Canon P - shutter bounce help?

Filzkoeter

Filzkoeter

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Hi!
So I just got this lovely Canon P fresh from Japan and I'm giving it a CLA right now. From marks I can tell that someone at some point opened the bottom (or at least retightened the ring around the tripod mount), but other then that it seems like this camera has never been opened further.

I'm no stranger to working on cameras, repaired sucessfully 2 Rolleicords (one had busted focusing rails), rebuilt shutter curtains in one Zorki, did couple other soviet rangefinders, CLAd a IIIf (+ 1 new curtain) and worked on an M2.

Since this is my very first Canon rangefinder, I'm not yet 100% accustomed to everything that goes on inside of the shutter, yet it is very similar to screwmount Leicas and their derivatives, so not really difficult for me.

Long story short:
I'm currently getting a second curtain shutter bounce at all speeds (see video) that I can't really wrap my head around at the moment.
https://youtu.be/IbLmdDmYNlY

I'm linking the part diagrams of the Canon P, as I will refer now to some parts from there:
https://pentax-manuals.com/manuals/service/canon_p_repair.pdf

The Canon P has two shutter brakes, one for the first curtain (seen from the opened bottom, braking the drum, sheet 10: C9057) and one for the second curtain (inside the shutter crate, next to the slow speed escapement, braking the gear that is connected to the second curtain roller, sheet 11: C9043). So the second curtain brake seems okayish to me, there is spring tension on it, the shutter sound of the second curtain also sounds dampened.
What I'm not understanding fully is the first curtain brake: so (bottom to top) there's the pivoting brake lever (C9057), a locking nut, a brass bushing with a coil spring around it, a washer and another locking nut on top that holds everything together. The coil spring is connected to the brake lever but otherwise just sits there?
https://youtu.be/2cIWbkPfzgs
Isn't it supposed to be, you know, what springs do, be springy? It doesn't move super easily but I guess there's not much braking action there, as the first curtain seems to be slamming with more or less full force against its stop (= loud). I know that screwmount Leicas use their first curtain brake (as there is no 2. brake) also for braking the second curtain, am I right to assume that this is also true for a Canon P? Am I right to assume that there is not enough braking action going on to stop the 2. curtain from bouncing because the first curtain brake doesn't work as intended? Maybe someone with Canon experience can help me figuring out if the first curtain brake should be springy or not?

Thanks 😎
 
I have no experience with the Canon rangefinders at all (other than selling a II or something a couple of years ago). So I won't even try to offer any specific advice. All I will mention is that if the camera seems to have been tampered with at some point—check the shutter speed accuracy. If the spring tensions have been dialled up too much, this can result in bounce with many focal plane designs because it will overwhelm the brake. Remember that most classic fp shutters are designed to run accurately with the minimum possible amount of spring tension in the interests of longevity and consistency. Simply ratcheting up the tension rarely achieves a good result if servicing is needed—it may get the curtains running faster, but tends to play havoc with the acceleration rates and exposure consistency across the gate—it can certainly cause bounce problems. I am certainly not suggesting you've done this—but someone else might have. So—check the times across the gate, the actual exposure achieved at the start, middle and end from max to sync (1/60?) may tell you much about what each curtain is doing. Also—until you have the curtains running fairly well there's not much point worrying too much about the brakes (as long as they're not making the curtains stick). First task is to get the curtain travel time right and exposures correct—if these two things are to manufacturer spec then you can worry about brake adjustment and elimination of bounce. Note as discussed above if curtain travel times are good the bounce may eliminate itself.
Cheers
Brett
 
If both brakes are working You can try to lessen the spring tension of the closing shutter curtain and see if that alleviates the shutter bounce, then compensate the tension of the 1st shutter curtain to bring the shutter speeds to within spec tolerance for the fast shutter speeds...this worked on my Canon FTB but YMMV on your Canon P .
 
Thank you all for the suggestions. I think I have figured it out and it seems the shutter bounce is now gone.


As it looks, there is a second brake for the 2.curtain that I have overlooked, as I was concentrated on the two brakes on the bottom. It is on top of the shutter crate and brakes the drum (sheet 12 part C9067). I gave the pivoting part a tiny bit of oil and it also seems that it's a bit adjustable by how the spring (C2265) is set, too much tension and the 2. curtain was stopping short and leaving a gap. With some playing around I was able to eliminate the bounce!
 
Congrats, thanks for the update! Iirc I also couldn't find that second curtain brake, I'm tempted to look into it again and try to get it all running with lower spring tension. Need to find the thread I posted in back then, about a year ago, can't remember much...
 
I've got to adjust mine, or I can just not use 1/1000 (which is the only speed it bounces on). I think I'd rather have it running correctly though, since all the speeds could be affected. Glad you got yours sorted out, Miko.


PF
 
retinax said:
That's exactly what happened with my P. It's still not exactly smooth and quiet, but the shutter works ok. Not using it much, if money comes my way I may send it to a professional...
Click to expand...

retinax said:
Congrats, thanks for the update! Iirc I also couldn't find that second curtain brake, I'm tempted to look into it again and try to get it all running with lower spring tension. Need to find the thread I posted in back then, about a year ago, can't remember much...
Click to expand...
I'd quite forgotten about that: but I think it was this one?

https://www.rangefinderforum.com/forums/showthread.php?t=170558

Thanks for the additional info Miko, very interesting and helpful information, and well done—great result.
 
And just because: my finished Canon P ✨

all speeds are now accurate (even the 1/1000 is a true 1/1000), no more squeaking, advance is buttery smooth, viewfinder clean, bright and contrasty ✨

XP207718.jpg
 
Update: since my P now worked fine with as low as possible tension on the curtains (as low as I could manage to get all speeds accurate) and no bounce but struck me as being too loud, so I decided to take another look at the 2nd curtain brake on top next to the drum. I know from working on my IIIf that a brake which doesn't work 100% as intended may be sufficient to stop curtain bounce but makes the shutter way louder then it should be.
I loosened the two screws (big one holding the brake lever, small one for the spring) and worked the shutter couple times. So in fact the lever was indeed still stuck too much and loosening the screws freed it up.

Now the closing of the second curtain is really dampened and thus whisper quiet (quieter then my IIIf and easily as quiet as my M2 was, maybe even more so)!
I still think the 1st curtain could be quieter (still closes with an audible 'click'). At some point I'll look more into the brake under the bottom of the camera and write my findings here.
 
Alright, took a look at the 1st curtain brake (fortunately the Canon P is really designed with accessibility in mind). So apparently the only mechanism working here is friction which is applied through the wave washer (C0185 sheet 10) pressing on the spring and brass part around which the spring is coiled.

Maybe the washer lost a bit of its power in the last 60 years? So I bent the small washer a tiny bit more = more force on the brake. It did the job, the 1st curtain is now quieter 😎
 
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