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01-22-2009, 09:46 AM   #1
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Is my Pentax-A 135mm f2.8 Fixable?

Hello

I just got back my Pentax after a long loan to a friend and one of the lenses is busted. No fault of my friend but I wondered if it was fixable. By me!

Basically the focus ring just spins around the barrel without having any affect on focus unless it is gripped really tightly. I don't know how this damage/fault occured. Anybody have any suggestions or know of what to do to fix this problem?

Thanks in advance.

01-22-2009, 10:40 AM   #2
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I haven't owned this lens and can't tell from photos how it is constructed. In general, Pentax primes have three screws that attach the focus ring to the focus mechanism. They are accessible from the front of the lens without much disassembly. Typically all you have to do is take off the beveled ring around the front element that has the lens name engraved on it on M or older lenses (blank on A lenses). When you grip your lens tightly, it might distort the focus ring enough to allow the loose screws to get a grip.

It doesn't look like your lens has this ring, so I'm not sure where to start. But other primes are built to allow you to set the infinity focus point with the lens assembled, except for one trim piece. If you can figure out the one piece to remove, the fix is easy. You'll also have to reset the focus ring in the proper position once you locate the screws.
01-22-2009, 04:19 PM   #3
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I actually have two lenses with similar problems, both M 50/2 s. With one, the focus ring is as you described--completely loose. With the other it slides around, but still adjusts the focus without difficulty. I think what happens is that the glue and/or rubber on the focussing ring simply dries out. Nothing that sounds really that hard to fix, if you find the right person to do the job.
01-26-2009, 04:53 PM   #4
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Thanks guys. I decided just to start unscrewing screws to see if I could free the focus ring and see what had given way to make it come loose. Annoyingly one of the screws I think I needed to remove was stuck and I've managed to do the idiots thing and strip the head in the process of frustratedly trying to remove it! Looks like it's a gonner... Oh well!

01-26-2009, 05:30 PM   #5
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QuoteOriginally posted by man_frotto Quote
Thanks guys. I decided just to start unscrewing screws to see if I could free the focus ring and see what had given way to make it come loose. Annoyingly one of the screws I think I needed to remove was stuck and I've managed to do the idiots thing and strip the head in the process of frustratedly trying to remove it! Looks like it's a gonner... Oh well!
It would sure help if you would tell us where you are located. Go to user CP and click on Edit Your Details. If you are in the US or Canada I would suggest that you contact Eric Hendrickson, and ask him if he repairs "A" lenses, but for all I know you are located on the upper reaches of the Limpopo River. If anyone can revive that lens, it's Eric. Eric Oh yeah, Eric is very reasonable!!!
01-26-2009, 09:34 PM   #6
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QuoteOriginally posted by man_frotto Quote
Thanks guys. I decided just to start unscrewing screws to see if I could free the focus ring and see what had given way to make it come loose. Annoyingly one of the screws I think I needed to remove was stuck and I've managed to do the idiots thing and strip the head in the process of frustratedly trying to remove it! Looks like it's a gonner... Oh well!
The five screws on the lens mount? Those are just there to trick you. You think, hey, here are some screws, I don't see any other way to start, let's just take these off. If you don't strip one and get the mount off, a tiny spring or a ball bearing is just waiting to fly off into space, never to be found again. After that, you'll almost always reach a dead end before getting to anything you can fix.

I still think the problem can be fixed by accessing the lens from the front. One possibility is that there are screws hidden underneath the rubber grip on the focus ring. I read something about screws like this on the Pentax-A 70-210 f4 zoom. You can peel the grip back and check, then reglue it later.
01-27-2009, 08:42 AM   #7
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QuoteOriginally posted by Just1MoreDave Quote
One possibility is that there are screws hidden underneath the rubber grip on the focus ring. I read something about screws like this on the Pentax-A 70-210 f4 zoom. You can peel the grip back and check, then reglue it later.
Screws under the leathering are common fixtures for the focus ring. Not only the A 70-210 has those, but many other lenses by Pentax and others have this simple system.

Just peel away the leathering near the rear of the löens and look, whether you can see three evenly spaced screws. These can get loose over time. Simply tightening them, will fix the loose ring. But obviously it makes sense to rotate the loose focus ring to the correct position (meter scale versus indicator) before fixing the screws.

Ben
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