[sergiogonzalez]

This is statistics and as much as S. Gonzales tries to make the opposite true and even speaks about the myth of the white solenoid:
S. Gonzales never ever had a white Japan-Solenoid in his hands, nor other green solenoids, just the one single unit from his K-S2.
So his research concering the white Japan-Solenoid is only based on guessing, which is .... well.... zero evidence.
His first approaches were research based on 'doing'/'trying' and well worth it!
But then this didn't work.
So now he makes claims about something he doesn't even know.
With all due respect, but to me this reminds me very strongly what these days is named "fake news"

Dear Photogem:

I inform you that I never touch either mechanically, and electrically the solenoid of my KS2.
I modify a Plunguer of a solenoid of a CD floppy disk that is identical, polishing it, and modifying its reluctance.
Testing both Plunguer come to the conclusion, that touching it not up to anything, and I help to propose a simple test, based on mechanical parameters of the diaphragm control, such as the tension of the spring that unlocks it, the design of the swich of the same control, and the parameters that you once give me.
In addition to studying thoroughly the workshop manual of the Ist camera, which gives a lot of information about it. Its logic design in diaphragm control is identical to the Ks2, and it also defines the correct lubrication criteria of the system.
I deeply respect your opinions,.
Please don't talk about Fake news or say I guess the criteria and if you can rehearse a white solenoid the same way I rehearse mine, and we may come to terms with what their differences are.
Greetings

---------- Post added 05-19-20 at 03:11 PM ----------

Had your ks2 completely failed or was it still intermitant? I would understand your point up to complete failure. At the point where one cannot get any picture other than a darkframe after every attempt has been made, then replacing the solenoid should not help but it does.
Cheers.

Dear Swanlefitte:

There was a time when the camera would take two dark photos for a well-exposed one. How it worked was not consistent.
Try to improve the solenoid, modifying the geometry of a sacrificial Plunguer, intelligently modifying its reluctance, in order to reduce the retention effort of the magnet up to 150 gr, so that the diaphragm control can retain the Plunguer in the rearm blow.
This showed that it improved performance, but under certain circumstances, it failed again, especially after the camera was idle for 1 or two days.
I started studying various manuals to understand the logic operating and decided to disarm the diaphragm control. That's where I found the surprise. The switch brushes did not do the correct pressure and one of them (there are 4 in total) never made contact. This explains everything. I gave geometry to the brushes and checked their proper operation before assembling.
The result was instantaneous, It’s doesn't fail anymore, even after being more than three days inactive. I assembly the solenoid with the original factory Plunguer. There's the big doubt. Why the brushes had so little tension and one was deformed. Was the camera mounted in this state? If so, with the use the brushes begin to fail soon.
I hope this helps.
Greetings

[photogem]

I inform you that I never touch either mechanically, and electrically the solenoid of my KS2.

Ah... but you always gave the impression that you did:

I modify a Plunguer of a solenoid of a CD floppy disk that is identical, polishing it, and modifying its reluctance.
A modified plunger will already behave differently!

How do you know that the solenoid of a floppy-disk is identical, if you never touched (mechanically nor electrically) the solenoid of your K-S2?
Nor having a Japan-Solenoid from a Pentax-DSLR-body in your possession?
Just testing the:

Testing both Plunguer I came to the conclusion, that touching is not up to anything, and I help to propose a simple test, based on mechanical parameters of the diaphragm control, such as the tension of the spring that unlocks it, the design of the switch of the same control, and the parameters that you once give me.

is not enough, particular because the Japan-Solenoid is very different in movement. If you once had the Japan solenoid just in your hands and you just move the plunger in and out and wobble it left and right and then do the same with your green Chinasolenoid you would notice a strong obvious difference! It is that obvious! But this means you'd have to unsolder your K-S2 solenoid of course.
That you haven't done so shows already that the way you approached this is not based on real research!
Possibly because like some you don't feel comfortable of soldering, fine, but then also accept that it stops there!


