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06-24-2020, 03:26 PM - 2 Likes   #76
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How to disassemble the block of the diaphragm control of Ks2

Complying with Photogem's desire in the post #73, attached a guide for dismantling the diaphragm control block.

This operation is very complex, and requires a high rating to perform the welds of the circuits that are involved.
50 welding joints must be disoldered and then rewelded with eco-friendly welding alloys, which require 10 to 20% more heat than conventional Tin Lead alloys, which significantly raises the qualification of the labor. There are critical solder joints on the motherboard and on the shutter curtain and bock control plate of the diaphragm control.

There is also another complex operation which is the reset the sensor registration distance (because it is absolutely necessary to disassemble the K-mount ring).

For this it is necessary to have comparators that are able to measure the hundredth of a millimeter, a guaranteed flat marble, cylindrical supplements of proven measures to enable measurement, and the most complex to perform the measurement procedure that guarantees the positioning of the sensor.
If this operation is not guaranteed, the camera will never bring infinity focus.

Anyone who ventures into this operation should thoroughly read some workshop manual from a similar camera. (I use the workshop manual of an IST camera), which describe the process very well and are on the internet.

For KS2, the surface disarm process given by Photogem is correct.

After disassembling the camera housing, the top cover must be disassembled. (there are 9 welds and a molex connector for this disassembly)
Then disassemble the back cover and display (two molex connectors and 4 screws)

Then disassemble the mother board. (nine molex connectors of different types, 26 welded joints, and four screws

Then disassemble the battery case (two flash capacitor welds, 6 curtain control welds, 4 FCC circuit diaphragm control welds, and 6 screws)

Then disassemble the K-mount ring and lock lens, trying to respect the mounting supplements, to reuse them in the assembly. (5 ring screws and one of the lens lock)

Then disassemble the diaphragm control block. (4 screws and 6 welds, 4 of the pulse counter, an 2 of the solenoid)

Verification of all parts, contacts and cleaning of all components, lubrication and reverse mounting of the diaphragm control.

Checking and correcting the registration distance, final assembly, testing and closing of the housing.

As you can see it is a very complex operation with two critical operations that determine the quality of the work; welding and checking the registration distance.

Attached some photos indicating the main screws for the disassembly of the battery box.

I hope you're a good guide.

Greetings

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06-27-2020, 03:39 PM   #77
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QuoteOriginally posted by sergiogonzalez Quote
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.

.
I just became aware of how liveview opens the aperture or not if the soleniod fails.
This is a stoppage in the cycle you talk about. The mirror stays up and the apperture stays open to *f/4 on my 40mm xs) although i have seen it once at perhaps f/8, i didn't measure. I heard it is suppose to be open to f/5.6.
I believe at shutter press the mirror falls, lifts and falls again like the cycle you describe. BUT in liveview the aperture stays closed down and mirror up, stops mid cycle.

This must have bearing on what is going on. I wonder if it stresses the solenoid or brushes. Doesn't the solenoid need constant current to remain at f/4 or and aperture?

I would appreciate thoughts on this.
06-27-2020, 06:31 PM - 2 Likes   #78
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QuoteOriginally posted by swanlefitte Quote
I just became aware of how liveview opens the aperture or not if the soleniod fails.
This is a stoppage in the cycle you talk about. The mirror stays up and the apperture stays open to *f/4 on my 40mm xs) although i have seen it once at perhaps f/8, i didn't measure. I heard it is suppose to be open to f/5.6.
I believe at shutter press the mirror falls, lifts and falls again like the cycle you describe. BUT in liveview the aperture stays closed down and mirror up, stops mid cycle.

This must have bearing on what is going on. I wonder if it stresses the solenoid or brushes. Doesn't the solenoid need constant current to remain at f/4 or and aperture?

I would appreciate thoughts on this.
Estimated Swanleffite

In Live view mode, while the camera is being used to display and measure with the Mid-Race trigger button, the diaphragm should be kept at f4 if the lens's east focal length is between 18 mm and 24 mm. Approx. With larger focal lengths, the aperture opens to the maximum available aperture on the lens. At least this happens on my KS2 with my telezoom 18 – 135.
This function is programmed in the system and makes it possible to have a display with good lighting and that the sensor can measure and determine focus and amount of light.
I have a 28 mm f 2.8 lens with position A, and this in Live view places the diaphragm approx in f4. I believe that the software available on the camera determines the values of the diaphragm for Live view as long as the camera has the electronic identification of the lens.
When you shoot in Live view, the mirror tops, then goes down, goes up again to open the curtain and expose the sensor to the given exposure time, then go down to complete the cycle and re-up to re-enable Live view. If you look through the viewfinder while shooting in Live view, you can see the moments when the mirror is low and identify the times.
If the diaphragm closes to maximum f when you turn on Live view, you're having trouble. It can be the solenoid or it can be the swich of the diaphragm control. Now if the solenoid passes the test I suggested in post 47, then you have to think about the swich of the diaphragm control.
The solenoid only receives a pulse of voltage at a certain time, after the microprocessor receives the swich signal from the diaphragm block, to produce the correct f, by releasing the ancora and stopping the diaphragm closure at the correct value. The solenoid will never receive a continuous pulse.

