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

[Andreas Thaler]

With the Minolta/Maxxum/Alpha 7000 AF Minolta ushered in the autofocus era in 1985.


Similar to the Minolta 9000 AF, the Minolta 7000 AF can have problems with the aperture control.

No matter what aperture is set, the 7000 always creates the smallest aperture.

I suspect that the contact surfaces of the switching magnets are contaminated. In order to get to the bottom of the problem, the mirror box must be removed.

I have a 7000 with this problem.

The following information sources are available for this project:

SPT Journal 1997

Issue dedicated to the Minolta Maxxum 7000

learncamerarepair.com

Minolta Maxxum 7000 Service Manual

Factory service manual and SPT repair guide

learncamerarepair.com

I fixed my Minolta 7000 (aperture magnet problem)

groups.google.com

We'll start next week.

An exciting project awaits us

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See also:

Minolta 7000: Memory backup lithium battery, main batteries, functionality, 7000 or 9000, disintegrated plastic, cleaning contacts, voltages

Completely unexpectedly, my neighbor gave me an obviously unused Minolta 7000 with two equally new Minolta AF zooms, complemented by a Minolta Program 2800 AF flash, which works just like all the other devices. Sometimes things just come to you on their own 😌 Today I looked at the built-in 3...

www.photrio.com

 

[Andreas Thaler]

SPT Journal 1997

Issue dedicated to the Minolta Maxxum 7000

learncamerarepair.com

On page 30 of the PDF, various causes of possible errors are listed.

This is extremely helpful.

 

[Andreas Thaler]

Minolta Maxxum 7000 Service Manual

Factory service manual and SPT repair guide

learncamerarepair.com

See here pages 181 and 206 of the PDF („Troubleshooting“).

@ogtronix:

Both sources could be helpful too with the aperture issue of the Minolta 9000 AF.

 

[Andreas Thaler]

I fixed my Minolta 7000 (aperture magnet problem)

groups.google.com

I made the two contact surfaces of the magnet rough (with a file), so
that it doesn't stick as strong to the lever. This seems to work, but
maybe you have a better idea. You should also check whether the
electro magnet still works.

Cleaning the contact surfaces may help, as suspected. Everything else will hopefully become clear on site.

Like the Minolta 9000, the 7000 is a highly complex electromechanical camera, and removing the mirror box is correspondingly complex.

I'm excited to see how it goes

 

[ogtronix]

That service manual is at least freely available on archive.org. https://archive.org/details/maxxum-7000-service-en Charging for copyrighted/ pirated materials like that is fairly scummy...

I'm very interested in how this goes, though. Looking at the exploded diagram, the aperture mechanism does look completely different to the one in the 9000. Which makes sense since it won't need the function of being set/ reset independent of the shutter and mirror. But i'd suspect it's the same issue with contamination/ degrading sticky coatings on the magnet surface.

 

[Andreas Thaler]

I'm very interested in how this goes, though. Looking at the exploded diagram, the aperture mechanism does look completely different to the one in the 9000. Which makes sense since it won't need the function of being set/ reset independent of the shutter and mirror. But i'd suspect it's the same issue with contamination/ degrading sticky coatings on the magnet surface.

This also seems to be the case with the Canon T90, and that's what I'm hoping for.

But a broken part in the aperture control has also been mentioned as a possible cause.

 

[Andreas Thaler]

Another indication that the problem with the aperture control is contaminated contact surfaces on the switching magnet:

In fact, it was the pole shoes of the aperture magnet! The aperture ring with the nose that grips the lens is rotated by the central drive (film transport, mirror mechanism, etc.). A vane wheel rotates, the rotation of which is measured optoelectronically. When it is in the correct position, current is sent through an electromagnet that compensates for the force of a permanent magnet. A lever that is magnetically attracted falls off and is pressed into a gear by spring force, so that the rotation of the aperture ring is stopped. The pole shoes and the counterpart are polished metal parts. A little grease (barely visible) has probably ensured that the two stick together and that the aperture ring always rotates at the maximum angle (largest aperture, underexposure). The problem with the Type 7000 is that despite the transparent plastic cover (see picture) of the magnet, the grease can creep onto the pole pieces (when taking frequent photographs and in high heat).

(Google Translate, German -> English)

Bastelecke » Minolta 7000 AF: Blendenmechanismus defekt

Die Kamera schliesst die Blende immer auf kleinste Oeffnung, unabhaengig von der eingestellten Belichtungszeit oder Blendenzahl. Dieses Phaenomen tritt mit zw

www.so-fo.de

 

[Andreas Thaler]

Approach in this project

I will approach this project in a strictly structured manner due to the complexity of the 7000.

• From page 19 and page 22 in the SPT Journal, the removal of the cover and the removal of the mirror box are described step by step with reference to illustrations in the text. I couldn't find any instructions for this in the Minolta Service Manual.
• The author of this SPT Journal is probably Larry Lyells, whom I follow as a reference author for service instructions. We owe Larry countless contributions, without which the functionality and service options for newer photo equipment would remain unknown.
• The removal of the mirror box comprises a total of 27 steps with extensive desoldering work.
• I will recreate the steps with my own photo documentation and report on them here.
• The goal is to reach and examine the switching magnet for the aperture control. My assumption based on the available information is that the contact surfaces of the magnet are contaminated.
• In order to gain experience, I will first do this on an abandoned 7000, which will then also be available for spare parts.
• I bought two defective 7000s for the project, one of which is still in the mail.
• In the meantime, I'm going through the SPT Journal, which I also have in print, which makes it easier for me to work through.

