IIIg slow speeds

[qqphot]

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All right, then, it's begun misbehaving again, and I wonder if I've caused this.    Sometimes (say at 125)  it fails to release the closing curtain at the appropriate moment but seems to wait until the opening curtain completes its travel.

For example:

 

 

Here's what it looks like in slow motion when it works properly:

 

Is it possible I caused this problem by messing with the opening curtain brake?  (It happens only occasionally, usually when the camera has been sitting a few hours at least, but it's enough to ruin two or three frames per roll)

[spydrxx]

Just a thought - in the future I'd find a different, more reliable, repairperson.

[qqphot]

6 hours ago, qqphot said:

All right, then, it's begun misbehaving again, and I wonder if I've caused this.    Sometimes (say at 125)  it fails to release the closing curtain at the appropriate moment but seems to wait until the opening curtain completes its travel.

For example:

 

 

Here's what it looks like in slow motion when it works properly:

 

Is it possible I caused this problem by messing with the opening curtain brake?  (It happens only occasionally, usually when the camera has been sitting a few hours at least, but it's enough to ruin two or three frames per roll)

Wait, no of course it wouldn't, since the closing curtain should start moving before the brake has even acted. 

[qqphot]

5 hours ago, spydrxx said:

Just a thought - in the future I'd find a different, more reliable, repairperson.

There aren't many, and those few are very busy and backlogged. I think it's worthwhile to learn to maintain my own equipment but I can appreciate that that's not for everyone.  I have a number of cameras, so I fortunately have the luxury of using one of the fully operational ones while learning about the operation and maintenance of ones that need work.

(unless your reply was meant sarcastically, in which case... ok)

Edited October 21, 2024 by qqphot

[spydrxx]

11 hours ago, qqphot said:

There aren't many, and those few are very busy and backlogged. I think it's worthwhile to learn to maintain my own equipment but I can appreciate that that's not for everyone.  I have a number of cameras, so I fortunately have the luxury of using one of the fully operational ones while learning about the operation and maintenance of ones that need work.

(unless your reply was meant sarcastically, in which case... ok)

No sarcasm, I was serious. I learned the hard way years ago.

[qqphot]

3 hours ago, spydrxx said:

No sarcasm, I was serious. I learned the hard way years ago.

These aren't rare or exceptional cameras, and I'm unemployed and have very little else to do. If I learn something and get a bit better at being able to do minor repairs on my own gear rather than having to depend on expensive and slow repairs from others, I'll take it as a win. I work on tiny surface-mount electronics under a stereo microscope regularly anyway, I have tiny tools, etc, and I've learned to be cautious. My biggest limitation here is understanding the mechanical interconnections, and Jerzy is amazing at explaining that stuff.

I think the fact that the community as a whole takes DAG and the rest as the divine sole proprietors of this knowledge is a big reason why so few new, younger people are trying to learn and take up the mantle.  I'm not going to start repairing anyone else's camera but if Jerzy is kind enough to share his knowledge clearly enough that I can follow along and fix something, I'm absolutely not going to turn that down.  FWIW this camera came back from DAG with all these problems, so short of sending it back to him and waiting another nine months, film testing, and then sending it back again, this seems like a better option.

Edited October 21, 2024 by qqphot

[jerzy]

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It looks like the pawl holding the second curtain does not work properly. When you press release button the pawl shall go down and here I believe does not go down fully. It could be that the shaft of the pawl ( goes through the frame down to flat spring) is dirty or the spring pushing pawl down (under top cover) is too weak. You may drop some alcohol on the shaft end, keep camera upside down, press release and you will be able to see the and of shaft. 
 

[qqphot]

On 10/21/2024 at 11:56 PM, jerzy said:

It looks like the pawl holding the second curtain does not work properly. When you press release button the pawl shall go down and here I believe does not go down fully. It could be that the shaft of the pawl ( goes through the frame down to flat spring) is dirty or the spring pushing pawl down (under top cover) is too weak. You may drop some alcohol on the shaft end, keep camera upside down, press release and you will be able to see the and of shaft. 
 

