Bronica S 105mm repair

[revdocjim]

I was very happy to find a fairly clean copy of this lens in the junk bin yesterday but when I got home I discovered the problem. The focus ring goes from MFD to about 5 meters and then binds and won't go any further. Where it stops it doesn't hit a hard stop with a clack like at the normal end of the range. It just suddenly gets tight and stops.

So I want to take this lens apart and see what's going on but don't know where to begin. The lens butt has about 7 or 8 tiny screws so I'm a bit intimidated, not knowing which ones to loosen. Should I start from the front?

Does anyone have experience disassembling this or similar lenses? How complicated is the focusing mechanism? Are there certain things I need to mark or note during dis-assembly in order to get it back together properly? And most importantly, does anyone have any convincing theories on what may be causing the problem?

Any help or advice appreciated!

 

[Steve Smith]

I don't have an answer to your question but I do wonder why people refer to lenses as copies. They are all originals!

I have taken lots of lenses apart. That's the easy bit. Putting them back together without ending up with spare parts is the tricky bit!


Steve.

 

[CGW]

I was very happy to find a fairly clean copy of this lens in the junk bin yesterday but when I got home I discovered the problem. The focus ring goes from MFD to about 5 meters and then binds and won't go any further. Where it stops it doesn't hit a hard stop with a clack like at the normal end of the range. It just suddenly gets tight and stops.

So I want to take this lens apart and see what's going on but don't know where to begin. The lens butt has about 7 or 8 tiny screws so I'm a bit intimidated, not knowing which ones to loosen. Should I start from the front?

Does anyone have experience disassembling this or similar lenses? How complicated is the focusing mechanism? Are there certain things I need to mark or note during dis-assembly in order to get it back together properly? And most importantly, does anyone have any convincing theories on what may be causing the problem?

Any help or advice appreciated!

This is among the few DIY sources on Bronica S/PS lenses I've ever seen. Might at least given some idea of what you're in for:

http://www.buonaluce.com/

The 105/3.5 S is a very sweet lens and worth saving. They're a bit of a rarity now. Snagged one a year ago in pristine condition for very little $. Actually prefer it to the 80/2.8 PS. Good luck!

 

[revdocjim]

Thanks Steve and CGW.
Steve, point well taken. I often hesitate when using that phrase, but end up doing so for lack of a better way to express it. "I was happy to find a fairly nice ??? of this lens in the junk bin yesterday..." I know I could rewrite the sentence differently, but if I want to say it that way, what is a good word to insert there? "version" doesn't sound right...

Anyway, thank you very much CGW for the very informative link and resource materials. Exactly what I was looking for. I'm still not sure how far I'll need to go to get at the focusing mechanism but will give it a try.

 

[Steve Smith]

I often hesitate when using that phrase, but end up doing so for lack of a better way to express it.

It could be worse. Model engineers building scale model steam locomotives refer to the original as the prototype!


Steve.

 

[John Koehrer]

The focus mechanism has two guides in the helical that keep the inner helix from turning So that's from the back.
You're going to likely take it apart from the front and back. The infinity stop will be at the front and prevent it from unscrewing. And the front.

Assembly is going to be more complicated. You're going to need to mark the helicals with a scribe mark to get the alignment right the first time.
It's not critical but it can be REALLY frustrating if you don't. Keep in mind there are five or six threads on each tube and only one will allow the guides, aperture mechanism and infinity focus to line up. You may need to adjust infinity when you're done anyway.
*It's really fun when you don't mark it =\ but is good for teaching patience, grasshopper.

 

[revdocjim]

Thanks John. I'll be sure to try and mark things as I take it apart.

 

[revdocjim]

OK, time for an update. First the good news; the lens works perfectly now.
Now the embarrassing part; it always worked perfectly!
The problem? It disappeared when I removed the rear lens cap! The rear-most edge of the rear group was hitting the rear lens cap, preventing it from going to infinity.
But why? Well, just a minor detail... I was using an ETR rear lens cap. When I found the lens at the store in the junk section it had no caps. So I went to the crates full of caps and started to hunt. I couldn't find an SQ rear cap but found an ETR one and tried it out. And it fits just fine! I thought, lucky me! Only now have I discovered that the SQ cap is deeper.
And the most embarrassing part: I had the lens almost fully disassembled before discovering the source of my problem. I removed the front ring and front element (rear cap still in place) and when I checked the focus ring it still wouldn't go to infinity. Then I removed the rear cap, the rear element and the rear plate and discovered that the focus ring worked fine. So I figured something had been jammed. Reattached the rear plate, re-inserted the rear element and it still worked fine. Now before reinserting the front element I attached the rear cap, flipped it over and started to insert the front element. Tested the focus ring and "oh no! the problem is back!" "Must be related to the front element"...

Anyway this foolishness went on for some time until the light finally clicked on in this cloudy brain of mine! "I can see clearly now..."

 

[NJS]

CGW - Thanks a lot for that italian link.

 

[sveamarcus]

The 105/3.5 S is a very sweet lens and worth saving. They're a bit of a rarity now. Snagged one a year ago in pristine condition for very little $. Actually prefer it to the 80/2.8 PS. Good luck!

For the record, I've seen one listed on ffordes for awhile now, if anybody's hunting for it.