Nikon F4: Mission Aperture Lever - two ways to fix the aperture problem

Andreas Thaler · Mar 16, 2024

Nothing has changed in my patient, the smallest aperture closes quickly. I have to look closely to notice any differences in speed.

The aperture lever in the mirror box no longer goes all the way down and there is a narrow gap between the mirror and the damper because the aperture lever does not fold all the way down. But that was the case before.

I go to bed, it's midnight in Vienna.

Tomorrow I will report on how the F4 survived the night

Andreas Thaler · Mar 17, 2024

That looks good

The F4 had eight hours of rest overnight and lay on the back door with the protective cover removed.

The scratching noise when pressing the stop down preview lever has disappeared. The button presses softly. Obviously the Nyoil needed time to get where it needed to be.
The smallest apertures, 22 on the Nikkor AF 35/2 D and 16 on the Nikkor AF 85/1.8 D, close quickly and completely. Also in CsH mode (fastest motor drive setting) at 1/8000s.
The aperture lever in the mirror box goes almost all the way down with the stop down preview button.
When the camera is released it only moves about 1/5 of the way. It must be noted here that when the lens is attached, the aperture lever on the lens acts with spring force on the aperture lever in the mirror box and essentially helps. I can only judge whether the behavior of the aperture lever is normal by comparing it with other F4s.

All in all, this looks very good.

Definitely a significant improvement over the previous situation, where aperture 22 on the 35mm only closed with a delay.

I will continue to monitor and am now convinced that the ratchet gear is indeed the main culprit. Because I sent not only benzine there, but also Nyoil.

Fingers crossed!

I will keep you updated.

Andreas Thaler · Mar 17, 2024

If someone would like to do the shortcut with a syringe, cannula, benzine and (Ny)oil on their F4, here are the dimensions of my equipment for orientation (1 square = 1 * 1 cm):

But I would wait until it is clear whether the aperture problem on my F4 has now been permanently solved/improved.

As always, of course:

+++

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

Andreas Thaler · Mar 17, 2024

Outlook/risks

I have eight more F4s here, some of them have the same aperture problem.

Even if the shortcut actually worked here (time will tell), I won't apply it to these F4.

These cameras are essentially stored for later use or part of a collection and therefore it is irrelevant whether the aperture works correctly.

I see the risks of the shortcut in the fact that the benzine eliminates lubrication that is still functioning in the mechanics respectively that the (Ny)oil creeps into places where oil does not belong.

A small drop of oil cannot be applied precisely because the area cannot be seen from the outside. So it takes a little more to hit.

But I think this risk is lower than dismantling/assembling the camera to address the problem.

Andreas Thaler · Mar 17, 2024

Success

It has now been 24 hours since the aperture mechanism was treated and the two small apertures also close quickly and completely. I can no longer see any abnormalities with my eyes.
The stop down preview button can be pressed without a buzzing noise.
I therefore consider this shortcut a success and will continue to use the F4 regularly for taking photos and observe its behavior.

Conclusion

The problem with slow or incomplete apertures could be solved with benzine and Nyoil.
To achieve this, small amounts of benzine and Nyoil were introduced into the aperture mechanism from the outside without dismantling the camera.
The insertion was done using a syringe with an adapted (curved and rounded) cannula.
The main cause of the problem is probably a ratchet gear on the mirror box that has run dry; resinification of its bearing or the bearings of other gears (dry run included) could also play a role.
Too much Nyoil may have been added, so the camera will be monitored for any traces of oil inside and outside in the near future.

Lubricant, Oil, Shutter 100gram

Lubricant, Oil, Shutter 100gram. NYOILIs a clear, odorless oil for lubricating, polishing, cleaning, and preventing rust. Formulated nearly 100 years ago, it remains the most highly refined oil ever produced. Applications: NyOil works great on cameras, roller blades, fitness equipment, locks...

www.micro-tools.com

+++

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

Thanks for all the contributions and tips!

I'll be in touch with an update over the next week

4season · Mar 17, 2024

Have you experimented with lubricants diluted in solvent? The solvent provides cleaning and penetrating action, and allows you to apply less oil than you might otherwise. Michio Ozeki suggests a 5% solution.

Andreas Thaler · Mar 17, 2024

4season said:
Have you experimented with lubricants diluted in solvent? The solvent provides cleaning and penetrating action, and allows you to apply less oil than you might otherwise. Michio Ozeki suggests a 5% solution.

Not yet, but Michio Ozeki needs to know because:

… where he worked assembling their main models (SP/F/F/F2/F4)

Let’s Try! - Repair and Maintenance of Cameras: Japan Hobby Tool https://amzn.eu/d/bwlQYr4

Thanks, that's interesting.

