Repair/Adjust/Clean Canon 17-55mm F/2.8 - Dropped and Slipping Focus

I dropped my main lens, the famous Canon 17-55mm f/2.8 IS, and broke the focus mechanism. Af wouldn't work at all, and the manual focus ring did nothing.

Repair costs are said to be very expensive, so I decided to accept the risks (as you will too if you choose to open your lens) and try it myself.

This instructable also tells you how to stop that annoying focus ring slip, as there is an adjustment inside.

Enjoy

Step 1:

Unscrew the 4 main screws, then the 2 tiny ones indicated by the red arrows.

Step 2:

Unclip at least 2 of the 4 plastic tabs underneath the steel lens mount, indicated by the green arrows. Be careful not to pull too hard on the ribbon cable connecting the electronics terminals.

This releases the plastic ring insert, which allows the terminal block to be released.

This will expose the circuit board and next layer.

Step 3:

Unscrew the small screw that secures the circuit board in place, and carefully unplug the ribbon cable as indicated. It just pulls out with moderate force.

Step 4:

Lift the top housing up vertically to remove. Be careful not to snag any other ribbon cables.

Step 5:

Lift the manual focus ring off.

Step 6: Keep It Tidy and in Order

Keeping your workspce tidy will help you with re-assembly. Also, laying out all the parts in the same order you remove them will save you time. Try to keep the sets of screws separate from each other, and with their relevant parts.

Step 7:

Undo the clips on the other ribbon cables. Do this with a very fine slotted screwdriver, or an exacto knife, as shown in the picture. The clips are hinged, and need to be lifted up to release the ribbon cable.

Do not pull the cable with any force. If it does'nt almost fall out, it isn't unclipped properly.

Step 8:

Undo the 6 screws marked with the green arrows. Then carefully lift the ribbon cable off the black plastic frame. It is adhered with double sided tape. Be careful not to kink it or yank it.

Step 9:

Lift the black plastic frame off, carefully freeing the ribbon cables as you do.

Step 10: The USM Focus Tension Assembly

The green arrow in the first picture shows the wave spring that keeps the USM motor under pressure against the full-time manual focus assembly. When this becomes weak, or experiences a jolt from a fall, it might not be putting enough pressure on the assembly to keep the MF ring engaged. The next step shows how to adjust this.

Step 11: Adjust the Manual Focus Ring Pressure

The green arrow indicates the flite that a tab on the silver steel ring screws into. From the factory, mine was about halfway along this flite.

After the fall, the blue loctite had released, allowing slop in the assembly, and causing the MF mechanism to not press hard enough to engage the focus mechanism.

Turn the Steel ring clockwise as indicated to increase the pressure on the wave washer, and the whole AF/MF assembly. You may not need to turn it all the way into it's thead, so test to see if you have enough pressure by replacing the MF ring and checking if it turns the focus mechanism. Then re-apply some quality loctite, or medium superglue. I used a toothpick to apply the super glue. It doesn't need much, as all it is doing is stopping th steel ring from unscrewing.

If you only needed to adjust the MF due to the focus ring slipping, then at this point you can re-assemble everything in the reverse order. If you want to also clean the front element, skip to the 2nd last step.

Step 12: Continue Disassembly to Make Repairs

Unscrew the 3 screws indicated by the green arrows, then lift the lens out. When replacing this lens, you must be careful to keep the black ribbon cable out of the way so it doesn't get pinched, and carefully align the lens with the plastic pins. It only fits in one way, so be careful not to force it.

Obviously, you should clean the elements as you re-assemble. This is a quote from https://www.instructables.com/id/Using-Ultra-Fast-Lenses-on-DSLR-Cameras/step2/Clean-It/

"Clean the glass by first giving a few puffs from a blower to remove dust (which might otherwise scratch the elements). If there are greasy fingerprints, use lens cleaning wipes or a swab moistened with alcohol to remove them. I like to do final touch-up using a lenspen.
Through all that, you should never have the lens elements or body wet -- using too much of any liquid can allow that liquid to seep inside the lens."

I suggest you do your own research on lens cleaning before attempting anything yourself. You can ruin a lens by using the wrong method.

Step 13:

Unscrew the 3 screws indicated by the arrows in the first image, then carefully lift the main housing up vertically, and slowly, making sure you don't catch any rippon cables.You should not need to use force. As you can see in the second image, 2 ribbon cables stay in the other piece.

Step 14: The Repair

The red box indicates the part that was damaged in the fall. The left hand side of the plastic tab was broken off. Fortunately, it fell out of the lens as I disassembled it. I glued it in with some quality medium superglue (CA), then waited for a couple of hours to let it flash off completely. I didn't want any CA fumes damaging my glass.

The second image shows the metal tab that engages with the plastic part that broke. When you re-assemble, ensure this is engaged again.

Step 15: Re-assembly

The other side has the focus actuator tab. It must engage with the focus element. Both are indicated with green arrows.

Step 16: Clean the Front Element

NOTE - You do not need to disassemble the whole lens to do this. You can start this whole instructable from this step if all you need to do is clean the front element.

Use something fine to catch the edge of the decorative ring with the writing on it in the front of the lens. It is secured with double sided tape.

Someone suggested using a toothpick. I think it's a safer option than what I used. It's up to you.

Before unscrewing the 3 screws, mark from the lens carrier to the threaded filter ring to ensure correct alignment upon re-assembly. The lens is NOT symmetrical and can fit back in other incorrect positions.

This is a quote from https://www.instructables.com/id/Using-Ultra-Fast-Lenses-on-DSLR-Cameras/step2/Clean-It/

"Clean the glass by first giving a few puffs from a blower to remove dust (which might otherwise scratch the elements). If there are greasy fingerprints, use lens cleaning wipes or a swab moistened with alcohol to remove them. I like to do final touch-up using a lenspen.
Through all that, you should never have the lens elements or body wet -- using too much of any liquid can allow that liquid to seep inside the lens."

I suggest you Do Your Own Research on lens cleaning before attempting anything yourself. You can ruin a lens by using the wrong method.

Now, re-assemble everything in the reverse order. and you're done!