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Tamron 70-300mm Tele-Macro Off error


12 Jul 2013 12:05AM
I recently got a tamron 70-300mm lens to repair online. (the auto focus was jerky) (stripped gear) I have alot of experience working on small electronics. I had a damaged 75-300mm lens around so i pulled the auto focus motor Assembly from that and put it inside the 70-300, It went back together fine. and first tests were promising, I have found a small problem that i don't understand.
Outside the lens takes a perfect picture at 300mm, macro, ect. but if it shoot at below 300 outside in the light i get a communication error on the camera. same zoom inside will focus and shoot with not problem. I looked over the lens i took apart and several others over the years and have not seen a light sensor inside the lens. does any one know what could cause this off behavior with this lens??
I will attempt to call tamron tomorrow and see if they have any suggestions.

Thanks for any help

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12 Jul 2013 12:16AM
Two questions? Was the other lens Tamron? Are them of the same maximum aperture value? Autofocus reliability greatly depends on light, and the system tuned to some limits may be not happy with elements of other system tuned otherwise. I applaud your brave experiment though... As for light sensor - lens does not have it, but camera does. And I have a Sigma that behaves differently on two different camera models from the same brand. Take it as a tipWink
12 Jul 2013 12:42AM
The other lens was a tamron 75-300mm almost identical. the aperture value was the same. I believe the aperture motor was on its own. should be completely separate from the auto focus. I will double check the ribbon cable to make sure it has good contract with the circuit. even weirder if it will still auto focus at 70mm outside when i half press the button, but when it snaps the picture it throws the error. The camera works perfect inside and out with an 18-55mm lens.
Its a shame that a 2cent plastic gear can pretty much make the lens worthless.

I got a quantaray lens to with the same gear messed up in it, Im not gonna modify that one right now just gonna keep it in manual mode.
12 Jul 2013 1:35AM
I wonder what would happen if you changed the motor with the chip. That may have possibly solved your problem, but mind it, I don't take any responsibility for the experiment results. However, in my understanding, there is not much chance to damage the camera this way - and the lens is already off anyway.
12 Jul 2013 1:08PM
I sat down last night and took apart the quantaray lens as well, pulled the auto focus assembly and managed to find a gear to replace its current gear, in the old broken auto focus for the tamron lens. I put that back together and tested it this morning and it seems to work perfectly at all zoom lengths and the auto focus worked nice and smooth.
I have enough parts I may try putting the original motor set back in the tamron lens and just redoing the gears in it. to see if that will fix the outdoor shooting issue.
12 Jul 2013 1:24PM
Wow! Congratulations, keep us updated....Smile

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