[Manel Brand]

Hi

Just bought a Vivitar TC with a PKA mount, mainly to use with a Tamron SP 90mm (PKA Adaptall2 mount) but it doesn't pass the lens aperture settings to the camera body; in other words, the aperture has to be set manually on the lens. I have cleaned the contacts with some alchool solution but to no avail; the adapter is in mint condition and nothing appears to be malfunctioning. The problem occurs with all pentax A lens that I've tried.

Does anybody have a clue on this issue?

Regards.

MB

[jerrymouse]

Hi
Does anybody have a clue on this issue?
Regards.
MB

I don't have 2X TC but I had 2x Vivitar MFTC that had the same problem. I fixed it thisway:

https://www.pentaxforums.com/forums/493608-post21.html

I'm not sure the 2x TC looks similarly inside, but it's worth a shot.

[Manel Brand]

I'm not sure the 2x TC looks similarly inside, but it's worth a shot.

Slightly different from the one you have.

Thanks for your help.

I’ve disassembled it and the connection between the front/rear mount is provided by pins mounted on each side of the springs, thus making a straightforward, direct pin to pin connection between the front/rear mount (no "L" shaped lugs to cling the springs on).

I can’t see why the electronic connection isn’t working; I’m going to clean all the pins and springs with some contact cleaning solution and see what happens; it´s fine to use manual aperture on the lens (actually, sometimes works better than the A set) but I’m going to try to fix it anyway.

BTW, there are two levers on the TC; one of the levers is attached and constrained to a position by a spring; the other is not and it runs freely, up and down, on is course. On yours second photo of the TC parts, we can see, on the TC front mount, the small flange with its half rounded shape (the diaphragm lever that operates DOF preview?); it’s the lever that can be operated by the rectangular flange on the rear mount. Is this normal or should it be also constrained to a position? I would appreciate if you could give me some info here.

Again, many thanks for your help.

MB

[jerrymouse]

Slightly different from the one you have.
BTW, there are two levers on the TC; one of the levers is attached and constrained to a position by a spring; the other is not and it runs freely, up and down, on is course. On yours second photo of the TC parts, we can see, on the TC front mount, the small flange with its half rounded shape (the diaphragm lever that operates DOF preview?); it’s the lever that can be operated by the rectangular flange on the rear mount. Is this normal or should it be also constrained to a position? I would appreciate if you could give me some info here.
Again, many thanks for your help.
MB

Oh sorry. I won't be much helpful in this case. I just remember I had to put that lever that floats "freely" (it's not floating freely once you attach lens to it) to the position where it can be operated by body lever (the one that moves if you push Av/Green button in M mode) - it closes down the diaphragm.
I think I dismantled the TC like 5 times before I got it right (but that's because I had to bend the lever too).

[Manel Brand]

It's Ok; I think my issue has nothing to do with the levers; aparently, it doesn't matter what position it is when coupled to the lens; it always operate the diaphragm correctly.

The problem, most certainly, has to do with the electric contacts and perhaps a good cleaning will fix it (not great deal here, it works fine on M mode).

Thanks again,

MB

[Just1MoreDave]

BTW, there are two levers on the TC; one of the levers is attached and constrained to a position by a spring; the other is not and it runs freely, up and down, on is course. On yours second photo of the TC parts, we can see, on the TC front mount, the small flange with its half rounded shape (the diaphragm lever that operates DOF preview?); it’s the lever that can be operated by the rectangular flange on the rear mount. Is this normal or should it be also constrained to a position? I would appreciate if you could give me some info here.

That lever doesn't do anything on Pentax DSLRs and some newer film cameras. On older film cameras, the lever tells the camera where the aperture ring is set, so the camera's meter can work properly with the lens held wide open for focusing.

[Manel Brand]

That lever doesn't do anything on Pentax DSLRs and some newer film cameras.

Thanks for the info; it doesn't do anything if you are shooting in A mode, right? I was thinking that it operates the diaphragm to control DOF and for metering in manual mode...

[Just1MoreDave]

Thanks for the info; it doesn't do anything if you are shooting in A mode, right? I was thinking that it operates the diaphragm to control DOF and for metering in manual mode...

That lever is the mechanical predecessor of the A setting on lenses. The basic requirements for the K-mount design were to

• allow setting the desired aperture on the lens aperture ring
• composing, metering and focusing wide open
• allow the camera to camera to stop down the lens for shooting or DOF preview

The two levers on the lens do that. One lever follows the aperture ring setting. One spring-loaded lever moves the aperture blades between that setting and wide open. If you set the aperture ring to f8 with the lens off the camera, the aperture closes to f8. Mount the lens and the lens is now wide open, but the camera can tell what the chosen aperture is for metering and stop down the lens for shooting.

When the lens has an A position on the aperture ring, it tells the camera its aperture range. The camera controls the spring-loaded lever much more precisely in this system. Before it was just open or close, now it can close to a precise aperture setting chosen by the camera. The second lever is obsolete in this system with the A lenses, but continued on camera bodies for a while and lenses for longer for compatibility with older lenses.

[Manel Brand]

Thank you Dave. Appreciate all the info you provided on the issue.

MB