You can only test those things if you have the complete original diaphragm-control-unit at hand connected to an identical powersupply as in your K-S2. And it has to be the same green China Solenoid exactly as in your K-S2. Not any green China-Solenoid because they differ as I had explained often before: Date of manufacture + there are OEM solenoids offered on ebay and Ali-express and others: Those do fit but differ mechanically.

In addition to studying thoroughly the workshop manual of the ist* camera, which gives a lot of information about it. Its logic design in diaphragm control is identical to the Ks2..

This is wrong, it is not identical! It is based on the same principal but up to the K100D/K200D it is not the same!

... and it also defines the correct lubrication criteria of the system.

Please show me were there is anything mentioned about lubrification! I have many service-manuals including those for most *ist-bodies and have not stumbled across any mentioning of lubrification.

I deeply respect your opinions.

I have my daubts about this. The way you presented you message #47 May 13th. in the thread I had started,

i.e.the manual for solenoid replacement K-S2

you gave this message of yours the heading:
"Let's end the white solenoid myth to solve the problem of dark photos".


It was deleted and you posted it in the correct thread (first again with a heading not true to facts).

Now you admit that you didn't even do all this research with the K-S2 solenoid but a CD-Rom solenoid.

This is very strange! Why not mention this before? You harm yourself with this because it adds to what I perceived as:

Please don't talk about Fake news

O.k.: Invented facts?

...or say I guess the criteria

But you did guess! You don't have the Japan solenoid from a Pentax camera.

...and if you can rehearse a white solenoid the same way I rehearse mine, and we may come to terms with what their differences are.

I did a lot of tests with different solenoids. I have all those solenoids here and so there was no need to invent things as you did.

I tried to improve the solenoid, modifying the geometry of a sacrificial Plunguer, intelligently modifying its reluctance, in order to reduce the retention effort of the magnet up to 150 gr, so that the diaphragm control can retain the Plunguer in the rearm blow.
This showed that it improved performance, but under certain circumstances, it failed again, especially after the camera was idle for 1 or two days.

Which shows again that modifying the plunger does not lead to any success!

I started studying various manuals to understand the logic operating and decided to disarm the diaphragm control. That's where I found the surprise. The switch brushes did not do the correct pressure and one of them (there are 4 in total) never made contact. This explains everything. I gave geometry to the brushes and checked their proper operation before assembling.

With "disarm the diaphragm control" you mean that you disassembled the diaphragm-control-unit out of your K-S2?
And it is now that you tell us you undertook such immense effort? You tell us such a lot but this most important part you hide?
C'mon!

Also: What do you mean with switch brushes?

[swanlefitte]

That's where I found the surprise. The switch brushes did not do the correct pressure and one of them (there are 4 in total) never made contact. This explains everything. I gave geometry to the brushes and checked their proper operation before assembling.
The result was instantaneous, It’s doesn't fail anymore, even after being more than three days inactive. I assembly the solenoid with the original factory Plunguer. There's the big doubt. Why the brushes had so little tension and one was deformed. Was the camera mounted in this state? If so, with the use the brushes begin to fail soon.
I hope this helps.
Greetings

This helps. It shows your different approach has lead to focus and thus enquiring on different aspects of the mechanisms that stop the camera from working. It also shows where the focus of Photogem has found other information. It has not been able to bridge the gap and connect the information from both points of view without contradictions. It might be the bridge needs more blocks of information, blocks modified, or new blocks.

Right now knowing more about the 4 brushes and how their geomtry came about seems helpful. 3 days working is hard to call a success. It can be called a prolonged time till failure. If it goes a month (?) This will give more strength to your idea of course. If it fails again and the brushes have altered again would also show support.

If you had looked at several cameras that failed and several that hadn't and found the brushes in all failed vs those working different there would be strong evidence. For now we have to fill in the knowledge with assumptions that may or may not all be correct.
As a metaphor. I hope you have found a parachute instead of a taller building to fall from. One gives a prolonged time to failure while the other gives a successful landing.
Cheers

[sergiogonzalez]

This helps. It shows your different approach has lead to focus and thus enquiring on different aspects of the mechanisms that stop the camera from working. It also shows where the focus of Photogem has found other information. It has not been able to bridge the gap and connect the information from both points of view without contradictions. It might be the bridge needs more blocks of information, blocks modified, or new blocks.

