What causes high speed > slow speed on Prontor shutter?

[MFstooges]

I have jammed prontor shutter from Zeiss Tenax. I am taking shortcut here cause I am not sure if I can reassemble it if I take it apart so I opened the cover and cleaned it thoroughly with solvent. I relubed the pivot points and now it is working. The strange thing is the shutter speed goes faster from B up to 1/10 secs until I set it on 1/25 where it sounds the same as 1 sec and 1/50 secs sounds like 1/10 secs.
Now I think I should take it apart but before doing that I want to see if anyone have advice on which part I should pay more attention to fix this anomaly.

 

[Sirius Glass]

Some will clean without dissembling or partially disassembling. I personally am more inclined to send it out to a lens repair expert like Carol Floutot www.flutotscamerarepair.com/ContactUs.htm who has done some excellent lens repairs for me.

 

[dxqcanada]

The entire shutter should be taken apart ... you cannot access the places that need the cleaning the most if you do not do this. If you just flood the shutter with fluid you just move the crap somewhere else. The blades should be taken out and individually cleaned. The speed retard escapement needs cleaning and especially positional adjustment, which is probably why the higher speeds are slow.
If you take the free Nat Cam courses from the Learn Camera Repair site, you will have all the info you need to service these leaf shutters.

 

[Dan Daniel]

Sounds as if the slow speed escapement is not disengaging. Shutters have a lot of designs so it's hard to be specific. In this photo, you can just see a small gear under the top cover that has a series of triangular pointed teeth. This is the star wheel. Below that is a silver part with a largish screw through it. this is the pallet. The pallet has a notch in the middle with two 'teeth' one at each end. these teeth rock back and forth on the star wheel for the slow speed escapement. For higher speeds, the pallet is pulled away from the star and does not engage and you get the faster speeds. A common cross-over point is between 1/10 and 1/25, which soulds like what you have going on.

There is usually a tab of some sort that gets moved by the cover plate to push the pallet away from engagement. In the photo, it is circled for that shutter. There will be a cut-out on the cover plate that moves this tab in and out.

No idea how this is handled on your shutter. Post a photo if this doesn't make sense. Anyway, basic issue: the tab is bent and not engaging. Not uncommon to put the cover on not knowing that this is an issue and the tab gets pressed down.

 

[MFstooges]

Sounds as if the slow speed escapement is not disengaging. Shutters have a lot of designs so it's hard to be specific. In this photo, you can just see a small gear under the top cover that has a series of triangular pointed teeth. This is the star wheel. Below that is a silver part with a largish screw through it. this is the pallet. The pallet has a notch in the middle with two 'teeth' one at each end. these teeth rock back and forth on the star wheel for the slow speed escapement. For higher speeds, the pallet is pulled away from the star and does not engage and you get the faster speeds. A common cross-over point is between 1/10 and 1/25, which soulds like what you have going on.

There is usually a tab of some sort that gets moved by the cover plate to push the pallet away from engagement. In the photo, it is circled for that shutter. There will be a cut-out on the cover plate that moves this tab in and out.

No idea how this is handled on your shutter. Post a photo if this doesn't make sense. Anyway, basic issue: the tab is bent and not engaging. Not uncommon to put the cover on not knowing that this is an issue and the tab gets pressed down.

Here are the pictures from internet blog. They are not mine but exactly look the same.
So it looks like A is what you call "sun wheel". "B" maybe the tab for the pallet? But "B" doesn't get pushed by the speed cam unless the speed is set to Bulb.
"C" is the axle of a gear that start to spin from close to the center when the shutter tripped open and when it reaches its resting position at the notch then the shutter closes.

Below is the shutter with the speed cam installed. On the right side the slope will disengage lever "B" on Bulb setting, that is the only protrusion on the speed cam that can touch lever "B". If you continue to rotate lever cam counterclockwise to 1 second then lever "B" will reengage the escapement and the notch at the bottom of the picture will give gear "C" full travel (1 second) and as you continue to rotate clockwise notch changed to slope where it reduces gear "C" travel time : 1/2...1/5 so on. Interestingly, as marked by arrow on the left, as you continue to rotate the speed cam to 1/25, the speed cam has another notch with same depth as 1 second which will give gear "C" full travel. Rotate counter clockwise again to 1/50 sec and the gear "C" position is about the same as 1/10 sec.

 

[dxqcanada]

The speed cam, when set to higher speeds pushes the pallet lever B outwards.
This disengages the gears connected to the star wheel A which the slow speeds use.
The retard post C is then freed to move inward, this controls the high speed rates (except the highest speed).
If B is not being pushed outward enough then the slow speed gears are still engaged.
FYI, this is all explained in the Nat Cam course material.

 

[MFstooges]

The speed cam, when set to higher speeds pushes the pallet lever B outwards.
This disengages the gears connected to the star wheel A which the slow speeds use.
The retard post C is then freed to move inward, this controls the high speed rates (except the highest speed).
If B is not being pushed outward enough then the slow speed gears are still engaged.
FYI, this is all explained in the Nat Cam course material.

So you are saying that lever "B" is pushed clockwise when higher speeds is set? At the point where the speed cam touches lever "B" on the second picture? But in my case the speed cam will just pass on top of lever "B". I was thinking that I might accidentally bent lever "B" inward and the cam should actually touches it but lever "B" won't move clockwise even if I use tool to try to push it.

 

[dxqcanada]

Yes, the cam pushes B outwards to put is into a disengaged setting.
If the speed cam is put in on top of the pallet lever it will not work correctly. You have to push the pallet lever outwards when putting the speed cam on.
I think you need to show what your shutter with the cam on looks like.

