Dark frames or dark expositure problems in KS2, K30, K50, etc.

sergiogonzalez · 04-10-2020, 02:27 PM

Dear Community:
With the utmost respect:
I will not comment more on the subject, unless my Pentax fails again whit dark photos.
It has been very entertaining to investigate the engineering of a Pentax and for me very important to share it.
I've tried to dump with the utmost honesty, all my knowledge collected during the life of the one who has to maintain machines.
There is a lack of information with what the Murphy Law for which he investigates this type of issues is always applied. Even myself.
I apologise a thousand times if anyone has been offended or considered my comments and suggestions to be superb.
I am also very grateful that I was able to extract other important information from this forum.
Hoping that everything has not been in vain and that it serves the community.
Greetings

Last edited by MarkJerling; 05-13-2020 at 03:18 AM. Reason: Minor cleanup.

sergiogonzalez · 05-14-2020, 02:33 PM

Finally, my Ks2 failed again after having tried countless solutions, which were a temporary palliative, as can be inferred from all the posts written on this thread, which led me to investigate more deeply the solenoid and finally intervene the diaphragm control block and repair its switch.
It was the solution.
The camera doesn't fail anymore.
The two most important posts are the #29 and #35 where it is already quite clear that the solenoid is not the cause of the failure. It is not the solenoid that causes dark photos in cameras provided with electromechanical diaphragm control block. (ks1, Ks2, ist, K50, etc.)
To make sure that the solenoid, whatever the color is, they can do the following tests:

Static:
Ohmic coil resistance 29 ohm
Magnet locking effort: approx. 230/240 grams applying the load gradually and very slowly.
This value should not be less than 150 grams, because the magnet of solenoid, will not have enough power for mechanical rearmament by cam of the diaphragm control and may not be blocked

Dynamics:
Unlock test with a load of 30 gr. (load that applies the spring of the diaphragm control block)
Minimum unlock voltage: 2.5 volt with a consumption of 76 m amps. (the solenoid must unlock the Plunguer with these values at the minimum contact with a load of 30 gr))
If this does not happen then the solenoid is out of specification.

What is needed:
A plastic container of approx. 250 ml capacity
A syringe graduated in milliliters
An adjustable DC source from 0 to 7 volts equipped with voltmeter and ampmeter.
Water 250 ml

How to do it.

Static test:
Hang the solenoid from a secure support with its original Plunguer mounted. At plunguer hang the empty plastic container. Start filling it slowly with water. When you reach 230/240 ml = 230/240 gr., the Plunguer must be mechanical unlocked.

Dynamic test:
Hanging of the mounted solenoid for static testing 30 gr. (the 250 ml plastic container, weigh approximately 30 gr)
In that circumstance, connect the DC electrical source to the solenoid, respecting the polarity with which the solenoid is mounted on the camera.
Start raising the tension.
When you reach approx. 2.5 volt, the Plunguer must be unlocked. If the current is measured in that situation, just over 75 m Amp should be checked.

Electric specifications of solenoid design:
Voltage: 7 volt
Current consumption at 7 volt: 900 m Amp.

We must understand that the solenoid is a very simple electrical machine, which does not present major technical drawbacks. In our cameras electrical power is used only to unlock it. It is blocked or rearm through a mechanical blow from a cam. For this reason, the material with which the coil reels are manufactured, nor the magnetic quality of the materials, is not more important.
It should be noted from the previous test, and from the design specifications that with only 3% of the design power the solenoid is decoupled with the force applied by the camera spring.

In conclusion, the problem that the solenoid does not unlock, is that it does not get enough energy at the right time.

No power can result from the mirror position switch, wiring and welding problems, or problems with command SRS.
The mirror position switch will most likely fail, as its brushes (which are mounted on the last gear of the diaphragm control block) may be deformed, and may not produce good contact at the precise time needed, not sending the precise signal to the SCR electronic system. (The switch generates 2 pulses for three mirror positions. One short and one long. It is essential for the electronic system that both pulses are transmitted. If the short the solenoid fails)
This problem had my KS2. The four brushes discharged very little pressure on the switch plate, and one of them directly did not touch it (The contact plate barely featured a micro contact line, which disappeared over one of the areas where the signal that will make the solenoid work) (in these conditions, no solenoid, White or Green works)
Therefore, if you have problems with dark photos, and verify that the solenoid meets the tests, there is no other to send the camera to the responsible technical service, that you have very clear this problem, because getting to the mirrows switch is not simple; it requires knowing the design of the camera so as not to lose any calibration and also have great ability to weld flat printed circuits, because you have to crumble the mother board and other critical components.

I hope this will work, and a better criterion for diagnosing this problem.

In addition, I would especially like to thank the moderators in this thread, who allow to develop these topics in a healthy, respectful and high technical level environment.

Best regards.

