100-400 strange noise

Started Nov 9, 2009 | Discussions thread
GoldenSpark Senior Member • Posts: 1,037
Re: 100-400 strange noise

Hi, your symptoms sound a bit like what happened to my 100-400.

There is a design "weakness" in the 100-400mm lens in that as it wears the zoom lock mechanism it goes progressively looser and looser. The first sympton can be inability to fully lock the zoom, or it gets lumpy as you zoom.

What you might find as well is that the locking collar moves through a smaller arc from loose to tight. With mine this was because some of the ball bearings escaped(There are no needle bearings).

With mine it got progressively worse (quite quickly over a few days) til it jammed up with the barrel locked at 100mm. Then I could not pull the zoom out (don't force it!).

In effect the locking collar needs to be adjusted in order to keep it tight. As it wears it goes looser, to the point that ball bearings can get round a cover shim.

With mine I opened it up - not recommended if you don't know what you are doing, reassembled it, putting the escaped balls back in place, then adjusted to get the correct tightness again. Now it works as new.

The problem is, Canon do not attempt to reassemble it like this as far as I can tell - it's too time-consuming. (There are 500+ ball bearings!).
The assembly replacement is $200 or so before you add labour.

I read somewhere that pros who use this lens get it serviced regularly and tightening the zoom lock is one of the things they do to avoid it getting to the stage of losing ball bearings.

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