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11-16-2010, 06:46 PM   #1
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Repairing Pentax-f SMC 70-210mm lenses

I was able to pick up two "parts/repair" Pentax-F SMC 70-210 lenses off of Ebay for $46 shipped.. Awesome deal.

There are slight differences in the build of the two lenses. From the serial numbers they look like they were probably made in different years.

Both of them had really tight zoom.... one was locked completely and I am going to have to get a couple parts to fix it.... going to go camera shop parts/junk lens shopping in a day or two because I really don't want to cannibalize my perfectly good 28-80 for the couple of pieces I need.

One of them is going well and needs no actual parts.. except for the fact that the focusing is stiff... so stiff that it gets stuck in one place and my K10D cannot move it past that place. I MAY have gotten it loose enough for my K10D to actually be able to not stick when trying to focus, but I really don't want to reassemble it before I have it completely fixed.

What I am having trouble with is the fact that the remainder/main reason for stiff focusing is due to the actual main piece that fits in the body of the lens. The part that has the numbers on it that shows through the little window in the lens body. I'm thinking that one of the felt pieces is messed up/kinked. Does anybody know how to get that part seperated from the body?

Also... is there anything that is supposed to be oiled/greased in the zoom assembly? And if so, is sewing machine oil what I should use?

11-16-2010, 11:42 PM   #2
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I figured out how to get the focus ring assembly off. There are three screws behind the rubber and the distance meter window.

There was a tiny piece of dirt buildup but not really anything else. I put it back together and it is a bit freer than before, but still kinda tight. Maybe this lens just hasn't seen a lot of use or maybe it is binding a bit due to plastic shrinkage.

In any case, the only thing that is going to free it up anymore is a whole lot of use or me sanding down the plastic so it is looser.

I'll put it all back together tomorrow and see how it works.

I still need to know about the oil though. So if anybody has a clue, I sure would like to know.
11-17-2010, 12:29 AM   #3
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Oil is not a good idea. It can easily move to some place where you don't want it (glass, aperture blades). Use a stable synthetic grease with a large temperature range. And don't use much. Just a very very thin layer only in places where the parts clearly move against each other. Oh and check that the grease is suitable for plastic parts.
11-17-2010, 09:26 AM   #4
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QuoteOriginally posted by ovim Quote
Oil is not a good idea. It can easily move to some place where you don't want it (glass, aperture blades). Use a stable synthetic grease with a large temperature range. And don't use much. Just a very very thin layer only in places where the parts clearly move against each other. Oh and check that the grease is suitable for plastic parts.
O.k. thanks for the tip.

After doing some searching, it looks like a lot of people like Super Lube synthetic grease for doing camera work.

Now the trick is to find somewhere that sells it that isn't 30+ minutes away.

After searching without sucess for the last 30 minutes, I decided to see if Harbor Freight by some chance has it. According to their web site they do carry it. :-)


Last edited by cyclone3d; 11-17-2010 at 09:41 AM. Reason: info
11-19-2010, 12:09 AM   #5
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Finally got it all back together.

From the looks of this lens, it probably sat around for years without being used.

One of the reasons I think this is because where the brass adjustment cams had caused the aliminum to corrod a little. The aluminum even had started to bump a little and I had to take alittle off because it was causing the zoom to rub/stick.

Another reason it looks like this lens may have sat around and not been used much is because the focusing is so tight compared to my 28-80 and the other 70-210.

Getting it to be loose enough for it to auto focus on my K10D was the hardest part... I had to mess with the 3 set screws that hold the barrel to the front element until it was just right. It isn't getting any looser except through use.

The Super Lube synthetic grease with PTFE (their version of teflon) is a very nice grease. Not too thick.. not too thin. And it is compatible with plastic as is not supposed to separate over time.
11-19-2010, 04:21 AM   #6
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Congrats on your successful repair project! I've also been using Super Lube (with PTFE) and sometimes I feel it's a bit too stiff. I've used it on focus helicoids on some manual focus lenses and it works but sometimes I feel the focus feel could still be better. Of course this could be also due the lenses original build tolerances.
01-16-2012, 03:44 PM   #7
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QuoteOriginally posted by cyclone3d Quote
I figured out how to get the focus ring assembly off. There are three screws behind the rubber and the distance meter window.
I got one of this yesterday with the same problem. Focus kind of works and can live with it, but the zoom ring has now free rotation. Do I have to disassemble it completely? Or, just the mount removal will give access to the zoom ring repair.
01-16-2012, 04:17 PM   #8
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QuoteOriginally posted by ultraviolet Quote
I got one of this yesterday with the same problem. Focus kind of works and can live with it, but the zoom ring has now free rotation. Do I have to disassemble it completely? Or, just the mount removal will give access to the zoom ring repair.
Take a look at this link: Pentax 70-210 Repair

Also had this thread going for awhile: https://www.pentaxforums.com/forums/pentax-slr-lens-discussion/123586-pentax-f-70-210mm.html

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