MarkJerling · 05-14-2020, 11:51 PM - **1 Like**

Originally posted by sergiogonzalez

Finally, my Ks2 failed again after having tried countless solutions, which were a temporary palliative, as can be inferred from all the posts written on this thread, which led me to investigate more deeply the solenoid and finally intervene the diaphragm control block and repair its switch.
It was the solution.
The camera doesn't fail anymore.
The two most important posts are the #29 and #35 where it is already quite clear that the solenoid is not the cause of the failure. It is not the solenoid that causes dark photos in cameras provided with electromechanical diaphragm control block. (ks1, Ks2, ist, K50, etc.)
To make sure that the solenoid, whatever the color is, they can do the following tests:

Static:
Ohmic coil resistance 29 ohm
Magnet locking effort: approx. 230/240 grams applying the load gradually and very slowly.
This value should not be less than 150 grams, because the magnet of solenoid, will not have enough power for mechanical rearmament by cam of the diaphragm control and may not be blocked

Dynamics:
Unlock test with a load of 30 gr. (load that applies the spring of the diaphragm control block)
Minimum unlock voltage: 2.5 volt with a consumption of 76 m amps. (the solenoid must unlock the Plunguer with these values at the minimum contact with a load of 30 gr))
If this does not happen then the solenoid is out of specification.

What is needed:
A plastic container of approx. 250 ml capacity
A syringe graduated in milliliters
An adjustable DC source from 0 to 7 volts equipped with voltmeter and ampmeter.
Water 250 ml

How to do it.

Static test:
Hang the solenoid from a secure support with its original Plunguer mounted. At plunguer hang the empty plastic container. Start filling it slowly with water. When you reach 230/240 ml = 230/240 gr., the Plunguer must be mechanical unlocked.

Dynamic test:
Hanging of the mounted solenoid for static testing 30 gr. (the 250 ml plastic container, weigh approximately 30 gr)
In that circumstance, connect the DC electrical source to the solenoid, respecting the polarity with which the solenoid is mounted on the camera.
Start raising the tension.
When you reach approx. 2.5 volt, the Plunguer must be unlocked. If the current is measured in that situation, just over 75 m Amp should be checked.

Electric specifications of solenoid design:
Voltage: 7 volt
Current consumption at 7 volt: 900 m Amp.

We must understand that the solenoid is a very simple electrical machine, which does not present major technical drawbacks. In our cameras electrical power is used only to unlock it. It is blocked or rearm through a mechanical blow from a cam. For this reason, the material with which the coil reels are manufactured, nor the magnetic quality of the materials, is not more important.
It should be noted from the previous test, and from the design specifications that with only 3% of the design power the solenoid is decoupled with the force applied by the camera spring.

In conclusion, the problem that the solenoid does not unlock, is that it does not get enough energy at the right time.

No power can result from the mirror position switch, wiring and welding problems, or problems with command SRS.
The mirror position switch will most likely fail, as its brushes (which are mounted on the last gear of the diaphragm control block) may be deformed, and may not produce good contact at the precise time needed, not sending the precise signal to the SCR electronic system. (The switch generates 2 pulses for three mirror positions. One short and one long. It is essential for the electronic system that both pulses are transmitted. If the short the solenoid fails)
This problem had my KS2. The four brushes discharged very little pressure on the switch plate, and one of them directly did not touch it (The contact plate barely featured a micro contact line, which disappeared over one of the areas where the signal that will make the solenoid work) (in these conditions, no solenoid, White or Green works)
Therefore, if you have problems with dark photos, and verify that the solenoid meets the tests, there is no other to send the camera to the responsible technical service, that you have very clear this problem, because getting to the mirrows switch is not simple; it requires knowing the design of the camera so as not to lose any calibration and also have great ability to weld flat printed circuits, because you have to crumble the mother board and other critical components.

I hope this will work, and a better criterion for diagnosing this problem.

In addition, I would especially like to thank the moderators in this thread, who allow to develop these topics in a healthy, respectful and high technical level environment.

Best regards.

I have edited your heading to this post to remove reference to the white solenoid as being the problem as the white solenoid seems to work in almost all cases. Failure seems to be almost exclusively of the green solenoid. That's not to say that the white soenoid can't fail, but evidence from many testers seem to show that failure is almost always a green solenoid problem.

**OldChE** · 05-17-2020, 07:29 PM - **1 Like**

Originally posted by MarkJerling

I have edited your heading to this post to remove reference to the white solenoid as being the problem as the white solenoid seems to work in almost all cases. Failure seems to be almost exclusively of the green solenoid. That's not to say that the white soenoid can't fail, but evidence from many testers seem to show that failure is almost always a green solenoid problem.

Mark - Is there an easy way to check which solenoid I have on my K-70? I think it may be developing the aperture block problem. I know the early symptoms (first picture too dark when first picking up the camera and making a few shots that day) since I had this failure in my K-50. I've seen this "first photo dark" now appear about 3 times over the last 3 weeks, not every day, but 3 times is enough to concern me. I just did the "how to check your K70 to see if you have the aperture block problem" and both wide open and F22 still took proper exposure, but in my experience with the K50 I know it is an intermittent problem at first.

I got the K70 in December 2017, and I paid a bit extra for the Pentax 3 year warranty. So if this problem develops I want that to be detected soon, so I can send it in for repair under warranty before this coming December.

