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

Andreas Thaler · Mar 14, 2024

Cleaning the mechanics in the mirror box:

I ordered a rubber hose with a 1 mm diameter. This would allow me to get even closer to the spot for cleaning with benzine and the risk of damaging any of the mechanics is zero. Although the cannula cannot cause any damage if used carefully.

Let's see, the hose should fit my syringe.

Andreas Thaler · Mar 14, 2024

The hose can also be used to cover the cannula for protection or to extend it.

Then I just have to overcome myself and use the method on one of my beautiful F4

Christiaan Phleger · Mar 14, 2024

Excellent! I think creating a very thin oddly shaped curved tube to be able to twist into the correct spot from the mirror box would be good.

Andreas Thaler · Mar 15, 2024

Christiaan Phleger said:
Excellent! I think creating a very thin oddly shaped curved tube to be able to twist into the correct spot from the mirror box would be good.

I just remembered that I have thin shrinkable tubing that should fit tightly around the cannula. Five millimeters extension and protection around the tip.

I'm going to build this and use it to practice on my training F4

Andreas Thaler · Mar 15, 2024

A little benzine is distributed with a short and firm pressure on the syringe. In my experience so far, too much can't do any harm.

As I said, I don't see anything in this area that could be sensitive to benzine. The entire mechanics are also stable.

Then I'll test it on an F4 with the aperture problem and report back.

Andreas Thaler · Mar 15, 2024

I checked to see if I could find any information about the aperture problem in the three-part service manual for the F4.

The search was unsuccessful, and there was no information about the lubrication of the mechanics.

But I found an interesting information in the SPT Journal & Service Notes January/February 1993, dedicated to the Nikon F4.

The buzzing noise when firing the shutter or operating the depth of field preview button is due to a lack of lubrication on a ratchet gear on its pivot in the mirror box.

This can therefore be lubricated from the outside without dismantling the camera:

This can also result in incorrect exposures.

I wonder if this is the cause of the aperture problem?

Probably to some extent, because cleaning the gears in the affected area brought a significant improvement if not the ideal situation

@F4user:

The culprits for defective work are: aperture lever spring and hardened shaft grease of toothed gears.

The benzine dissolves the hardened grease and gives the gears free movement again. I observed this myself on the removed mirror box.

There's nothing I can do about the spring, but maybe it's not necessary. I would also have to dismantle the F4 to do this.

I think I now have all the information to be able to carry out the fix with a syringe, a curved cannula and benzine.

Before oiling the ratchet, I will also clean the area with benzine, which is also what @F4user recommends in his tutorial.

It starts tomorrow (CET), I will extend the cannula with shrinkable tubing and determine the angles for inserting the cannula so that I have a template for treating all of my affected F4s - if it works

SPT Journal: January-February 1993

Society of Photo-Technologists Journal

learncamerarepair.com

Andreas Thaler · Mar 15, 2024

Now I'm undecided.

Maybe it's actually enough to just oil the ratchet gear on its pivot?

The exposure errors described are caused by the aperture not closing properly. And the rapidly spinning ratchet gear plays a role here.

Let's see, maybe I'll try it just with oil like recommended in the SPT Journal. But I have to see how I can bring it in from the outside.

If that doesn't work, then benzine comes in, which immediately removes the oil.

Stay tuned!

Andreas Thaler · Mar 15, 2024

I decided to try oil to lubricate the axle of the ratchet gear as recommended in SPT Journal.

My first attempt was a long time ago with electronic spray, which I sprayed liberally behind the aperture lever in the mirror box.

At the beginning this seemed to be the solution, the aperture worked perfectly again. But then the function deteriorated and the aperture remained open at the low values. The scratching noise had also become stronger.

Since electronic cleaner, like benzine, acts as a solvent, this was probably the wrong approach.

Now I'm wondering which oil I should use.

„Shutter oil“ can only mean the lightest oil, as the shutter has a fast-acting mechanism.

Choices include Nyoil, Ballistol (which lubricates and cleans) and Ballistol silicone oil (which tends to spread).

I think I'll try Ballistol.

Only a small amount is needed to oil the gear and it has to sit precisely on the axle of it.

