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.

[photolady95]

Try pressing the little black auto aperture button while trying to move the black tab and see if it frees up

That's what the problem is, it won't budge.

Do you have instructions on taking it apart? And what did you use for lubrication?

And thanks for your help Marcus.

[marcusBMG]

Ah Ok jammed auto aperture button. I've had that problem too. It is possible for this wee push button to dislodge from its slot and snarl up. There is a spring in there too... bit fiddly but not hard to fix if i remember right. In essence:

1. First remove the black shield from the back of the mount - 3 small screws* around the outside of the black adaptall bayonet. This exposes the innards as per my pic post #38 above.
2. The electrical block E needs to be removed - with care don't bend the contacts.
3. Now the 3 screws S can be removed and this allows the moving plates to be separated exposing the black auto button. Straighten it out and reassemble.

* there are some other screws fixing other bits as well. Inspect and figure it out.
I can't be more precise without going through it again for myself, but if you reach an impasse post here again with pics....

[photolady95]

Thanks. I'll give it ago one day when my hands aren't shaking so badly as they are today.

Do you think, just a squirt into the adapter at the critical point with CRC QD Electronic cleaner would help?

[marcusBMG]

Not if its jammed, needs to be unjammed. maybe a bit of careful prying with a needle....?

[photolady95]

Not if its jammed, needs to be unjammed. maybe a bit of careful prying with a needle....?

I'd have to borrow a needle. I don't own one.

[photolady95]

Marcus and all. I have decided to return the PK/A adapter to seller. Ebay contacted seller and seller accepted a return. I was given a return address prepaid label in order to return it.

As a side note, seller sent me a note saying I needed to understand how it works. I replied with a message of my own. Politely telling him "I know how it works" end quote.

[photolady95]

I bought another and it too will not move the Coupling key. I don't know if it's something I'm doing or if the coupling ring is frozen like the first one. I can tell you, I bought this with a lens attached and the coupling key was not positioned in the correct place.

Question. Moving the coupling key, how is that achieved? Maybe that's my problem and I'm not understanding how to slide it into place.

[marcusBMG]

Terminology: I refer to the 2 small black protrusions/ears that key into the spaces on the aperture ring on the lens as "tabs" (at ten after and twenty of in the pic above). Then there is the small black auto aperture button, I already linked to a pic of that (at half past in the pic above). And there is the silver locking button to press to take the lens off (at quarter after in the pic above).
I think you are talking about the tabs? Does the small auto aperture button depress? If it does then when you depress that you should be able to move the "tabs"

[photolady95]

Then there is the small black auto aperture button

In the manual they call that a "coupling key" and mine won't move. The tabs move but using my fingers not with the aperture button.

[marcusBMG]

Is the lens at wide open aperture?

[photolady95]

I installed the adapter per the instructions. Move aperture to wide open, match the blue marks on the lens and adapter, push down and turn clockwise.....and that's as far it gets installed because of the immovable coupling key.

[marcusBMG]

You should be able to line up the tabs with their engagement slots before rotating the mount into locked position. Do the tabs move freely with the mount off the lens?

[photolady95]

Do the tabs move freely with the mount off the lens?

Yes. I can move them with my fingers.

You should be able to line up the tabs with their engagement slots before rotating the mount into locked position.

But I didn't try that.

[photolady95]

Now it's not locking in place and one tab won't move to the correct slot on the lens. Before both tabs were moving freely.

[vonBaloney]

One tab can get locked into position because of the black button -- press that button to free the tab (when unmounted) -- then black button should spring back (so protruded -- if it doesn't, pull it out with fingernails). When mounting you should line up the tabs beforehand to the slots -- if they are just a bit off you can slide them in afterward but don't rely on the turning when mounting to get them into place. Also as noted lens must be in wide-open position to mount (or unmount). Once mounted with tabs in slots, aperture should move freely between stops. Then to get it into 'A' position (might say AE on lens), stop down all the way, press black button and move one more position (and again, make sure black button comes back up after locking in). So black button acts same way as 'A' lock button on a Pentax lens that has an aperture ring.