Thanks - Richard.

swanlefitte · 05-17-2020, 07:54 PM - **1 Like**

Originally posted by sergiogonzalez

Finally, my Ks2 failed again after having tried countless solutions, which were a temporary palliative,

I appreciate all the write ups.
In this last one you say it is the power not getting to the solenoid. Why would a temporary fix to this part be reconnecting the power for this temporary time? All I can think is that the missed power is putting the solenoid out of the spec. Then the white could be seen as more resistent to this than the green.

**photogem** · 05-18-2020, 03:19 AM

Originally posted by OldChE

Is there an easy way to check which solenoid I have on my K-70?

All K-70's have improved made in China green solenoid, they all were manufactured past Dec.2015.
S. Gonzeles K-S2 has the older much more failing solenoid inside his K-S2 which was manufactured February 7th 2015!

There is no easy way other than opening your K-70 according to the tutorial but due to the fact that you have the 3 years warranty
"for the time being" (i.e. until the warranty is off) you are best off to send your camera for repair.

Originally posted by OldChE

I think it may be developing the aperture block problem. I know the early symptoms (first picture too dark when first picking up the camera and making a few shots that day) since I had this failure in my K-50.

So if you still have your K-50 with that failure, you can do the tests there to compare.

Originally posted by OldChE

I've seen this "first photo dark" now appear about 3 times over the last 3 weeks, not every day, but 3 times is enough to concern me.
I just did the "how to check your K70 to see if you have the aperture block problem" and both wide open and F22 still took proper exposure, but in my experience with the K50 I know it is an intermittent problem at first.

That's how it is. Of course it has nothing to do with the powersupply, that is a myth! The reasons have been explained many times.
One has to have a made in Japan solenoid in one's hands and just "wobble a bit around" the plunger in the body and then do the same
with the green China solenoid to "sense or feel" the difference. And then one pulls on the plunger and right there can tell the difference.
Nothing more is really necessary for those who undertake the DIY repair.

Originally posted by OldChE

I got the K70 in December 2017, and I paid a bit extra for the Pentax 3 year warranty. So if this problem develops I want that to be detected soon, so I can send it in for repair under warranty before this coming December.

Of course you can wait but often just when one needs the camera the problem gets firm.
So best to do it when you know your camera isn't in use much anyway.
And then you have another 1 year warranty on the repair.
If then it fails again, you can apply DIY.

MarkJerling · 05-18-2020, 01:53 PM - **2 Likes**

Originally posted by OldChE

Mark - Is there an easy way to check which solenoid I have on my K-70? I think it may be developing the aperture block problem. I know the early symptoms (first picture too dark when first picking up the camera and making a few shots that day) since I had this failure in my K-50. I've seen this "first photo dark" now appear about 3 times over the last 3 weeks, not every day, but 3 times is enough to concern me. I just did the "how to check your K70 to see if you have the aperture block problem" and both wide open and F22 still took proper exposure, but in my experience with the K50 I know it is an intermittent problem at first.

I got the K70 in December 2017, and I paid a bit extra for the Pentax 3 year warranty. So if this problem develops I want that to be detected soon, so I can send it in for repair under warranty before this coming December.

Thanks - Richard.

Richard, I'd suggest, as Photogem has done, that you make use of your 3-year warranty before it expires, and not open the camera yourself under warranty.

sergiogonzalez · 05-18-2020, 04:46 PM

Originally posted by swanlefitte

I appreciate all the write ups.
In this last one you say it is the power not getting to the solenoid. Why would a temporary fix to this part be reconnecting the power for this temporary time? All I can think is that the missed power is putting the solenoid out of the spec. Then the white could be seen as more resistent to this than the green.

Dear Swanlefitte:

It is necessary to understand that the solenoid, is a very simple machine that does not have to fail. I have given the guidelines in the post #47 to be able to test it, and I have also explained how it is locked and how it is unlocked in the camera.
If you test both white and green you will see that the two work within the parameters
I specify for the test. (these parameters are what the diaphragm control needs)
It would be very important for the one who has a white one to test them according to this criterion and share the values, to establish the difference. (if any)
The solenoid of my KS2 is original factory, has no modification, and it is not necessary to modify anything for it to work trying to compensate for the lack of energy.
The solenoid starts working badly when it doesn't receive the energy that unlocks it in quantity and in the right time.
This energy is managed by the diaphragm control mirror swich, by the electronic command and logically by the wiring.
Any of these items can fail and prevent that energy from coming and you will have dark photos and/or other problems.
In my case the problem was in the swich of the diaphragm control. I put it on specification and the problem is over.
It's not a temporary repair. It is to put the mechanism back up according to the manufacturer's specifications.
I hope this helps.
Greetings

swanlefitte · 05-18-2020, 06:21 PM - **1 Like**

Originally posted by sergiogonzalez

It's not a temporary repair. It is to put the mechanism back up according to the manufacturer's specifications.
I hope this helps.
Greetings

I am saying people replace the solenoid and it works again. If the problem is not the solenoid then why does the electricity now get to the solenoid? It either brings electricity back to the solenoid or it restores function to a solenoid damaged by lack of electricity or why would replacing the solenoid ever stop the problem. We have ample evidence that the replacement makes the camera work properly again at least temporarily.

