Adaptall M42 issue

[film_man]

Hey people, I have a little issue with an Adaptall M42 adapter. I have a Tamron 90mm f/2.5 lens which when used with an Olympus adapter works fine, stops down correctly.

When I put the M42 adapter on it and I push the pin myself it works fine too, stops down all the way to f/32. However, when I put it on the camera it doesn't stop down beyond f/5.6 or so.

Comparing it with a 55 Takumar it appears that with the adapter on, the pin on the Tamron doesn't go out as much as on the Takumar. Which explains the problem. I'm not sure what the issue is here though. It appears the Tamron is not pushing the adapter enough for the pin to protrude as it should but I don't have another adaptall lens to try it.

I don't see how the adapter can be faulty, it is literally nothing there to stop it working and, as I said, if I push the pin myself it works fine. I can see that the adapter has enough travel internally for the pin to protrude as it should. It is just that the Tamron lens does not do it.

Has anyone encounterd something like this? Do I need another adapter? I could just glue it I suppose or put some heavy tape or whatever on it to keep it down...

 

[AgX]

That adapter itself is so simple that hardly anything can go wrong with it...

Well, I checked mine (as a sole piece):
idle pin-protrusion = 3.4mm
it can be depressed flush

 

[albada]

It appears that the camera is not pushing the pin far enough. Have you tried a different M42 body?

 

[AgX]

As the lens works normal at a different adapter/camera combo, and its aperture can be closed fully manually at the M42 adapter, unless the pin is too short, the camera seems indeed the only suspect.

 

[GRHazelton]

I had a similar problem with my M42 Praktica LTL. The device within the camera wouldn't depress the pin on the various auto diaphragm lenses I had far enough to reach the smallest f stops. I glued a piece of card stock, cut to the shape of the acuator in the camera, painted the card stock black. Simple, but worked well. Whether or not this would solve your problem I don't know, but it would be easily reversible.

 

[tokam]

I had a similar problem with a Pentax S2 that didn't seem to fully depress the stop down pin on an Auto Takumar 55mm lens. Worked OK on an SMC Tak 28mm and Super Tak 135mm.

Solution in my case was to cut a short length of insulation from a fine piece of cable and sleeve this over the pin at the end of the Auto Tak lens. I left the sleeve about 2mm proud of the pin thus 'extending' it. Seems to now be fully stopping down.

Edit: Oops. Just went to check the S2 plus Auto Tak. Haven't touched it in about 18 months. The little bit of sleeving I applied to the lens stop down pin has dropped off and the lens is now permanently stuck in stop down mode. It won't stay at full aperture when I cock the external lever on the lens. A bit of investigation required. Be careful if you try to extend the length of the pin on the lens. This technique may / may not work on your Adpatall.

PS I have the Adaptall 2 version of the SP90mm f2.5, Canon FD mount Adaptall 2. Very happy with it.

 

[film_man]

In the end the issue was the lens...

Basically this is what happened. The little arm on the lens wouldn't push back as much as it should. The OM adapter "seemed" to work fine, I don't have an OM camera so I assumed that since rotating the OM adapter arm was stopping down the lens fine the lens was fine. But...the OM adapter also had a tiny bit of play in the start, just like the M42 adapter had a bit of play in the pin before it engaged the aperture. So looks like the lens has something bent or whatever. Anyway, sent it back and getting my money so that's that.

 

[tokam]

Edit: Oops. Just went to check the S2 plus Auto Tak. Haven't touched it in about 18 months. The little bit of sleeving I applied to the lens stop down pin has dropped off and the lens is now permanently stuck in stop down mode. It won't stay at full aperture when I cock the external lever on the lens. A bit of investigation required. Be careful if you try to extend the length of the pin on the lens. This technique may / may not work on your Adaptall.

Seems OK now. The bit of cable insulation I sleeved over the lens stop down pin was sitting in the bottom of the camera mirror box. I refitted it and trimmed it back about 1mm, about 2-3mm are sleeved over the stop down pin. Now get full aperture viewing for focussing and the lens stops down when shutter button is pressed. Have a feeling this is not going to be a permanent fix. Not to worry as this camera only comes out to play once a year or so.

 

[eli griggs]

In general terms, if a pin is all steel or brass/bronze and can be removed without damaging the lens, you can or should get a jeweler to silver solder a small extension to the pin.

The solder job must be sound, and you'll need or the jeweler will have to remove excess solder and, perhaps use a fresh cold pickle to remove excess flux.

A extra long extension wire can be used for a 'better' positioning of the piece for soldering.
A THIN Dremel cutoff can remove the excess and a fine Dremel sandpaper disk can be used to round the tip of the new extension, before cleanup of flux and solder

Cheers