The Tamron 17-50mm f2.8 is a good variable focal length glass, once it was a competitor to the Sigma 17-55 and much cheaper than the Canon 17-55 f2.8 IS ISM. It is still much cheaper than the original.
Cheap and fragile loops of focal length control and focusing diaphragms are a Tamron trademark. That cheap zooms like 70-300 and many of their other variable focal lenses are equally susceptible to this disease. Specifically, the Tamron 17-50 f / 2.8 has another unpleasant feature - the comb responsible for controlling the focal length electronics is screwed to a metal part, which, in turn, is attached to the lens body through a single screw. And one fine day, you grab the zoom ring and hear a "crunch". The ring wedges, and the lens remains operational in the focuser position in which it is jammed.
Damage in this case - as luck would have it. Only the loop can be damaged, and maybe both the loop and the comb. The issue is resolved with little blood, if the cable is damaged only in one place - you can straighten the comb, thoroughly lock the screw of its metal holder, and continue using it. In the place where there is not enough contact pad, the electronics will show a focal length of 32mm. And that's all. You can solve the issue more radically - throw out the comb, and leave only the metal holder. At the output - about the same effect, only 32mm focal length electronics will register in the entire range.
The metal part on which the comb is attached is the only linking mechanism with the focuser helicoid. Therefore, the repetition of the malfunction is a matter of time.
The lens spreads out easily and naturally, the main thing when disassembling is attention and accuracy. The ribbon connectors on the control board are made of paper, so be careful with them.
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