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05-16-2010, 11:35 AM   #1
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How to fix a auto-only M42 lens so it becomes a manual one

Just got two lenses, a Tokina EL28mm/2.8 and a Yashinon DS 50mm/1,9. Both lenses only support auto-aperture and therefor only can be used wide open.

I'm quite sure I encountered some threads about fixing this, but don't seem to be able to find them. I might also be mistaken.

I'm looking for a way to fix this.

My first thought is to drip some superglue round the aperture activator pin (while it's pushed in), but I'm a bit worried that I might fix the aperture blades as well (or do other damage) with excess glue.

The second thought is to just open them up and see if I can't fix the aperture activation lever in some way.

Can somebody advise or point me to the threads that I don't seem to be able to find.

Thanks in advance

05-16-2010, 12:24 PM   #2
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Probably the easiest way is an adapter with an extra ring to press in the aperture pin.

http://www.srb-griturn.com/m42-lenses-on-pentax-k-206-p.asp
05-16-2010, 12:33 PM   #3
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Another possible option.

Manual Focus Lenses :: View topic - "Repair" How to - make Helios 44M-6 usable with N

how to fix the aperture pin in an m42 lens
05-16-2010, 02:16 PM   #4
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I've read about people attaching a rim to their M42 adapter which holds the pin in. If you had a brass washer of the right size, you could solder it on - many adapters are plated brass. The M42 mount is usually accessable enough that disabling the pin is easiest.

05-16-2010, 03:00 PM   #5
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QuoteOriginally posted by sterretje Quote
My first thought is to drip some superglue round the aperture activator pin (while it's pushed in), but I'm a bit worried that I might fix the aperture blades as well (or do other damage) with excess glue.

The second thought is to just open them up and see if I can't fix the aperture activation lever in some way.
The problem with opening up the lens is that you may dislodge a detente spring and ball, the ball will inevitably fly across the room and never be retrieved. You could dismantle it in a plastic bag. Another option (this is what I do) is tape the aperture ring so that I don't accidentally dislodge it.

I have performed this surgery on a Hoya lens and inserted a tiny piece of plastic to keep the activator pin held in.

As to the superglue option, well you could always hold the lens so that the camera end is pointing downwards and use capillary action rather than gravity to insert the glue around the pin.
05-16-2010, 10:12 PM   #6
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Thanks people, I will read through the links and see what suites me best. The spring loaded pin was indeed a worry for opening up.

WimS
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