Copal S(quare) Shutter: Testing when removed?

Andreas Thaler

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I am currently working on the Minolta 9000 AF shutter, which has problems with a rotting damper that is sticking the blades together.

An attempt to clean it from the outside while it was removed was unsuccessful; the shortest times of 1/4000 to 1/1000 s are not formed or are not formed correctly. So I am going to disassemble the shutter and cleaning it.

I assume that the sticking is hindering the movement of both curtains, but that the mechanics and electronic control of the two solenoids by the camera are OK.

I am wondering how I can test the shutter while it is removed or still mounted in the housing to measure the running speed of the two curtains.







The camera cannot control the shutter when it is disassembled or the shutter is removed.

Anyway it is possible to release the shutter mechanically if it is built into the housing, as can be seen in the pictures. But both curtains are probably triggered at the same time and the shutter tester does not see a slot that it can measure and evaluate.

Otherwise, my only option is to reassemble the camera after each cleaning cycle to test it, which is not possible.

Any hints?
 
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Andreas Thaler

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By the way, our member @monopix (I assume it is him) gives an excellent description of the mechanically controlled Copal S in a Nikon FM2, unfortunately the pictures are not available for guests to see:

Nikon FM2n shutter adjustment/service

I'm looking for any information on servicing the above and/or adjusting the speeds. I have a couple that are slow on the top speeds. Any info appreciated. Sent from my iPhone using Tapatalk
rangefinderforum.com

(see there post #5)
 
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Andreas Thaler

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And we have on PHOTRIO an older thread about Copal S issues in a (electronically controlled) Nikon FE:

Nikon FE shutter issue

I bought a used but decent condition Nikon FE recently and I ran through a roll of Ilford HP5 400 iso film. I processed the roll and only frame 0, 9, and 36 were exposed. The rest if the roll was transparent. I remember shooting during a bright day and having the dial set to auto. Im testing out...
www.photrio.com

Problems with the short shutter speeds are also mentioned there.

Perhaps it is not sticky dirt on the slats of the Copal S in the Minolta 9000 AF, but a problem with the shutter mechanism or the camera's controls?

I have not found any further information, anyway I will continue to look into the topic and report back.
 

ic-racer

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You should be able to set the curtain speeds. If those are good , you should be able to put it back together to do the rest of the testing .
 
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Andreas Thaler

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ic-racer said:
You should be able to set the curtain speeds. If those are good , you should be able to put it back together to do the rest of the testing .
Click to expand...

I should be able to set the curtain speeds, but how can I test the settings if the removed shutter is not electronically controlled by the camera?

What is possible without the mirror box is to tension the shutter using the winding lever, release it manually and release the winding lock for the next cycle.

But when the shutter is released, both curtains obviously move at the same time and therefore I cannot measure the speed of each curtain with the tester.

I have to remove the shutter from the 9000 AF again to see more.
 

ic-racer

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Some shutters like the Nikon FM I was working on, would fire each curtain individually. Are you saying both curtains go at the same time with no slit?
 
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Andreas Thaler

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ic-racer said:
Some shutters like the Nikon FM I was working on, would fire each curtain individually. Are you saying both curtains go at the same time with no slit?
Click to expand...

Yes, I assume this but have not observed in detail.

I will investigate this as soon I have the shutter removed.
 

vandergus

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If you just want to fire the curtains individually, you can usually put a voltage across the electromagnets to activate them. That will hold the curtains in place instead of them being immediately released when the mechanical latch is triggered. You can use an external power supply or just hook up a battery. That would allow you to measure curtain speeds, as ic-racer suggested. Setting it up to fire at particular speeds is probably a bit more difficult. Sometimes you can use jumper wires to make connections while the camera is still disassembled. Whether or not this is feasible for the 9000 AF just depends on the architecture of the electronics.
 
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Andreas Thaler

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Thanks!

I'll try that once I've removed the shutter.
 

Light Capture

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You can trigger it manually.
I used old Nikon V1 when needed to take a video of the shutter in motion at 1200fps. There are other cameras that can do higher fps. Lots of light is needed for clear image.
Shutter curtain speed needs to be measured and then the main springs for each curtain can be adjusted to reach required curtain speed.
Consideration in this is that working camera with correct speeds should be used as a comparison if this data isn't available in the service manual.
With this method it can be adjusted very accurately. It's relatively slow as it's needed to download the video to PC and go frame by frame but it's very accurate.

Solenoids can also be used during measurement to trigger but I held the levers by hand (with small screwdriver) when doing this and recorded video during manual release.
It's much simpler this way. Results are excellent with much less than desired 10% variance. It's the same procedure if something's broken on the shutter.
 
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Andreas Thaler

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Thank you!
 
