Minolta (Maxxum/Alpha) 9000 AF: Removal of the mirrorbox/assembly, investigating the aperture issue, replacing the sticky damper in the shutter unit

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Andreas Thaler

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Cleaned in acetone bath and reworked with cleaning swabs.




It's clean here again too.




The last sticky residue has been removed.

I didn't install a replacement for the damper. I want to see if the shutter works without it.










The assembly requires a steady hand and good photo documentation.

There are two springs arranged on the two shutter curtains. The second one is clearly positioned after opening, the first one comes loose at one end, you cannot see its original position because the shutter cover lies over it and fixes the spring.

I have tried all possible anchoring methods, only one position is possible.

I hope I'm right about this.




This ring was left over, I didn't see it until it was on the table.

Oh well.




The shutter is back in its place.

Cocking and releasing works, nothing is blocked, nothing is banging.

I'm not trying to measure the speed of the two curtains anymore. The shutter is factory-set, clean again, I'll take a chance and reassemble the 9000 AF.

Then I'll use the shutter tester to see if the intervention was successful.

Fingers crossed!
 
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Andreas Thaler

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A busy day, but success had to wait

First I mounted the 9000 AF, whose shutter I had disassembled and cleaned.

The camera did not release afterward.

The error: I had cocked the shutter and the aperture mechanism before inserting the mirror box, but not the mirror.

So I disassembled the camera again and found that the mirror mechanism behaved differently than expected, something was not engaging, I could not understand why.

I removed the shutter and put it in another 9000.

This time the camera behaved as expected but the shutter opened the front curtain only sporadically.




I noticed before that the lever that cocks the shutter (red arrow) swung when I did so, which I had not experienced before. So it was obviously a mechanical problem.

I remembered trying to move the shutter curtains and pulling the lever, which lifted the curtains briefly. Maybe that was the cause of the problem.




At least I was able to measure the 1/4000 second on the shutter tester.

The two curtains move with a difference of 0.20 milliseconds, which results in significant overexposure in the upper part of the image (+2.11 EV).

I will now disassemble the second removed shutter, clean it, reinstall it and see if it works this time. And I will use a piece of shrink tubing as a replacement for the damper.






The damper of this shutter is also heavily rotten.

Anyway I will not touch the mechanism, the shutter will remain in the released state.


Checking the position of the upper spring

@ogtronix recommends checking the correct position of the upper spring by looking from the side.

One end of the spring is held by the upper frame, if you remove the frame when opening the shutter, it jumps out of position.

The other position is clear, a hook that grips into an opening.






On the left is the shutter I assembled, on the right is an unopened original. One end of the upper spring must be in this position.


I've made up my mind to get at least one 9000 AF ready for work.

I still have some and now I work almost like a fitter in production at Minolta

I'm not giving up


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Andreas Thaler

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Conclusion
  • Since I assume that every 9000 AF has this rottening damper installed, I consider all of them to be defective.
  • The stickiness means that the shutter does not work reliably and makes the camera useless for photography.
  • You can check this even without a shutter tester. Open the back cover, hold the camera up to bright light and trigger the shutter at 1/4000 s, which is automatically set. Light should come through the shutter, even when shooting in series. If not, the shutter is defective.
  • But it must be possible to clean the Copal shutter and, if necessary, adjust the running times of the two curtains. I just don't want to touch the mechanism with the next shutter and only clean it to avoid problems.
  • Even if the curtains run at the same speed, there is still no guarantee that the shutter will set the times correctly or work without problems. To test this, it has to be installed and the camera mounted. It's quite a lot of work.
  • The most plausible explanation for me is that the sticky damper is causing the problems. But it could also be due to the two magnets in the shutter or the electronic control of the camera.
  • In any case, there are spare parts such as the two magnets for the aperture control, which is also a weak point of the 9000. If you enjoy working, you will be served here
 
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Andreas Thaler

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I'm currently looking at the service manual for the Copal Square shutter, which was built in various variations.