Right now knowing more about the 4 brushes and how their geomtry came about seems helpful. 3 days working is hard to call a success. It can be called a prolonged time till failure. If it goes a month (?) This will give more strength to your idea of course. If it fails again and the brushes have altered again would also show support.

If you had looked at several cameras that failed and several that hadn't and found the brushes in all failed vs those working different there would be strong evidence. For now we have to fill in the knowledge with assumptions that may or may not all be correct.
As a metaphor. I hope you have found a parachute instead of a taller building to fall from. One gives a prolonged time to failure while the other gives a successful landing.
Cheers

Dear Swanlefitte:

Thank you for your recognition:

Yes, the trial time is short. I've only taken 100 photos after the diaphragm control intervention.
I don't miss any. Either way, the noise generated by diaphragm control feels soft and safe. You can tell it looked good!
As always, I will keep the community informed about how this camera works.

The four brushes of the mirror position detector switch are mounted on a metal bridge on the last wheel gearbox of the diaphragm control. It's mean, they have electrical continuity.
Two of them rub on a 360-degree of the contact disc. This disc is connected to negative potential of the camera circuit.
The other two brushes, rub over three sectors, which correspond one to the sector where the mirror is in the race of ascent, another that corresponds to where it is above, and another in the sector of the downhill race. Each of these sectors produces two pulses of negative potential. One short and one long.

It is so fast the movement of this gear, containing the brush, that, if they do not discharge enough pressure on discs, and sectors will not provide the negative electrical signal in adequate time and intensity, producing the lack of energy and lack of synchronization that will deceive to the electronic SCR that sends the signal to the solenoid.

On my camera, one of the brushes of the sectors, never touch the driving areas, and the other three had barely marked their career on discs and sectors. They could barely follow and overcome the small lack of flatness (normal for their construction) of the support of the rubbing areas.
As soon as these brushes gathered some dirt, and they found the old lubricant started the failure. It is for this reason that the fault begins with the first take.
Once the brushes move they start working, but this is an unstable situation that will end in an almost chronic failure.
Unfortunately, getting to this brush is a complicated task, it requires dismantling the mother board, and the K mounting ring of the lens, so then you have to guarantee the registration distance of the sensor.
Precision instrumentation is needed to recalibrate the sensor and then do quality testing to ensure the work is ok.

Finding technical services that comply with these routines is difficult, and surely the official services do not do this maintenance, because the amount of man hours that is needed, and the supposed spare parts, is not amortized against the cost of a new body.

I did well with the intervention, because I did not suffer any accidents, I had the marble and comparators to recalibrate the sensor and thank God the constant correction of the sensor was stamped on its electronic plate, which allowed me to make the decision to disassemble the ring and reach the brushes. Without this data the intervention is impossible.

All of this I believe will help more than one technical service and logically users who will be able to have more authority over budgets and diagnostics.

Best Regards.

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Last edited by sergiogonzalez; 05-20-2020 at 02:56 PM. Reason: Mistake

[swanlefitte]

As soon as these brushes gathered some dirt, and they found the old lubricant started the failure. It is for this reason that the fault begins with the first take.
Once the brushes move they start working, but this is an unstable situation that will end in an almost chronic failure.

I think I got ya. There are still questions going to be answered going forward of course.
I quote the above because I believe your hypothesis would mean that the rapid fire of the shutter shakes debris free allowing enough electrical conductivity. This aligns with both sitting and age and refailure. It doesn't explain a replacement solenoid working. It seems very possible it can be explained going forward. It might partly be explained by a good blowing out being done when any camera is opened in due coarse. Indeed just trying this as a quick fix seems a good easy experiment going forward. Someone who goes out of the way to get the good solenoid is also more likely to do a good cleaning. Pure conjecture now.
Glad you could put your camera back together. Hope it continues to work.

Hope my ks2 doesn't fail but i appreciate all the input on this thread.

