Vivitar TX lens adapter with a problem???

xkaes · Feb 25, 2023

I just picked up a Vivitar TX lens adapter -- basically new, in the box, with the user manual.

I'm familiar with TX lens adapters, and this one goes on and off the lens as it should. No problem.

The unusual part is that I can't get the M/A lever on the adapter to move. It's set to the A setting, but I can't get it to switch to the M setting. This is the case regardless if the adapter in on or off the lens.

The genuine user manual, tells you how to get the adapter on and off the lens, but it makes no mention at all about this A/M switch.

I'm not a Pentax kind-o-guy, and need to know if there is some trick to getting this switch to move from A to M -- other than a hammer, of course?

BradS · Feb 25, 2023

Mmmm, wild guess. There may be a little pin in the surface that mates to the camera body. Sometimes that pin has to be pressed to enable movement of the auto/manual switch....my memory is a little foggy on this but this is how I remember the late SMC Takumar lenses working.

BradS · Feb 25, 2023

Well, I've just found my Vivitar 135mm f/2.5 lens and a matching TX M42 mount adapter. It does not have the pin I mentioned above and it does not have any issues moving the A/M switch.

What lens do you have? and what adapter ?

Can you post a few photos?

BradS · Feb 25, 2023

Are both lens and and adapter marked, “TX”?

If using an M42 mount adapter, I think you have to set the aperture to the orange 5.6 then line up the arrow on the mount adapter with the arrow on the back of the lens. See attached photos.

xkaes · Feb 25, 2023

Thanks, I've got the instruction booklet, and it installs fine. It is a TX lens, and I have different TX adapters that work with the lens fine. The TX M42 adapter installs on the lens and works fine -- but only in A mode. I can't move the switch to M regardless of the adapter being on the lens or off the lens. My guess is something is stuck, but since I'm not much of a M42 user, I figured maybe there is something I need to do in order to move the switch form A to M -- other than pushing it with my thumb. Perhaps I'm using the wrong finger????
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Does your switch move freely from A to M when the adapter is OFF the lens?

BradS · Feb 25, 2023

xkaes said:
Does your switch move freely from A to M when the adapter is OFF the lens?

Just checked... Yes. It moves freely. It is spring loaded. When letting go, it springs back into the (unmarked on the adpater I have) A position. When I press it to the '--->M' position, a little, round metal piece on the side that faces the back of the lens sinks away from the surface.

xkaes · Feb 25, 2023

That pin on the back is the aperture activator, and it should retract when put in M mode. It doesn't on mine, because my switch won't move into the M mode.

Even if I manually push in that pin and hold it, I cannot move the switch to the M setting.

I could tape that pin so it's always pushed in, but then the lens would always be in M mode, and I would not be able to use A mode.

The adapter is held together with three screws on the outer side -- just like a T-mount adapter -- so I could always take it apart.

And, yes, the lens and adapter are both marked TX -- and they are both Vivitar products.

BradS · Feb 25, 2023

more info...I have another, similar but different Tokina TX (or T4?) to M42 adapter and the -->M switch on it does not move when the adapter is off the lens. This one is marked with a green PX on the surface that mates with the camera.

xkaes · Feb 26, 2023

Problem solved.

I took the TX adapter apart this morning. There is a plate inside that has a pin/tab that was stuck (out-of-place) that kept the A/M switch from moving. Once I unstuck that pin/tab, the A/M switch moves as it should.
I have no idea how the pin became stuck -- the adapter is in mint condition.

This would only be an issue with the TX Pentax ES adapters, but other TX adapters are probably taken apart in the same way -- there are three TINY Phillips screws on the outside that are removed (and easily lost).

Vivitar TX lens adapter with a problem???

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