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Andreas Thaler

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Here is my report on disassembling and cleaning the Copal shutter of a Minolta 9000 AF (1/4000 s shortest shutter time).

I have installed the shutter, cocking and releasing work, nothing is suspicious. So I'll take a chance and put the 9000 back together, then I'll see if it was successful.

It's certainly not the first attempt, there are still a few 9000s waiting to be serviced.

Post in thread 'Minolta (Maxxum, Alpha) 9000 AF: Removal of the mirrorbox/assembly, investigating the aperture issue, removing the sticky damper in the shutter unit'
https://www.photrio.com/forum/threa...amper-in-the-shutter-unit.208476/post-2877472
 
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Andreas Thaler

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What could be the cause of this discrepancy at 1/4000 s on a Copal S (Minolta 9000 AF?)?




Could this be explained by the different speeds of the two curtains? Measured here at 1/1 second?


Post in thread 'Minolta (Maxxum, Alpha) 9000 AF: Removal of the mirrorbox/assembly, investigating the aperture issue, replacing the sticky damper in the shutter unit'
https://www.photrio.com/forum/threa...amper-in-the-shutter-unit.208476/post-2878593
 

ic-racer

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Curtain 2 is catching curtain 1; the slit gets smaller. It is almost capping ( no opening at all),
 
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Andreas Thaler

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ic-racer said:
Curtain 2 is catching curtain 1; the slit gets smaller. It is almost capping ( no opening at all),
Click to expand...

The curse of high-performance shutters!

Thanks!

It's a shame that I can't find a way to test the shutter without the camera assembled.
 
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Andreas Thaler

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But this is the solution, since I can trigger both curtains separately.

To do this, I need to connect the removed shutter to the sensor and trigger the curtains one after the other.

Then I turn the adjustment wheels for the springs to adjust them.

I'll try that.
 
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Andreas Thaler

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Adjusting the curtain speeds of the Copal S shutter on the Minolta 9000 AF

I managed to adjust the curtain speeds on my decommissioned Copal S shutter of a Minolta 9000 AF very precisely.






For testing, the shutter is inserted into the back of a 9000 AF, which is now used exclusively for this purpose.




The speed of the opening curtain (C1) is adjusted using the lower adjustment wheel (red arrow).

The speed of the closing curtain (C2) is set on the upper adjustment wheel (blue arrow).






Lifting the two tabs releases the spring tension on the curtains. This means the curtains no longer roll down; they are reset.






Now the adjustment wheels can be turned clockwise against the spring tension. The lock clicks, indicating the position. I turn each wheel approximately 15 clicks.






On the camera tester, I first manually trigger C1, then C2. This is done with a screwdriver, which must not be placed in the tester's light path to avoid affecting the measurement result.




My target speed per curtain was 3.40 milliseconds. That's almost there. Perhaps C1 needed just another click to make it faster.

This sets the curtains mechanically.

The camera's job is to trigger them electronically using the two shutter magnets at the correct speed.

Now I just need to determine the target speed for the curtains. I know it for the Minolta 7000 AF.

If I can't find anything about it in the service manual for the 9000 AF, I'll use that and the preset speeds displayed by the camera tester as a guide.


A great thing!

This allows me to test and adjust the cleaned shutters on my 9000 AF whenever necessary

Thanks to everyone, especially to @Light Capture for describing the method!

I'll use this for my tutorial on cleaning and adjusting the shutter on the 9000 AF.


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Andreas Thaler

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Adjusting the curtain speeds of the Copal S shutter on the Minolta 7000 AF

To determine the curtain speeds on the camera tester, the shutter must be connected to a voltage source.

This supplies the two shutter solenoids with power, allowing them to hold their armatures by becoming magnetic.





  • Green arrow: Lever of opening curtain (C1)
  • Red arrow: Lever that is pulled upwards and tensions both curtains.
  • Yellow arrow: Lever of closing curtain (C2)



For testing, the shutter is inserted into the back of a Minolta 7000 AF, which now serves only this purpose. If necessary, the shutter can be secured with adhesive tape.

Screwing it on is not possible, as the shutter is secured on two axes with circlips.




Connection to my laboratory power supply.




A two-volt supply voltage is applied. The solenoids are now activated and magnetic.




Insert into the camera tester.




Tension the two curtains by pulling their lever up with a hook.




Triggering the opening curtain (C1) by pulling the lever up against the magnetic force of its solenoid.




The closing curtain (C2) is triggered by interrupting the supply voltage. The associated solenoid loses its magnetic force and releases its armature.




The target time for both curtains is 7.2 milliseconds (SPT Journal). Therefore, C1 is too slow and needs to be adjusted.
 
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Andreas Thaler

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Adjusting the curtains





Reset both curtains by pushing the locking pawl upwards. The springs will lose their tension.