Perhaps it is dirty, or the holes in the chassis are  - the closing curtain starts very late if I have left the camera alone a couple of hours or overnight with the shutter spanned.  When it doesn't stick, the speeds are ok.  It is hard to test because I have to wait a long time between tries!     I wonder though if somehow when reassembling last time i misaligned something causing this.

Edited November 3, 2024 by qqphot

[qqphot]

On 10/21/2024 at 11:56 PM, jerzy said:

It looks like the pawl holding the second curtain does not work properly. When you press release button the pawl shall go down and here I believe does not go down fully. It could be that the shaft of the pawl ( goes through the frame down to flat spring) is dirty or the spring pushing pawl down (under top cover) is too weak. You may drop some alcohol on the shaft end, keep camera upside down, press release and you will be able to see the and of shaft. 
 

Do you mean the shaft that goes through the center of the film sprocket and seems attached to the release button on one end, and the flat spring on the bottom? 

[qqphot]

 

 

[jerzy]

vor 21 Stunden schrieb qqphot:

Do you mean the shaft that goes through the center of the film sprocket and seems attached to the release button on one end, and the flat spring on the bottom

no, this is relase shaft. What I mean is pawl, shaft goes inside the crate, behind shutter drum, approx so as marked blue. When you press release buttaon flath sprong goes down and the small flat spring located right to the pawel shall push it down. I meant a drop of lighter fluid under the flat spring, approx when the bule arrow points.
But of course there could be anpther reasons like sticky curtain (low probability), dirty riveted gear that resets slow speeds governor or something else within the second curtain movement.  From your last vide I have impression that releasing the disc is just on edge, you may try nto reposition the flat spring as shown on the second photo, But only minimal. And disc rotates with the first curtain, so nothing to do with the second being delayed

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[qqphot]

Ok, I've come back to this camera, and now it's apart for better visibility.  Disassembly was no problem.

 

When it's been sitting for more than an hour or two, there's a catch and delay when the shutter button is pressed. It's hard to experiment with because I have to let it sit for an hour in between each test!

When it catches, I believe the area circled in red here is where it gets stuck:

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In this picture I am holding it in place with my thumb to prevent it from passing by so I can take the picture. When it's working normally the cam strikes the smaller screw head and continues without a pause. When it's not working normally, it catches there and there's a delay before it comes free and continues.

 

Here is a set of higher quality images of the mechanism, on flickr. It looks like someone has slathered a lot of grease all over everything inside there.

 

Edited April 2 by qqphot

[jerzy]

your camera might benefit from CLA. A  bit of explanation how it works: "A" is firmly attached to speed dial and it rotates when the first (opening) curtain runs. Second curtain is hold by the pawl and is approx there where B points to. Both marked screws are excentric , higher one is for adjusting 1/ 1000, lower one for 1/500 and below. When shutter is spanned and not released and speed set to 1/500 "A" is approx there where arrow points. When you press release openinig curtain starts to run, part A rotates and after some time hits the lower screw pushing pawl away and releasing the closing curtain. When speed is set to 1/250 the initial position of A is as marked. As you may see the opening curtain has to open (travel) more than with 1/500 before closing curtain will close. And so on - with longer speeds the travel for opening curtain is increasing before closing curtain is release, thus slit width is bigger.  Opening curtain needs  some momentum to be able to push the pawl away and this momentum (as well travel speed) is bigger with 1/125 than with 1/500.
And because both screws are excentirc they determine when the A will hit the screw and push the pawl away. It is not reccomended to turn on both screws unless you have equipment to observing lit width acorr the whole frame and shutter tester to measure the speed.

What shall not be done in situation as you have is increasing the tension of the spring of opening curtain - this might cure the problem of not releasing the closing curtain but it changes travel parameters of the curtain and impact the slit width. Rather then shutter has be taken apart, cleaned (including the springts for both curtain, they were lubricated and it dried) and lubricated.

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[qqphot]

 

I managed to catch it in action, in slow motion. Surely lubrication, it only does this after the shutter has been left spanned for an hour or two.   I suppose i could just get into the habit of winding-on before rather than after making an exposure, haha.