 

[Andreas Thaler]

These two completely neglected 7000s are ideal for going through the process of removing the mirror box.

The cameras are dirty, and a mouse might jump out when you open them

 

[Andreas Thaler]

And here is a third one with an electronic fault that is cleaner.

I will take this one to disassemble.

 

[Andreas Thaler]

One of the two 7000 may actually have had a mouse as a guest, as can be assumed from the droppings.

Both go straight into the garbage, there is a certain threshold for disgust.

Sometimes dealing with old cameras is stressful

 

[Andreas Thaler]

One of the packages also contained a Minolta Program 2800 AF flash. The battery contacts are heavily corroded by battery electrolyte.

I will disassemble the flash as a study object, I have several of them.

See

Minolta Program 2800 AF flash: Dissection

For study purposes, I disassembled a Minolta Program 2800 AF flash whose battery contacts were heavily corroded by battery electrolyte. The flash belongs to the Minolta 7000/9000 AF system. ⚠️ ⚡ A word of caution What we as DIY repairers WITHOUT electronics training should definitely not...

www.photrio.com

 

[Andreas Thaler]

And last but not least, the third 7000 came with a Minolta AF 35-70/4 in good condition. The optics are flawless and the aperture is not oily.

Very welcome, as oil seems to be a problem with this lens, see

Minolta AF 35-70/4, Minolta AF 70-210/4 and Minolta AF 35-105/3.5~4.5: Removal and cleaning of oily aperture registers

In my current thread on improving several Minolta/Maxxum 9000 SLRs, I had already introduced these four associated lenses: These Minolta AF lenses also come from the box of defective/untested photo equipment: 2 x AF 35-70/4 1 x AF 35-105/3.5~4.5 1 x AF 70-210/4 All four have lame apertures...

www.photrio.com

 

[Andreas Thaler]

From page 19 and page 22 in the SPT Journal, the removal of the cover and the removal of the mirror box are described step by step with reference to illustrations in the text. I couldn't find any instructions for this in the Minolta Service Manual.

Erratum orange:

The procedure for removing and installing the mirror box is described with illustrations in the Minolta Service Manual starting on page 159 (PDF) and supplements the instructions in the SPT Journal.

 

[Andreas Thaler]

Erratum orange:

The procedure for removing and installing the mirror box is described with illustrations in the Minolta Service Manual starting on page 159 (PDF) and supplements the instructions in the SPT Journal.

Removal top cover and front plate on page 74 service manual (PDF).

Now we have all the information we need to remove the mirror box.

We can start.

 

[Andreas Thaler]

Removal bottom plate, handgrip assembly, top cover and front plate

Unsolder hot-shoe wires blue, violet, white, brown, black.

Protect LCD from scratches or solder with tape.

 

[Andreas Thaler]

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Interim conclusion

• With the step-by-step instructions in the SPT Journal and the exploded drawings in the service manual, disassembly was problem-free.
• The adhesive tape on the prism must be carefully removed so as not to damage the soldering points of the cables on the circuit board.
• The front decorator panels are attached to the front plate with double-sided adhesive tape. They can be carefully pried off.

 

[Andreas Thaler]

Further disassembly steps

The LCD is folded towards the prism, pay attention to this cable.

The two flexible circuit board parts are held in position by two pins and are now separated.

Desolder

The light-shield plate for the finder LCD is held by double-sided tape. Be careful to avoid distorting the plate.

 

[Andreas Thaler]

 

[Andreas Thaler]

Desoldering with desoldering braid.

Desolder

Desolder

Fixing the camera in a grounded vice for soldering work on the bottom of the housing.

Desolder

Loosen this screw.

Exposing the cables.

 

[Andreas Thaler]

Desolder …

… this makes the mirror box mounting screw accessible.

Done!

The mirror box is removed.

The mounting screws for the mirror box.

Electronic shutter control with magnets.

Shutter made by Copal.

The goal of the journey: the switching magnet for the aperture control.

 

[Andreas Thaler]

The contact surfaces of the magnet are accessible after removing the cover. Cleaning them should solve the problem with the aperture, which always closes to the smallest setting.

That is the assumption.

Faites vos jeux!

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Conclusion

• Removing the mirror box is feasible. The SPT Journal together with the Minolta Service Manual guide you through the process in a clear manner. In a few places you have to interpret what the instructions mean.
• If you like soldering, you'll have fun here.
• I followed the service manual for the soldering work; it lists which cables and circuit board connections need to be desoldered. There are illustrations, which unfortunately have poor scan quality (hard contrast).
• All screws were easy to remove.
• The SPT Journal contains information on which camera functions can be carried out after partial disassembly.
• You need to read the documentation; there is no tutorial that describes each step with photos.
• This report is not a tutorial, for that the individual steps would have to be verified, but it should be helpful when removing the mirror box.

+++

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

 

[ogtronix]

Wow that's almost completely different to the 9000. Nice work, though!

 

[Andreas Thaler]

Wow that's almost completely different to the 9000. Nice work, though!

True, what the Japanese thought up, designed and manufactured is unbelievable!

 

[Andreas Thaler]

Wow that's almost completely different to the 9000. Nice work, though!

I'll take a look at the documentation. There should be a way to test the aperture control directly after attempting to repair it, before assembling the 7000.

If that's possible, I'd be motivated to try to repair my 7000 with the aperture problem