Compur Rapid Shutter Not Fully Open at B

[btvarner]

I am in the process of completing my first CLA of a shutter & aperture. The lens is a Compur-Rapid Jena Tessar 2.8 from a Zeiss Ikonta B. I am sure it is just my lack of experience but an issue has surfaced.

The shutter will not fully open when set to the "B" position. I have included 3 images of the partially disassembled mechanism. One with the shutter closed. One with the shutter as far open as it goes when shutter actuating lever is pushed. One while holding the shutter fully open. Note the white arrows which indicate the difference between how far the arm will push open the shutter & how much further it needs to travel to be fully open. This part was functioning correctly before I started. Need suggestions as to what might be occurring.

I have had the actuating lever & its attached spring loaded arm disassembled. My reassembly might be in wrong but I do not see how. I can manually move the lever attached to the bottom of the case which easily & completely opens the shutter fully so the shutter its self is not binding. Also you may notice that the booster spring seems out of place in some of the pictures. This is only the case for the photos, not when attempting to actually open the shutter.

A second clue to note is that after putting the shutter back together for testing, I also noticed that when releasing the shutter at all speeds, the mechanism would not return as it should. It would have to be pushed back because of what appeared to be a slight binding or rubbing. Could not tell where this was occurring either when the unit was together or after removing the face or speed ring again.

Thanks,
Bruce

 

[epatsellis]

If I'm not mistaken, you need to have the cocking ring on this shutter in order for it to work properly. Though I may be wrong.

 

[btvarner]

The photos were taken apart so that you could see the inside. I tried it both with & without the cocking ring & it responded the same. Thanks!

Bruce

 

[John Koehrer]

I see that there is a lever over the pivot for the release linkage that seems to be latched on a different lever in each picture.
You know it's going to be one of those forehead slapping moments when you figure it out don't you?

 

[btvarner]

John,
As best as I can decipher, you are talking about the lever which I have a red arrow pointing towards in the image below?

This lever is positioned against the cocking ring when that ring is in place. However since it has tension on it, this lever rides as far to the left as it can when the ring is off as during these images.

I did hold this lever away from contact with the other parts when attempting to have the linkage function. I also did observe this lever during the tests with the speed ring in place and id did not appear to cause any obstructions at that time either.

Could you be more specific as to what you are questioning? Thanks!

 

[btvarner]

I guess this is as good a time as any to provide some more details. I am guessing that everything below relates to #1-Some constriction / resistance in the shutter release linkage and #2-The booster spring not connected correctly. Could be totally wrong but this is my guess after several times breaking the shutter down & reassembling.

Before CLA Problems: Camera issues progressed as follows:
1) Speed dial ring became increasingly hard to turn
2) Shutter increasingly became sluggish & at times stick open
3) Shutter release would not return to its normal position after shutter was tripped
4) Focusing eventually froze
5) Finally noticed that the aperture blades began sticking (When set to a given aperture size, the hole was not round)

Suspected Causes:
1) Possible that attempts were made to cock the shutter when the speed dial was set to "B"?
2) Shutter/aperture needed CLA from years of service?
3) Possible that the second lens element had come loose?

Post CLA Test Results (Cocking ring, speed ring, & face place reinstalled):
1) In "B" bulb position the release would not open the shutter fully. A small portion of the blades remained visible equivalent to stopping the aperture down to almost f4.
2) At 1", 1/2", 1/5", 1/10", & 1/25" the shutter would open fully but not close.
3) At 1/50", 1/100", 1/200", & 1/400" the shutter seemed to open & close as expected although I could not be sure if the shutter opened fully before closing.
4) At all shutter speeds the release lever would fail to return to its normal position & would have to be manually pushed back into position for the next trigger.
5) Delayed action release button functioned through 1/50". Would not function at 1/100" or above. Would cock but shutter release would not work. Had to move shutter speed below 1/100" in order to get shutter to trip. Also seemed to take too long (approx 20 seconds) before the shutter would trip. Do not know if this much of a delay is normal.

Suspected Causes:
1) Working of mechanism while disassembled indicated lever which pushes shutter blades stopped before blades fully opened?
2) While disassembled could not resolve how the booster spring functioned. Did not seem to be under tension when the cocking lever was in any position?
3) While disassembled could not resolve but noticed that sometimes there appeared to be a bind in the release mechanism when returning for next release?
4) No idea? Bent release parts?

Need some specific feed back if possible. Thanks!

 

[archphoto]

This is a typical problem of a retardment that needs an oil change.

Take-out the 3 screws marked and wash the part in lighterfluid.
Then re-oil with synthetic clock-oil and remount.

Good luck !
Peter

 

[John Koehrer]

Nah! I was looking at the blade operating ring. It's the pin you have indicated with the white arrows.
My mistake.
The shop I worked n got leaf shutters on occasion, not regularly. Sometimes you would find the problem halfway around the shutter, just covered by another part. Making it invisible.

 

[btvarner]

Thanks Peter,
Did not help at all. Any other ideas? It still "feels" like the release mechanism is binding?

I found one question I need to ask assuming I ever get the shutter otherwise functioning correctly. Noticed that the escapement spring, which I assume controls how fast the the escapement works has what looks like 4 slots. See image. I am unable to get this spring to stay in any of the slots. It instead rides as far left (in image) as it can set. When I try to place it in any of the slots, it pops out after the first movement.

Which slot should I try to place this spring end into? Thanks!

 

[btvarner]

Ok, someone needs to explain to me exactly how the boost spring (spring that looks like a six in the images above) works. I swear that it is not doing anything. What does it push against & at what point so that it can function? I am convinced this is what is keeping the shutter from closing at the slower speeds.

Thanks!

 

[archphoto]

Send you a PM

Peter

 

[archphoto]

Solution ! Part of it anyway

Please see the photo:

Spring (1) should be connected on one side with position (2) and the other end at position (4).

Position (4) determines the tension and thereby your shutterspeed accuracy.
You can start in the middle position, but you need a shutterspeed tester for the right position.

I don't like position (3): it should be straight, but bending it back can de tricky as it can break off.......

Peter

 

[btvarner]

Peter,
Thanks for the info on the escapement spring. I have followed your instructions the spring is attached as you described. I placed the end into the second slot. It stays & the escapement seems to function when put back togaher. Has not improved or seemed to have affected the other issues in any way. Will get with you shortly offline with more data. Once I have futher along I will post results here. Thanks!