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Cooltouch
Tinkerer
Username: Cooltouch
Post Number: 253
Registered: 01-2009
Rating: N/A
Votes: 0 (Vote!) | | Posted on Monday, April 08, 2013 - 08:37 am: | 
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I asked for advice here about this lens a couple years ago, and never received a response that was of any benefit. The lens is still sitting on a shelf and I would really like to put it into service. To recap: the lens is a Vivitar Series 1 28-105mm f/2.8-3.8. It is an update of the original 28-90 Series 1 and is made by Cosina (mfg S/N code 09), whereas the 28-90 was made by Komine (mfg S/N code 28). This lens is in Canon FD mount. I've never had the S1 28-90 apart, so I don't know about any internal similarities between the two lenses, but I suspect there are.
The problem is I can't reach the aperture iris to clean the blades. I'm trying to approach it from the rear. I've already loosened the rear group of elements, but I can't get them off the lens because of a restriction in the mount. I've loosened the mount -- removed the screws that hold it in place -- but the linkage for the aperture stop-down mechanism is hung up on something and won't come free.
One fellow I mentioned this to said I had to approach things from the front, which means dismantling the lens completely, and which I'm trying to avoid. If I could just free up that linkage, I can reach the aperture blades and clean them in place with naphtha and many q-tips.
So, any ideas or recommendations? |
Gardener
Tinkerer
Username: Gardener
Post Number: 10
Registered: 02-2013
Rating: N/A
Votes: 0 (Vote!) | | Posted on Monday, April 08, 2013 - 10:15 am: |
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There are very few lenses where you have to in from the rear. Usually you go either from the front or from both ends. I've never the particular lens you have, but if it is based on Komine design you most definitely go from the front side only. If it is based on Kiron 28-xx designs, you'll have to open the front as well, it'll just be that much harder. |
Cooltouch
Tinkerer
Username: Cooltouch
Post Number: 254
Registered: 01-2009
Rating: N/A
Votes: 0 (Vote!) | | Posted on Monday, April 08, 2013 - 08:00 pm: |
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Prior to trying to dismantle this 28-105, I cleaned the blades on another Vivitar Series 1 in Canon FD mount -- the 24-48mm f/3.8. It has the Kiron S/N code (22xxxx). I was able to get to the aperture blades by removing the rear mount and the rear lens group only. A couple of teaspoons of naphtha and many q-tips later, the blades were clean and the lens was back in service. So, that's at least one lens that is amongst the "very few" you mention. It was because the 24-48's blades were so easy to get to, in fact, that I was encouraged that the 28-105 would be equally easy. Wrong. 
So, I should just suck it up and dismantle the lens. It ain't gonna do it by itself and I'm tired of seeing it just sit there. |
Gardener
Tinkerer
Username: Gardener
Post Number: 13
Registered: 02-2013
Rating: N/A
Votes: 0 (Vote!) | | Posted on Tuesday, April 09, 2013 - 11:46 am: |
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So I took my 28-105 apart today. Tedious, but not complicated. However, I committed a major error along the way. I could not get out the second group, which sits directly over the aperture - it was coming apart, so I started working on taking apart the rear of the lens, which is required to get the aperture assembly out. I tell you here - that design solution is just mean-spirited and purposely overcomplicated. Once I got the rear apart I saw that I still need the second group out, so I drilled a couple of holes for a spanner. Got the group out and what do you know - aperture blades are not there. Apparently someone has been there before me. Had I removed the second group sooner I would have saved myself quite some time. I'm not sure if I am going to bother putting it back together again.
In any case - you can get to the aperture by removing two front groups. Then you can try to clean it up with q-tips. |
Cooltouch
Tinkerer
Username: Cooltouch
Post Number: 256
Registered: 01-2009
Rating: N/A
Votes: 0 (Vote!) | | Posted on Tuesday, April 09, 2013 - 11:24 pm: |
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Wow, thanks for the timely advice, Gardener. Geez, I can't believe your luck, though. Who on Earth would completely remove the blades and then put the lens back together? And then no-doubt sell it to some unsuspecting sucker?
Okay, so just so I'm clear on this -- do you reckon that your second front group was atypical in its tightness? Or should I plan on drilling holes also?
Also, to get started, do I need to remove the front bezel with a large rubber stopper or something similar, or does the front group come apart along with the front part of the barrel? I noticed some small grub screws up there at the flared out part of the lens, which is why I ask. |
Gardener
Tinkerer
Username: Gardener
Post Number: 14
Registered: 02-2013
Rating: N/A
Votes: 0 (Vote!) | | Posted on Wednesday, April 10, 2013 - 07:10 am: |
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Yeah, I know, I mean once you are there you can clean it up reasonably well just by wiping. But there a lot of people who fashion themselves lens repairman but try to do
About the second group - do you a ring right around the front element? In theory you should be able to use to unscrew the group, but in my case the element came out. There are ridges on the face of the group and they should really help with a rubber tool, but I did not much luck there either. Fortunately, front element sits on a flange about 4mm wide and the housing is aluminum so drilling holes took seconds. |
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