Zenzanon-s 80 fix

DMJ

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Is it possible to fix the focusing system in this lens? Mine does not focus to infinity and the scale on the lens does not match the view in the focusing screen. I'm not going to send it out because it will be more expensive than buying a new one.
I have cleaned and fixed some older lenses but nothing with electronics and I don't mind trying.
 

DWThomas

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It's obviously about Bronica gear but you don't say which one. A couple of questions come to mind ...
Do other lenses focus correctly on the body?
Do results on film show lack of focus?
I'm just speculating the focus screen is not seated properly.
 
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DMJ

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What do you mean I don't say what gear? The Zenzanon-S 80mm is a Bronica SQ lens.
Yes, my other lenses work great. It only happens with the 80mm and the focus is off on film. It's the lens, not the focusing screen. What I want to know is if it is possible to disassemble the lens and fix it or better use it as a paper weight.
 

4season

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My first thought is that someone took apart the focusing helicoid and reassembled it incorrectly. Often these things can be screwed back together in a couple of different ways, but only one way is actually correct.

The lens should otherwise be pretty simple and modular:
Front and rear lens cells
Shutter unit connected to rear of lens via spiral of flexible PCB (don't disassemble that shutter unit).
 
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DMJ

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Thanks @4season . I don't even know where to start with this lens. I think there is a flexible PCB that connects the shutter system to the pins. Does the whole lens need to be disassembled? I can still use it at small apertures though.
 

4season

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DMJ said:
Thanks @4season . I don't even know where to start with this lens. I think there is a flexible PCB that connects the shutter system to the pins. Does the whole lens need to be disassembled? I can still use it at small apertures though.
Click to expand...
It shouldn't, but I can't provide more specifics because I have not serviced that particular lens.
 
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DMJ

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Attached.
 

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DMJ

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and btw, does anyone prefer shooting with the 105mm or 150mm over the 80mm? I'm thinking on getting either; I only have the wider lenses.
 

shutterfinger

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I'm not familiar with this lens or Bronica, however mechanical assembly is similar between brands. I'm currently reassembling my 60mm f2.8 AF Micro Nikkor working from a 2.8 D diagram. It was not auto focusing.

Now, the 5 screws at the white arrows hold the mount ring to the rear of the lens assembly. The 4 screws at the red arrows hold the electrical contact pin plates to the mount ring. You can remove the 5 screws (white arrows) and carefully lift up the mount ring and tilt it to one side to inspect access to the focusing assembly. Remove the 4 screws (red arrows) only once the mount ring screws are removed as the pins may be spring loaded, if they are solid then it will be safe to remove the screws holding the pin blocks to the mount plate before removing the mount screws (white arrows).
Post another picture with the mount plate removed.
 
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DMJ

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Thanks a lot @shutterfinger. I will try it and post, it will take some time.
 

Horatio

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I’m subscribing. I have a Bronica 50mm lens with focusing issues I’d love to repair. I think it was reassembled incorrectly.
 
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DMJ

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So far...
 

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DMJ

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Everything inside moves forward
 

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shutterfinger

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I see what appears to be thread start points which I have typed thread start on. There may be more around the circumference of the barrel.
What I cannot tell is if the barrel comes off the front or the rear, need more pictures.
The cells appear to have fixed stop points so the only way they would be in the wrong position is if shims were left out.
 

4season

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Here's a service manual for the ETR's 75 mm lens; I'd expect the SQ lenses to be very similar:
https://learncamerarepair.com/product.php?product=412&category=2&secondary=33

I had another idea which may involve a lot less disassembly: Let's start by assuming that the focus helical is actually fine, but see if there's a relatively easy way for you to change the position of the focus end-stops and rotation of the focus ring, from the focus ring itself. On my ETR lens, I peeled off (carefully so as not to tear it) the rubber grip, revealing black sealing tape. I removed this, revealing a series of small setscrews. Possibly all that you need to do is loosen these (I doubt you need to actually remove them), rotate ring so that focus scale agrees with viewfinder focus, and when you're satisfied, reassemble.
 
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DMJ

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Great idea @4season , will investigate further. Thanks @choiliefan. And now a picture of the ring stopper (I believe)
 

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hsandler

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I can't help with the repair, but it happens that I have a spare Zenzanon-S 80mm lens I could part with for not much money, as an opportunity came up for me to get the -PS version. So if you need to replace it...
 
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DMJ

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hsandler said:
I can't help with the repair, but it happens that I have a spare Zenzanon-S 80mm lens I could part with for not much money, as an opportunity came up for me to get the -PS version. So if you need to replace it...
Click to expand...

Sounds like a good idea. I will send you a message.
 
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DMJ

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So this works for the SQ-A too. There are 3 screws for adjusting the focusing scale. Unfortunately the lens does not focus to infinity and I think the problem is the position of the helicoid.
 

flavio81

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DMJ said:
Is it possible to fix the focusing system in this lens? Mine does not focus to infinity and the scale on the lens does not match the view in the focusing screen. I'm not going to send it out because it will be more expensive than buying a new one.
.
Click to expand...

When you have such a problem you need to check many things:

1. The focusing screen. It is really sitting correctly? On the ETR (and probably the SQ as well), the focusing screen matte side should rest on four beautifully polished points. Around the screen there are leaf springs that should have some tension to keep it into place.

2. The mirror angle. Is it really 45°? An easy way to check is to focus in some infinity or far object using the top of the focusing screen, and then checking if the same object placed at the bottom of the focusing screen is still in focus. If it isn't, then the mirror angle is off.

If those two are ok, then one can check the lens. First, it is important to check that all screws are tight and that all the front/rear lens elements are screwed tight (ruling out the possibility of them being slightly unscrewed).

If all this is OK then the infinity stop on the lens should be adjusted!! And problem solved.
 
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