**photogem** · 05-19-2020, 12:04 AM

Originally posted by swanlefitte

I am saying people replace the solenoid and it works again. If the problem is not the solenoid then why does the electricity now get to the solenoid? It either brings electricity back to the solenoid or it restores function to a solenoid damaged by lack of electricity or why would replacing the solenoid ever stop the problem. We have ample evidence that the replacement makes the camera work properly again at least temporarily.

Not temporarily, the white Japan solenoid never ever failed in any of those:

ist*-D
ist*DS
ist*DS2
ist*DL
ist*DL2
Samsung GX1
Samsung GX1s
Samsung GX1L
K10D
Samsung GX10
K20D
Samsung GX20
K100D
K110D
K200D
K-m (2000)
K-x
K-r

Plus, if correctly used, it never failed when replaced against the green Chinasolenoid in:
K-30, K-50, K-500, K-S1, K-S2, K-70

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"

**OldChE** · 05-19-2020, 06:50 AM

Thanks. So, if I contact Pentax and tell them I suspect this problem and send it in for the repair, will they replace it with the better solenoid and all will be well? I'm concerned that since it is only happening some times (right now) they might get it and say "we checked it and it works fine, returning it to you."

**ehrwien** · 05-19-2020, 07:43 AM

My K-S2, bought 4 years and 3 days ago, might have just shown the first sign of the problem: First frame was dark when it shouldn't have been, and the next were correctly exposed, even at the same settings under the same circumstances as the first dark frame.

A small glimmer of hope remains: could it have been the lens' fault? It was the first shot with a new to me, but bought as "used" 16-85, although the seller described it as unused and the lens did not show any sign of usage. Could it have been a little sluggish aperture in a lens that may have sat unused for a longer time? I hope so

Will have to keep my senses sharp towards the possibilty of solenoid failure. I'm at least half prepared, I have an istD that I could get a white solenoid from. For the rest, I will have to rely on the great guides here and that I will not destroy anything beyond repair in the process

**photogem** · 05-19-2020, 10:55 AM - **1 Like**

Originally posted by OldChE

Thanks. So, if I contact Pentax and tell them I suspect this problem and send it in for the repair, will they replace it with the better solenoid and all will be well? I'm concerned that since it is only happening some times (right now) they might get it and say "we checked it and it works fine, returning it to you."

They will replace it with the same solenoid, i.e. the one you have inside your K70.

Also they should very well know that it starts some times and then gets worse.
It is a known problem.

@ehrwien:
Just keep an eye on it and if the dark photos return more often, you know how to check it:
1. Av Mode and wide open: Photo should be dark
2. Av Mode and full closed: Photo should be fine
As you have the old *ist, nothing can go wrong if you do it right and you have peace and quiet concerning the function of the solenoid.

sergiogonzalez · 05-19-2020, 01:59 PM

Originally posted by swanlefitte

I am saying people replace the solenoid and it works again. If the problem is not the solenoid then why does the electricity now get to the solenoid? It either brings electricity back to the solenoid or it restores function to a solenoid damaged by lack of electricity or why would replacing the solenoid ever stop the problem. We have ample evidence that the replacement makes the camera work properly again at least temporarily.

Dear Swanlefitte:
You are right.
This conclusion you make is logical.
The solenoid, while simple, can also fail.
These faults are detected with the instruction that passed them in the post #47.
If the solenoid passes the test, then we have to look the other way. Always you have dark fotos!
If the solenoid doesn't meet the parameters, you replace it with one that meets the parameters, the color you want. The problem is insulated.
The solenoid may fail due to lack of insulation in its winding, because it has lost power its magnet or because it is rusty, as some users have reported, this you can verify it and help you in the diagnosis.
Now the symptom of failing once and then starting to walk well, is typical of failures in the diaphragm control switch. That's how my Ks2 and all this research started. I hope to help.
Greetings

swanlefitte · 05-19-2020, 02:08 PM

Originally posted by sergiogonzalez

Now the symptom of failing once and then starting to walk well, is typical of failures in the diaphragm control switch. That's how my Ks2 and all this research started. I hope to help.
Greetings

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.

