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02-20-2009, 03:07 PM - 1 Like   #1
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M42 Auto Only Lens Modification

QuoteOriginally posted by hinman Quote
I recently got a Soligor 200mm f/2.8 in M42 mount. The lens is in pristine condition but I have not taken any shots from it except few product shots. My lens has a serial number starting with 37 and the lens may be related to Tokina as Vivitar brand has serial number starting 37 were manufactured by Tokina.


Soligor 200mm Tele-Auto f/2.8 in M42



Soligor Tele-Auto f/2.8 MC, 72mm, No 37....




I fell short in showing a picture of the long pin sticking out of the M42 mount. This older M42 lens does't come with a A/M switch. It has a long pin sticking out with the aperture wide open and my K20D body won't depress it to the close down the blades according to aperture stops

I am planning to do some modification to make the lens manual permanently. I researched on various discussions with questions to all my buddies such as Mis, Peter, Frank, and few others from another forums, here is the summary of possible remedies:
  1. Use some way to jam the pin with cotton swap
    - Converting Auto-Aperture M42 Lens to Manual Aperture on Flickr - Photo Sharing!
  2. Crazy clue to press down the pin in position
    - Peter reported success with Helios-44M
    - Unfortunately, my pin is long and the spring seems very strong underneath
    - Subject to glue used, possible to undo the change
  3. Use of Kindai M42 to K mount adapter
    - https://www.pentaxforums.com/forums/pentax-slr-lens-discussion/46880-helios-44m-5-good-k10d.html
    - thanks to Frank for the subjection

To OP, when you get your lens, make sure you have the A/M switch and you need to have the M switch for the K bodies to work; otherwise, you need to make the changes such as the above.
My 1st attempt is trying to replace the pin using various kinds of pin that I could find last night. My attempt does not go well as the replacement is not strong enough to work with the aperture switch. The AUTO pin is not the same in every lens though the mechanism is similar. Some pictures of my failed attempt



Soligor 200mm Tele-Auto f/2.8 in M42

Original auto aperture pin
No A/M switch


Need to push the pin in to close down aperture
according to f/stops


Replacement with pen ink inner tubing
and clips to permanently engage the
underneath spring to close down aperture
with f/stop




It partially works from f/4.0 to f/22 but not for f/2.8 wide open as the replacement is not strong enough to work with the underneath spring to engage with aperture stops.

I will try again. I could have attempted with crazy glue on the pin opening but I don't want to cut the pin short or modify the lens with irreversible mod. and hence I try to mimic the original mechanism without jamming the original pin in place.

If you have suggestions and experience to share, please comment.

02-20-2009, 03:11 PM   #2
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Instead of trying to replace the pin, find a piece of tubing you can slide onto it.

For example, I found the tube from a pressurized can of air ("Dust Off") fitted perfectly -- snip off a short piece (2mm for example) and slide it onto the pin before pushing the pin back into its hole in the mount plate.
02-20-2009, 03:12 PM   #3
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QuoteOriginally posted by duncsuss Quote
Instead of trying to replace the pin, find a piece of tubing you can slide onto it.

For example, I found the tube from a pressurized can of air ("Dust Off") fitted perfectly -- snip off a short piece (2mm for example) and slide it onto the pin before pushing the pin back into its hole in the mount plate.
That is the perfect idea. Thank you! I will report back.

Hin
02-20-2009, 03:15 PM   #4
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You're welcome Hin -- I just did this exact same operation on a Helios 44M so it's still fresh in my mind.

02-20-2009, 03:16 PM   #5
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Did the same thing with a ca 2mm broad piece of Duct tape. Works well....
02-26-2009, 03:32 PM   #6
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Shame on HinTheMan, I am no handy man. Few attempts with the jamming the pin to Manual has failed on my Soligor. I may have ruined the aperture ring in the process.

This is the closest insert, the white hollow tube in the picture, that I get to cushion the pin underneath effectively pressing the pin down to turn the Auto diaphragm to manual diaphragm




My major issues is in the spring-mounted arm that the pin interact with, it is not stable after the modification, frequently bounced back to Auto only diaphragm. My worse experience was screwing the original pin with crazy glue trying to keep the pin in position. The glue, a bent pin, wrecked lens housing in the lens rear all work together against me. And worse happen when I lose the aperture click when I turn the aperture ring. I was able to get it to change aperture but there is no click in between the f/stops and half stop.


spring-mounted arm underneath
the Manual/Auto aperture pin



Oh, what have I done!!!

Last edited by hinman; 02-26-2009 at 05:02 PM.
02-26-2009, 03:47 PM   #7
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I had good mood this morning though the repeated failed attempts with the mod. I played out the worst scenario in shooting the lens wide open in f/2.8. Some test shots from Soligor 200mm f/2.8 in M42


All shots wide open in f/2.8
Soligor 200mm Tele-Auto f/2.8 in M42




















Not certain, but I noted some amount of CA from the test shots but I love the ease of handling on this Soligor. It is not heavy! Very compact for a 200mm and lightweight in my book for f/2.8 speed. It has a built in lens hood. Sharpness is not the best in f/2.8 but I am impressed with the casual test shots. It kills me in ruining another good lens and not able to fix it for smaller apertures.