I assume I can find information about it in his book just mentioned.

So far I only knew the graphite/benzine mixture.

Andreas Thaler · Mar 18, 2024

Performance drop

In today's test with various MF and AF Nikkors, the smallest aperture worked for all but one lens. Then the performance dropped, and even a lens that previously worked perfectly now closed the smallest aperture significantly too less.

The aperture lever in the mirror box only moved a little, but the spring tension on the Nikkore's aperture levers was obviously enough to push it down sufficiently.

I injected benzine again, once downwards towards the ratchet gear and once into the upper area.

This made the aperture lever moveable again, it now folds halfway down.

If that doesn't work, I finish the treatment with a syringe, benzine and Nyoil. So that didn't work.

All that remains is to disassemble the F4 and try to examine the mechanics with the mirror box removed. I can also then clean the inside of graphite and Nyoil, as a lot went into it.

My main concern is that the mirror box will no longer be able to be installed correctly once it is removed. However, I found no information about this in my documents.

There will be some work ahead, but I also hope to gain further knowledge

Andreas Thaler · Mar 18, 2024

Worried that my other F4s were also affected by this unspeakable aperture problem, I checked all eight.

The result:

three in perfect condition, the aperture lever in the mirror box folds all the way down,
one acceptable with 50% unfolding, which is still enough,
one with a slow aperture and
two that cannot form the small apertures

No reason to be happy.

I'm now unsure what to do:

disassemble and try to solve the problem directly on the mechanics,
find a workshop to do the repair, or
another trial with the syringe.

I would be tempted to disassemble and reassemble, although the chance of something going wrong is significant.

In particular, coupling the mirror box to the shutter is tricky. Different levers have to work together.

Then I ask myself whether I can achieve anything with on-site cleaning.

My idea is to clean the entire mechanics there with benzine to also remove the graphite and Nyoil from the last attempts. Then oiling selectively. The mobility of the mechanics can be checked directly.

Or I can find a workshop that can do it better or maybe has its own method for it.

Injecting oil and benzine with the syringe was unsuccessful. And it's not professional either. But it was worth the try, I think.

Not easy.

What do you all mean?

Andreas Thaler · Mar 19, 2024

It also depends on your own perspective.

Instead of being sad that three F4s have the aperture control problem, I might as well be happy about having three repair projects.

Here's what I do:

When the F4 that I had treated with the syringe decreases, I disassemble it and try to solve the problem directly.
If this F4 stops down sufficiently, it remains my work device and I try to get one of the three F4s repaired (disassembly). To do this, I will study all the documents available again and plan the project over several days.
I agree with @Mamiya_Repair:

The issue with the aperture lever you are having is not uncommon. From my experience servicing the F4, this is almost always caused by the ratchet gear on the side of the mirror box. It needs very light lubrication, just one drop of oil on the gear shaft. Unfortunately, there is no way to reach this part without removing the mirror box, no shortcuts. Squirting lubricants into the camera will not fix the issue and only cause more problems as the lubricant gets in places it does not belong.

Post in thread 'Nikon F4: Quick fix for gummed mechanics parts?'
https://www.photrio.com/forum/threa...or-gummed-mechanics-parts.203274/post-2747148

This means that the mirror box needs to be removed, but the aperture mechanism does not need to be dismantled.

I realize that most readers are less interested in these details and would like to see a solution.

But I think it's important to also show the connections and why one thing works but the other doesn't.

At least I hope so

Christiaan Phleger · Mar 19, 2024

Ok, I feel what you're going thru is normal; I seem to recall spending far too much time (and cans of cleaner) working on this. I think you're not being as aggressive as you could be with both the cleaning and the lubing, and I suggest being more liberal with each. For the Benzine I used a long thin tube to draw up a considerable amount and then would add in air pressure of a compressed air can to 'diffuse' it more. The lube as I mentioned was dripped down past the extended aperture arm, but I dripped many (6+) drops down the wire. I felt and still do that a bit more lube in that area is better than less!
Get back in there champ! You can do it.

Andreas Thaler · Mar 19, 2024

Christiaan Phleger said:
Ok, I feel what you're going thru is normal; I seem to recall spending far too much time (and cans of cleaner) working on this. I think you're not being as aggressive as you could be with both the cleaning and the lubing, and I suggest being more liberal with each. For the Benzine I used a long thin tube to draw up a considerable amount and then would add in air pressure of a compressed air can to 'diffuse' it more. The lube as I mentioned was dripped down past the extended aperture arm, but I dripped many (6+) drops down the wire. I felt and still do that a bit more lube in that area is better than less!
Get back in there champ! You can do it.

Thank you Christiaan for your encouragement and support!

What do you think about removing the mirror box and checking for the problem on site?

