Minolta (Maxxum/Alpha) 7000 AF: Aperture issues resolved/shortcut; LCDs, aperture ring, shutter unit replaced; aperture solenoid cleaned

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Andreas Thaler

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Replacing the aperture ring in the camera bayonet and cleaning



The reason for the aperture always being open on this 7000 was the rotating aperture ring in the camera bayonet, which jumped out of its roller and blocked.




I was able to put it back into its original position what resolved the problem.

Since the aperture ring is also bent, I will replace it.

And while I'm at it, I'll also clean the area underneath and the entire accessible part of the mirror box.


Rollers

As far as I understand it, the pair of rollers opposite (on the left in the pictures) is responsible for two processes:
  • Lower roller: turning the aperture ring to the intended position for setting the aperture in the lens.
  • Upper roller: spring pressure to return the aperture ring to its original position.
I hope I can find more details about this in the service manual.

When replacing the aperture ring, it is important to install it in exactly the same position as the old one so that the apertures are formed correctly.

You also have to pay attention to the spring so that it does not relax or jump out.

Inserting the ring should work by opening the two rollers on the right, which are only there to guide the ring.


Those are my assumptions.

We will see today whether this is actually the case.
 
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Andreas Thaler

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Replacing the aperture ring

From a 7000 for spare parts, I removed and reinstalled the aperture ring for demonstration purposes.

Removing















Here is the roller with spring, which I fix in this position with my finger so that the spring does not relax.

It is not important here, as it is a demonstration on the spare part camera. When changing the aperture ring on the repair candidate, the finger remains until the ring is latched into the roller.




The aperture ring is removed.


Mounting



In this position the ring to the mirror box must be reinstalled so that the apertures are formed correctly.

To do this, the aperture ring is inserted into the two rollers on the left with gear rings.




Then the lower right roller is engaged.










The aperture ring is reinstalled.
 
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Andreas Thaler

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Exchanging the aperture ring on the repair candidate



The repair manual lists two aperture ring variants: steel and aluminum. The steel ring can replace the aluminum ring, but not the other way around.

This one is magnetic, so it is the steel variant.








The repair candidate where the aperture ring is to be replaced.







The bayonet is removed.




Likewise the ring under the bayonet with tabs for holding the lens.






Removed parts.




The ring has been replaced, the area underneath cleaned.




To be able to blow off the bottom of the prism, I remove the focusing screen.




The removed ring is not magnetic, i.e. made of aluminum.






I was able to clean the mirror to a certain extent.
 
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Andreas Thaler

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The mirror box is now cleaned with isopropyl alcohol.






And the eyepiece is free of dirt.




The brown cable to the hot shoe has come off at the top cover.






Stripping …




… resoldered.




It's time to assemble.




The ring under the bayonet.

According to the service manual, it gets some grease on both sides of the tabs.




The aperture ring rotates as it should.






The exchange was successful. The aperture closes perfectly.

Mission accomplished
 
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Andreas Thaler

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And now we move on to the next mission: checking/replacing the shutter unit



I should have checked this 7000 more thoroughly before doing the repairs. Then I would have noticed that the shutter only closes with a delay.

Cleaning the shutter curtains with Zippo lighter fluid didn't help.

That means removing the mirror box again and checking the shutter unit.

I have a replacement shutter unit from the 7000 for spare parts. But I have to get it out first.

Now that I know how to remove and install the mirror box, it's not a problem, but good practice.

Stay tuned!


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ogtronix

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Interesting there's no adjustment on the aperture ring like with the 9000. It'd be easier to see it as a sign of poorer quality but it could just as easily be the opposite with the 7000s being made in such volume that the manufacturing process was more refined and precise, while the 9000 was made to poorer tolerances in smaller volumes with the expectation of hand fitting and adjusting parts.
 
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Andreas Thaler

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For comparison, would you like to show a few photos of the Minolta Dynax 7000i that you took apart?

I would be particularly interested to see to what extent the electronics of the direct successor have been further integrated and what the wiring looks like.
 
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Removal of the shutter unit from the spare parts 7000



This 7000 has an additional circuit board mounted on the prism.




The mirror box has been removed, allowing access to the shutter unit.




The shutter is fixed at two points to the rear part of the housing.




Fixation point 1 …




… and fixation point 2.




All cables for the shutter control have already been desoldered when the shutter box was removed.






The cables remain on the shutter unit.








