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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You can only test the full functionality of a camera after it has been completely assembled. If something goes wrong along the way, you might not notice it straight away. Then you have to take it apart again and look for the fault.

With the 7000, this is a complex game with the many soldering points and tricky circuit board parts which are probably easier to separate than to put together.

I still have to learn to work on a camera for several days, maybe that will come with age
 
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Andreas Thaler

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I find this gear transmission an attractive mechanical detail.

Without the photographer knowing it, power is transmitted directly above his eye
 
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Andreas Thaler

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Service hatch: A shortcut to solve the aperture problem?

Given the effort and uncertainty of disassembling and then reassembling, I'm looking for a shortcut to solve the aperture problem.

If it really is a matter of dirt on the contact surfaces of the aperture magnet, an electronics cleaner should be able to fix it. This also works with the Canon T90.

The problem with the 7000 is described as the magnet no longer electrically disconnecting and therefore the smallest aperture is always formed. So you would have to separate it and then clean the contact surfaces.

The prerequisites for this from the outside, without disassembling the 7000:
  • Access to the area of the aperture magnet,
  • removal of the protective plastic housing,
  • mechanical separation of the contact surfaces
  • insertion of the electronics cleaner.
  • This would require an opening in the housing.



Position of the aperture magnet.




The cover can be pried off, it is only fixed with adhesive in one place (red spot). Isopropyl alcohol can be used to loosen the adhesive.

The cover then remains freely movable in the mirror box, where it must not interfere with the mechanics (this must be checked).




A hole could be drilled from the outside to access the magnet (green, „service hatch“). This can be sealed with Sugru.

Red: both contact surfaces of the magnet separated.




Area from the outside.


I'll take a look at the disassembled 7000 to see if that's a realistic option.
 
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Andreas Thaler

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A service hatch does not need to be drilled, it is easier



The mirror box is inserted into the back. A bulky affair, with cables and flexible circuit board parts everywhere.




Here is the plastic cover of the aperture magnet. It can only be lifted back about 3 mm before it hits the shutter control.




But now I see that the top edge of the plastic cover is against the edge of the case. There is just a flexible plastic shield here, so there is no need to drill a hole to get to it from the outside.

If I open the part of the cover of the aperture magnet where the arrow points, I have direct access to the two contact surfaces. I can try to separate them with the pointed probe and apply electronics cleaner.

This should work with a small milling head on the Dremel Stylo or a drill. However, the removed plastic will then fall into the interior of the camera and perhaps on the contact surfaces. But this is still better than conductive metal of the housing, which might be attracted by the permanent magnet.

I will screw on the mirror box in the next step and try the procedure. Then I will see if that is an option.
 
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Good news, the two contact surfaces of the aperture magnet can be separated using the pointed probe.

I don't know how the aperture control works in detail and whether it will work on the intact 7000 with the aperture problem, but it's worth a try.

All I have to do is remove the top cover and possibly the front cover.

Before that, I'll try opening the aperture cover with the Dremel Stylo on the disassembled 7000.

If it doesn't work, nothing is lost, I'll just have to disassemble the intact 7000 and to look what can be done.
 
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Mirror box mounted.




The top of the aperture magnet cover is accessible.






To make room, I cut out part of the plastic shield.




Small milling head on the Dremel Stylo.




A hole has been milled, but the plastic cover has come loose, which is not a disadvantage as it has very little room to move.






The two parts of the magnet can be separated using the pointed probe. The magnetic switch can be closed again using the lever to the left of the hole.






Apply electronic cleaner without seeing the contact surfaces. The cleaner is harmless and does not attack anything.




The mirror box has been removed again to check the work.




When the hole was milled out, plastic debris got onto the contact surfaces. Although the magnetic switch closes, this is not acceptable. The contact surfaces must be clean, which is why the plastic cover is there. Also, part of the magnet frame is damaged. By blowing it out with the bellows, the plastic debris is distributed on the aperture control.




Alternatively I try using the hot soldering tip, which creates a cleanly outlined hole.




That looks good. And there is no pollution from plastic abrasion.
 
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The small collar does not bother, the two parts of the magnet have enough space.




Working in space conditions such as in a submarine
 
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Conclusion
  • Cleaning the contact surfaces of the aperture magnet from the outside, without having to disassemble the 7000 in depth, seems to be a realistic option.
  • The test will show whether this can solve the problem with the aperture always closing to the smallest value.
  • I still assume that contamination on the contact surfaces of the aperture magnet prevents the magnet from opening.
  • The next step is to partly dismantle the 7000 with the aperture problem in order to reach the aperture magnet. This is much less effort and risky than removing the mirror box. I'm excited to see what happens.

