Bronica SQ Shutter "Occasionally" Firing

I have a Bronica SQ that seems to be selective about when it will open the lens shutter...

1/500 has been okay because it's the default mechanical setting if the battery dies I presume, but other speeds work sometimes and sometimes they don't. I've checked the electrical contacts throughout the body and they appear to be clean and clear, brand new battery does't seem to work, I've tried different lenses (three) with similar results as well as different backs (two) and still the shutter only fires half the time.

Through exhaustive digging and sifting through various forums, the only relatable mentions parallel to what I'm experiencing have chalked it up to a battery contact issue; allegedly, if the battery isn't perfectly seated against it's contacts in the compartment, the circuit fails and thus, no power to the shutter in the lens. The recommended remedy is a small cardboard "shim" of sorts to place between the battery and the battery door to hold it snugly against it's respective contacts. I've tried this and it also doesn't seem to work...

Any ideas? Has anyone else experienced or even heard of something similar? Previous threads mention similar issues where the shutter just doesn't fire at all and the film back was the culprit the majority of the time. Could I just have two bad backs?

I experienced the same 'sometimes' shutter action on my ETRSi. It turns out that the 'film advanced' interlock pin (on a film back purchased used) protruded too far into the body, and that would sometimes cause the reflex mirror to not flip up fully; when that happened, the mechanical lever to trigger the shutter in the lens would not always actuate the shutter. I sent the body to GMI Photographic, the importers at the time (prior to Bronica company purchase by Tamron) who told me to send body and back for adjustment.

1. I note that your experience is with multiple backs, so the problem is likely not the interlock pin in the back, but could be in the mechanical components needing adjustment inside the body.
2. It is definitely NOT electrical issue, as 1/500 always works and it is a purely mechanical actuation when the battery is absent/dead...it should ALWAYS fire the shutter at 1/500 if it were electrical issue! battery power is only for timing the shutter speeds that are slower than 1/500.
3. Set your body so lever for multi-exposure is set; that removes interaction between the film back interlock pin and the body's corresponding lever...the shutter should always actuate in this mode, even if there was interference between the interlock pin and the body mechanism. If shutter works reliably in this mode, that is an indication of film-advanced interlock issue, similar to what I experienced -- mine in the back, yours perhaps in the body mechanism.

Thanks so much for your response and advice!

wiltw said:

It is definitely NOT electrical issue

Click to expand...

I kind of figured the same, but I'm relieved to hear you confirm it!

With the lever set in multi-exposure mode, it still only fires part of the time... With no back on the body, the shutter seems to engage every time at all speeds, so you're definitely right in diagnosing it as an issue between the back and the body! I've tried three different backs now so I'm getting more convinced its an issue with the mechanism within the body.

I have a fairly ugly film back that I wouldn't be opposed to attempting to file down the interlock pin as I've read that's merely what Bronica Technicians were doing when customers were experiencing similar issues. I don't know if that's true, but in my research it has seemed to remedy the situation for some people. Should I go for it?

There are two pins with collars on the film back, the one pictured below circled in red is the one I believe to be the Interlock Pin can you confirm?


Thanks again for your time and help, I really appreciate it! What a mystery!

roamandclick said:

I have a fairly ugly film back that I wouldn't be opposed to attempting to file down the interlock pin as I've read that's merely what Bronica Technicians were doing when customers were experiencing similar issues. I don't know if that's true, but in my research it has seemed to remedy the situation for some people. Should I go for it?

There are two pins with collars on the film back, the one pictured below circled in red is the one I believe to be the Interlock Pin can you confirm?

Thanks again for your time and help, I really appreciate it! What a mystery!

Click to expand...

That pin is the darkslide interlock, so the body knows the shooter screwed up and is trying to make an exposure with the dark slide in place. You can verify that action simply by removing the darkslide and watching the pin withdraw.
(Note: If the back has a darkslide lock to prevent users from removing the slide while the back is not mounted on the body, there is a very small pin close to the darkslide handle that you have to depress first to pull the darkslide out).

The other pin, close to the film advance gear, is the film advance pin. If you put a roll of film into the back and advance it, a pin should rise to indicate back is ready for next exposure. I would NOT file it down too far...do it progressively. And I would use a fine grinding tool in the Dremel, not a file, to remove material off the end of the inner pin (not the outer sleeve)

wiltw said:

(Note: If the back has a darkslide lock to prevent users from removing the slide while the back is not mounted on the body, there is a very small pin close to the darkslide handle that you have to depress first to pull the darkslide out).

Click to expand...

This particular Film Back doesn't have that pin, but the other two I have do.

Thanks for the descriptions! Very helpful! I think I'll continue researching before I pull any tools out and modify anything as it cannot be undone and I'd prefer to be sure before altering anything physically!

My SQ-A has a similar problem. With some advice from Jimmy Koh it turned out to be the pin at the top left of the screen, which indicates whether you have an AE finder installed. This can be tested by installing an AE finder, at which point the camera becomes absolutely reliable (with the finder on).

The solution (which I haven't done, due to personal issues and a fear of breaking a mostly working camera) is to remove the side of the camera around the exposure dial, and clean/adjust the contact attached to the pin. This is documented in the ETR-Si manual, and appears to be very similar on the SQ.