Overview
 
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Andreas Thaler

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Now I'm doing the same thing again with the 7000, whose shutter I want to replace.

And because I want complete instructions for each step, I'm going to make a tutorial out of it.
 
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Andreas Thaler

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Shortcut and a problem in close-up

The shortcut described earlier in the thread, i.e. releasing the stuck aperture magnet from the outside, can be seen here.

It is the 7000, whose aperture always closed to the smallest value, regardless of which aperture value is set.

In doing so, I melted a second hole in the plastic cover of the magnet with the tip of the soldering iron and was able to separate the two parts, but then had to rework it so that it closed again.

The cause of the problem was melted plastic on one of the two contact surfaces.



The double hole, so I wanted better access to both contact surfaces.




Position of the magnet in the aperture control.






The magnet closes and opens as it should.




The plastic cover has been removed.




Traces of file work on this contact surface.




Here, too, there are traces of the file and remains of the melted plastic that prevented both parts of the magnet from closing.

By reworking it with the file, I was able to get the magnet working again. But that was only an emergency measure.


Conclusion
  • One single hole for the shortcut is the safe solution, but you need a makeshift device to clean the contact surfaces through this hole.
  • An alternative is to use a syringe to inject electronic cleaner through the hole. This should not degrease the mechanics underneath if you do it selectively.
  • Regular repairs mean removing the mirror box and cleaning the magnet directly.

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ogtronix

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I think i've posted most of these already but there's a couple extra.


Spinning it around with the covers off.


Winding mechanism taken out of the base, and the side of the mirror box with the aperture control mechanism removed. Unfortunately i've got no better photos of the electronics since I removed them with scissors. It was the aperture mechanism I was curious to see. Also all of this except for some potentially useful ancillaries went right into the bin since i'm running outta space for storing camera giblets.

I felt nothing looked at all similar outside of being stuff generic to most cameras, along with the dorky lens mount Minolta got themselves stuck with. It's all very unique otherwise.
 
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ogtronix

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The engineering teams that designed these cameras obviously knew alot more about this stuff than I do, but I don't get why it took them so long (till the Dynax 7?) to just drive the aperture ring directly with a servo motor. The earlier cameras that even include a DoF preview mechanism have to clonk the whole mirror box to reset after using it, and obviously can't be adjusted on the fly while stopped down. It can't have been for battery life since Minolta insisted on trying to make the autofocus run constantly the second you touch the camera (I wanna get one of the xi cameras at some point, the stupid the automatic zoom stuff seems very funny). Did somone just have a patent on the idea of setting the aperture with a motor?
 
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Andreas Thaler

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Andreas Thaler said:
Now I'm doing the same thing again with the 7000, whose shutter I want to replace.

And because I want complete instructions for each step, I'm going to make a tutorial out of it.
Click to expand...

See

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

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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Thanks!

A beautiful mechanism and a powerful camera that is being sold for a pittance today.

Unjustly.
 

ogtronix

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Guess the problem is that cameras with more features are also being sold for a pittance. A big part of Minolta's appeal today is, aside from the way cheaper lenses, the cameras being more weird and silly than what Nikon or Canon offered. Consumer products haven't really been made since around 2008 and more people are starting to notice, so there's alot of current fascination with past 'innovations' and goofy attempts to capture or create corners of the market. Which is something Minolta did alot of.

The X000i series cameras are in a kinda limbo though of not being all that distinct and weird relative to peers... and really lacking that depth of field preview to make up for it.
 
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Andreas Thaler

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I can't see anything on the removed shutter unit that could explain the delayed closing of a shutter curtain. With the exception of the solidified dirt visible here, which could not be dissolved with lighter fluid. Otherwise, the shutter curtains slide off easily.

We'll see how the replacement shutter behaves.

I think an electronic problem is less likely, because as soon as the two shutter magnets release the curtains, they are moved by spring force.

That's my assumption.
 
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Andreas Thaler

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Replacing the shutter unit



Today I replaced the defective shutter unit with one from a spare part 7000.

The installation went without any problems.




I noticed that one curtain of the replacement shutter was blocked. A small plastic part had got into the mechanism and jammed.

No idea where it came from.

After removing the part, the shutter worked perfectly.




Measuring shutter speeds on the Reveni Labs Camera Tester after assembling the 7000.




1/2000 s




1/250 s




1/30 s

I am satisfied, the replacement of the shutter unit was successful.


A problem with the autofocus quickly resolved



When testing after assembly, the autofocus suddenly started on its own or could not be activated using the shutter release.