Andreas Thaler · Mar 19, 2024

I'm hesitant to apply more oil via syringe because I saw how lively it spreads on my practice F4.

There should be an optocoupler directly under the ratchet gear, no oil should go there, see arrow:

Andreas Thaler · Mar 19, 2024

Just in case, I wrote to three workshops in Germany and one in Austria to see if they had any experience with the problem.

As a last option

Andreas Thaler · Mar 19, 2024

I'm confident about removing the mirror box and cleaning the parts, and I've already gained experience with the training F4.

But when assembling, as already mentioned, the mirror box and shutter must be coupled. And I'm still missing an overview here.

Andreas Thaler · Mar 19, 2024

Four inquiries to renowned workshops in Germany and Austria as to whether they would accept the F4 have already resulted in three rejections. Amongst other things that such major interventions (disassembly mirror box) would not be economical for them.

I didn't bother writing to Nikon, they have a hard time remembering their older products

But that also helps me, because then all I have to do is do it myself

According to the motto: I am the last one, there is no one behind me

Andreas Thaler · Mar 19, 2024

I was now able to find an F4 Repair Manual with better photo illustrations (more details visible):

https://uscamera.com/product/nikon-f4-f4s-repair-manual/

The assembly is also clearer to me now.

This means that nothing stands in the way of attempting to repair an F4 with the aperture problem by removing the mirror box, cleaning/lubricating and assembling it.

Since this will be a multi-day project in which I will proceed with maximum care, the preparation will take some time.

It is also pleasing that my F4, which I have treated with the syringe for the last time, still closes its aperture satisfactorily.

So things are moving forward

Andreas Thaler · Mar 20, 2024

I can report success with the syringe method:

Even on the second day after the last two injections with benzine, the smallest apertures on the test Nikkors close perfectly.

The aperture lever only goes down about 2/5, but should run freely enough against the spring pressure of the aperture lever on the lenses.

I take the camera back to take photos and continue observing.

Andreas Thaler · Mar 21, 2024

Finally a success

One last update on my F4S, which I treated with the syringe:

The aperture lever has improved and now folds down to 50%:

That is sufficient to close the small apertures completely and happens quickly enough.

The camera can be used.

A success, even if it took several attempts

Conclusion

The shortcut with syringe, cannula, benzine and Nyoil works.
How often and where the cannula needs to be inserted is a matter of experimentation.
Benzine should not have a negative effect on the affected area in the mirror housing. However, it dissolves oil, even resinous oil, and can thus eliminate lubrication.
Nyoil is a light oil for fast-moving parts such as those found here. It should be used sparingly and in specific areas. This is not possible when flying blind with the cannula. This can lead to the oil spreading over the affected area, which could impair functions in the long term.
Whether you choose the syringe method or removing the mirror housing must be considered. The shortcut has risks, as does disassembly and assembly, which is very extensive here.

Andreas Thaler · Mar 21, 2024

Oiling: Mirror box and surroundings

In order to be able to assess how an excess of oil can affect components in the vicinity of the aperture mechanism, a disassembled F4 is helpful.

The front part of the housing, viewed from the back.

In the middle is the mirror box, and below it is a circuit board.

The left side of the mirror housing with a pulley for the cable of the aperture simulator, whose position is transferred to a round resistance track using wipers.

The resulting voltage values as analog signals are probably digitized and processed by the CPU of the F4.

The right side of the mirror housing with the mechanics for aperture control.

The red rectangle shows the area where benzine and Nyoil are injected using the cannula. This is done through the opening for the aperture lever in the mirror box.

Here is also the position of a (green) power transistor on its cooling plate.

The area under the mirror box.

This is where the electronics for a photometer cell with a filter and the AF module are located.

The AF module is at the top and the photocell is below.

The two parts of the F4's housing.

The rear part houses the shutter and its mechanism.

The mirror box with the circuit board underneath is pushed into the rear part of the housing during assembly.

The components sit close together.

Where can too much oil go and what damage can it cause?

Oil spreads in all directions, it creeps persistently. However, it spreads and becomes thinner and thinner.

The electronics should be insensitive to oil.

But it is possible that it finds its way to the photocell and the AF module.

It could also get onto the shutter blades, but for that to happen the oil would have to overcome a number of obstacles.

In summary

the possible spread of oil to internal components of the F4 should not be a reason to rule out the method with the syringe.
However, care should be taken to introduce as little oil as possible, which requires the cannula to be placed as precisely as possible.
@Christiaan Phleger has presented a very interesting method for this in this thread.

I will of course continue to monitor my F4S and report back if necessary.

The next goal is, as I said, to dismantle an F4 with the aperture problem in order to examine the mechanics directly, clean and lubricate them.

