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Frank McLean
Rating: N/A
Votes: 0 (Vote!) | | Posted on Tuesday, March 14, 2006 - 09:43 am: | 
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This lens is in great optical shape, but the aperture blades are sticking. If I set to f32 and very gently flick the diaphragm lever, er, thingy, the aperture opens briefly and then snaps back ok. If I flick it slightly harder, the aperture sticks open at a wider setting.
So, I'm thinking 'just' clean the aperture blades. I won't need, I hope, to touch the lens groups at all. 'Just' get the diaphragm out, very gentle swab with Ronsonol, work it a load of times, until smooth, then put it back.
Can anyone tell me the way to get the diaphragm out with the absolute least amount of disturbance? There are three screws in the ring just out from the aperture ring (the one that says 'f 200mm') and it looks like undoing these will allow the rear section to slide out. Any ideas?
I will, of course, be snapping everything with a digicam, wearing gloves, not touching the lenses, etc. Also, I ain't doing anything until I know for sure what's up, so don't worry, Pentax heads. :-)
Your help appreciated! Thanks.
Frank |
Harv
Rating: N/A
Votes: 0 (Vote!) | | Posted on Thursday, March 16, 2006 - 10:40 am: |
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I recently tackled an SMC Pentax-M zoom 1:4.5 80-200 with sticky blades. I don't know if it is a version 1 that you refer to but there is a lot going on inside there and I was in over my head very quickly. It was a "what have I got to lose?" situation because I was quoted $100 at the repair shop and there was a nice used one there for the same money. Something I didn't see right off is that the rubber covering on the barrel comes off with some mild persuasion and you'll see that it covers the area where the outer shell comes apart. That doesn't get you to where you need to be but it's a part of it that had me fooled for awhile. The moving parts inside are lubricated and somehow some of it bled into the aperture blades. Ronsonal cleaned it up and I was successful in getting this to go again - but it was a stretch! |
Frank McLean
Rating: N/A
Votes: 0 (Vote!) | | Posted on Friday, March 17, 2006 - 03:24 pm: |
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Hi Harv,
Yes, I see. Interesting. You seem to be saying that this is not relevant to the blade problem, though, or am I wrong? Is it the start of the long journey? Can you tell me exactly what you did, as it sounds like a good job, after your initial struggles? Particularly your form of mild persuasion? I'm dying to get this thing on my camera...
Thanks for replying,
Frank |
Harv
Rating: N/A
Votes: 0 (Vote!) | | Posted on Friday, March 17, 2006 - 08:14 pm: |
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Frank - I did this over a year ago and quite honestly I can't recall the procedure. I'm not an experienced repair guy and as I mentioned I jumped into it because it was either try it or throw it out as I couldn't find any repair info for it. The blades were sticking to the point where I could barely move them manually. I remember going at it from the mounting end and removing the screws you spoke of on the ring that reads 200 mm. That only took me so far until I removed the textured rubber sheath on the outer movable tube which exposed the split in the tube. I very gently slipped a dull kitchen knife under the sheath and slowly freed it up and slightly stretched it until I could slide it off. The fact that the outer tube does two jobs, focusing and zooming, makes for quite a complicated assembly of parts within. The diaphragm assembly eventually did come out however and I was able to clean it OK, but how I ever got it all back together was a bit of a miracle. One piece of advice - use a quality screwdriver with a proper handle - not one from those sets of various tips with skinny handles. The screws are tight. I did the whole job with a 00 Phillips although I don't know if that was the proper tool. It may have called for a cross point of similar size but the Phillips worked OK.
Good luck. |
Frank McLean
Rating: N/A
Votes: 0 (Vote!) | | Posted on Sunday, March 19, 2006 - 10:13 am: |
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Hi Harv,
OK, thanks for the info. I like your 'use a quality screwdriver with a proper handle'... I tried one of those screws with my Radio Shack set and thought I'd stripped the head, as it looked messed up. Turned out the screw was fine, but had completely chewed off the end of the driver, and it was the residue of that sitting in there that made it look stripped. :-) I'll be getting a proper set now. Them's tough buggers...
All right, since I can't find any other advice anywhere, I suppose I'm going in. Carefully.
Cheers!
Frank |
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