Minolta (Maxxum/Alpha) 9000 AF: Blockage fixed, shutter cleaned/adjusted, exposure system checked, AEL, aperture control base plate, mirror stop

Andreas Thaler · Mar 27, 2025

A common problem with the 9000 AF, that has not yet been investigated, is a blocked shutter/mirror/aperture sequence.

The mirror stops halfway, the winding lever can no longer be moved, and the camera is locked, it can no longer be used.

I have two 9000 AFs with this problem, and I will remove the mirror box on one of them to get to the bottom of the problem. The mechanics of the shutter and film transport, as well as of the mirror and aperture, are then separated and can be examined directly.

These four videos by Alex Jordan, which show the mechanical processes on the mirror box, are very valuable for this purpose:

Alex Jordan

Share your videos with friends, family, and the world

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To assemble the 9000 AF, the shutter, mirror, and aperture must be preloaded. These videos should make it possible to identify errors in this process.

Blockages are one of the four weak points of the 9000 AF.

Others are a misaligned mirror (solved), a sticky shutter (solved), and faulty aperture magnets (pending).

I am looking forward to another interesting journey into the interior of a fascinating SLR

Andreas Thaler · Mar 27, 2025

Malfunction resolved

I suspected the blockage was in the mirror box area, as the process flow there was interrupted.

I could tension the aperture mechanism, the mirror mechanism was already tensioned, but I couldn't trigger the mirror to flip up. The armature of the mirror magnet wasn't holding and was loose.

So I looked to see if I could get to the mirror magnet by removing the aperture mechanism on a spare mirror box. That worked, but when I reinstalled it, the aperture mechanism no longer tensioned. So I abandoned the idea.

When I then carefully pushed the mirror upwards, the submirror stayed folded out. And then I saw that a small metal plate was blocking it.

The simplest of all possibilities!

After I removed the plate, the mirror box and aperture mechanism worked perfectly again. I'll tested it several times.

Hopefully the service manual will tell me where the plate comes from.

This gives me a good chance of getting this 9000 AF working again. As soon as I have it installed, I'll know.

Before doing this, the shutter must be disassembled and cleaned, as the damper for the closing curtain (C2) is rotten and sticky.

Andreas Thaler · Mar 27, 2025

Here's the location of the metal plate under the mirror. It was glued on and had come loose blocking the underlying submirror.

It forms the stop for the eccentric that adjusts the mirror height.

And this leads directly to another weak point of the 9000 AF: a partially blurred viewfinder image if this stop, to which the mirror is adjusted, is missing.

To compensate, the mirror can be readjusted using the eccentric if the plate got lost.

Andreas Thaler · Mar 28, 2025

Disassembling the shutter unit for cleaning

Once again, one of the four flat-head screws securing the frame for the shutter won't come off. I was able to loosen the other three screws by turning them clockwise and then counterclockwise.

This is particularly annoying because applying the screwdriver exerts pressure on the unit, which I can't directly compensate for with a counter bearing at this point; it's all very narrow and sensitive.

So I'm going back to my Dremel and this time I'll flatten the screw head with the cylindrical diamond cutter.

To protect the shutter, especially its mechanism with the two magnets, from metal abrasion, I've wrapped it in food-grade plastic wrap.

Andreas Thaler · Mar 28, 2025

That worked. The screw head is removed, and all the components underneath can now be removed.

The damage around the screw hole is only cosmetic and does not affect the function of the shutter.

I did the fine work with a narrower and conical diamond burr.

The rest of the screw remains in the thread, flush with the bushing onto which the parts are mounted. The parts are then secured with epoxy.

The sticky damper residue has been removed. There were only a few sticky spots on the closing shutter curtain (C2), which is cushioned by the damper. I cleaned them with acetone and a cotton swab.

Everything's clean, now I replace the damper with a piece of rubber band, which I cut to size and glue with Loctite 401. Then the shutter is assembled and the curtain travel times are set on the camera tester.

For details see

Minolta 9000 AF: Shutter disassembled, cleaned, tested, adjusted; exposure metering system checked - passed

Today I had a good day: I was able to put the first 9000 AF from my repair collection into service 🙃 It's the 9000, whose shutter I accidentally and irreversibly misaligned. Today I installed a replacement. I had previously also replaced the counter base plate because the switch contact for...

www.photrio.com

Andreas Thaler · Mar 28, 2025

Of course, non-destructive removal of the screw would be preferable.

