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01-05-2010, 01:52 PM   #1
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K50mm/1.2 beyond repair?

I picked up a K50/1.2 knowing it had the start of fungus internally and after cleaning it would work out to be a good lens. I decided (because it is a 1.2) to send it into a local shop for cleaning instead of trying it myself. It's been in the shop for about 10 months and I've checked in every 3 months or so to see what is going on.

Long story short, they can't get it apart. Apparently the outer ring is sticking to the inner ring, so when they try to unscrew it, the 2 rings start to bind after about a quarter turn (as the threads are different inside). He has stated that he can get plenty of torque on it but if he tries any harder he'll end up destroying it. He has stated that he used to be able to drill the outer ring in a number of places to remove it in pieces, then replace the ring after the lens is clean, but obviously he can no longer get a replacement outer ring.

I thought of sending it off to Eric but after paying for the lens and the first attempt to fix it, it's starting to become cost prohibitive (especially if the second attempt would run into the same issue).

It's too bad....as it's in really nice shape were it not for the fungus that is starting. If anyone has any ideas, or knows where one can get a replacement outer ring, please let me know. It'd be a shame to let the fungus eventually destroy the lens.

Cheers,
Steve

01-05-2010, 01:57 PM   #2
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That's too bad. Here is an idea, it doesn't seem to be a terribly scarce lens, can you look for an "ugly" copy for parts? That way you could get a replacement outer ring.

NaCl(just a thought)H2O
01-05-2010, 01:59 PM   #3
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That's a good idea....if I can find one that is already dead I could at least save this one....
01-05-2010, 02:04 PM   #4
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Have you thought about sending it to Eric? Home

01-05-2010, 02:07 PM   #5
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I have..and I have sent quite a bit of stuff his way and I may end up sending it to him. Eric's charges are quite reasonable, but I also have to ship it to him through Canada Post.... If he has the same problem this could end up being a $$$ lens...
01-05-2010, 02:37 PM   #6
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I have Tomioka 55mm F1.2 with some fungus for 6 years now, I keep it in dry place with silicagel. Use it from time to time, I do not see that the fungus is growing. it looks completely dead to me. It may make pictures a little softer, but not to a degree that i do not want to use this lens.


QuoteOriginally posted by smc Quote
I have..and I have sent quite a bit of stuff his way and I may end up sending it to him. Eric's charges are quite reasonable, but I also have to ship it to him through Canada Post.... If he has the same problem this could end up being a $$$ lens...
01-05-2010, 03:02 PM   #7
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Thanks awo425. I remember reading that sunlight (presumably ultraviolet light?) kills fungus? There currently isn't enough fungus within the lens to make an impact on image quality....if I could stop it / kill it off then at least the lens won't eventually end up in the garbage.

There was one post that I can find now that outlined how to get rid of yellowing in some Takumars by leaving the lens out in the sun for a month or two, and there was one post that had someone taking it to work to put it in some sort of a light, where it was cleared up in a day. If someone remembers what was used, please let me know.

Thanks
01-05-2010, 03:06 PM   #8
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Removing that name plate will allow you to remove the first 2 elements and access the front side of the 3rd element which seems locked in from the other side. I had to clean up my bargain 50mm f1.2 and had a dented filter ring to fix first before being able to remove the name plate and accessing the glass. Fortunately all the fungus was in the first 2 elements so I didn't need to access the lens from the rear.

01-05-2010, 03:12 PM   #9
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Thanks xjjohnno. It's actually the nameplate ring that is fused inside to the ring below, (if I'm understanding your suggestion correctly). It turns but turns the ring beneath as well...which will damage the lens if it is turned to far.
01-05-2010, 03:29 PM   #10
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QuoteOriginally posted by xjjohnno Quote
Removing that name plate will allow you to remove the first 2 elements and access the front side of the 3rd element which seems locked in from the other side. I had to clean up my bargain 50mm f1.2 and had a dented filter ring to fix first before being able to remove the name plate and accessing the glass. Fortunately all the fungus was in the first 2 elements so I didn't need to access the lens from the rear.
I think what the repair shop is having trouble with here is the small rings used to hold the lens elements together into a group. These have spanner slots so you don't need a friction tool and are usually no trouble. But they are aluminum threaded into aluminum. Aluminum has a very strong oxide and the oxide can effectively bond the rings together. It is extremely frustrating to have a part that maybe cost a nickel get in your way like that. That probably explains this destruction:



Anyway, I would vote for attempting to kill the fungus in place. If the problem is as I describe, the shop is right, and the only solution is finding a replacement ring. That may take a while. You can use the lens in the mean time. Take photos of the fungus, keep it dry and monitor the progress.
01-05-2010, 03:46 PM   #11
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QuoteOriginally posted by smc Quote
Thanks awo425. I remember reading that sunlight (presumably ultraviolet light?) kills fungus? There currently isn't enough fungus within the lens to make an impact on image quality....if I could stop it / kill it off then at least the lens won't eventually end up in the garbage.

There was one post that I can find now that outlined how to get rid of yellowing in some Takumars by leaving the lens out in the sun for a month or two, and there was one post that had someone taking it to work to put it in some sort of a light, where it was cleared up in a day. If someone remembers what was used, please let me know.

Thanks
Do a search for fungus here. We have a thread that has just been revived, where we discuss the different methods to kill and clean (or not) the lens and I think, it will be helpful.
Some links:

https://www.pentaxforums.com/forums/pentax-slr-lens-discussion/37118-cleaning-fungus-lens.html

Another intersting thread concerns lens disassembly:
https://www.pentaxforums.com/forums/pentax-slr-lens-discussion/44776-disassem...ce-needed.html

I myself once had a lens, where I couldn't remove the name ring. Pentax applied lots of glue sometimes and effectively glued the name ring inside the threads. No way to remove it purely by force. I heated the ring, until the glue became soft and then could remove the ring easily. It way a dangerous operation (on an expensive lens), because the glass could have easily been damaged by the tiny gas welder I used for that - but it survived. The lens is now in excellent condition... One just has to be careful and take some time.

Ben
01-05-2010, 04:06 PM   #12
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Thanks Dave...I'll still dig into why the name ring isn't coming off and what it is sticking to...eventually it would be nice to figure out how to get it open without making it look like that one you have a pic of

Thanks Ben. I might try to pick up a UV light to see if it slows down the spread (and to clean up some of my yellowing taks). The first ring apparently will rotate almost a half turn but it is rotating another ring inside as well (according to the guy at the shop). Your trick with the heat might just work but that would be a last resort (I don't yet trust myself enough)

Steve
01-05-2010, 06:16 PM   #13
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Steve, I see that you still haven't resolved your lens' issue yet. had you tried bringing or sending it to the Vancam service just here in Vancouver? they say that most of the guys that work there were former Pentax employees or pretty much accustomed to Pentax gears. you might want to give them a ring and try them out. you can call them for free estimates and other matters concerning your lens. here is there website btw >>> VANCAM Service | Contact Us

Last edited by Pentaxor; 01-05-2010 at 08:25 PM.
01-05-2010, 07:04 PM   #14
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Steve,
Tell your repair guys to take off the rubber cover on the focusing ring first. There are screws there that you need to take out before you can unscrew the front name ring.

Cheers,
Jake
01-05-2010, 08:24 PM   #15
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So they are going to charge you for doing nothing?
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