Problem with Bronica ETR and Zenzanon lenses (blank frames)

[neilt3]

Before I start a new thread, or provide a lot of details about my very similar problem with the same lens on this thread, along with what I have tried so far, I want to see if this post will even be noticed because the thread is so old. Please say hello or something if you are even somewhat familiar with Bronica lenses in general. Thank you!

Well , most of the posters in this thread will have received an email saying there's been a new post in the thread , as old as it is .
So , what's your question then ?

 

[Rick_P]

@MattKing Thank you for the warm welcome, and @neilt3 thank you for the tip!

For all, here's what's going on with my Zenzanon 75/2.8 MC and how it relates to this thread. This initial post is a long read because I did/tried a lot of things before I started seeking a forum.

Important side notes, I have two working Bronica ETR (first generation) bodies and two lenses, one lens works, one doesn't. The one that doesn't work doesn't even work in full mechanical mode (no battery, so no electronics involved). The non-working lens does not work on either working body. This sort of eliminates the failure stemming from the body. With that said, here are some things I've tried...

I am a tinkerer with tools, which either makes me dangerous, or resourceful. In this same thread, @moto-uno points out that there is a ribbon cable that can be checked with minimal effort. So, I removed the back cover and inspected the ribbon cable visually, and used my voltmeter in continuity mode to make sure there was connectivity through the six contacts on the circuit board inside through the ribbon to the six gold pins on the outside of the plate, the ones that contact the body contacts when the lens is mounted on the body.

While I had the plate off I noticed the tiny lever going through the bayonet of the lens, I soon learned this lever has a name, it's a interlock lever, which prevents movement of the shutter actuator (sliding) pins until the lens is mounted. After putting the back plate back on the lens I discovered (through brave experimentation) that when the lever is pushed in from the outside with a small screwdriver, it releases the locking mechanism and allows you to move the shutter actuator pins on that back of the lens, and when I did that (slid the pins to the end of the slots) the shutter actuated and I saw the flicker of light thought the lens. And you can feel the spring tension when you rotate the pins back to the locked position, which I assume cocks the shutter. After all this I reinstalled the lens on the camera and fired it a couple of times but did not see the flicker of light looking into the back of the camera. No surprise there because I didn’t fix anything.

Important note, when you release the interlock lever, there is almost no tension or resistance as you slide the pins until you get to the end of the travel, and then there is only a slight resistance as you release the shutter mechanism inside the lens. Point being, it’s not “sticky” or “gummed up” in terms of mechanical operation here.

Another not as important note, I compared the amount of distance the interlock lever needed to be pushed in before it released the interlock on both lenses and they are the same, they both release before they are even flush with the bottom of the channel in the bayonet. I even took the cover off again to see if there was a way to adjust it and have it release earlier, but there is nothing to adjust, and nothing looks worn or loose. And while the lens is mounted on the camera I tried adding a little pressure to the outside of the lens right where the interlock lever is while releasing the shutter, just to make sure any slack might be taken up, but none of this made it work.

So, I feel like it’s some minor mechanical issue, but I don’t know what else to try. Any suggestions? Note that I didn’t take pictures, but I can if it will help.

 

[Rick_P]

Maybe no one has any additional ideas to try, or has any additional knowledge on this issue, or maybe I should have started a new post instead of resurrecting an old one.

 

[koraks]

Welcome aboard @Rick_P
Feel free to make a new thread and in case you do so, including pictures will likely help getting some responses.

 

[reddesert]

Maybe no one has any additional ideas to try, or has any additional knowledge on this issue, or maybe I should have started a new post instead of resurrecting an old one.

Your problem is not simple and there isn't an obvious answer to it. You fired the lens shutter mechanically with the lens off the camera by depressing the mount-interlock button and pushing the cocking pins away from the cocked position, and the shutter closed and then opened briefly (presumably at the mechanical speed 1/500 second). You should also see the lens stop down to the taking aperture when this happens. This suggests that the shutter is operating mechnically, it isn't stuck or something.

Then, you put the lens on the camera and fired it and said that it didn't open at all. This is hard to understand because the camera is basically doing the same mechanical operation you just did by hand.

It would be easier to understand if it opened at 1/500 but never fired at the longer speed you set on the camera. It is possible that happened and you missed it. That would point to an electronic problem with the shutter timing - the camera is supposed to send a hold-open electrical signal to the shutter and the shutter's supposed to hold open with I think a solenoid.

There are some fairly detailed writeups by Max Vettore of how the lens shutter works that were at buonaluce.com and you can access on the Internet Archive, see https://web.archive.org/web/20160317091931/http://www.buonaluce.com/

 

[Rick_P]

Your problem is not simple and there isn't an obvious answer to it. You fired the lens shutter mechanically with the lens off the camera by depressing the mount-interlock button and pushing the cocking pins away from the cocked position, and the shutter closed and then opened briefly (presumably at the mechanical speed 1/500 second). You should also see the lens stop down to the taking aperture when this happens. This suggests that the shutter is operating mechnically, it isn't stuck or something.

Then, you put the lens on the camera and fired it and said that it didn't open at all. This is hard to understand because the camera is basically doing the same mechanical operation you just did by hand.

It would be easier to understand if it opened at 1/500 but never fired at the longer speed you set on the camera. It is possible that happened and you missed it. That would point to an electronic problem with the shutter timing - the camera is supposed to send a hold-open electrical signal to the shutter and the shutter's supposed to hold open with I think a solenoid.

There are some fairly detailed writeups by Max Vettore of how the lens shutter works that were at buonaluce.com and you can access on the Internet Archive, see https://web.archive.org/web/20160317091931/http://www.buonaluce.com/

@reddesert Thank you, this is more helpful than you might think, I suppose it’s possible I might have just missed the flicker of light through the lens when mounted, I’ll try that again.

 

[wiltw]

Any news on this topic, Rick_P?

 

[Rick_P]

Any news on this topic, Rick_P?

I had to put this on the back burner when other priorities came up, but the whole kit is still sitting on my workbench waiting for me to resume, which I hope to get to this week. I’ll keep you posted.