Perhaps it would be possible to drill out the screw and tap a new thread, but since the steel screw sits in a bushing (made of softer metal?), that would be difficult.

Since I don't want to subject the shutter further to mechanical stress, and I don't have a precision mechanics workshop, I'll stick with the method shown.

The success will be determined on the camera tester, where the curtain travel times and shutter speeds are measured.

Andreas Thaler · Mar 28, 2025

Assembly of the shutter.

The replacement damper in lemon yellow is glued in, the closing curtain C2 is inserted.

I had to trim off the damper strip on the right with a knife because the curtain was lifted a bit.

First measurement of the curtain travel times on the Reveni Labs Camera Tester. C1 is slower than C2.

Since an increase in time requires resetting the respective curtain, I adjust C1 to match C2.

I don't know the reference curtain travel time; following Minolta, it's around 3.3 milliseconds. I will go for 3,18 milliseconds.

Perhaps this will shorten the shutter speeds, but as long as the speeds series shifts in parallel, that's secondary. The first priority is that both curtains travel at approximately the same time to prevent uneven exposures.

After a few adjustments/tests, the curtain travel times are almost identical. I'll leave it at that.

The shutter in a 9000 AF back, which I specially prepared for adjustment on the camera tester.

Now it's time to assemble the 9000 AF.

I won't know if everything works until the end

Andreas Thaler · Mar 28, 2025

The missing screw has been replaced with epoxy, which is now drying.

My heavy magnifying glass, the front lens of a former Minolta MD 35-135/3.5~4.5, serves as weight.

Andreas Thaler · Mar 28, 2025

Mission achieved

The repair was successful; the aperture - mirror - shutter sequence now works as intended. The blockage has been resolved.

The shutter is also stable after cleaning and delivers consistent exposure times.

As with the 9000 AF before it, the AEL button for saving the measured values doesn't work. I suspect a defective switch on the counter base plate. I'll have to wait for a replacement part, then I'll take a look. Maybe I can repair it.

I'm also looking for the small cover plate on the dial for the diopter correction with the +/- label.

The fact that the base plate is held in place by only two screws instead of three is due to a stubborn screw that involuntarily lost its head

Andreas Thaler · Mar 28, 2025

Measurement results on the camera tester

1/4000 second

The fastest shutter speed isn't reached, but the exposure is almost even.

I think I'll set the curtain travel times a bit shorter next time.

1/2000 s

1/1000 s

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

Andreas Thaler · Mar 28, 2025

1/1 s

Test of the automatic exposure in program mode. Brightness distribution during the shutter release and exposure deviation in EV. The exposure metering system is OK.

Andreas Thaler · Mar 28, 2025

Conclusion

I'm particularly pleased with this successful repair. The 9000 AF is in mint condition, but I had already earmarked it for spare parts (hence the red dot on the body).
I didn't install the metal plate for the mirror stop. The risk of it coming loose again and blocking the submirror is too high for me. The viewfinder image is sufficiently sharp. I attribute the blockages known with the 9000 AF to this plate.
I'd like to point out again that every 9000 AF now has a sticky shutter, as the rotting damper apparently was standard. Therefore, the shutter needs to be cleaned to ensure reliable operation again.
The 9000 AF is an impressive SLR, inside and out. It's worth investing time and effort in.
This concludes my Minolta 9000 AF series here in the forum. Should there be any highlights or new findings while repairing my other candidates, I'll post them

+++

All information provided without guarantee and use at your own risk.

Andreas Thaler · Mar 29, 2025

Andreas Thaler said:
View attachment 394877

As with the 9000 AF before it, the AEL button for saving the measured values doesn't work. I suspect a defective switch on the counter base plate. I'll have to wait for a replacement part, then I'll take a look. Maybe I can repair it.

This time it was just a contact fault and not a defective switch. The AEL button is working again.

The switch with AEL button and contact on the top cover

The mating switch is located on the counter base plate, which is marked here with an arrow.

In order to remove and examine it, the dial above it must be removed.

The underside of the counter base plate. The arrow points to the contact actuated by the AEL switch.

The contact on the plate …

… and the mating contact on the circuit board.

Electronics cleaner solved the problem.

Andreas Thaler said:
View attachment 394874

I'm also looking for the small cover plate on the dial for the diopter correction with the +/- label.

Done

Andreas Thaler · Mar 30, 2025

This should make this and the 9000 AF I was working on previously ready for shooting.