I will use my curved cannula for this, which I may attach the tip of a foam cleaning swab soaked in Ballistol. Then I just need to press the cannula onto the axle of the gear.

All of this, of course, without seeing anything. Therefore I have to practice it on my training F4.

The blue arrow points to the axle where the oil has to go:

Andreas Thaler · Mar 15, 2024

I should reach the axle exactly with the cannula.

Andreas Thaler · Mar 15, 2024

First clean the axle with a drop of benzine, then oil.

That's how I do it

Christiaan Phleger · Mar 16, 2024

Ha that's funny, I just ordered that SPT manual but had a busy shooting day (3 1/2 rolls B+W EK 5222 and TX, 35mm) so I've not had a chance to read it (tomorrow over coffee), but quite interesting that they had the diagnosed problem as the same and the fix with the shutter oil (lubrication) is the same, I think we can call this a a very rare 'weakness' on this normally tough camera. I personally think that its due to under use rather than over use, when I had many F4s in weekly wedding use I had no issues, it was only when those bodies were packed away in a move for a period of inactivity did this issue arise.

As I mentioned I hit upon that notion that it was not just cleaning it but a tiny amount of lubrication, I settled on a very thin wire that I twisted into a position that I thought (and felt ha!) was that particular set of gears, then I would drip a drop of thin silicone greaseless lube down the wire. I like your solution especially creating the correct shape and angle to get to the gear pivot accurately from the mirror box. Success is upon you!

Andreas Thaler · Mar 16, 2024

Christiaan Phleger said:
Ha that's funny, I just ordered that SPT manual but had a busy shooting day (3 1/2 rolls B+W EK 5222 and TX, 35mm) so I've not had a chance to read it (tomorrow over coffee), but quite interesting that they had the diagnosed problem as the same and the fix with the shutter oil (lubrication) is the same, I think we can call this a a very rare 'weakness' on this normally tough camera. I personally think that its due to under use rather than over use, when I had many F4s in weekly wedding use I had no issues, it was only when those bodies were packed away in a move for a period of inactivity did this issue arise.

As I mentioned I hit upon that notion that it was not just cleaning it but a tiny amount of lubrication, I settled on a very thin wire that I twisted into a position that I thought (and felt ha!) was that particular set of gears, then I would drip a drop of thin silicone greaseless lube down the wire. I like your solution especially creating the correct shape and angle to get to the gear pivot accurately from the mirror box. Success is upon you!

Yes, it's an exciting project, thanks for the good wishes!

If oiling doesn't work, you can use benzine to remove it.

My only regret is that I removed that one gear and the associated spring tension was no longer correct. This would give me a fully functional mirror box to practice with. But it will work that way too.

Just a few more hours and then it starts!

Andreas Thaler · Mar 16, 2024

I practiced introducing benzine and Nyoil with a syringe and cannula on my training F4.

It turned out that the cannula is too big for oiling and releases too much of it. I also couldn't reach the ratchet gear reliably. The result was oil on the gears above.

Then I went to the F4S I work with and its small apertures are slow to close.

The introduction of benzine worked, once on the first gear and then on the ratchet gear, which I obviously reached easily, because as soon as the benzine was sprayed out, the buzzing noise when pressing the stop down preview disappeared. It came back weaker after a few minutes.

A test with the Nikkor AF 35/2.0 D shows that even the smallest aperture of 22 is now closed quickly and completely. Via the stop down preview button as well as via the camera.

I will check the further behavior over the next few hours and leave the mirror box open so that any benzine residue can evaporate.

Obviously the SPT Journal is right about the ratchet gear as the culprit.

Andreas Thaler · Mar 16, 2024

Now I'm thinking about how I can lubricate the ratchet gear safely with Nyoil without disassembly.

Because I'm not sure whether cleaning with benzine only solved the problem permanently, since the cause (according to SPT Journal) is a lack of lubrication. In any case, any resin buildup in this area should now be removed.

Andreas Thaler · Mar 16, 2024

The aperture lever in the mirror box now folds all the way down:

Andreas Thaler · Mar 16, 2024

I adjustet the cannula with the Dremel and pliers and sent two drops Nyoil towards the ratchet gear. I managed to get oil onto the axle of the training camera. I'll see if it works for my work camera too.

