[Tsuken]

My Takumar 135mm (m42) has all of a sudden this morning gone funny: the last wee bit of throw in the focus ring (going from <7m to infinity) has become stiff and scrapey-sounding - to the point that at the longest end of things it will start to unscrew the lens rather than focus.

There are no visible signs of scraping, and it was absolutely fine yesterday; I can't figure it.

Any ideas???? Places to start?

Thanks in advance

[tim60]

Strange. Can you see anywhere where it rubs?

I had some screws come loose on the part with the gap where you see the distance scale. Fixed that by nipping them up with screw driver.

More likely, an internal screw came loose and fell out. So it lodged inside and made it stiff. Reason for thinking this: I had STak 28/3.5 where the front part that holds the filter thread suddenly came very loose. On taking off the vanity ring I found one of the screws fallen out and the other two loose.

So, I guess you need to start a disassembly. Be very careful - you probably have a screw already loose, so it will fall out when you do not expect it. Work where it will not fall away - those screws are tiny (hard to find and handle) and very hard to get replacements.

[Tsuken]

I can't, no.

That internal screw sounds a worry :/ The disassembly part is what worries me. I'm not sure how much I want to (a) risk destroying it, or (b) spend in sending it to a tech.

[tim60]

I hope someone else sees your thread and comes up with some plausible explanation.

There is a thread here about lens repair database which gives links to methods of servicing certain lenses. I think the 135/3.5 was so common that there is a link to instructions for how to open it.

I have done a couple of minor repairs on mine (only taking elements out of the 55/2). What I found there was that the design was very good - very difficult to reassemble wrongly because the design is based on tightening things to their proper stopping point. Most likely the hardest part is seeing and handling the tiny screws.

If you do not want to open it, I wonder what happens if you rotate the focus ring to the end where it is free moving and then clasp the lens in one hand, fingers around the barrel, and then hit your hand with your other hand to apply some shock load, to see if you could dislodge the screw which might have caught in the mechanism. If that works it will rattle.

[Tsuken]

Popped in to the local Camera House. The guy rang his tech guy. If the tech guy can fix it, it's be almost $200 all up.

If.

For a lens I paid $55 for.

I think if I can't find some un-scary instructions for greasing up the focus ring (oo-err), I'll just live with it.

[tim60]

Try this page - there are instruction linked for STak 135/3.5.
https://www.pentaxforums.com/forums/114-maintenance-repair-articles/179884-pe...-database.html

[Tsuken]

Thanks for that I'll see how it goes

[Just1MoreDave]

I had a great theory about what is wrong with your lens, based on a couple of 5omm lenses I've seen: the distance scale glue fail. Here's a photo:



It's a design flaw, the glue barely lasts 50 years. When this happens, the scale unravels and touches the inside of the ring with the depth of field scale. That scraping noise really sounds like "time for a new lens".

The bad news is, I just took apart my Super-Takumar 135/3.5 and the distance numbers are engraved right into the focus ring, not on a piece that could unravel. Rats, I loved that theory. It still could be true, especially if your lens is the Super-Multi-Coated version. And some construction changes happened on a running basis. You may be able to see whether the distance number scale is part of the focus ring or not.

If you have a tiny straight-blade screwdriver* that fits the three grub screws on the DOF ring, you can test my theory without any other disassembly. Those three screws are 120 degrees apart, to the left and right of the aperture numbers on the scale and one directly opposite the orange dot and line marking the point of focus. The screws have pointed tips and are pinching the DOF scale in place. If you loosen all of them a few turns, the scale can rotate. Now try focusing past 7m. The DOF scale ring might just move along with the focus ring. If you are really lucky, you could rotate the DOF scale ring so the "window" in it allows you to see the seam in the unraveling scale, and glue it back in place. Otherwise the repair means taking off the name ring, filter ring and focus ring, reattaching the scale and reassembly. If you focus the lens to infinity before you start, you can put the focus ring back on in the same spot without resetting infinity focus.

I suppose some debris could have fallen into that same window in the DOF scale ring, causing similar symptoms to a loose distance scale. Rotating the ring like I've described might help you get it out.

Ask me if you have other disassembly questions.

*Eyeglass repair kits often have a screwdriver that fits these screws. The 135 may have straight or JIS screws, possibly both. Some of the screws are way inside, so screwdrivers with thin shafts for about the first 25mm are necessary.

[Tsuken]

Cool. Thanks for the suggestions; I'll try that first, I think.