Help with a loose Tamron AD2 SP 3.5-4.2/28-80mm

[ovim]

I've once again relapsed into buying vintage lenses

I just received a Tamron Adaptall-2 SP 28-80mm f/3.5-4.2 (27A) lens with the rear section of the lens barrel loose. All the glass and focus ring are as they should but the whole back section (zoom and aperture rings and the ad2 mount) of the lens exterior is loose. I can move the rear section 1-2mm by pulling and also the looseness can be felt when zooming or adjusting the aperture

Otherwise the lens is in great shape and everything seems to still work so I'm thinking it cant be that difficult to get this lens back to it's sturdy self.

Does anyone have any hints on where to start looking for the reason for the looseness? I suspect there are some screws somewhere (holding the front and rear sections together?) that have worked themselves loose and need tightening.

[cooltouch]

I have successfully repaired two different Tamron zooms for looseness, but they are both push-pull zooms, and the 28-80 is two-ring, so two entirely different mechanisms. So I can only pass along my approach to this if it were in my hands.

First of all, can I assume you have a collection of the proper tools?

The first thing I would do would be to peel back the rubber sleeve on the rear ring. Check for tightness every single screw you find under this sleeve. Sometimes screws will be covered by a thin brass shim. Make sure to check those too.

Find anything loose? Did this take care of the problem? If not, repeat the process with the front ring.

How about now?

If not, this is where it starts getting tricky and potentially messy. You'll want to record each step with your digital camera. Each of the sleeves can be taken loose by removing certain screws. This is your next step. Removing the sleeves by sliding them forward (typically) should reveal more screws. Check them all for tightness. If this didn't fix your problem, then we'll need to remove the complete barrel sections. Underneath the barrel sections (held in place by small grub screws) you might find more screws. It is very likely this is where your problem lies if none of the above fixed your problem. Once the barrels' grub screws are removed they can be slid forward typically, far enough to be out of the way.

The only other thing I can think of is if barrel sections thread into each other and are tightened this way. If it appears this is the case, then try screwing one section back into the other until it's tight.

Good luck!

[ovim]

Thanks for your reply!

It turned out to be a very easy fix. I took off the rubber grip from the zoom ring and underneath it there were six screwholes. The screws lined up with the holes when zoomed at the 50mm mark and then it was just a matter of tightening the screws.

Now the lens is almost as good as new!

[cooltouch]

I'm glad it was an easy fix for you. I love it when that happens.

[ovim]

It seems that I was too quick to say the problem was solved. I tested the lens today and noticed that the infinity focus was way off at the wide end.

I now suspect that the six screws that were loose might actually be there for this infinity adjustment. They do line up with holes on the zoom ring also at 28mm position. So I loosened them again and adjusted the front and rear part distance from each other back and forth until I got sharp infinity at 28mm using magnified live view on my A7. It was quite fiddly and I'm afraid that front and rear lens groups might not be perfectly aligned now and this might lead to uneven sharpness in the frame. Also now the zoom ring rattles a bit and I couldn't find any way to tighten it. I wonder If this really is the way to adjust the wide end infinity focus?

Tomorrow I will test again the lens if it now focuses correctly and also holds focus when zoomed.