download test RAW file.

Bonus - Some pictures taken from that spot


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