There might still be some surprises with the flange focal distance and the AF; I can't test that at the table. But I don't think so, because the cameras had been adjusted at the factory, and after that the flange focal distance shouldn't change unless the camera has been subjected to force. In any case, no deviations were noticeable when installing the mirror box, and joining it to the back was problem-free.

The AF adjustment shouldn't have changed either; the user would have to open the camera and tinker around with it for that.

But it still remains exiting. The test with film will take place tomorrow.

Andreas Thaler · Mar 31, 2025

Final test on film

Today, the project was completed with the usual test on film.

Here are some shots taken around the Votivkirche in Vienna's 9th district and at home.

Lens was the Minolta AF 50/1.7

The negatives are evenly exposed, the autofocus is accurate.

Images 2 and 8 are overexposed.

A closer look reveals that they were clearly shot at the widest aperture of f/1.7. There's vignetting and blur, typical of wide apertures.

It's possible that the 9000 didn't stop down, which could be a problem with the aperture mechanism.

I'll look into this.

Kodak UltraMax 400
Nikon Coolscan 5000 ED
VueScan
Adobe Lightroom Classic
NegativLab Pro with default settings
no further processing

Andreas Thaler · Mar 31, 2025

Conclusion

The blocked, and thus inoperable, 9000 AF in mint condition has been resurrected.
The cleaned shutter, fitted with a new damper, and adjusted, works perfectly.
Exposure errors caused by a rotting damper that clogs the shutter blades can no longer occur.
There could be a problem with the aperture mechanism that occurs sporadically. That would explain the two overexposed images. I'll look into it.
The slight blur in the viewfinder is caused by the broken stop on the mirror (metal plate) and does not affect the images. I will replace the plate. Loctite 401 should prevent it from blocking the submirror again.
The exposure metering system works as it should.

Andreas Thaler · Mar 31, 2025

I just haven't noticed any aperture issues with the Minolta Winder AW-90, even in continuous use. I've fired about 100 times, including manually.

We'll see what happens on my next photo trip.

Andreas Thaler · Mar 31, 2025

Assuming it's a problem with the aperture mechanism, my approach is as follows:

The aperture magnets (two) are probably not working reliably.
Problems with the aperture mechanism/aperture magnets are one of the weak points of the 9000 AF.
The aperture magnets can be cleaned or replaced.
In the C & C Associates Troubleshooting Guide for the sister camera, the 7000 AF, Larry Lyells recommends replacing the aperture magnet (one) rather than cleaning it if there are problems with it.
Cleaning and replacing it is time-consuming because for this the mirror box must be removed.
Since there are not any new spare parts for the 9000 AF available, it's advisable to use them sparingly.
Therefore, I'll first try to fix the problem by cleaning the magnets.
If that doesn't work, I have several replacement magnets from discontinued 9000 AFs.
It could also be a problem with the coupling between the camera aperture ring and the lens aperture lever.
Before I get to work, I observe the situation with shutter releases without and with film.
Maybe the error won't occur again, or it'll occur more often. Then I can decide whether to address the issue or live with it.
The 9000 AF keeps us busy

Andreas Thaler · Mar 31, 2025

For todays test results of another 9000 AF see

Minolta 9000 AF: Shutter disassembled, cleaned, tested, adjusted; exposure metering system checked - passed

Today I had a good day: I was able to put the first 9000 AF from my repair collection into service 🙃 It's the 9000, whose shutter I accidentally and irreversibly misaligned. Today I installed a replacement. I had previously also replaced the counter base plate because the switch contact for...

www.photrio.com

+++

All information provided without guarantee and use at your own risk.

Andreas Thaler · Apr 1, 2025

Replacing the aperture control base plate

Today I looked at how I can solve the problem with the aperture magnets, in case it should become necessary with my 9000 AF.

It turns out that cleaning the magnets first makes sense.

If that doesn't work, the best option is to replace the complete aperture control base plate from a spare 9000 AF.

The aperture control base plate with the two aperture magnets SL1 and SL2 is located inside on the right side of the mirror box.

While SL1 is easily accessible for cleaning/replacement, SL2 is installed behind a flexible circuit board and can only be accessed after removing the aperture control base plate.

Following the Minolta service manual SL2 is a possible cause of the open aperture problem (aperture not closing to the specified value).

If cleaning of SL2 doesn't help, I'll replace the entire aperture control base plate. This will save me the hassle of removing and reinstalling SL2, which also has to be removed from the dispenser unit first.

