[muraliy]

I found my Tamron 70-200mm lens' aperture info was not showing on my K1. It would show only when pressed and tilted at an angle. When I tried to clean the contact pins, found that the Aperture info pin is missing (3rd contact pin on the lens). Is there a way to fix it myself or do I need to send it for repairs? I don't know how this happened. It was fine when I used it before.

Thanks.

[stevebrot]

Are you saying there is a hole instead of a contact in that position?


Steve

[muraliy]

Steve, Thank you for your reply. The metal conductor ("button") is missing in that position. You can see that in the attached photo.

Are you saying there is a hole instead of a contact in that position?


Steve

[stevebrot]

Steve, Thank you for your reply. The metal conductor ("button") is missing in that position. You can see that in the attached photo.

Wow...that is very much not there. That would be a Tamron part. It would probably be worth getting a bid on a repair.


Steve

I found my Tamron 70-200mm lens' aperture info was not showing on my K1. It would show only when pressed and tilted at an angle. When I tried to clean the contact pins, found that the Aperture info pin is missing (3rd contact pin on the lens). Is there a way to fix it myself or do I need to send it for repairs? I don't know how this happened. It was fine when I used it before.

Thanks.

I have looked at several of my original Pentax lenses, among which the Pentax F 70-210, and in the same position there is no pin. On some of them it is closed with a nylon part and some are just unopened metal (just like your Tamron). I do not think there is a problem with your lens. Might be the K-1 or one of the other contacts on the lens that seem in order malfunctions. There is nothing missing. Most of my F lenses look exactly the same as your Tamron.
If instead you see -- it might be that the A position on the lens malfunctions and shows the manual aperture sign --, that is what I saw with a lens of mine. It also means that the set aperture is the one closest to the A position.

[Crooski]

I can confirm that none of my F lenses have a pin at that location

[muraliy]

I checked a couple of my other lenses and did find the pin in that position in those lenses. That is why I suspected that the pin on the Tamron has fallen off. My K-1 does not have any problem with my other lens and shows the aperture value which I can adjust normally. On this Tamron, when I push and hold the lens in a particular way, the aperture value is displayed and can be adjusted. But I get a pair of dashed lines (manual aperture sign) when I let go.

I have looked at several of my original Pentax lenses, among which the Pentax F 70-210, and in the same position there is no pin. On some of them it is closed with a nylon part and some are just unopened metal (just like your Tamron). I do not think there is a problem with your lens. Might be the K-1 or one of the other contacts on the lens that seem in order malfunctions. There is nothing missing. Most of my F lenses look exactly the same as your Tamron.
If instead you see -- it might be that the A position on the lens malfunctions and shows the manual aperture sign --, that is what I saw with a lens of mine. It also means that the set aperture is the one closest to the A position.

[stevebrot]

I have looked at several of my original Pentax lenses, among which the Pentax F 70-210, and in the same position there is no pin.

I can confirm that none of my F lenses have a pin at that location

Good points. That position is not the "A" pin; rather, it is one of two pins that code for f/32 minimum aperture. What is missing would be an insulating disk.


Steve

I checked a couple of my other lenses and did find the pin in that position in those lenses. That is why I suspected that the pin on the Tamron has fallen off. My K-1 does not have any problem with my other lens and shows the aperture value which I can adjust normally. On this Tamron, when I push and hold the lens in a particular way, the aperture value is displayed and can be adjusted. But I get a pair of dashed lines (manual aperture sign) when I let go.

I had this with a Pentax 80-320. I think that the lens needs servicing. In the case of my Pentax, Pentax refused to repair it because it was not worth it anymore. The aperture ring needs to be reassembled to get al the inner contacts in place with the contact points you see on the bayonet. Hence your holding it tight in a certain position forces something inside the lens and then seems to work well. That is also a reason that it could not be a missing contact point, otherwise you would not have gotten the result that it works when forced into position.

---------- Post added 02-10-20 at 01:19 PM ----------

Good points. That position is not the "A" pin; rather, it is one of two pins that code for f/32 minimum aperture. What is missing would be an insulating disk.


Steve

It is not a case of missing an insulating disk, because there is no insulating disk. It is just a blind spot for the inside contacts and bayonet as well. So that contactpoint is not necessary for transporting electrical information back and forth to the camera. That is why it is closed.

[stevebrot]

It is not a case of missing an insulating disk, because there is no insulating disk. It is just a blind spot for the inside contacts and bayonet as well. So that contactpoint is not necessary for transporting electrical information back and forth to the camera. That is why it is closed.

Interesting interpretation. That spot is normally occupied by the M1 contact which in tandem with the M2 contact codes for minimum aperture. Lenses on my shelf have flat metal, a conductive plug, an insulator, or a ball contact with insulating collar* at this location. I have none with a pit, though I have several with an insulating disk.

Addendum: I did a survey of Tamron 70-200/2.8 at auction and they appear to have a translucent plug at this location. Perhaps another owner could check in. (@northcoastgreg ?)



On non-AF bodies, the contacts are passive and code for aperture range and minimum aperture by simple continuity test. The table with the aperture encoding is at:

Features and Operation of the KA Mount | The K-Mount Page.


Steve

* This type can code either high or low depending on the wiring behind the mount.

[brewmaster15]

Pic attached..hth.
Al

[muraliy]

Thanks for the picture. So, my lens' pins are OK. Looks like I need to send it in for repair. Do you know where I can get it fixed economically in USA?

Pic attached..hth.
Al

---------- Post added 02-10-20 at 03:22 PM ----------

Thanks for the logical analysis. I am now afraid the repair will not be "cheap"

I had this with a Pentax 80-320. I think that the lens needs servicing. In the case of my Pentax, Pentax refused to repair it because it was not worth it anymore. The aperture ring needs to be reassembled to get al the inner contacts in place with the contact points you see on the bayonet. Hence your holding it tight in a certain position forces something inside the lens and then seems to work well. That is also a reason that it could not be a missing contact point, otherwise you would not have gotten the result that it works when forced into position.

---------- Post added 02-10-20 at 01:19 PM ----------


It is not a case of missing an insulating disk, because there is no insulating disk. It is just a blind spot for the inside contacts and bayonet as well. So that contactpoint is not necessary for transporting electrical information back and forth to the camera. That is why it is closed.

[brewmaster15]

Thanks for the picture. So, my lens' pins are OK. Looks like I need to send it in for repair. Do you know where I can get it fixed economically in USA?


---------- Post added 02-10-20 at 03:22 PM ----------

Thanks for the logical analysis. I am now afraid the repair will not be "cheap"

If your lens was original purchase and less than 6 years old maybe its under warranty still.. ( Lens Registration, Tamron USA)


.. might be good to start with a call to tamron... at least see if they have any service centers..


al

[muraliy]

I bought it used from adorama about a year ago. So, no luck.

If your lens was original purchase and less than 6 years old maybe its under warranty still.. ( Lens Registration, Tamron USA)


.. might be good to start with a call to tamron... at least see if they have any service centers..


al

[mlt]

Pic attached..hth.
Al

Or just try cleaning the contacts first, particularly if the lens is stopping down to the correct aperture for exposures in all modes.