[MarkJerling]

The four brushes of the mirror position detector switch are mounted on a metal bridge on the last wheel gearbox of the diaphragm control. It's mean, they have electrical continuity.
Two of them rub on a 360-degree of the contact disc. This disc is connected to negative potential of the camera circuit.
The other two brushes, rub over three sectors, which correspond one to the sector where the mirror is in the race of ascent, another that corresponds to where it is above, and another in the sector of the downhill race. Each of these sectors produces two pulses of negative potential. One short and one long.

It is so fast the movement of this gear, containing the brush, that, if they do not discharge enough pressure on discs, and sectors will not provide the negative electrical signal in adequate time and intensity, producing the lack of energy and lack of synchronization that will deceive to the electronic SCR that sends the signal to the solenoid.

On my camera, one of the brushes of the sectors, never touch the driving areas, and the other three had barely marked their career on discs and sectors. They could barely follow and overcome the small lack of flatness (normal for their construction) of the support of the rubbing areas.
As soon as these brushes gathered some dirt, and they found the old lubricant started the failure. It is for this reason that the fault begins with the first take.
Once the brushes move they start working, but this is an unstable situation that will end in an almost chronic failure.
Unfortunately, getting to this brush is a complicated task, it requires dismantling the mother board, and the K mounting ring of the lens, so then you have to guarantee the registration distance of the sensor.
Precision instrumentation is needed to recalibrate the sensor and then do quality testing to ensure the work is ok.

I think it would be useful to have a photo to illustrate a number of components you write of, specifically:

"Brushes", "Disks", "Sectors". I'm also intrigued by your mention of "and they found the old lubricant started the failure". Could you please explain what you mean?

[sergiogonzalez]

I think it would be useful to have a photo to illustrate a number of components you write of, specifically:

"Brushes", "Disks", "Sectors". I'm also intrigued by your mention of "and they found the old lubricant started the failure". Could you please explain what you mean?

Dear Mark,

Thank for your interest.
Attached PDF file that shows the terminology for the diaphragm control switch.
The service manual of the Ist DL OEM 76570 camera on page 16 explains which areas lubricate with different lubricants for assembly.
The cleaning and lubricating procedure of the switch explains it on page 17.
In terms of the subject of lubrication, this type of switch is essential to maintain good conductivity. Here are selected conductive fats specially developed for this function.
The switch is very exposed, as it is very close to the connection window with the lens lever. }
In addition, it should be noted that when wearing telezoom lenses, and especially when they are not Pentax, which is my case, are not so airtight, the body of the camera is pressurizing and depressurizing every time one changes the focal length.
If a small fluff is going to stop to the track of any contact, we have a problem. That's why the brushes are double.
In my case with a useless for not making contact, as soon as the other got dirty, I had the permanent failure. In addition to having all little pressure.
I also attach the last photo taken with my Ks2.
I think the subject doesn't matter. All that's left is to keep using my Ks2 and see how long it runs smoothly.
Greetings

Attached Images

View Picture EXIF

File Date

   

Attached Images

Definicion de partes conmutador Control de diafragama.pdf (356.9 KB, 61 views)

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Last edited by MarkJerling; 05-20-2020 at 11:27 PM. Reason: Image added.

[MarkJerling]

Thank you Sergio. Very clear information, thanks! Do you mind if I turn that into an image so that users need not open a pdf to see it?

[sergiogonzalez]

Thank you Sergio. Very clear information, thanks! Do you mind if I turn that into an image so that users need not open a pdf to see it?

Of course Mark. You can do it. It's everybody's information.

Thank you!

[MarkJerling]

Done.

[photogem]

Sergio
you did yet not answer this question:

Did you DISASSEMBLE the DIAPHRAGM-CONTROL-UNIT of your Pentax K-S2?

This question is very simple to answer.

Yes or No

[sergiogonzalez]

Did you DISASSEMBLE the DIAPHRAGM-CONTROL-UNIT of your Pentax K-S2?

Affirmative Photogem.
I completely disassembled the diaphragm control, prior to the study of the disassembly procedure to alter as little as possible the manufacturing calibrations.