Definitely an improvement on the situation before. Aperture 22 closes completely and quickly. Maybe sometimes a touch too slow (?)

I assume that the oil is still spreading and keep the shutter moving.

Christiaan Phleger · Mar 16, 2024

Yes, I see what you are doing, and I must stress when I would do my version of this after either benzine or lubrication I would cycle the camera many times, dozens perhaps, on all drive modes, cycling thru both shorter *and longer* speeds. One of the bodies would on slower speeds the aperture arm action would gain like an extra mm or two on a 1/2-1 sec exposure, and you could see the lens aperture kick down right at the end. I believe the shutter can handle the cycles.

I am thinking an even smaller tube to administer the oil. I think and am pretty sure with all your tests that the benzine would evaporate and there is little chance of extra damage from that but the oil I really want to hit that bearing on that gear pivot, I was thinking an actual hypodermic needle but the size I was considering is far to brittle to be shaped into the curve I think it will need, perhaps you can think of something. Perhaps not metal.

Andreas Thaler · Mar 16, 2024

It's devilish, because with the mirror box dismantled, the cannula can be placed directly on the ratchet gear. But when installed, the shutter mechanism is directly opposite the point, blocks and the cannula cannot reach it.

I tried to see if a long pin that I had bent would work as a slide for the Nyoil, but that didn't work. I couldn't control the rubber hose and it's too thick.

I understand that makes you want to blow a can of WD-40 into it

Even if you dismantle the F4 and have the mirror box mechanism in front of you, it is not clear exactly where the problem is.

Under no circumstances would I dismantle the gears, otherwise, as said, a spring would lose tension and it would be unclear how to return it to its original state.

The buzzing noise is still there, weaker, and the small aperture closes. In my opinion it's fast enough.

Let's see what it's like tomorrow.

Andreas Thaler · Mar 16, 2024

In practice I have no problems with this F4, all exposed negatives are fine. If there is now an improvement with the aperture lever, I will be happy. I don't take photos with the two small apertures anyway.

But the ambition

Andreas Thaler · Mar 16, 2024

I don't think the benzine will cause any harm. The Nyoil shouldn't do any harm either.

It's not nice when oil is where it shouldn't be, but from what I saw on site it shouldn't cause any problems.

Andreas Thaler · Mar 16, 2024

But it doesn't make sense to think about it too much. This is about a short cut to avoid the risk of disassembly/assembly.

Similar to the Canon A cameras with their „asthma“, where a drop of oil is placed with the cannula.

Andreas Thaler · Mar 16, 2024

Time will tell whether it works in the long run or not.

My work camera has to endure these experiments, the remaining F4s in the closet wait to see what happens

When I look for a repair shop to fix the problem, I don't know what they do with the F4 there. Maybe they'll just shoot oil into it. And when they disassemble/assemble, that's labor time that costs. We all know these scenarios...

Andreas Thaler · Mar 16, 2024

With the lens bayonet removed, the cannula on the training F4 didn't work any better.

This means there is more space for maneuvering, but the problem is the shutter mechanism, which is very tight when the F4 is assembled.

Andreas Thaler · Mar 16, 2024

When screwing on the bayonet, the contact pin got stuck at 2 o'clock.

It was only later that I noticed the cause: the aperture driver was sitting too deep and so the bayonet ring was not lying flat. This means that the bayonet was unevenly loaded by the five tightened screws, which is not good for the back focus.

It's good to have these experiences on a training camera, they are valuable anyway

Andreas Thaler · Mar 16, 2024

Christiaan Phleger said:
I am thinking an even smaller tube to administer the oil. I think and am pretty sure with all your tests that the benzine would evaporate and there is little chance of extra damage from that but the oil I really want to hit that bearing on that gear pivot, I was thinking an actual hypodermic needle but the size I was considering is far to brittle to be shaped into the curve I think it will need, perhaps you can think of something. Perhaps not metal.

Yes, that would be a possibility.

But you have to position the tip exactly on the axle of the ratchet gear and you can't see anything. And even then it doesn't mean that the lubrication is successful. Actually, I don't even know where the oil goes.

An enigma

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

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