Last edited by hinman; 02-26-2009 at 04:05 PM.
02-26-2009, 04:24 PM   #8
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QuoteOriginally posted by hinman Quote
.. And worse happen when I lose the aperture click when I turn the aperture ring. I was able to get it to change aperture but there is no click in between the f/stops and half stop...
A small ball bearing has probably escaped! The clicks on a Pentax lens (probably this one too) are caused by a bearing trapped between the aperture ring and the lens body. The bearing is held by a spring against grooves in the aperture ring's inner surface. Here is a picture of a lens with the aperture ring removed and the bearing still in place, on the left just above the orange diamond:



Here's the aperture ring, with the grooves on the right rear:



I know Microtools carries the bearings in various sizes. You may have trouble finding the right size without the bearing. I have some extras that work for Pentax M lenses which I can send to you.

02-26-2009, 04:35 PM   #9
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Dave, you are one of a kind. Thank you for the pointer. Yes, I am into that same thinking, I searched all place when I tried to modify my lens and to no avail of seeing the missing piece as in the bearing. Thank you so much. That really give me the incentive to keep trying.

I am proud to be Pentaxian, having friends around for support. You have made my day
02-26-2009, 04:36 PM   #10
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QuoteOriginally posted by Just1MoreDave Quote
A small ball bearing has probably escaped! The clicks on a Pentax lens (probably this one too) are caused by a bearing trapped between the aperture ring and the lens body. The bearing is held by a spring against grooves in the aperture ring's inner surface.
.....
You may have trouble finding the right size without the bearing. I have some extras that work for Pentax M lenses which I can send to you.
This happened to me more than once. Now when I have to remove the aperture ring from a lens (or when I suspect something may jump), I put the lens in a large Zip-Lock back and slowly lift the ring. If something jumps or falls off, it will stay in the bag.

About the little ball, I replaced it with a ball taken from the tip of ballpoint pen. More often than not, the ball is too small, but you may get lucky (my wife keeps asking why I collect so many pens at tradeshows ).
02-26-2009, 04:38 PM   #11
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QuoteOriginally posted by SOldBear Quote
This happened to me more than once. Now when I have to remove the aperture ring from a lens (or when I suspect something may jump), I put the lens in a large Zip-Lock back and slowly lift the ring. If something jumps or falls off, it will stay in the bag.

About the little ball, I replaced it with a ball taken from the tip of ballpoint pen. More often than not, the ball is too small, but you may get lucky (my wife keeps asking why I collect so many pens at tradeshows ).
Thanks for the pointer and the good and sage practice with zip-lock bag.
02-27-2009, 10:18 PM   #12
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I finally get some success in turning the auto-only diaphragm into manual diaphragm using rubber band. As noted before, the crazy glue, pin insert with a hollow tube does not work for me. It is mainly due to my poor workmanship that the best hollow tube idea ends up in failure.


Rubber band to tide the diaphragm lever as if I push it to manual







Shame on me with the hollow tube trial
with crazy glue. The rubber band
replaces all these



Unfortunately, I am only 80% done as I lost the ball bearing that works on the f/stop turning. I don't manage to find any ball bearing resembling the tip of a ballpoint pen. Perhaps, I simply don't have a ball point pen. And for now, I compromise using a plastic cut out that is big enough to provide the friction against the groove on the aperture ring f/stop




Small plastic cut out as
temporary ball bearing



It ain't easy for me. But something cheerful tonight as I can use the lens in all apertures and feel the aperture stop when I change apertures.

NOTE: if you know how to find the ball bearing, please comment and make suggestions.

Last edited by hinman; 02-27-2009 at 10:24 PM.
02-27-2009, 10:33 PM   #13
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QuoteOriginally posted by hinman Quote
I finally get some success in turning the auto-only diaphragm into manual diaphragm using rubber band. As noted before, the crazy glue, pin insert with a hollow tube does not work for me. It is mainly due to my poor workmanship that the best hollow tube idea ends up in failure...
I like the rubber band idea. I might have to borrow that some day.

QuoteQuote:
NOTE: if you know how to find the ball bearing, please comment and make suggestions.
A magnet might work, if the bearing is magnetic. If you have a rare earth magnet from some old hard drive or headphones, that would pull it out of carpet.
02-28-2009, 10:37 AM   #14
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QuoteOriginally posted by Just1MoreDave Quote
I like the rubber band idea. I might have to borrow that some day.

A magnet might work, if the bearing is magnetic. If you have a rare earth magnet from some old hard drive or headphones, that would pull it out of carpet.
Thanks! Here is a user comment on my blog post

Soligor 200mm Tele-Auto f/2.8 in M42 - Hin's Tech Corner

to finding the hollow tube from a electrical wire. A good picture tutorial but in a different language working on Helios 44M

Modification H44M-4

I wish I see the picture tutorial first, but I think it is easier to mod on the 44M while my 200mm has a long focusing ring extension with two lever arms the length about 1 inch on each dangling with a spring arm on top and fixed level on bottom to engage in manual diaphragm. And I find the electrical wire will work just as well if not better compared to cotton swap. Cotton swap idea is similar except that not all cotton swaps have plastic hollow tube. The 2mm size is important and I cut the hollow tube too long that failed me the 1st attempt




Last edited by hinman; 02-28-2009 at 11:38 AM.
02-28-2009, 11:13 AM   #15
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These are the bearings I have used to replace my escapees:

http://www.micro-tools.com/store/item_detail.aspx?ItemCode=BB-1-5M

The 1.5mm size works for Pentax-M lenses. Takumar bearings seem to be larger and Pentax-A bearings are smaller. I don't know the exact original merasurements
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