Light Leak on Bronica SQ Ai Back

[Shangheye]

OK, this is for starters, since I will post a scan of the negatives when I get home. I have spent the last few days trying to find something remotely similar to my problems (including here in APUG) and could find nothing.

I have three backs for my bronica. One seems good and not to exhibit this problem, the one of the others has a crack on the edge of the body though not in the sealed area of the insert (and the crack is at the top and so probably not the problem..see the relevance below...but I will ignore this back), and I have another back which had a 220 insert, in to which I switched the 120 insert from the cracked one. The leak still appears to be there (alot fainter, but in the same location...and I did take the pictures in quite quick succession, but in bright sunlight)...remember no leak on the other good back...so the camera is not the problem?

The light leak is regular though of varying brightness along the different frames but exhibits itself as a slim (2mm line expending to almost the middle of the frame ending at a point..fading towards the middle) and starts at the edge so includes the rebate area outside the image. It almost always appears in the same location about 1.5cms down the frame on the right hand side as I would have composed the picture...which to me means the bottom left hand side of the back? But it does sometime appear in between two frames (rarely).

I assume the leak would be in front of the film plane, since I read somewhere that a leak in front exhibits as a white light mark and behind is a red light mark (I know the colour because I have seen the leak on a colour slide film). Where it becomes confusing is that this would lead me to believe that the insert can not be the source of the leak, but the back is. Is it possible that both the backs I have tested that leak, have a leak in the same exact place!...I assume that place would have to be the dark slide curtain? I did read somewhere that a dark slide curtain leak exhibits itself on the opposite side to the curtain ...something to do with reflection? Tis would be on the opposite side to where I am seeing the leak.

I would like to add here that occaisionally some frames do not exhibit the light leak at all...

One other possibility is the failure to tighten the film when loading the spool, but I can't believe that would generate the same regular patter I see from these two backs...I'm not that gifted :rolleyes:

Anyway, I have debated taping the damn things up...which reduces the convenience but solves the problem (I assume) while I resolve this. I would appreciate if anyone has any insight, and as I promised, I will have a scan posted in the next few hours....but it's driving mad enough to write this post straight away! :confused::confused::confused:

Thanks for any help you can give me!

Rgds, Kal

 

[Shangheye]

The scan

The scan
...can see now the leak is much bigger than I thought!

 

[DWThomas]

Yes, take a look at the last four shots on my SQ-A page.

There's a foam seal across the latch side of the back shell that turns to goop and disappears over time. In response to someone else's question on P.net I put up the three views with approximate dimensions of seals. Some work with a kit of seal material from Jon Goodman ("Interslice" on ePrey) solved my problem.

One thing is that I believe it's actually the next blank frame being exposed where it comes over the rollers, not the frame that is taking the photo. That can confuse the analysis sometimes.

Good luck with it.

DaveT

 

[Shangheye]

Thanks Dave..I actually saw your page in my search over the last few days, since I am also on pbase! I thought at the time my leak was a lot thinner, but now I can see it's the same. I already contacted Jon Goodman, so hopefully a response. By the way, looked at the back today and I can confirm that the foam is not goop, but it's split (there are two bits of foam stuck together, but on one side, they have come apart. It happends to be on the left side, and is so consistent with the location and your theory! Brilliant..Thanks you...also consistent with quick wind on reduces the leak effect!!!K

 

[wclavey]

I had a very similar light leak on one of my Bronica S2a backs and it turned out to be where the dark slide was inserted, a bit of the felt seal was worn away worse than the remainder of the seal (...probably from inserting the upper corner of the slide in first before pushing the slide all the way in...). Had Dave not suggested the light seal on the back itself, I was going to suggest this. Replacing the felt cured mine.

 

[Shangheye]

I believe the kit from Jon Goodman resolves that too...I will do it by order of ellimination. Thanks Westley ;-))K

 

[evilhomer78]

I've had the same light leak in one of my bronica sqa backs. I replaced the light seals using Jon Goodman's kit (excelent by the way). Now all of my backs (3) are light leak free. Check out DWThomas's link for photos on the light seals. My leaky back was actually missing one of the small side seals next to the top of the back.

 

[vdonovan]

I had the same leak. I read the info on DW Thomas's web page. I bought the kit from Jon Goodman. All is good now.

 

[DWThomas]

... I read the info on DW Thomas's web page. I bought the kit from Jon Goodman. All is good now.

Wowie, my 15 minutes of fame!

I'm glad to know that page has been helpful, it was originally put up to help an enquirer just shortly after I had hacked my way through a repair. I should probably add the disclaimer that I have yet to see a repair manual for the SQ*** series, so all the dimensions I show there are based on measuring with a small scale -- and not really knowing 100% what the pieces should look like before they've shredded a bit or turned to goo and smeared away. I made the measurements on the back I had that looked the newest (and worked).

Between light leaks and film indexing errors (my 1st acquired back cranked fim all the way through without stopping), the back seems like it's the Achilles heel of this series.

It's a great system when it works though.

DaveT

 

[vdonovan]

It's a great system when it works though.
DaveT

Hi Dave, did you ever fix your other body that stopped working? Funny how it's IMPOSSIBLE to find an SQ-series repair manual. I've got a locked-up body too. It's cheaper to buy a new one than to get the old one fixed, but I would like to take it apart some day.

 

[DWThomas]

Hi Dave, did you ever fix your other body that stopped working? Funny how it's IMPOSSIBLE to find an SQ-series repair manual. I've got a locked-up body too. It's cheaper to buy a new one than to get the old one fixed, but I would like to take it apart some day.

Nah, it's laying around here somewhere in the massive 40-year accumulation of "stuff." I snagged a body in really nice condition shortly after I came back from that trip, then a month later, bought another. I figure with a working spare available, the first replacement should work forever. In theory, if I'm not too decrepit to see what I'm doing when I finally get time to try, I would like to try and get it apart. I think its problem might be pretty simple -- if I knew how to see inside! The second replacement is a little more "used" then the first, so I used it for my pinhole adaptor shots for this year's WPPD just in case that had anything to do with my problem in the original.

I've seen repair manuals for some earlier models, maybe we just have to wait until the SQ stuff passes some magic age boundary and the successor company will release the stuff to the public.

(Can't believe I'm sounding that optimistic! :rolleyes

DaveT