05-14-2020, 02:33 PM	#47
sergiogonzalez Forum Member Join Date: Nov 2019 Location: Mendoza Posts: 63 Original Poster	My method Finally, my Ks2 failed again after having tried countless solutions, which were a temporary palliative, as can be inferred from all the posts written on this thread, which led me to investigate more deeply the solenoid and finally intervene the diaphragm control block and repair its switch. It was the solution. The camera doesn't fail anymore. The two most important posts are the #29 and #35 where it is already quite clear that the solenoid is not the cause of the failure. It is not the solenoid that causes dark photos in cameras provided with electromechanical diaphragm control block. (ks1, Ks2, ist, K50, etc.) To make sure that the solenoid, whatever the color is, they can do the following tests: Static: Ohmic coil resistance 29 ohm Magnet locking effort: approx. 230/240 grams applying the load gradually and very slowly. This value should not be less than 150 grams, because the magnet of solenoid, will not have enough power for mechanical rearmament by cam of the diaphragm control and may not be blocked Dynamics: Unlock test with a load of 30 gr. (load that applies the spring of the diaphragm control block) Minimum unlock voltage: 2.5 volt with a consumption of 76 m amps. (the solenoid must unlock the Plunguer with these values at the minimum contact with a load of 30 gr)) If this does not happen then the solenoid is out of specification. What is needed: A plastic container of approx. 250 ml capacity A syringe graduated in milliliters An adjustable DC source from 0 to 7 volts equipped with voltmeter and ampmeter. Water 250 ml How to do it. Static test: Hang the solenoid from a secure support with its original Plunguer mounted. At plunguer hang the empty plastic container. Start filling it slowly with water. When you reach 230/240 ml = 230/240 gr., the Plunguer must be mechanical unlocked. Dynamic test: Hanging of the mounted solenoid for static testing 30 gr. (the 250 ml plastic container, weigh approximately 30 gr) In that circumstance, connect the DC electrical source to the solenoid, respecting the polarity with which the solenoid is mounted on the camera. Start raising the tension. When you reach approx. 2.5 volt, the Plunguer must be unlocked. If the current is measured in that situation, just over 75 m Amp should be checked. Electric specifications of solenoid design: Voltage: 7 volt Current consumption at 7 volt: 900 m Amp. We must understand that the solenoid is a very simple electrical machine, which does not present major technical drawbacks. In our cameras electrical power is used only to unlock it. It is blocked or rearm through a mechanical blow from a cam. For this reason, the material with which the coil reels are manufactured, nor the magnetic quality of the materials, is not more important. It should be noted from the previous test, and from the design specifications that with only 3% of the design power the solenoid is decoupled with the force applied by the camera spring. In conclusion, the problem that the solenoid does not unlock, is that it does not get enough energy at the right time. No power can result from the mirror position switch, wiring and welding problems, or problems with command SRS. The mirror position switch will most likely fail, as its brushes (which are mounted on the last gear of the diaphragm control block) may be deformed, and may not produce good contact at the precise time needed, not sending the precise signal to the SCR electronic system. (The switch generates 2 pulses for three mirror positions. One short and one long. It is essential for the electronic system that both pulses are transmitted. If the short the solenoid fails) This problem had my KS2. The four brushes discharged very little pressure on the switch plate, and one of them directly did not touch it (The contact plate barely featured a micro contact line, which disappeared over one of the areas where the signal that will make the solenoid work) (in these conditions, no solenoid, White or Green works) Therefore, if you have problems with dark photos, and verify that the solenoid meets the tests, there is no other to send the camera to the responsible technical service, that you have very clear this problem, because getting to the mirrows switch is not simple; it requires knowing the design of the camera so as not to lose any calibration and also have great ability to weld flat printed circuits, because you have to crumble the mother board and other critical components. I hope this will work, and a better criterion for diagnosing this problem. In addition, I would especially like to thank the moderators in this thread, who allow to develop these topics in a healthy, respectful and high technical level environment. Best regards. Last edited by MarkJerling; 05-14-2020 at 11:26 PM.

05-18-2020, 03:19 AM	#51
photogem Site Supporter Join Date: Apr 2015 Posts: 3,520	Originally posted by OldChE Is there an easy way to check which solenoid I have on my K-70? All K-70's have improved made in China green solenoid, they all were manufactured past Dec.2015. S. Gonzeles K-S2 has the older much more failing solenoid inside his K-S2 which was manufactured February 7th 2015! There is no easy way other than opening your K-70 according to the tutorial but due to the fact that you have the 3 years warranty "for the time being" (i.e. until the warranty is off) you are best off to send your camera for repair. Originally posted by OldChE I think it may be developing the aperture block problem. I know the early symptoms (first picture too dark when first picking up the camera and making a few shots that day) since I had this failure in my K-50. So if you still have your K-50 with that failure, you can do the tests there to compare. Originally posted by OldChE I've seen this "first photo dark" now appear about 3 times over the last 3 weeks, not every day, but 3 times is enough to concern me. I just did the "how to check your K70 to see if you have the aperture block problem" and both wide open and F22 still took proper exposure, but in my experience with the K50 I know it is an intermittent problem at first. That's how it is. Of course it has nothing to do with the powersupply, that is a myth! The reasons have been explained many times. One has to have a made in Japan solenoid in one's hands and just "wobble a bit around" the plunger in the body and then do the same with the green China solenoid to "sense or feel" the difference. And then one pulls on the plunger and right there can tell the difference. Nothing more is really necessary for those who undertake the DIY repair. Originally posted by OldChE I got the K70 in December 2017, and I paid a bit extra for the Pentax 3 year warranty. So if this problem develops I want that to be detected soon, so I can send it in for repair under warranty before this coming December. Of course you can wait but often just when one needs the camera the problem gets firm. So best to do it when you know your camera isn't in use much anyway. And then you have another 1 year warranty on the repair. If then it fails again, you can apply DIY. Last edited by photogem; 05-18-2020 at 03:26 AM.

