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06-08-2012, 11:31 AM   #1
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Unscrewing mount

Hey all, I've got an M35/2.8 with a dirty aperture, so I want to open it up and clean it out. However, the screws that hold the mount seem to be particularly stubborn on this one. I might have already worn them out, but as far as I can see, the screws are mostly wearing out my screwdriver. I'm using a philips head 000 which seems to fit perfectly, but maybe I'm missing something. Is there some trick to loosen up these screws?

06-08-2012, 11:49 AM   #2
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try a little heat from a hair dryer. Also some adhesives dissolve in alcohol
06-08-2012, 11:56 AM   #3
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QuoteOriginally posted by urje Quote
I'm using a philips head 000 which seems to fit perfectly, but maybe I'm missing something.

Some of those lenses have JIS screws, not Philips.
06-08-2012, 12:19 PM   #4
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QuoteOriginally posted by lytrytyr Quote
Some of those lenses have JIS screws, not Philips.
If it is crosshead and on a Japanese camera or lens JIS is pretty much assumed. Use Phillips at your own risk.


Steve

06-08-2012, 12:36 PM   #5
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If you've already stripped the heads, try the rubber band method.

Remove a Stripped Screw with a Rubber Band

Then invest in a JIS driver set so you don't do it again.
06-08-2012, 02:31 PM   #6
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Did you foret to remove the do not open sticker?

This is not the way to open a lens and actually there is not way to open and clean a lens for the casual user - for a good reason.
06-09-2012, 02:43 AM   #7
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Thanks for the good advice, all! The alcohol I already tried, the hairdryer is up next, as soon as I find a JIS screwdriver. They don't seem to be readily available in Europe, but if I read this jis , it's exactly the problem I'm experiencing. The heads are not stripped yet, but they're also not virgin anymore. We'll see whether it's already too late.

QuoteOriginally posted by zapp Quote
This is not the way to open a lens and actually there is not way to open and clean a lens for the casual user - for a good reason.
Oh well, I guess I'll just throw the $40 lens away then. And I do think the way to get to the diaphragm is to unscrew the mount and rear lens element, but if you have a better suggestion, I'd be happy to hear it

Last edited by urje; 06-09-2012 at 03:39 AM.
06-09-2012, 09:27 AM   #8
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QuoteOriginally posted by urje Quote

Oh well, I guess I'll just throw the $40 lens away then. And I do think the way to get to the diaphragm is to unscrew the mount and rear lens element, but if you have a better suggestion, I'd be happy to hear it
You wo'nt access the aperture blades from the bayonet side.
Do you really have oil on the aperture blades, or is that your conclusion because they don't react fast ?
If you don't see any oil, something else may be the problem, I have tried to repair the sticky, but not caused by oil, apertures of various M35/2.8 and M 28/2.8 without much lasting success.
If the speed of opening of the aperture is different between pointing up or down, you may have a lens with the 'sticky aperture without oiled blades' problem.

06-09-2012, 09:31 AM   #9
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QuoteOriginally posted by urje Quote
as soon as I find a JIS screwdriver.
Micro-Tools Europe Werkzeuge | Miniaturwerkzeuge zur Kamera und Uhrenreparatur


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06-09-2012, 10:03 AM   #10
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Glasbak: up or down makes no difference, and I can see a bit of liquid on one of the blades. I got the idea that this is the proper route from this site: The Classic Camera Repair Forum: Sticky Aperture - Pentax-M 28mm 2.8 Although I won't be surprised if I can't fix it (or at least not for long), I'd like to try anyway, there's nothing to lose...
Steve: bookmarked! that site seems a lot better than the sketchy 'console and mobile phone tools'-websites I keep running into.
06-09-2012, 10:17 AM   #11
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QuoteOriginally posted by urje Quote
Glasbak: up or down makes no difference, and I can see a bit of liquid on one of the blades. I got the idea that this is the proper route from this site: The Classic Camera Repair Forum: Sticky Aperture - Pentax-M 28mm 2.8 Although I won't be surprised if I can't fix it (or at least not for long), I'd like to try anyway, there's nothing to lose...
Steve: bookmarked! that site seems a lot better than the sketchy 'console and mobile phone tools'-websites I keep running into.
Front view of a M 28/2.8 model 1:



The m35/2.8 is similar IIRC.
Otherwise, you live a hour on bike from me, just drop the lens on my doorstep .
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