 

[Dan Daniel]

So you are saying that lever "B" is pushed clockwise when higher speeds is set? At the point where the speed cam touches lever "B" on the second picture? But in my case the speed cam will just pass on top of lever "B". I was thinking that I might accidentally bent lever "B" inward and the cam should actually touches it but lever "B" won't move clockwise even if I use tool to try to push it.

This tab was probably pushed down and it is bent on the lower side and hanging up inside the escapement. If you can pull the tab back up gently, it may start pivoting again.

You are in the realm of the light but firm touch. Hard to explain bending small metal parts, but go slow and gentle. and find leverage points that won't be putting pressure on other parts of the escapement. All in all the part that is bent is pretty high tolerance and should come back to life, but you won't be this lucky with other parts.

 

[MFstooges]

Yes, the cam pushes B outwards to put is into a disengaged setting.
If the speed cam is put in on top of the pallet lever it will not work correctly. You have to push the pallet lever outwards when putting the speed cam on.
I think you need to show what your shutter with the cam on looks like.

OK I am sorry, upon careful checking it seems my unit is a little bit different than that picture. The lever B is different. Let me see if I can take clear picture of it and post here.

 

[MFstooges]

This tab was probably pushed down and it is bent on the lower side and hanging up inside the escapement. If you can pull the tab back up gently, it may start pivoting again.

You are in the realm of the light but firm touch. Hard to explain bending small metal parts, but go slow and gentle. and find leverage points that won't be putting pressure on other parts of the escapement. All in all the part that is bent is pretty high tolerance and should come back to life, but you won't be this lucky with other parts.

Well, after comparing the pictures it turns out that my shutter is exactly the same. This lever "B" that disengaged when shutter is set to B will always engaged in any other speed settings. Scratching my head here. And there is no other lever that engages/disengages when hitting above 1/15 secs. Am i missing any parts?

 

[dxqcanada]

Put the speed cam back on top ... and then look at where the levers and things interact with it.
The speed cam is the one that sets the position of the palette lever.

 

[dxqcanada]

This might help visualizing what it is ...

 

[dxqcanada]

I have a post that tries to explain this ... https://oldcam.wordpress.com/2021/03/21/compur-not-so-rapid/

 

[MFstooges]

This might help visualizing what it is ...

Thank you. This is really helpful. Let me put it in slo mo and rewatch over and over again.

 

[Dan Daniel]

Well, after comparing the pictures it turns out that my shutter is exactly the same. This lever "B" that disengaged when shutter is set to B will always engaged in any other speed settings. Scratching my head here. And there is no other lever that engages/disengages when hitting above 1/15 secs. Am i missing any parts?

If that is your shutter, the cocking ring is not installed properly. The B lever has only the upper tab riding on the cocking ring. It should have the lower part, now hidden by the cocking ring, riding along the side of the cocking ring. The tab that projects up rides along the speed cam slot. Maybe, as suspected, the B lever has been bent downwards and is riding under the cocking ring, not the cocking ring not being seated down enough? It looks seated at the 'timing tab' position (wrong term, but the little gray tit at other end of escapement).

Well, I think. Again, need to see speed cam in place.

 

[MFstooges]

If that is your shutter, the cocking ring is not installed properly. The B lever has only the upper tab riding on the cocking ring. It should have the lower part, now hidden by the cocking ring, riding along the side of the cocking ring. The tab that projects up rides along the speed cam slot. Maybe, as suspected, the B lever has been bent downwards and is riding under the cocking ring, not the cocking ring not being seated down enough? It looks seated at the 'timing tab' position (wrong term, but the little gray tit at other end of escapement).

Well, I think. Again, need to see speed cam in place.

There is no lower part. As you can see from post #5 with pictures from another person on internet, 1st photo shows lever B. And 2nd photo shows the speed cam in place.

See also the video --> Shutter in Action

 

[Dan Daniel]

Wel;l, in my note on the yellow background photo of a shutter which may be yours or may not because #5 is it but then it is called not yours but yours sort of exactly or something, there is a part of the B lever under the cocking ring which I called the lower part but maybe I should have called it the notched or the base and the tab is what you are seeing or referring to maybe except for slanted #5 makes me think not and this part of the b lever under the cocking ring which might be a notch or might be lower or maybe is just a figment of my imagination should be riding along the outer edge of the cocking lever and the speed cam will move the tab or the lever or the not-lower b lever move in and out except you say that the b lever doesn't move out so until it can do that the lower part which might be a notch or maybe it's the reversed part from #5 can't really tell needs to be unstuck by bending it upwards carefully and with knowledge of where it needs to sit which is when the lower becomes the middle and the tab which may not be a tab at all but a lever stuck on the side of another lever sort of a meta-lever eh follows the speed cam.

 

[MFstooges]

Say what?

 

[dxqcanada]

Say what?

Makes sense to me

 

[MFstooges]

If that is your shutter, the cocking ring is not installed properly. The B lever has only the upper tab riding on the cocking ring. It should have the lower part, now hidden by the cocking ring, riding along the side of the cocking ring. The tab that projects up rides along the speed cam slot. Maybe, as suspected, the B lever has been bent downwards and is riding under the cocking ring, not the cocking ring not being seated down enough? It looks seated at the 'timing tab' position (wrong term, but the little gray tit at other end of escapement).

Well, I think. Again, need to see speed cam in place. View attachment 368322

Turned out you are correct, lever B was bent 0.0000001 mm downward. Its protrusion should sit higher and makes contact with the speed cam exactly at 1/25 secs and higher speed. Thank you!

 

[dxqcanada]