Waiting for this to clarify the subject a little
Best Regards
06-29-2020, 02:20 PM - 3 Likes   #79
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QuoteOriginally posted by sergiogonzalez Quote
Dear Community:

With this thread, I finish my research (for the good of Photogem) and I will not use too many words.

I've tried to be as objective as possible, so anyone understands.

Everything is explained in the threads #29 and #35

In order to reach these conclusions, it is necessary to understand Newton's law, the Ohms’s law, the management of electrical powers (as generated, how they are transformed and where their losses occur) and the physical properties of the materials used and their relationship with the environment.

You should also be able to understand that the function of the complete assembly, was to be designed and analyzed.

If you are not prepared to isolate the fault, surely everything will be a fairy tale and you don't need to write anything in red letters.

To say that everything is wrong, lets you see clearly the limitations of Photogem.

I hope I have contributed to this community

Best Regards¿
Thank you Sergio. Your findings agree with my research. I am sorry you have been harangued for your contribution, but forums are sometimes that way.

Thank your again for your thoughts and analysis.


Steve

06-30-2020, 03:46 PM   #80
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QuoteOriginally posted by stevebrot Quote
Thank you Sergio. Your findings agree with my research. I am sorry you have been harangued for your contribution, but forums are sometimes that way.

Thank your again for your thoughts and analysis.

Thank you very much Steve for your recognition.

It's very important to me.

I greet you especially and take the opportunity to inform the community, that my Ks2 continues to work well after repair, with the original factory green solenoid.

Greetings

Last edited by sergiogonzalez; 06-30-2020 at 03:50 PM. Reason: mistake
07-02-2020, 01:46 AM   #81
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QuoteOriginally posted by sergiogonzalez Quote
Attached some photos indicating the main screws for the disassembly of the battery box
Well, why not upload all the original photos?
That would be helpful for anybody who wants to undertake either the repair or his K-S2
07-03-2020, 03:26 PM - 1 Like   #82
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QuoteOriginally posted by photogem Quote
Well, why not upload all the original photos?
That would be helpful for anybody who wants to undertake either the repair or his K-S2
Unfortunately, I do not take pictures of the process, nothing more than those necessary to reference the wiring connection of the camera.

It is very simple to assemble engineering and can be observed without further difficulty.

The guide I wrote the post #76 is quite clear about the difficulties they encountered.

I hope everything's useful.

Greetings
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07-03-2020, 04:10 PM   #83
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QuoteOriginally posted by sergiogonzalez Quote
.

The guide I wrote the post #76 is quite clear about the difficulties they encountered.
Unfortunately the difficulties exist as you say in #76 and conclude in #47. Unless a camera is used for parts your camera might be the only one examined in such a way. It is still interesting and I am glad you share your experience and thoughts.

07-04-2020, 01:17 AM   #84
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Photos of post#76 would be fine, including exif-data.
07-19-2020, 04:41 PM - 1 Like   #85
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Hello Pentaxforum community!

My Ks2 camera continues to work perfectly, even in very cold climates.

The original green solenoid works wonders, which confirms that the problem in my camera was caused by the electromechanical command of the diaphragm control according to everything developed in this thread.

It was useful to study the responsibility of the solenoid in this type of failure and to be able to determine the relation between electrical pulses and mechanical energies of the springs.

It is important to note that the duration of the electric pulse is determined by the diaphragm control and not by how quickly the solenoid is unlocked.

The correct way to test the solenoid dynamically is by applying the force exerted on the Plunguer by the crossbow spring of the ancora.

With this force applied in the test, a pulse of less than 10 msec. Release the green Plunguer.

I clarify this because in post expicated in discussion threads of the K30/50 cameras, on May 31, 2020 it is said that a green solenoid can take 100 msec to unlock using 7.2 volts.

That can't be.

If that were my Ks2, it wouldn't work.

Please reread the post #47, where you can observe that the tension (volt) applied to the green solenoid are in the order of 2.5 volts, and it decouples smoothly. You can verified that.

I attach a photo taken lately with my Ks2, Plata mountain, 6300 mts snm, near my city of Mendoza.

Greetings
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