Removing the aperture control base plate is easy. However, the unit requires some preparation before installation.

Removing the aperture control base plate

Circlip

3 screws

Done

Preparing the aperture control base plate for mounting

Move the aperture ring tab to its end position (minimum aperture setting).

Corresponding position of the transmission gear, note the marking.

Push the charge pin in the direction of the arrow and fix it.

Push the roller on the gear in the direction of the arrow.

Engage gear with lever.

Now you can release the charge pin.

Push the lever in the direction of the green arrow.

The arched gear moves upwards.

Check that both markings are opposite each other (white arrow).

Press the roller on the arched gear gently in the direction of the green arrow.

This engages the first claw of the aperture stop gear with the lever above (white arrow).

Check also the position of this mark (red arrow).

Mounting/checking the function of the aperture ring

Circlip

3 screws

After mounting move the pin gear in the direction of the green arrow.

Andreas Thaler · Apr 1, 2025

This brings the tab on the aperture ring in this position (maximum aperture setting).

Push this lever …

… to bring the aperture ring to the minimum aperture setting.

Pushing this lever brings the aperture ring back to maximum setting.

The aperture ring can now be moved up and down.

Tensioning and releasing the mirror

Push lever upwards.

Pushing this lever in the direction of the green arrow releases the mirror (white arrow).

Pushing this lever brings the mirror down.

Andreas Thaler · Apr 1, 2025

The aperture and mirror mechanisms are interconnected. By going through these processes, you'll understand the connections.

This determines the solution to a problem with the aperture mechanism or the aperture magnets:

Cleaning the magnets,
if unsuccessful, replacing the complete aperture control base plate from a donor 9000 AF, whose aperture mechanism and magnets are functioning.

All processes shown are described in detail in the Minolta service manual starting on page 87 (reader) „Mirror Box Assembling 2“.

Minolta Maxxum Alpha Dynax 9000 Service Troubleshooting Manual : Minolta : Free Download, Borrow, and Streaming : Internet Archive

The service manual for the Minolta Alpha/Dynax/Maxxum 9000 (or A9000/α9000) film SLR.

archive.org

+++

All information provided without guarantee and use at your own risk.

Andreas Thaler · Wednesday at 6:15 AM

Blur in the viewfinder: Reattach the mirror stop

One of the known issues of the 9000 AF is blurriness in the viewfinder, even though AF and manual focusing via the LED light balance produce sharp images on the film.

This is caused by a small metal plate attached to the underside of the mirror frame as a stop, which has since come off.

The height of the metal plate is part of the adjustment. If it's missing, partial blur occurs in the viewfinder because the mirror is no longer perfectly parallel to the focusing screen.

The metal plate rests on an eccentric screw in the mirror box, which serves as a support for the mirror.

The metal plate that is glued on is stressed by the mirror impact and after decades the glue can loosen and the plate falls off.

This plate was blocking the submirror on my 9000 AF and thus the camera.

If the plate is lost, you can adjust the mirror using the eccentric screw while looking through the viewfinder.

I still have two plates and reattached one of them today.

The remaining old adhesive on the mirror frame can be removed with acetone.

Two metal plates that have come off. You can see the stop point on the eccentric screw as a bare spot.

After a bath in acetone, adhesive residues can be completely scraped and rubbed off the plate.

The plate must lie flat on the underside of the mirror.

The plate is back in its position, glued with a double application of Loctite 401, which dries quickly.

The submirror can be carefully spread slightly away from the mirror to get better access.

Adhesive tape and the spudger from iFixit with hook fix both mirrors against spring tension while working.

A first check through the viewfinder of the 9000 AF.

The subject is again in focus in the viewfinder.

+++

All information provided without guarantee and use at your own risk.

Andreas Thaler · Wednesday at 10:59 AM

Loctite 401, highly fluid, didn't hold; there are probably minor bumps on the two bonding surfaces.

So I'll try Loctite Gel.

Andreas Thaler · Sunday at 8:07 AM

Adhesive holds

With Loctite Control, which is somewhat viscous, the metal plate holds.

My goal of getting two Minolta 9000 AF ready for photography has been achieved

A Dynax 7000i has been added, and this SLR will keep me busy for a while.

Minolta (Maxxum/Alpha) 9000 AF: Blockage fixed, shutter cleaned/adjusted, exposure system checked, AEL, aperture control base plate, mirror stop

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