05-19-2020, 12:04 AM	#55
photogem Site Supporter Join Date: Apr 2015 Posts: 3,520	Originally posted by swanlefitte I am saying people replace the solenoid and it works again. If the problem is not the solenoid then why does the electricity now get to the solenoid? It either brings electricity back to the solenoid or it restores function to a solenoid damaged by lack of electricity or why would replacing the solenoid ever stop the problem. We have ample evidence that the replacement makes the camera work properly again at least temporarily. Not temporarily, the white Japan solenoid never ever failed in any of those: ist-D istDS istDS2 istDL istDL2 Samsung GX1 Samsung GX1s Samsung GX1L K10D Samsung GX10 K20D Samsung GX20 K100D K110D K200D K-m (2000) K-x K-r Plus, if correctly used, it never failed when replaced against the green Chinasolenoid in: K-30, K-50, K-500, K-S1, K-S2, K-70 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" Last edited by photogem; 05-19-2020 at 12:46 AM.*

05-19-2020, 01:59 PM	#59
sergiogonzalez Forum Member Join Date: Nov 2019 Location: Mendoza Posts: 63 Original Poster	Originally posted by swanlefitte I am saying people replace the solenoid and it works again. If the problem is not the solenoid then why does the electricity now get to the solenoid? It either brings electricity back to the solenoid or it restores function to a solenoid damaged by lack of electricity or why would replacing the solenoid ever stop the problem. We have ample evidence that the replacement makes the camera work properly again at least temporarily. Dear Swanlefitte: You are right. This conclusion you make is logical. The solenoid, while simple, can also fail. These faults are detected with the instruction that passed them in the post #47. If the solenoid passes the test, then we have to look the other way. Always you have dark fotos! If the solenoid doesn't meet the parameters, you replace it with one that meets the parameters, the color you want. The problem is insulated. The solenoid may fail due to lack of insulation in its winding, because it has lost power its magnet or because it is rusty, as some users have reported, this you can verify it and help you in the diagnosis. Now the symptom of failing once and then starting to walk well, is typical of failures in the diaphragm control switch. That's how my Ks2 and all this research started. I hope to help. Greetings Last edited by sergiogonzalez; 05-19-2020 at 02:05 PM. Reason: mistake

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04-10-2020, 02:27 PM	#46
sergiogonzalez Forum Member Join Date: Nov 2019 Location: Mendoza Posts: 63 Original Poster	Dear Community: With the utmost respect: I will not comment more on the subject, unless my Pentax fails again whit dark photos. It has been very entertaining to investigate the engineering of a Pentax and for me very important to share it. I've tried to dump with the utmost honesty, all my knowledge collected during the life of the one who has to maintain machines. There is a lack of information with what the Murphy Law for which he investigates this type of issues is always applied. Even myself. I apologise a thousand times if anyone has been offended or considered my comments and suggestions to be superb. I am also very grateful that I was able to extract other important information from this forum. Hoping that everything has not been in vain and that it serves the community. Greetings Last edited by MarkJerling; 05-13-2020 at 03:18 AM. Reason: Minor cleanup.