Lubrication is mentioned there.

I'll check to see if I can find any traces of it before cleaning the next shutter. The axes for the curtains are probably running dry.
 
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Andreas Thaler

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From the service manual for the Minolta 7000 AF, which also has a Copal S shutter.

I think you should take such instructions seriously.

This also applies to opening the shutter unit when using a screwdriver, so as not to put any strain on the construction.
 

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Andreas Thaler

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A new attempt with another shutter

This time I'm using the shutter that I had replaced with the one I had already cleaned, which then didn't work properly.





As with all Minolta 9000 AF shutters examined so far, the damper on the bottom has rotten and become sticky.




When disassembling it, one of the four screws on the cover could not be unscrewed. I used the diamond cutter on the Dremel to remove the screw head and the rest of the screw could be unscrewed. The faulty shutter provides a replacement screw.

The cutter slipped a few times, but only caused paint damage. There is a replacement part for this too.






The rotten damper was removed by scraping and cleaning with acetone. The shutter blades were also cleaned with acetone.








The damper is replaced by parts of a rubber ring which I reduced in height by one third using a cutter knife and a steel ruler.




Glued with Loctite 406.

It fits perfectly.
 
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Andreas Thaler

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The shutter has been reassembled.

I also think I have identified the positions of two small brass rings.

I found an original replacement screw for the milled screw on the cover of the shutter in my spare parts supply.




I installed the shutter in the housing of a spare part 9000 and tested it. Both shutter curtains are released, and the tension lever on the bottom, which is coupled to the camera's winding lever, this time works without any wobble.




This means that everything is ready for removing the faulty shutter and installing the shutter that was cleaned today.
 
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Andreas Thaler

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Examining the faulty shutter



The removed faulty shutter should be examined.

I want to find out how I can trigger the two shutter curtains individually to measure their running speed.




This lever tensions both curtains. It is moved by the camera when the winding lever is operated.




Both magnets hold their anchors.




This lever releases both curtains at the same time.




The magnets have released their anchors






I desolder the connecting cables of the magnets in order to trigger them individually with my laboratory power supply, but this does not work.




I can manually release the rear shutter curtain using this lever.

When I pull the lever on the bottom up it sometimes doesn't engage and the front curtain doesn't release via this lever (left of the green arrow).

Clearly a mechanical defect that was also apparent when this shutter was installed.




I release the front shutter with this lever.


However, this does not produce any comprehensible values on the shutter tester.

That doesn't matter, as long as the 9000 AF can release the shutter, I'm happy

As soon as I have partially assembled the camera, I can test the shutter and than I'll see whether this replacement is successful or not.

Stay tuned!


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forest bagger

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Hello Andreas!
Andreas Thaler said:
I desolder the connecting cables of the magnets in order to trigger them individually with my laboratory power supply, but this does not work.
Click to expand...
You have to add power of ~ 3 V to generate a magnetic field with opposite polarity to the magnetic field of the permanent magnet.
 
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Andreas Thaler

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This time it worked

The 9000 AF is whole again, the cleaned shutter works, it was another exciting race




One shutter curtain did not fire. I had forgotten to solder the red cable from the shutter to the circuit board. I was able to find it in the camera and pull it out without having to disassemble the 9000 again. Since it was too short at this point, I extended it.






When I tested it after assembly, the AEL measurement memory, which is activated via a button above the thumb rest on the back, did not work.

A follow-up inspection revealed that the relevant switch on the counter base plate under the dial was defective. A replacement part was available.

To repair it, I had to take off the top cover, the dial and to replace the counter base plate. Since this is part of every disassembly and I have done it many times, it was done quickly.

The catch for the first position of the winding lever doesn't work. I had that repaired on a Minolta X-700. I'm leaving it as it is here, I don't want to go into the camera again. It doesn't bother me.




This was a challenging project that took several days.

It was worth it, this 9000 AF no longer has a sticky shutter.

