EF 24-105mm lens repair - screws missing!

Hello all

Apologies for the somewhat long first post, but I am looking for some fairly specific help. I was recently gifted a 24-105mm EF lens which soon developed a fault with the aperture flex cable. I don't have a lot of spare cash at the moment to buy a new lens and I understand the lens is fairly old for repair shops to touch now, so I did some research and found it to be a fairly common issue. I purchased a new flex cable and found a good YouTube video on replacing the cable and set to work. Unfortunately when I got to the aperture flex cable and attempted to replace it, the plastic bit which the cable attaches to (shutter unit?) was also faulty (one of the pins to solder the cable to was down to a single strand of copper and came apart in my hands).

Rather than give up on it, I ordered a new part which included the flex cable already attached. As it took a while to arrive I very carefully took note of the screws I had and the order in which I had removed them, took a photo of them and then carefully packed the whole lot away until the parts arrived.

Fast forward to this morning when I finally had both the parts and the time to fix the lens, only I didn't get very far before realising I seem to be short 3 screws. They are the screws which sit inside the white plastic rings, seen being put in at time stamp 44:45 on

I'm really perplexed as to how I managed to lose exactly 3 screws and only these 3 screws as I was so careful trying to keep everything together. Does anyone know where I can obtain them, or what the specs of the screws are so I can try and find them please?

Thank you,
Simon

 

Quick update, after some more research the part number for the screws is XA9-1518-000 - anyone know where I can get some? I may have found a place in the US but at up to 30 days and $15 shipping I'd like to try and find them closer to the UK if possible.

 

Well, not exactly overwhelmed with responses but to draw the issue to a close for anyone else struggling, I managed to get some screws for £10 delivered from 1st Aid Repairs in Kent.

 

Well congratulations on repairing your lens.
Unfortunately if you followed that video then your lens is probably now decentred. What the video doesn't show is that the spacers under the screws that hold the zoom tube together are eccentric and these have been positioned in the factory to get correct lens alignment. If you don't have the right equipment to realign them then you should mark the position and location of each spacer so that it can be refitted to original position.

 

if you need to test for decentered lens, use this chart either printed out or on a lap top full size, focus the lens on the center, on a tripod, then manually defocus the lens, if the dot in the center appears to move to one side then you have a problem

also test the lens for critical focus on a cereal box with fine detail or a bank note to test its clarity and render

 

Thanks guys, I just got finished reassembling this lunch time and early indications are that it all works perfectly.

Thank you. I don't know if you meant to link a chart but I don't see any links in your message.

 

I managed to find a decenter test grid and followed the instructions, and the lens appears to be perfectly centered.

Following the other advice and photographing a bank note to check focus, and I'm not so sure. Does this look to be reasonable to you? First image was taken with my 100mm macro for comparison, and second with the 24-105mm (at 105mm) - both at F8 from the same distance (about half a metre or so). Naturally both have been converted to .jpg and compressed / resized to fit the forum rules.

Of course there are clear differences, the 100mm macro is way sharper and more vivid. But having never compared images between them like this I don't know if it's a fair comparison. I've also not had the lens for long at all so looking through my photos and I don't have any which prove one way or the other if the disassembly has changed anything.

Does the second image seem acceptable from this lens?

 

looks alot less defined but i'm not familiar with the lens in question, zoom vs macro prime the macro lens is or should out perform the zoom of coarse
looking at the difference i have returned lenses for that weaker performance.
from this side of the net the image of the macro lens seems very good so its not a case of the images being crushed in rescaling etc though media
i'd say it needs calibrating or rejecting myself

also apologies for forgetting to include the star chart for de centering but it seems you found it.

looking at mpb the lenses are around £300 to £400 second hand, so i doubt its worth sending it away for work as i assume a good condition second hand one would be the cheaper option if its a lens you want rather than just a gifted fixer upper, but its good to tinker with it and learn about them.

not sure if there are any test rigs you can set up to align it any better, i've not actually looked into how they do it, shine light through them to calibrate or imagery wise, might be worth a youtube search myself.

that image of the test chart

 

My attempt to replicate your results:
Canon 7D Mk II ISO 200 using EF 100mm macro USM (not IS version) and EF 24-105 L IS USM at 105mm, both lenses at f8.
I was not able to get as close as you did with the 24-105 so I took them both a bit more distant.
Taken in raw and converted using Canon DPP with lens correction and minimal unsharp mask.
First one is the 100mm

 

Thank you both for going to the trouble of giving your feedback, and replicating the photo using the same lens. It's quite clear the 24-105 should be a lot sharper after seeing that last photo, Ray. I'll certainly be researching the best way to try and calibrate it myself rather than throw more money at it. As stated above, it'll be good to learn and tinker for my own benefit really.

The only information I've found is the below video on disassembling for calibration, followed by the link provided in the video on how to calibrate. My thoughts are to start by marking and photographing the eccentric screws, set them to the default position as described in the link, and then try adjusting them on a trial-and-error basis to see if I can get the image any sharper. I can then re-run the decenter test again.

Video of the disassembly process :


Calibration process :
https://canonrepair.wordpress.com/2...the-3-lens-group-in-an-ef-24-105-is-usm-lens/

 

That's a very interesting link, thankyou.
I have sent you a private mail which may be of interest to you.
Ray

 

Made an attempt at adjusting the eccentric screws on this, I can certainly see a difference in focus when making fine adjustments and I can get a sharper image, but not consistently across the frame and nothing close to Ray's picture above. I can't seem to find any logic in the adjustments I'm making versus the changes I'm seeing, it currently seems very hit and miss. I'll give it more time.

Surprised at how little information there seems to be out there, which suggests it's really beyond the home tinkerer.

 

I may be able to help:
Tell me what numbers you have written on the 2 cables shown in picture below.

Lens Cables. by Ray-UK posted Apr 10, 2024 at 5:13 PM

 

The large cable says "UK2212-04"

The small cable is, I believe, the one I have replaced and as such has no numbers on it. The broken one has been disposed of, though it may still be in the outside bin if it's critical?

 

It would be better to have both numbers, but even only one is still a help.
The important bit is the 04, only problem is that it could be +04 or -04, can you determine if that is a minus sign or a comma ?
Anyway you should be able to work something out using the info below (the 4G cable is the largest one)



Obviously you have to have all 3 eccentric collars in the same direction.
I hope that makes some sense to you.

 

Oh wow that's really useful thank you. It is a minus on the large cable as I assumed it was a dash.

I'll have a proper look after work, and I might be going through the bins tomorrow!

 

Well, the good news is I managed to find the other cable, which is marked UK1303 -02.

The bad news is one of the screw towers which holds the eccentric collar in place has broken off with the screw.

I'm starting to think I'm fighting a losing battle on this one.

 

So the collars need to be set at position 1.
As regards the broken tower perhaps a spot of epoxy resin might hold it together, getting into the correct position is of course extremely important. I wouldn't use super glue because you don't get time to re-position it.

Whether you repair the lens or consign it to the spares bin make sure you write the original number onto the new cable, you never know you may just need it in the future.

 

Good idea. I'll persevere with it.

Just to be clear, once the collars are set to position one it's a case of fine-tuning the small metal pins in my post on calibration? And they don't necessarily all point the same way?

 

Yes that's correct, once you have done all that, the only other adjustment is infinity focus but that is done on the front element fixing screws before you put the beauty ring back on (thats the bit of sticky plastic with the lens info printed on it)
There are other adjustment but these require specialist equipment and there is no reason to suspect that the original settings would have been disturbed by the work you have done.