Canon EF 24-105 – changing the aperture flex cable

If You have to repair a 24-105 aperture flex cable, take care that the aperture module is not intended to be disassembled. Of course, here is possible to order only the flex cable for it, but be careful with the dismantle of the front element of the aperture module. It is not only fixed with 3 screws to the body, but it is adjustable with 3 tiny excentric pins, when the 3 screws are tightened only a little.

I believe that this operation (the optical alignment) must be difficult even in a professional workshop, in home conditions probably impossible – but if You look to this small adjustment pins, You will see, that they have a marking point on their head.


That point marks the thinnest (minimum) point of the excentric. Make a sketch with the original position, then take them out from their hole. They are simply pressed in the plastic.

24-105-3 24-105-1 24-105-2

After changing the cable, You only have to put back in the same position. Not so precise, like changing the whole aperture module, but it works.

And another interesting thing: in this lens You will find 2 apertures on the same aperture module!

One is controlled by the “normal” stepper motor during the exposure, the second is controlled fully mechanically, with a cam-profile in the tube in which is mounted the aperture module. So if You are moving the zoom ring, the second aperture will modify the aperture – I suppose, this is for the fix F4 maximum aperture in the whole zoom-range.




A 24-105 esetében a blendemodul tulajdonképpen nem szétszedhető, vagyis hát persze szétszedhető, de két lencsetagból áll, amelyeket három kis excenteres tengellyel kell összehangolni (gondolom, hogy az optikai tengely egybeessen). Namármost ezt a beállítást  szerintem valószínű, hogy szervizkörülmények közepette sem lehet elvégezni, vagyis a szakszervizekben egyben kell cserélniük (értelemszerűen nem kevés pénzért).

Ettől még nyilván kicseréltem a kábelt – ha már egyszer lehetett kapni hozzá.

amúgy a 24-105-nél a kábeltörés – szerintem – törvényszerű, pont mint a 17-85-nél, mert túl kis ívben van meghajlítva.

A fotókon látszik, hogy blendemodul két tagját 3 darab excentrikus csapocska tartja. Szétszedés előtt meg kell nézni a pozíciójukat. A kis bizbaszok fejének a homlokfelületén van egy kis pötty, az jelöli a legkisebb vastagságot a két lépcső között. Imbusznyílású, de iszonyú kicsi, egyelőre egy PH csavarhúzóval forgattam meg.

Ja még valami: ebben az optikában 2 blende van!!!

A második csak kb 80%-ra tud bezáródni és a tubusban lévő horony vezérli zoomolás közben. Gondolom ezzel oldották meg, hogy a teljes fókusztartományban tartsa a stabil max  rekeszértéket .

About canonrepair

Ruzsa János. Amatőr fotós, Canon DSLR váz. Amateur photographer. Canon DSLR user.
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20 Responses to Canon EF 24-105 – changing the aperture flex cable

  1. jkenny23 says:

    Interesting about the mechanical linkage to the aperture, I wonder if it was bypassed could you get perhaps an f/3.5-4.0 or better equivalent lens instead of the constant aperture (though I assume at a loss of quality wide open).

    • canonrepair says:

      I am sure, that the picture quality will be much worse, and of course the exposure measuring will be false (on all values, excepting the wide open aperture) , as the body calculates the exposure based on the facrory data, which takes in count the second aperture too.

  2. Vivek Raj Singh says:

    Hi there,

    So glad I found your site. I have the same issue as bertus b: I’d sent in my 24-105 for a replacement of the aperture cable and it came back performing poorly at f/4-f/5.6 – with a “mist” or fuzziness around edges, very visible at full crop. The problem seems to go away at smaller apertures like f/6.3 and beyond.

    Am I correct to understand that this happened due to incorrect alignment of the elements after the repair? I just wished to confirm so as to not be a total doofus when I return to the service centre tomorrow to have them fix the issue. Thanks a ton!

  3. Adam says:

    I’d like to report a successful flex cable replacement without changing the whole aperture module. I had to remove the excentric screws, which I’ve previously marked to remember it’s original positions. After soldering the flex cable I’ve put the excentric screws back into the holes as marked before. My 24-105 works fine and is perfectly sharp as before the repair. Thanks for the instructions.

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  6. ray says:

    i have done my repair for about 8 hours…. huhuhuh but i have a problem… the images were soft and not so sharp compared to my other lens… i think my lens needs to have calibration… what can you suggest? i dont know where to start…

  7. ray says:

    i have the same problem of err01 before and squeaking sound but that was fixed 1 yr ago.. they replaced the IS mechanism and flex cable for aperture… now the err01 problem comes back but i guess this time it is only the flex cable since i cannot change aperture other than f/4… other than that i would get err01… no squeaking sound now… i already purchased a new aperture flex cable… i badly need a guide to do this… can you help me? i dont want to spend much anymore… i do surgical operations of laptops, mobile phones, other gadgets, etc… but i am very afraid of the misalignment you were talking about… i am not sure of how to calibrate the lens after i put the lens back after replacing the flex cable…

    • canonrepair says:

      hi, I have no special itiner for this.
      Only be carefull to make a sketch on a paper, how the excenters are on their place. or a macro photo.

      • Ray says:

        thanks pal you’re the man… i will definitely make a good sketch so i wont have a hard time putting it all back… my lens is completely dead now.. i am just waiting for the flex which i ordered in 2 different locations. the other cable will serve as a spare as this is like a consumable part of this typical lens.

  8. Misu says:

    Üdv János!

    A 28-105-ös obiknál is fenn áll ez a konstrukciós hiba? Vagy tudsz-e esetleg gyakran előforduló hibákról ezeknél az objektíveknél?

  9. bertus_b says:

    I had a canon 24-105 with a broken flex cable last week and because I had seen this page on your site I was aware of the excentric pins. I marked the pins and replaced the flexcable. After re-assemble the lens I made some shots and was shocked about the picture quality. The pictures where unsharp and had a kind of mist around sharp edges. I cannot imagine that the position of the excentric pins is that critical to give these unsharp pictures. Can there be another problem that can cause these unsharp pictures. I didn’t make any pictures before the repare so I’m not shure if the lens already was unsharp. Is it possble to send you an example of a picture?

    • canonrepair says:


      You will find a picture here.
      I think this lens has beside the element with the 3 special excenters minimum one more element which has to be adjusted – or should not be moved from it’s position (in the same group). Possibly it is fixed with 3 normal screws, which are glued (adjustment screws) – You can adjust the position of this lens element in it’s own plane (coaxiality).
      Normally You need a special device to do this.
      But You can send me the photos of course: ruzsa.janos at

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