Greetings

[photogem]

And you took photos to document the process, I mean this kind of work without step-by-step photos is impossible to achieve?

[sergiogonzalez]

And you took photos to document the process, I mean this kind of work without step-by-step photos is impossible to achieve?

Dear Photogem:

Thanks for taking an interest.

I have photos of the fundamental areas that need to be documented for rearming, and I can do a procedure to disassemble the minimum number of elements that allows access to the diaphragm control with guidelines to try not to lose calibrations.

But first I must ask you: rehearse a white solenoid, according to the instructions described in the post #47 of this thread.

After all the researched, and all the time spent, it should be clear what are the advantages of using a Japanese solenoid and assessing in that way what the manufacturer's intention is to increase the power of the magnet and use cheaper materials.

I need 4 values, the ohmic impedance of the coil, the static retention force (in gr) and the minimum voltage (in volts) of unlocking with a load of 30 gr with its consumption in milliamps at the time the release is reached.
It is assumed that the design tension is 7 volts. If you could verify consumption in milliamps at 7 volts, I would also appreciate it.

If you have any questions, do not hesitate to contact me.

The data provided by you in the post #16 are incomplete and the unlocking times are inconsequential, because 7 volts on terminals of the solenoid of the camera, it is impossible to achieve them. SCRs will never send more than 5 volts at best.

After we finish this evaluation, we continue with the diaphragm control disassembly procedure.

Greetings

[sergiogonzalez]

It has been a month of starting my KS2, after repairing the swich of diaphragm control (post #64 and 67), and after taking about 260 photographs there have been no dark photos due to diaphragm control failure (green solenoid included).
I also did a test to leave the camera for a week without using it, to check the time to make the first shot and it worked smoothly.
The repair and isolated of the fault was successful.

Too bad Photogem that he has not performed the physical assay of a Japanese solenoid, because this other does not consider what differences there are and fortify the conclusions of the thread.

Let's go to the green solenoid theme to understand how it works and make it clear that after passing the proposed test this will be reliable.

The solenoid is a very simple electrical machine that is designed to perform only two functions:

1) Lock the Plunger (keep it glued to the magnet's magnetic circuit)

2) Unlock the Plunger (by sending a DC voltage pulse to its coils, which cancels the magnet's magnetic field)

The responsibility to remove the Plunger (exit stroke) is from the crossbow spring that assists the lever of the anchor (Ancora).

The responsibility for introducing the Plunger (entry stroke) is a cam mounted on the penultimate gear of the diaphragm control that acts on the lever of the anchor (Ancora) and causes the magnet to lock the Plunger again.

In my post #47 considers the physic evaluation of the two functions.

Static, evaluates the solenoid's ability to keep the Plunger glued, checking how much weight it can withstand.

The dynamics, evaluates the ability of the solenoid to override the magnetic field of the magnet, verifying that: loading the Plunger with a weight equivalent to the effort made by the crossbow of the anchor (ancora) lever (30 grams), applying an instantaneous voltage pulse of 2.5 volt this decouple. This voltage is the minimum that will exist in the camera, if your entire voltage pulse generation system is in order.

Logically, that the solenoid for our Pentax cameras KS2, must have an ohmic resistance of 29 ohm and have the matching physical dimensions for assembly.

By doing this test and repeating it a reasonable number of times (say 20 times), we will conclude that, if the solenoid never fails, we can rate it as good and reliable for use.

Whoever does this test will verify, that any solenoid, supplied in a Pentax camera, will mostly pass this test, and one may conclude, that the quality of plastics, metals, magnets and the winding of solenoids supplied by Ricoh, does not influence their behavior.

Only damage to the reels of the coils, in the coils, oxidation in the metals that make up it or the presence of iron files in the Plunger displacement guides, will be able to alter the results of this examination. These would be the only reasons for changing the solenoid.

Attach a terminology graph and description of the components mentioned for a better understanding.

I also attach the last photo, similar to the first after repair, taken in AUTO mode, where the entire camera system is tested.

Best Regards