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08-15-2013, 06:20 AM   #1
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disable/fix SDM on Tamron 2x TC

I have a Tamron 2x Teleconverter that has SDM contacts but the SDM isn't working (I figure it was about time something SDM of mine stopped... I'm just glad it was a teleconverter!). The screw drive focus works fine, so it isn't a matter of the electrical contacts/autofocus being out of whack. So any screw-drive lens is fine, SDM is not.

I know that if it doesn't detect SDM it will 'revert' to using the screw drive. Is it possible to cover up the contacts on either the back or the front (I'm thinking front) without gumming up those on my 16-50 or 50-135? I was thinking electrical tape, but I do have this anxiety that I'll get goo all over either the teleconverter, or worse, the lens.

Thoughts?

08-15-2013, 07:23 AM   #2
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I wouldn't recommend using electrical tape. They tend to come off too easily after a while.

I suggest that you paint the contacts with nail polish. If you're bit more adventurous, remove the inner black plastic ring (held by three screws) on the rear of the converter and either remove the two contact pins entirely or again, use the nail polish to paint the inner part of the contacts.

By the way, I assume you've already tried cleaning the contacts on the converter. There are no electronics involved with the Pz (Power Zoom) contacts on the converter. It's just a straight transfer of electricity from the lens to the camera. There isn't much that can go wrong. If you have a multimeter, test the continuity from the front pins to the back pins. If both contacts are closed, then the converter should work normally. If both are open, then the camera should fail to detect SDM and work with screwdrive AF as you say. I suspect ONE of the contacts is open.

Last edited by tom1803; 08-15-2013 at 07:35 AM.
08-15-2013, 10:55 AM   #3
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I donīt understand what stopped working. If you mount your DA16-50 and DA50-135 on your camera, Does SDM works? If so, then I guess the teleconverter contacts must have failed but it should be an easy fix, as they are only a bridge between the SDM contacts on your camera and on your lens. I mean, there arenīt any electronics between the front and rear contacts of the TC.
08-15-2013, 01:56 PM   #4
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The sdm on the 16-50 and 50-135 work great. When I put on a tamron 1.4x converter the sdm on both work gret. When I put on the tamron 2x converter they turn into manual focus lenses. When I put an fa 100 macro on the tamron 2x the 100 focuses. I figure its probably easier to make the camera not recognize the sdm than it is to fix the sdm contact. Make sense?

08-15-2013, 02:26 PM   #5
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I think the camera recognizes SDM because of the lens ID, trasmitted by the lens contacts. So I donīt think tape on the SDM contacts will work at all. I think it shoud be easy to open the TC and see what is going on with the SDM contacts. Have you tried cleaning the contacts on the TC first?
08-15-2013, 08:04 PM   #6
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No, I'll try cleaning the contacts. I assume a q-tip with some rubbing alcohol should do the trick. I'm not afraid to get into the TC, but I feel that trying to spot the connection loss is going to be a tough go. I'll update as soon as I put a few things to the test.
08-15-2013, 08:09 PM   #7
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Q tip with alcohol is ok. Just beware of any excess.
If you have a multimeter, you could check for continuity between front and rear contacts to avoid disasebling right away.
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