We'll continue on Monday.

Stay tuned!


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ogtronix

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Melting a hole for access is a nice idea. If it had to be drilled i'd probably try do it slowly with a pin vice, removing the (ideally sharp) drill bit regularly to remove the chips. Maybe outright holding the camera upside down.

For cleaning the magnet though, does one of them pointed cotton cleaning sticks not fit? I feel dripping solvents onto the whole magnet probably wouldn't improve things, and while it's electronics safe I'm not sure if it'd be mechanics safe. If it's doing its job of dissolving oil contamination/ degraded conformal coatings then i'm sure it won't help if it gets into a pivot or something.
 
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The problem is that the contact surfaces of the magnet are not visible from the outside. I would have to make or adapt a cleaning stick, as everything is too big. Maybe a tiny piece of optics cleaning cloth on a pointed probe, cut to a strip so that it doesn't get lost in the camera.

Electronics cleaner is intended for cleaning contacts independently; I would have to try out whether it removes oil from bearings and axles, but my experience so far has been good.
 
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With electronics cleaner, it also depends on the amount applied.

At the beginning of my journey to the aperture control of the Nikon F4, I thought it was dirty and shot the stuff forcefully from the can into the mechanism from the outside. This removed the lubrication and the aperture no longer responded at all.

Here, with the 7000, the cleaner comes out of the fine syringe needle in small amounts. That shouldn't be enough to remove surrounding lubrication. But nothing is certain. Let's see how it works with the 7000, which I want to fix.

In the meantime, I'm looking at the aperture control in detail, maybe I'll think of something better for cleaning. I still have a couple of expensive plastic sticks with a small textile pad; they're narrow, I could trim them with a knife. But then I'll just have to poke around on suspicion because there's nothing to see.
 

ogtronix

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Still, it needs to go somewhere if its carrying the oils off of the magnet surface. If it just sits there it'd just dissolve the oils, and then evaporate away putting the oils right back where they were. I also felt I needed some Scrubbing Action to get the stuff off of the magnet in that 9000.

It seems the hole gives direct access to the gap between the magnets. Just a toothpick could probably work. Wood fibers are absorbent and... scrubby. Scrubalacious? Is there a word for an object having the properties of being good at scrubbing?

There's also pipe cleaners and interdental brushes and stuff.
 
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Andreas Thaler

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All good ideas, but you can't see where you're working, at best on the top right contact. The second one is a little below and the counter contact, long, is folded away at an angle.

I'll take a chance, if it doesn't work that way, I'll just have to remove the mirror box and fix everything again. I want a simple solution that anyone can do.

Whether it can all be brought to a common denominator remains to be seen.

Shortcuts that replace a repair are rare. Japan doesn't give you anything for free.
 
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Andreas Thaler

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The reason why I am working through the methods here is so that everyone can form their own opinion about what works and what doesn't.

I knew that milling would make a mess, but I still hoped that it would be acceptable.

Otherwise, I work with the tools I have. And I adore the small Dremel Stylo, it dictates my processes
 
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Andreas Thaler

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Shortcut works

The aperture control of this Minolta 7000 AF is working again. The aperture now closes to the set values and not always to the smallest value

This also verifies the cause of the error that makes many 7000s unusable for taking photos: contaminated contact surfaces of the aperture magnet.

A trivial cause with fatal consequences.






For the shortcut, the front panel of the 7000 must be removed, see the individual steps in the thread.

Here again the order of what has to be removed:
  1. bottom panel,
  2. top cover,
  3. handle
  4. plastic covers on the front panel,
  5. front panel



The aperture magnet is closed.




Using the hot round soldering tip (400 C/752 F) I manage to make a cleanly defined hole on the plastic cover of the aperture magnet without causing any further damage.




I can now separate the two magnet parts with the pointed probe. Maybe that would have been enough to get the magnet working again.




But I wanted to enlarge the opening to be able to reach the contact surfaces better for cleaning.

In the process, plastic melted inwards and prevented the moving part of the magnet from docking with its counterpart.




After many attempts, I managed to get the magnet to close again using a sharp knife, files and electronic cleaner on a cleaning stick.

The two contact surfaces now adhere less strongly to each other, but it is sufficient for full functionality.




Test








The aperture closes again to the preselected values. Previously it always stopped down to the smallest value. Quick tests in P, A and M mode were successful.