I'm excited to see the photos it takes
 
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Andreas Thaler

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Results on the shutter tester. The 1/4000 second remains untamed

The shutter works well up to 1/2000 of a second, but at 1/4000 of a second there is a deviation of 2.8 EV. Several consecutive releases worsen this value, but then it improves again.




The shutter curtains move with a delay of approximately 0.20 milliseconds. Measured here at a shutter speed of 1 second.




At a shutter speed of 1/4000 seconds, you can see that the shutter exposes the sensors at different speeds. This results in a considerable EV deviation.




At 1/2000 second the EV value improves significantly.




At 1/1000 second this is already a good value, which continuously improves towards slower shutter speeds.




1/500 s




1/250 s




1/125 s




1/60 s




1/30 s




1/15 s




1/8 s




1/4 s




1/2 s




1/1 s
 
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Andreas Thaler

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I cannot say why the shutter deviates so much at 1/4000 second. It is obvious that different curtain speeds are more noticeable as exposure deviations at shorter times.

It can't be the sticky shutter, that's been fixed. Perhaps a small irregularity in the shutter housing is affecting the process.

Unfortunately I see no way to adjust the curtain speeds in conjunction with a measurement, see further up in the thread. But you can live with deviations, provided you know about them.

The next few days will show how this affects film exposure and hybrid processing in practice.
 
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Andreas Thaler

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Conclusion
  • To my knowledge, this thread documents for the first time the removal of the mirror box and the dissection and cleaning of the sticky shutter, which probably affects all 9000 AF.
  • This issue makes the camera useless for taking photos, as the shutter no longer works or no longer works properly.
  • Cleaning from the outside by regularly removing sticky residue from the curtains does not improve the situation, as the dirt immediately returns.
  • Cleaning the shutter and replacing the rotten damper is a tricky job but it is possible.
  • I will do the cleaning on another 9000 AF and add the procedure to my existing tutorial on removing the mirror box.
  • The 9000 AF has four common weak points: sticky shutter, aperture control failure, mirror misalignment and mechanical blockage.
  • @ogtronix is working on the aperture control issue, I will look into the blockage problem. The mirror can be easily adjusted. And the sticky shutter no longer has to be a fate

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Andreas Thaler

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Unfortunately, I had some bad luck today

I removed the shutter, which I had previously cleaned and fitted with replacement dampers, to adjust it.



In doing so, I mistakenly turned the wrong ratchet gear, which is obviously responsible for creating the curtains slit. I couldn't reconstruct the original position, and the gear no longer locked; it only maintained its tension via one end of its spiral spring.

After reassembling the 9000 AF, I discovered that the shutter now only shoots at 1/20 of a second.

So tomorrow I'll continue with the shutter from a 9000 for parts for replacement.

I've lost count of how many times I've disassembled and reassembled a 9000
 

Alexander K

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What an interesting topic, thank you! I look forward to the continuation! I have three AF 9000 bodies and one successfully purchased working one. I shot a couple of films with them, specifically to check all the modes, the result satisfied me. I will be happy to restore other bodies according to your recommendations!
 
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Andreas Thaler

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You're welcome!

See also my other threads about the Minolta 9000 AF:

Photo equipment from the 1980s: Repair projects and recommendations

I would like to bring together a selection of my previous contributions here in the hope that they will help readers with their work or inspire them to get involved in repairs. It is always worth trying to repair something, because if you do nothing, a camera or lens will definitely remain...
www.photrio.com

Photo equipment from the 1980s: Repair projects and recommendations

I would like to bring together a selection of my previous contributions here in the hope that they will help readers with their work or inspire them to get involved in repairs. It is always worth trying to repair something, because if you do nothing, a camera or lens will definitely remain...
www.photrio.com

Good luck keep us updated please!
 

Alexander K

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Looks great! I will definitely study everything and try. Although my experience in precision mechanics is not great, I want to believe that it is better to try than to regret later that I did not do it.
I'll let you know about the results!
 
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