Adjust the spring force by turning the adjustment wheel clockwise. A click indicates the position.

Then test and correct if necessary.


Note

If a coil (part of the solenoid) has built up a magnetic field through applied voltage and this voltage is interrupted, the magnetic field collapses. Its energy is released through a high voltage spike with reversed polarity.

To prevent this voltage spike from damaging the circuit, circuit protection measures are implemented.

I assume this has already been done on the circuit board of the shutter.

I also assume that manually disconnecting the magnetized solenoid is safe for testing purposes.
 
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Andreas Thaler

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This allows to adjust the shutters of the Minolta AF sister cameras, the 9000 and 7000, as needed.

I will add to my two tutorials on both topics.

Thanks again for all the input received!


Minolta (Maxxum/Alpha) 9000 AF: Tutorial for removing the mirror box, notes on assembly

In order to access the shutter for repairs or replacement, the mirror box on the Minolta 9000 AF must be removed. The same applies to fixing problems with the aperture control or the mechanics of the mirror box. This tutorial provides information with direct reference to the Minolta Service...
www.photrio.com

Minolta (Maxxum/Alpha) 7000 AF: Tutorial for removing the mirror box and shutter unit, notes on assembly

In order to access the shutter for repairs or replacement, the mirror box on the Minolta 7000 AF must be removed. The same applies to fixing problems with the aperture control or the mechanics of the mirror box. This tutorial shows the necessary steps. The basis for this is the Minolta Service...
www.photrio.com


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Andreas Thaler

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The question is whether the deviation in curtain speeds can be properly corrected by adjusting the spring tension. After all, dirt or a lack of lubrication in the shutter mechanism could also affect the curtain speeds.

In the case of the Minolta 9000 AF, with the contamination of the blades from the sticky damper, this is certainly the case.

With the Minolta 7000 AF, whose shutter has no damper, it is more difficult to determine the cause of the deviation.

You could completely disassemble the shutter, clean everything, and lubricate it on a hunch. Then adjust the curtains. That would certainly be a worthwhile project.

But if the only goal is to make a curtain move a few milliseconds faster, I don't see the cost-benefit ratio. Retensioning is the simpler solution.

We'll see.

In any case, there's no shortage of work to be done here
 
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Andreas Thaler

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Minolta 7000 AF: Electronic release of the curtains when the shutter is removed

In order to avoid having to manually trigger the opening curtain C1 against magnetic force and thereby getting into the beam path of the camera tester, I looked into how this could be done with two switches.




The shutter of the Minolta 7000 AF removed.




I measured the resistance of the two coils on the relays with an ohmmeter; it's approximately the same (109 ohms and 112 ohms).

Two capacitors (C1, C2) of 47 picofarads (?) each are connected in parallel with the coils (not to be confused with the curtains C1, C2). Their function isn't clear to me (I assume they are capacitors).

The red wire supplies both relays with 1 V input voltage. The yellow and white wires are the negative terminals.


Circuit simulation for setting up a test circuit


The input voltage is applied to both coils, the armatures are attracted by the resulting electromagnetic force, and both curtains are tensioned.

The two capacitors are charged.


C1, the opening curtain, is triggered. This occurs via a switch that interrupts the power supply to the coil of relay 1. The magnetic field collapses, and the relay releases the armature.

A short delay is caused by capacitor C1 which discharges through the coil and supplies it with voltage for a short time.


The same process occurs with C2, the closing curtain. Here, too, a switch releases the armature.

Both curtains are triggered, C2 closes the film window.


My test rig is again set up using the back of a 7000 AF, into which I insert the shutter to be tested.

The shutter terminals are connected via a breadboard with two switches, and the lab power supply provides the input voltage.

This makes testing the shutter not only trouble-free but also more convenient.

I will show the process in my tutorial.


EveryCircuit: Animated interactive circuit simulator

Interactive real-time circuit simulation and animated visualization inspired students and engineers to design 2.6 million circuits online and in mobile app.
everycircuit.com


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Andreas Thaler

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Minolta 9000 AF: Making a back door with an opening for the camera tester



In order to be able to check all exposure times of the Minolta 9000 AF with the camera tester, I made a back door with an opening.

For this purpose, I had the original back door for the 9000 AF from my spare parts inventory with the worst condition of the plastic handle.




I made the opening in the back door using the Dremel and a thin metal cutting disc. I smoothed the edges with a diamond file and sandpaper.






This back door as before activates a switch on the frame counter, which causes the camera to advance from 1/4000 s to the remaining exposure times.

With the back open, the 9000 AF always releases at 1/4000 s and aperture 22. This combination ensures that the film leader is not exposed when advancing to frame #1.






This saves me from having to install a temporary solution to permanently activate the switch.






The sensor can be placed directly on the film window.

Now the exposure times can be tested one after the other.


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