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Fixing Tamron Adaptall P/KA Adapter
Posted By: Class A, 02-11-2009, 04:18 AM

Do you have a problem with a Tamron Adaptall PK/A adapter whose "A" functionality is not available or only if you do not completely mount the adapter to the camera, i.e., twist it back a little after mounting?

Chances are that it does not index on the body too far clockwise and that you can fix it within a minute.

The culprit may be one of the three screws which are fixed using a glue that electrically insulates them from the camera mount. If this is the cause of your problem then removing the glue from the end of the screw which is closest to the other electrical contacts (i.e., the top rightmost in the image below), e.g., with the tip of a knife, will make establish contact to the body mount again. This made my adapter work and I'm indebted to marvintm whose post "Re: How to fix bad Tamron KA mount" provided me with the solution.

However, since the illustrating images from his post are no longer available, I initially had trouble finding the screws. I finally found them and below is an image showing the location of the screw ends.

Contrary to marvintm's description, the glue on my screw end was not easily discernible by a light blue/green colour. I just lightly scratched on the screw end just in case and the adapter now works like a charm.

Good luck!

P.S.: This explanation of the KA-mount contains all the information required to know for which lens (minimum and maximum f-ratio) the pins should be shorted to the ground by the adapter. This should help troubleshooting if the camera doesn't use the correct aperture range. Note that the adapter does not fully support lenses with a minimum f-ratio slower than f/4 if the maximum f-ratio is f/22 and there is an "AE" setting or f/32 and there is no "AE" setting. Alternative explanations of contacts are Mark Roberts matrix metering mods page and this detailed explanation of the adapter contacts.

P.P.S.: You may want to try to convert a P/K adapter to one that supports P/KA functionality for a specific lens.

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Last edited by Class A; 09-15-2009 at 06:50 PM.
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09-19-2016, 12:42 PM   #61
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One black tab moves freely off camera, the other one doesn't move at all and pressing the black button has no affect on it whatsoever.

I think what I need is someone close by who can attach this thing to my Tamron 90mm and return it to me fixed. I'm having no luck at all. So, for the time being, I've reattached the one I had on there to start with, the PK adapter.

10-25-2016, 01:02 PM   #62
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QuoteOriginally posted by photolady95 Quote
I'm having no luck at all.
I might have another idea about your stuck PK mount, photolady. Have a look at the small screws that hold on the black ears/tabs that connect with the aperture ring on the lens. Does it look like these have been tampered with or even changed? If a screw of a slightly different length has been used to replace one that has been lost, it can easily cause one of the rings the tab/ear attaches to on the mount to jam. You could try slackening a suspicious screw to see if that frees things up (need ideally 00 JIS screwdriver or similar size cross head may with care suffice).
10-25-2016, 06:13 PM   #63
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QuoteOriginally posted by marcusBMG Quote
might have another idea about your stuck PK mount, photolady. Have a look at the small screws that hold on the black ears/tabs that connect with the aperture ring on the lens. Does it look like these have been tampered with or even changed? If a screw of a slightly different length has been used to replace one that has been lost, it can easily cause one of the rings the tab/ear attaches to on the mount to jam. You could try slackening a suspicious screw to see if that frees things up (need ideally 00 JIS screwdriver or similar size cross head may with care suffice).
Thanks Marcus. I'll try that when I get a set of those screwdrivers. I been meaning to order a set just other things needed more than a set of JIS screwdrivers. I can look at the adapter tomorrow with a magnifying glass to see if they're different though. I'll let you know then what I find.
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