I suspected a mechanical problem with the shutter release contacts and quickly found the problem after removing the top cover. I had obviously bent a contact when putting the top cover on.




This was quickly corrected with pliers.




Back in service, cleaned, with a new aperture ring and shutter.

Mission achieved


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Summary of repairs performed

In total, I had seven Minolta 7000 AF on the table.

Five of them work, two became spare parts depots.

I had carried out the following repairs/operations:
  • Aperture always at the smallest value, cleaning the aperture magnet from the outside as a shortcut.
  • Aperture always at the largest value, replace the aperture ring on the camera and insert it correctly.
  • AF turns itself on, solving a contact problem on the shutter button.
  • Replacing the leaking main LCD with a flawless.
  • Replacing/cleaning the viewfinder LCD, which was showing almost no digits anymore.
  • Adjusting the viewfinder LCD.
  • Fixing contact problems on both LCDs.
  • Replacement of the shutter unit where a curtain was running too slowly, removing and installing the mirror box, see tutorial.
  • Clearing a blockage on the replacement shutter.
  • Backup batteries tested, special features of open circuit voltage and terminal voltage discussed during battery testing.
  • Falling plastic coatings on the housing were removed and options for repair were explored.
  • Behavior of aperture control explored.
  • Battery holder cleaned of corrosion caused by battery electrolyte.
 
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Andreas Thaler

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The shutter speeds

of all five 7000s are fine, tested with the Reveni Labs Camera Tester.


Exposure metering test



To do this, I positioned the five 7000s in front of a slide light table and noted the determined shutter speed in aperture priority mode at ISO/ASA 100 and aperture f = 4 (Minolta AF 50/1.7).




My work camera Nikon F4E served as a reference.




The results are pleasing. The deviations are less than one f-stop, which is negligible given my use of negative film and hybrid processing.




With the 7000, the exposure values can be easily read on the main display.
 
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Functional test for plausibility

All five 7000s show plausible behavior, ie the operating modes, aperture function, autofocus, sound signals and film transport behave in a comprehensible manner.

No abnormalities/malfunctions can be detected.


Conclusion
  • The Minolta (Maxxum, Alpha) 7000 AF is easy to repair.
  • The key to all more in-depth repairs is removing and installing the mirror box. This is a bit of work, but it is doable.
  • Spare parts are plentiful in defective 7000s, which - like working 7000s - are inexpensive to get.
  • The inner workings of the 7000 are well organized and of good quality. It is worth picking up a screwdriver.
The 7000, on which I replaced the shutter and aperture ring, will be my work camera of the five; I have grown fond of it


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Andreas Thaler

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Still something to do

Here I have still one 7000 with a problem with the aperture control, which was OK when last checked in January.



The aperture only closes to the smallest setting, I used the shortcut, but I saw an aperture magnet from the outside that was different from the previous ones. No plastic cover, contact surfaces not visible.



Gently pull on the fitting and put in very little electronic cleaner with the syringe to be on the safe side, and the aperture started working again.

However, it closes irregularly. So I have to take a look and dismantle the 7000.
 
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Cleaning the aperture magnet not successful



Mirror box removed.




A new type of switching magnet is presented to me.






This switching magnet does not have a transparent plastic housing under which the contact surfaces are exposed. Here, the contact surfaces are built in and cannot be cleaned either from the outside via the shortcut or directly.




To separate the armature from the solenoid it must be removed.






The armature …




… which I clean with electronic cleaner ...




… as well as the contact surfaces under the cover.

After cleaning, I use the bellows to blow off the contact surfaces so that they are dry and do not stick together due to cohesion.




The switching magnet is reassembled and installed.




After reassembly, the camera works, but the aperture closes again always to the smallest value.


Conclusion
  • A different version of the switching magnet makes it impossible to use the shortcut from the outside.
  • The technical documentation gives several reasons for the problem with the smallest aperture, I will look into it.
  • I will definitely try using a magnet from one of my spare parts 7000.

So it remains exciting


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ogtronix

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How do the serial numbers of the two cameras compare? Like, I wonder if that was an earlier or later revision. It feels like it'd be earlier. But man there really is no way to clean that from outside.
 
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Andreas Thaler

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I've got the hang of it now, I need 1.5 hours each time to remove and install the mirror box, so a total of 3 hours.

That's why the checks on the test points in the circuit without disassembly are interesting.

I'll come back to that.
 
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