Bronica SQ 6x6 back - interlocks, pins and collars

This is a question aimed at those who are really in the know about the ins and outs of Bronica SQ cameras and backs.

On the bottom right of a Bronica SQ back, there is a small silver pin in a plastic collar (see attached photo) .

The collar is a moulded piece that appears to come through from inside the back, where it seems to be part of another moulding. (correction welcomed if not true)

It engages with a corresponding hole on the camera body so it locates & lines up the pin properly with a similar pin in the camera body.

So far as I understand the workings of the SQ backs, this pair of pins form part of the interlock mechanism that stops the camera being fired with the darkslide still in. (I'll welcome correction on that if I have misunderstood that either.)

I have acquired a back where the plastic collar has broken off.

So far as I can tell, the two pins still act properly together to enable the interlock to function correctly and the back is otherwise in excellent mechanical order.

But without the collar, I wonder what the chances are of - over time - the two pins jamming or otherwise causing problems because - without the collar - they have the possibility of being imperfectly axially aligned when they are actuated.

I'm less concerned that the back may break or become useless -- it was acquired at a price that makes it almost "disposable" -- rather that it may damage the SQB body (which isn't at all disposable).

It doesn't "look" like an economically viable repair.

Any comments from Bronica experts?

thanks

I used one like that for years and you could definitely release the shutter with the dark slide in! It did not cause any problems, other than the occasional blank frame.

Hi,
I wish I had an answer. Email Jimmy Koh, he is an expert repairing Bronica equipment. Send him exactly what you posted here.
sales@kohscamera.com
Until you know for sure I would not mount the back (but chances are it is OK). Backs are very cheap these days, just get another. The newer the better, which would be a SQ-Ai. SQ have black plastic dark slides, SQ-A have Gray plastic.
best of luck,
Rick

thanks chaps

ParkerSmithPhoto said:

I used one like that for years

Click to expand...

That's reassuring!

RichardJack said:

Until you know for sure I would not mount the back

Click to expand...

Too late! Already tested it with a roll of backing paper to make sure it worked ok.
Didn't notice the pin problem 'til I took it off again.

It's an Ai back, btw, though I think all early SQ backs of any type had a black grip, and all later ones had a grey grip.
But again, I will stand corrected.

I'll email Mr. Koh, though, thanks.

fwiw, backs are not incredibly cheap here in the UK - we don't have a KEH unfortunately! A back in good order from a trustworthy retailer usually costs GBP50 - GBP80. They can be got cheaper from private ebay sales of course but then it can be a bit of a lottery - just like this one!

There is an outer frame that essentially captures the dark slide. That tube is part of a section at the next level under that. If the breakage is only down to the outer surface, I wouldn't think it should be that critical, as I think the pin alignment portion of the fitting is deeper into the back. I currently have had a back partially disassembled so long I fear I may have trouble reassembling it, but the intent was to make and install a new dark slide light seal. For that I didn't have to dig deeper than removing the outer rectangular frame.

The tube/interlock is part of the back shell, not the insert, so one option would be snag a 220 back for maybe peanuts and swap the shell portion, as they are the same for 120 and 220.

If it were mine I might look at hobby materials to see if a chunk of styrene or brass tubing is available to match the inner and outer diameter of the tube. If so, one might take the outer frame off and trim the broken tube down to the next layer, then superglue (or whatever) a short bushing in the outer frame -- a sort of splice without a splicer.

Oh --- but I'm not actually an expert, I only try to play one on The Interwebz!

DWThomas said:

f it were mine I might look at hobby materials to see if a chunk of styrene or brass tubing is available to match the inner and outer diameter of the tube. If so, one might take the outer frame off and trim the broken tube down to the next layer, then superglue (or whatever) a short bushing in the outer frame -- a sort of splice without a splicer.

Click to expand...

Oh boy, Dave, to me a complex piece of engineering work is cutting up a piece of paper on my kitchen worktop with a scalpel and a straight edge.
Plus, if I start playing with superglue I'll end up walking around with a piece of camera kit permanently affixed to my thumb.
I've got a screwdriver, a junior hacksaw and a hammer, mind you, so I suppose precision work is not entirely off the table.

Wow Mr. Koh is an obliging fellow, and quick with his emails too!

Jimmy Koh said:

you don't have to do anything, it is not going to damage anything. if you need the part to replace just let me know.

Click to expand...

pdeeh said:

Oh boy, Dave, to me a complex piece of engineering work is cutting up a piece of paper on my kitchen worktop with a scalpel and a straight edge.
Plus, if I start playing with superglue I'll end up walking around with a piece of camera kit permanently affixed to my thumb.
I've got a screwdriver, a junior hacksaw and a hammer, mind you, so I suppose precision work is not entirely off the table.

Click to expand...

Hehe, if you just add a pair of needle-nosed pliers to that tool set you'll be able to CLA an Argus C3!

I'm glad to hear Mr. Koh confirmed my educated guess. My original suggestions point to the approaches we might take to keep these machines going. (Like those repair guys in Cuba who learned to adapt generators from ancient farm tractors to keep their 1953 Pontiacs on the road, etc.)