05-14-2020, 11:51 PM - 1 Like	#48
MarkJerling Moderator Site Supporter Join Date: May 2012 Location: Wairarapa, New Zealand Photos: Gallery \| Albums Posts: 20,406	Originally posted by sergiogonzalez Finally, my Ks2 failed again after having tried countless solutions, which were a temporary palliative, as can be inferred from all the posts written on this thread, which led me to investigate more deeply the solenoid and finally intervene the diaphragm control block and repair its switch. It was the solution. The camera doesn't fail anymore. The two most important posts are the #29 and #35 where it is already quite clear that the solenoid is not the cause of the failure. It is not the solenoid that causes dark photos in cameras provided with electromechanical diaphragm control block. (ks1, Ks2, ist, K50, etc.) To make sure that the solenoid, whatever the color is, they can do the following tests: Static: Ohmic coil resistance 29 ohm Magnet locking effort: approx. 230/240 grams applying the load gradually and very slowly. This value should not be less than 150 grams, because the magnet of solenoid, will not have enough power for mechanical rearmament by cam of the diaphragm control and may not be blocked Dynamics: Unlock test with a load of 30 gr. (load that applies the spring of the diaphragm control block) Minimum unlock voltage: 2.5 volt with a consumption of 76 m amps. (the solenoid must unlock the Plunguer with these values at the minimum contact with a load of 30 gr)) If this does not happen then the solenoid is out of specification. What is needed: A plastic container of approx. 250 ml capacity A syringe graduated in milliliters An adjustable DC source from 0 to 7 volts equipped with voltmeter and ampmeter. Water 250 ml How to do it. Static test: Hang the solenoid from a secure support with its original Plunguer mounted. At plunguer hang the empty plastic container. Start filling it slowly with water. When you reach 230/240 ml = 230/240 gr., the Plunguer must be mechanical unlocked. Dynamic test: Hanging of the mounted solenoid for static testing 30 gr. (the 250 ml plastic container, weigh approximately 30 gr) In that circumstance, connect the DC electrical source to the solenoid, respecting the polarity with which the solenoid is mounted on the camera. Start raising the tension. When you reach approx. 2.5 volt, the Plunguer must be unlocked. If the current is measured in that situation, just over 75 m Amp should be checked. Electric specifications of solenoid design: Voltage: 7 volt Current consumption at 7 volt: 900 m Amp. We must understand that the solenoid is a very simple electrical machine, which does not present major technical drawbacks. In our cameras electrical power is used only to unlock it. It is blocked or rearm through a mechanical blow from a cam. For this reason, the material with which the coil reels are manufactured, nor the magnetic quality of the materials, is not more important. It should be noted from the previous test, and from the design specifications that with only 3% of the design power the solenoid is decoupled with the force applied by the camera spring. In conclusion, the problem that the solenoid does not unlock, is that it does not get enough energy at the right time. No power can result from the mirror position switch, wiring and welding problems, or problems with command SRS. The mirror position switch will most likely fail, as its brushes (which are mounted on the last gear of the diaphragm control block) may be deformed, and may not produce good contact at the precise time needed, not sending the precise signal to the SCR electronic system. (The switch generates 2 pulses for three mirror positions. One short and one long. It is essential for the electronic system that both pulses are transmitted. If the short the solenoid fails) This problem had my KS2. The four brushes discharged very little pressure on the switch plate, and one of them directly did not touch it (The contact plate barely featured a micro contact line, which disappeared over one of the areas where the signal that will make the solenoid work) (in these conditions, no solenoid, White or Green works) Therefore, if you have problems with dark photos, and verify that the solenoid meets the tests, there is no other to send the camera to the responsible technical service, that you have very clear this problem, because getting to the mirrows switch is not simple; it requires knowing the design of the camera so as not to lose any calibration and also have great ability to weld flat printed circuits, because you have to crumble the mother board and other critical components. I hope this will work, and a better criterion for diagnosing this problem. In addition, I would especially like to thank the moderators in this thread, who allow to develop these topics in a healthy, respectful and high technical level environment. Best regards. I have edited your heading to this post to remove reference to the white solenoid as being the problem as the white solenoid seems to work in almost all cases. Failure seems to be almost exclusively of the green solenoid. That's not to say that the white soenoid can't fail, but evidence from many testers seem to show that failure is almost always a green solenoid problem.

05-17-2020, 07:29 PM - 1 Like	#49
OldChE Loyal Site Supporter Join Date: May 2008 Location: Chicago area Photos: Gallery \| Albums Posts: 484	Originally posted by MarkJerling I have edited your heading to this post to remove reference to the white solenoid as being the problem as the white solenoid seems to work in almost all cases. Failure seems to be almost exclusively of the green solenoid. That's not to say that the white soenoid can't fail, but evidence from many testers seem to show that failure is almost always a green solenoid problem. Mark - Is there an easy way to check which solenoid I have on my K-70? I think it may be developing the aperture block problem. I know the early symptoms (first picture too dark when first picking up the camera and making a few shots that day) since I had this failure in my K-50. I've seen this "first photo dark" now appear about 3 times over the last 3 weeks, not every day, but 3 times is enough to concern me. I just did the "how to check your K70 to see if you have the aperture block problem" and both wide open and F22 still took proper exposure, but in my experience with the K50 I know it is an intermittent problem at first. I got the K70 in December 2017, and I paid a bit extra for the Pentax 3 year warranty. So if this problem develops I want that to be detected soon, so I can send it in for repair under warranty before this coming December. Thanks - Richard.

05-17-2020, 07:54 PM - 1 Like	#50
swanlefitte Pentaxian Join Date: May 2015 Location: Minneapolis Photos: Gallery Posts: 4,068	Originally posted by sergiogonzalez Finally, my Ks2 failed again after having tried countless solutions, which were a temporary palliative, I appreciate all the write ups. In this last one you say it is the power not getting to the solenoid. Why would a temporary fix to this part be reconnecting the power for this temporary time? All I can think is that the missed power is putting the solenoid out of the spec. Then the white could be seen as more resistent to this than the green.

05-18-2020, 01:53 PM - 2 Likes	#52
MarkJerling Moderator Site Supporter Join Date: May 2012 Location: Wairarapa, New Zealand Photos: Gallery \| Albums Posts: 20,406	Originally posted by OldChE Mark - Is there an easy way to check which solenoid I have on my K-70? I think it may be developing the aperture block problem. I know the early symptoms (first picture too dark when first picking up the camera and making a few shots that day) since I had this failure in my K-50. I've seen this "first photo dark" now appear about 3 times over the last 3 weeks, not every day, but 3 times is enough to concern me. I just did the "how to check your K70 to see if you have the aperture block problem" and both wide open and F22 still took proper exposure, but in my experience with the K50 I know it is an intermittent problem at first. I got the K70 in December 2017, and I paid a bit extra for the Pentax 3 year warranty. So if this problem develops I want that to be detected soon, so I can send it in for repair under warranty before this coming December. Thanks - Richard. Richard, I'd suggest, as Photogem has done, that you make use of your 3-year warranty before it expires, and not open the camera yourself under warranty.

