pressure plate, springs, and flatness

[qqphotos]

I'm discovering occasional exposures on my IIIg are soft at one edge, always the same (the supply side, rather than the take-up spool side). I've mostly ruled out things like a decentered lens or loose collapsible. It almost seems like the film is lifting away from the guides just at the edge. Not always, though. Seems to happen for a few frames in a row mid-roll, and sometimes not at all. Maybe film tension or lack thereof.

Can the springs behind the pressure plate lose tension and need replacement, can they become displaced and do this, or is there some other likely explanation?

 

[Ambro51]

Remove the lens and fire the shutter on bulb. That will show you the pressure plate. They are actually a separate piece which slides into the body shell as it’s inserted with the shutter drums etc. it springs sit into recesses. If the plate is at all out of place no film will run through. Quite unusual for these to be a problem.

 

[qqphotos]

Remove the lens and fire the shutter on bulb. That will show you the pressure plate. They are actually a separate piece which slides into the body shell as it’s inserted with the shutter drums etc. it springs sit into recesses. If the plate is at all out of place no film will run through. Quite unusual for these to be a problem.

Yeah, I can feel that the pressure plate is sprung and not noticeably jammed, though it has some freedom to slide around a few mm in different directions. I assume this is normal since it's a separate piece. May need to look elsewhere for an explanation for the occasional out of focus edge.

 

[Coldkennels]

Mis-aligned lens mount, maybe? Shims removed on one side?

 

[Dralowid]

Ambro is right, the springs are two very simple bits of 'spring' steel with a bend in them. They sit in recessed areas and should offer up minimum pressure when a film is in there. If they have slipped this will probably get a little tighter but I have never heard of them being out of place UNLESS someone idiot has not put the camera back together properly. I would advise against taking the springs out and bending them so that they exert more pressure.

(By the way, the pressure plate shape changes over time.)

I do not think they will be the problem.

 

[raydm6]

Not sure if this is helpful, but here is a tear-down and reassembly of a IIIc.
http://tunnel13.com/blog/leica-iiia-cla-and-repair/

I'm not sure if the film pressure plate/spring configuration is similar to your IIIg, but the author alludes to (and as Ambro51 mentioned above) making sure the plate rides in its own milled grooves and the leaf springs aligned in their slots - perhaps one of these is off/misaligned a bit if that is the case? But it seems you already checked that.

Lets put it back together. The film pressure plate rides in it’s own groove milled into the back of the body shell. The two leaf springs have their own slots as well.

 

[qqphotos]

Not sure if this is helpful, but here is a tear-down and reassembly of a IIIc.
http://tunnel13.com/blog/leica-iiia-cla-and-repair/

This and the photos are very helpful, thanks - seeing how it all fits together leads me to think there's nothing wrong going on with mine, all four corners of the pressure plate have spring to them and it covers the whole frame area. I'm starting to go through a few dozen scanned rolls of film looking for anything else the affected exposures have in common.