 

 

Edited April 8 by qqphot

[qqphot]

 

Now I am not sure that's even where it's catching.  In any case, the camera came back to me from "CLA" like this so I suppose it's time to find someone else to CLA it properly.

 

[Jerry Attrik]

In his 1975 book "The first Fifty Years" G. Rogliatti, on page 10, states that the transit time of the exposing blind for the iiig camera is 1/50th of a second ( 20 m.sec ).  I have been, as yet, unable to confirm or correct this.  As one might expect, with two blind focal plane shutters, the capping blind must have the same transit time. Thus for a one second exposure there must be a 980 m.sec. (or so) delay  before the capping blind is released. This delay is produced by a clockwork mechanism and as it runs down one can hear a zizzing sound.  If that sound is not heard then there may be a problem with the slow speed timing mechanism.  ( I think ).

[qqphot]

14 hours ago, Jerry Attrik said:

In his 1975 book "The first Fifty Years" G. Rogliatti, on page 10, states that the transit time of the exposing blind for the iiig camera is 1/50th of a second ( 20 m.sec ).  I have been, as yet, unable to confirm or correct this.  As one might expect, with two blind focal plane shutters, the capping blind must have the same transit time. Thus for a one second exposure there must be a 980 m.sec. (or so) delay  before the capping blind is released. This delay is produced by a clockwork mechanism and as it runs down one can hear a zizzing sound.  If that sound is not heard then there may be a problem with the slow speed timing mechanism.  ( I think ).

The "high speed camera" on this phone (Samsung Galaxy S10) seems to be 960 frame/sec and using that i've timed the transit to be pretty close to 1/50th on the IIIg, so I think it's correct. It's really fun to be able to watch these things operate at a speed you can actually see.  The problem with this particular camera seems to be that when it's cold or hasn't been fired for a bit there's insufficient momentum from the curtain springs, from what Jerzy is saying.   Unfortunately it seems the repairer who previously worked on this camera maybe didn't sufficiently disassemble, clean, and relubricate.  Though I'm still trying to figure out exactly where it's getting stuck - it almost seems like it's pausing (at least sometimes) *before* the opening curtain opens. But maybe not.

[Woodallp]

I bought a second hand Galaxy S10 just for this purpose. The only problem is that the 960 fps mode only lasts about 0.4 seconds and afterwards it drops to 240; it is longer on later model I think. I find it quite tricky to hold everything, start the filming and fire the camera in this short time slot without moving too much.

[qqphot]

8 hours ago, Woodallp said:

I bought a second hand Galaxy S10 just for this purpose. The only problem is that the 960 fps mode only lasts about 0.4 seconds and afterwards it drops to 240; it is longer on later model I think. I find it quite tricky to hold everything, start the filming and fire the camera in this short time slot without moving too much.

Yeah, it often takes a couple of tries, but it's been invaluable in diagnosing problems and adjusting shutters once I get it to trigger at the right time. I've been using a little clamp mount to hold the phone which makes it a bit easier.

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[qqphot]

Ok at some point soon I'm just going to put this back together and set it aside, but I've just seen that it's actually delaying in starting the *opening* curtain, as well as in starting the second curtain!     (the flickering visible in reflections on the right side is 60 Hz room light, to give a sense of time scale)

 

Now below, winding and firing a second time immediately afterward, it works correctly.

 

Firing it a second time immediately afterward works fine.

 

@jerzy - The person who serviced this camera this past August told me that he had fully disassembled it and lubricated everything, and adjusted the shutter. Is it possible that he just put too little tension on both shutter springs when re-tensioning it? 

The first delay seems to happen before the rotating cam even comes near the pawl that releases the closing curtain.

I hesitate to completely release and retension the curtains, but if this is the answer, I could do it - i can measure the slit width at various positions using a laser spot, photodiode, and oscilloscope; and I can see the slit transit time with the 960fps high speed camera.

I'm sorry for asking so many questions, but it's been really educational!