05-18-2020, 04:46 PM	#53
sergiogonzalez Forum Member Join Date: Nov 2019 Location: Mendoza Posts: 63 Original Poster	Originally posted by swanlefitte I appreciate all the write ups. In this last one you say it is the power not getting to the solenoid. Why would a temporary fix to this part be reconnecting the power for this temporary time? All I can think is that the missed power is putting the solenoid out of the spec. Then the white could be seen as more resistent to this than the green. Dear Swanlefitte: It is necessary to understand that the solenoid, is a very simple machine that does not have to fail. I have given the guidelines in the post #47 to be able to test it, and I have also explained how it is locked and how it is unlocked in the camera. If you test both white and green you will see that the two work within the parameters I specify for the test. (these parameters are what the diaphragm control needs) It would be very important for the one who has a white one to test them according to this criterion and share the values, to establish the difference. (if any) The solenoid of my KS2 is original factory, has no modification, and it is not necessary to modify anything for it to work trying to compensate for the lack of energy. The solenoid starts working badly when it doesn't receive the energy that unlocks it in quantity and in the right time. This energy is managed by the diaphragm control mirror swich, by the electronic command and logically by the wiring. Any of these items can fail and prevent that energy from coming and you will have dark photos and/or other problems. In my case the problem was in the swich of the diaphragm control. I put it on specification and the problem is over. It's not a temporary repair. It is to put the mechanism back up according to the manufacturer's specifications. I hope this helps. Greetings

05-18-2020, 06:21 PM - 1 Like	#54
swanlefitte Pentaxian Join Date: May 2015 Location: Minneapolis Photos: Gallery Posts: 4,068	Originally posted by sergiogonzalez It's not a temporary repair. It is to put the mechanism back up according to the manufacturer's specifications. I hope this helps. Greetings I am saying people replace the solenoid and it works again. If the problem is not the solenoid then why does the electricity now get to the solenoid? It either brings electricity back to the solenoid or it restores function to a solenoid damaged by lack of electricity or why would replacing the solenoid ever stop the problem. We have ample evidence that the replacement makes the camera work properly again at least temporarily.

05-19-2020, 06:50 AM	#56
OldChE Loyal Site Supporter Join Date: May 2008 Location: Chicago area Photos: Gallery \| Albums Posts: 484	Thanks. So, if I contact Pentax and tell them I suspect this problem and send it in for the repair, will they replace it with the better solenoid and all will be well? I'm concerned that since it is only happening some times (right now) they might get it and say "we checked it and it works fine, returning it to you."

05-19-2020, 07:43 AM	#57
ehrwien Site Supporter Join Date: May 2016 Posts: 2,782	My K-S2, bought 4 years and 3 days ago, might have just shown the first sign of the problem: First frame was dark when it shouldn't have been, and the next were correctly exposed, even at the same settings under the same circumstances as the first dark frame. A small glimmer of hope remains: could it have been the lens' fault? It was the first shot with a new to me, but bought as "used" 16-85, although the seller described it as unused and the lens did not show any sign of usage. Could it have been a little sluggish aperture in a lens that may have sat unused for a longer time? I hope so Will have to keep my senses sharp towards the possibilty of solenoid failure. I'm at least half prepared, I have an istD that I could get a white solenoid from. For the rest, I will have to rely on the great guides here and that I will not destroy anything beyond repair in the process

05-19-2020, 10:55 AM - 1 Like	#58
photogem Site Supporter Join Date: Apr 2015 Posts: 3,520	Originally posted by OldChE Thanks. So, if I contact Pentax and tell them I suspect this problem and send it in for the repair, will they replace it with the better solenoid and all will be well? I'm concerned that since it is only happening some times (right now) they might get it and say "we checked it and it works fine, returning it to you." They will replace it with the same solenoid, i.e. the one you have inside your K70. Also they should very well know that it starts some times and then gets worse. It is a known problem. @ehrwien: Just keep an eye on it and if the dark photos return more often, you know how to check it: 1. Av Mode and wide open: Photo should be dark 2. Av Mode and full closed: Photo should be fine As you have the old *ist, nothing can go wrong if you do it right and you have peace and quiet concerning the function of the solenoid.

05-19-2020, 02:08 PM	#60
swanlefitte Pentaxian Join Date: May 2015 Location: Minneapolis Photos: Gallery Posts: 4,068	Originally posted by sergiogonzalez Now the symptom of failing once and then starting to walk well, is typical of failures in the diaphragm control switch. That's how my Ks2 and all this research started. I hope to help. Greetings 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.