This 7000 is now usable again
 
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Conclusion
  • This shortcut is a real opportunity for many Minolta 7000 AFs to get back into working order. With a defective aperture control that always stops down to the smallest value, the camera is useless for work.
  • The regular repair means removing the mirror box, cleaning the contact surfaces of the aperture magnet and reassembling the complex camera. This is a lot of work and there is a risk that the 7000 will no longer work or will no longer work properly afterwards. The repair requires repair knowledge and a variety of tools. Anyone who manages to do this the first time within a day can be proud. It is questionable whether a repair shop will undertake this work. If so, then it will be at a corresponding cost.
  • This shortcut requires only minimal and risk-free disassembly. All you need is a JIS 00 crosshead screwdriver, a soldering iron, glue, a pin, electronics cleaner and a suitable stick for cleaning. Opening the cover of the aperture magnet is critical. It may be enough to separate the two magnet parts once to restore the function. With a cleaning tool that is small enough, you can try to clean the contact surfaces of the magnet. Or try using a targeted electronics cleaner. Duration of the shortcut: around an hour.
  • The method shown can of course be improved. Perhaps someone has ideas or would like to try it themselves and report here.
  • I will try to get two more 7000s with defective aperture controls, on which I will repeat the shortcut. I will see if it can be done just by separating the magnet parts without further cleaning.
  • Until I have verified the shortcut by repeating it, I consider this result to be „encouraging“.
  • The problem with the melted plastic was a complication, but should not change the cause of the aperture problem and its solution. I still assume that the contact surfaces on the aperture magnet are contaminated, which should be remediable by moving or simply cleaning.

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ogtronix

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Nice! I do like the idea of keyhole surgery for cameras. If nothing else it's just cool, like safecracking...

Also I finally ordered one of these cameras. Secretly I want to try repainting one.
 
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Andreas Thaler

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For the classic repair

i.e. removing the mirror box, there are instructions for reassembly in the Minolta Service Manual on page 162 and in the SPT Journal on page 22.

It is important to correctly couple the mechanism of the shutter and mirror box, for which there are instructions there.

I think the classic repair is feasible with organization and patience, especially if you document the soldering work carefully.

Desoldering the circuit board in the base of the 7000 can be a challenge, as it is attached to several soldered pins. I made good progress here with the desoldering pump.

Separating two soldered circuit board parts on the prism with desoldering braid works just as well.

Apart from that, it is a matter of keeping track of which of the numerous cables is soldered where.

In any case, the in-depth disassembly and reassembly of the 7000 offers interesting insights into a masterpiece of Japanese electromechanical precision work. For this reason alone, it is worth trying
 
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Andreas Thaler

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ogtronix said:
I do like the idea of keyhole surgery for cameras. If nothing else it's just cool, like safecracking...
Click to expand...

In this case, it is a dramatic reduction in the amount of work required. One hour - one day, depending on skills.
 
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Andreas Thaler

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I wonder how many 7000s with the aperture problem were thrown away because a repair was too expensive or complicated.

It pains me.
 
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Andreas Thaler

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The opposite case: the aperture always remains open

Here I have another 7000 that is intended as a practice camera and spare parts carrier due to the dirt in the mirror box and shutter (animal hair?).




With this 7000 the lens does not stop down even though the aperture magnet closes. The ring with the aperture coupling on the bayonet does not move downwards (arrow) when the camera is triggered. So the opposite of what happened before.




In any case, I opened the plastic housing of the aperture magnet again with the hot soldering iron tip, moved the two magnet parts and applied electronic cleaner with the syringe to practice the process. But it did not change the problem.

There is probably something wrong with the aperture mechanism, so I would have to remove the mirror box from the camera to investigate, which I do not want to do here.




The camera can also be operated without the top cover if these three contacts of the main switch on the circuit board are bridged.


But more defective 7000s have been ordered, which might have the error of always stopping down to the smallest value, which is considered to be the typical 7000 error.

Then I can hopefully verify the shortcut presented here.


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Andreas Thaler

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The handicap with such complex cameras is, as has been said several times, disassembly and assembly. This almost always means removing the mirror box.

Hours of work and the risk of making a mistake when assembling. Then you have to start all over again.

If you stick with one camera model, you get practice and it goes faster and more reliably. Nevertheless, you need sufficient motivation.

In my case, I prefer to concentrate on the common errors and possible shortcuts. Otherwise, I spend my life at the workbench
 
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Andreas Thaler

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Some time ago I managed to buy a printed copy of the C & C Associates Troubleshooting Guide for the Minolta (Maxxum) 7000 AF.

These guides, presumably written by Larry Lyells, are very hard to find.

Among other things, they describe test methods for the cameras related using the externally accessible circuit board areas for error diagnosis.

This means that a complex disassembly of the camera is not necessary.

Together with the SPT Journal for the 7000 and the Minolta Service Manual, I have all the repair documents that I know of.

I will use them to investigate this error (the aperture is always open).
 
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