Report to follow

Andreas Thaler · Mar 21, 2024

Andreas Thaler said:
Four inquiries to renowned workshops in Germany and Austria as to whether they would accept the F4 have already resulted in three rejections. Amongst other things that such major interventions (disassembly mirror box) would not be economical for them.

I didn't bother writing to Nikon, they have a hard time remembering their older products

But that also helps me, because then all I have to do is do it myself

According to the motto: I am the last one, there is no one behind me

Today the fourth workshop also responded to my query.

Yes, they will accept the order, there are only a few spare parts left for the F4, and it would cost around EUR 350,- (USD 380,-).

They did not want to answer my question about whether they would approach the matter from the outside or from the inside. It is already obvious that this is a trade secret

So I am paying and do not know what for.

That is, for the next time, the end of the workshop chapter for me.

Now I have to do it myself

Andreas Thaler · Mar 22, 2024

A third option?

I wonder if there isn't a third option to solve the F4's aperture problem, beside repair and shortcut as discussed.

That is, to do nothing at all.

Automatic exposure compensation

At another point in this thread I suggested that the F4 checks and adjusts the exposure again in automatic modes shortly before opening the shutter.

If the aperture does not close sufficiently in A (aperture priority), P(h) (programm modes) and S (shutter priority) this would have to be compensated by adjusting the shutter speed.

This should also apply in S, where the shutter speed is preselected, otherwise the exposure would not be correct.

This means that the achieved exposure should always be correct even if the preset aperture or shutter speed is not formed. In P(h) the camera itself decides anyway.

You would have to try out whether this (suggested) compensation also works with an aperture that closes slowly.

Affected smallest apertures avoided anyway

In fact, the aperture problem only affects the smallest apertures, which are avoided anyway due to diffraction effects.

However, the aperture mechanism may have become so sluggish that even larger apertures are no longer formed correctly. This means that you increasingly lose control over the intended apertures and shutter speeds.

For the apertures and shutter speeds set in M (manual mode) this presumed automatic exposure compensation cannot work, since the camera does not intervene as intended.

But here too, you will avoid the smallest apertures anyway

All of this would have to be systematically investigated and evaluated

but at least not intervening is an additional option to repair and shortcut.

This means that a tired F4 does not necessarily have to be abandoned, to be repaired or fixed.

Andreas Thaler · Mar 22, 2024

As for the syringe and cannula method, no one should claim that Nikon did not warn them about it.

From the manual

Andreas Thaler · Mar 22, 2024

I looked in the Nikon Repair Manual for the F4 to see if I could find any information about the ratchet gear, which plays a central role in the aperture problem. Presumably due to a lack of lubrication.

The ratchet gear (blue arrow) rotates quickly when the aperture mechanism is triggered.

It is coupled to a disk (white arrow) that runs through a U-shaped photointerruptor below.

There are notches on this disk that interrupt the light beam (infrared supposed) between sender and receiver of the photointerruptor. This generates electronic pulses that work as a counter.

For example, after X pulses per unit of time an action is completed or an action is started. This could be closing and opening the aperture (my assumption).

It is therefore clear that this ratchet gear with the coupled disk has a control function within the surrounding aperture mechanism.

What is a Photointerrupter? | Electronics Basics | ROHM

Photointerrupter information

www.rohm.com

Andreas Thaler · Mar 23, 2024

Andreas Thaler said:
The next goal is, as I said, to dismantle an F4 with the aperture problem in order to examine the mechanics directly, clean and lubricate them.

Preparations

This project will take longer and needs to be prepared accordingly.

Since I don't have a permanent workshop, I have to organize it so that I have all the removed parts of the F4 clearly laid out on the table the next day.

To do this, I will use small plastic boxes that I will number. These boxes will hold the removed parts.

Unfortunately, I cannot arrange the parts on the table in the way that is best for me as a visually inclined person. So the upper screw is at the top, the lower screw at the bottom and to the right of it the removed rewind crank etc., as it is arranged in the camera. But I will take more documentation photos than usual.

The template for removing the mirror box is the tutorial by @F4user, supplemented with information from the Nikon F4 Repair Manual and the SPT Journal.

Since I have already disassembled an F4 to study the aperture mechanics, my experience so far will also come into play.

All of this is complex and I will proceed deliberately slowly and precisely. I don't want to make a mistake during assembly and then hours of work will have been in vain.

The F4 reminds me of a PC in terms of its structure, with its ribbon cables and connectors. If you had to solder all the connections, it would be a real challenge.

I think I'll start in the middle of next week.

Before that, I'll take another look at coupling the mirror box to the shutter on my already disassembled F4. This seems to me to be the critical point in the assembly.

Nikon F4: Mission Aperture Lever - two ways to fix the aperture problem

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