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M* / A* 300mm disassembly/cleaning guide
Posted By: RXrenesis8, 01-30-2012, 06:44 PM

(Posted as a request) . If anyone can take this a step further and elaborate on the rear elements I'd be grateful!

Also note: I am using made-up names for some of the parts (front element assembly?) Any corrections will be appended to the text of the post.

Step 1: focus the lens at 4 meters (< 14 feet).

Step 2: grip the lens by the aperture ring (or mount, or anything attached to the mount, ie: a camera) and the front protective cover and twist the front protective cover clockwise until it falls down and hangs loosely.

Step 3: grip the focus ring and the front element assembly and twist the front element assembly counter-clockwise until it disengages.

Step 4: remove the lens hood from the front protective cover and set aside.

Step 5: attach the front element assembly securely to the lens by turning it clockwise

Step 6: attach the front protective cover to the front element assembly by pressing it up and turning it counterclockwise.

(I could swear I took a picture of this...)

Step 7: continue turning the front protective cover counterclockwise until the front half of the lens disengages from the back half and set the back half aside.

Step 8: remove the front element assembly from the front protective cover by turning counter clockwise.

Step 9: twist the front element assembly apart by rotating the front element counter clockwise.

In this state of disassembly you can clean most of the lens surfaces and the aperture blades.

I think that's it for the easy stuff. Pretty sure the rest requires unscrewing tiny little screws on the mount but I haven't gone that far yet.

Last edited by RXrenesis8; 02-17-2012 at 10:54 AM.
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01-30-2012, 07:43 PM   #2
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although my A*300 does not need disassembling, bump for you.

stored this for future reference.
01-30-2012, 08:04 PM   #3
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Moving this to the articles section. Excellent resource!

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01-31-2012, 01:58 AM - 1 Like   #4
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I was that request!!

Thanks for taking the time to post such a detailed guide to dissasembly of this lens. The sliding hood on my otherwise perfect copy was quite loose, so I wanted to replace the felt slider inside it. There is no way I would have figured out how it came off, but now I know.

Many thanks for providing such a useful article, and in under 24 hours of my post to you! Guys like you make Pentaxforums the great resource it is!

02-17-2012, 10:54 AM   #5
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Another tip (worked out from helping another forum member disassemble his M* 300): If the elements are stuck: use a big rubber band around them for grip!
02-18-2012, 03:12 AM   #6
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Anyone know what the specification is for the felt like slider materials that are fitted between the inside the hood and the lens body, or where to get them? I want to replace these worn strips on my A*300 to stop the hood sliding under its own weight.

There is a 3/8ths inch wide grey flat strip of material attached to the inside rear end of the hood, and a thinner more rounded black velvet like material around the body near the front of the lens.

I'm in the UK but any ideas or sources of material are of interest.

Thanks for any help or advice!
02-18-2012, 04:41 AM   #7
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Ditto Ed. My glass is clean but the hood has a mind of its own. Great article! Thanks.
02-18-2012, 05:43 AM   #8
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I'll email or have a chat with pentax support to see if I can't find out. Mine flops around as well.

02-27-2018, 10:56 AM   #9
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Images are gone... would love to see this.

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