Confirming troublesome stop down metering behavior

**photogem** · 10-10-2019, 01:45 PM

I guessed you would do the filing method as a very quick choice on your side to repair it, so no time to get a white solenoid.

Anyway: This black wire was soldered to the silver coloured metal connector being part of a metal ring beneath the K-bayonet. The connection is situated above the solenoid and is important because it connects essential parts of the main circuit with minus/negativ/ground (which in this cas is the same)

You might not necessarely notice any disadvantage yet but it is like having no earth connection on a mains-plug in your house!

It is protective and if some parasitic voltage builts up which shouldn't be there it cannot be dissipated away anymore.
This metal ring and the K-bayonet are integral part of the bodies grounding.

So make sure you solder this connector back there!

The attached photo shows were it is connected on the other side.

Last edited by photogem; 04-16-2020 at 12:07 AM.

**Marktax** · 10-10-2019, 03:23 PM

Thanks again for the helpful information. I'll need to get a precision soldering kit, and a clamp system to hold the camera while I do the work. This was an unexpected discovery. But now I know how to open the camera, at least. Thanks again for the earlier pictures.

**photogem** · 10-10-2019, 03:37 PM

Then better change the solenoid as well.
I saw the pictures of your plunger, it gave me the shivers.
Don't take this wrong, I think you are brave and you go and do things, but it is worth to do it the right way.
Your K-S2 is a great camera and worth having it done the right way.

**Marktax** · 10-10-2019, 08:06 PM

Originally posted by photogem

Then better change the solenoid as well.
I saw the pictures of your plunger, it gave me the shivers.
Don't take this wrong, I think you are brave and you go and do things, but it is worth to do it the right way.
Your K-S2 is a great camera and worth having it done the right way.

. Yes, I know I did a sloppy job of it. I refined the filing and cleaned the plunger up some after that picture. I was surprised by the loose wire. I can't help saying that it looks like an extremely tenuous and weak connection to start with. And stripping the wire a bit to resolder it looks very difficult also. There is very little slack to work with.

**photogem** · 10-11-2019, 01:37 AM

The problem is the filing method, which is not at all less difficult work, it is the opposite:
Losening the green solenoid with the wires attached is not what was intented the way those Pentax bodies are built.

The K-S2 (and K-70 with the same body!) are small bodies, so everything is even more tight.

The wires are and have to be thin!

If the wires are unsoldered properly, nothing gets damaged. The pins of the solenoid just hold those wires, nothing else.
But trying to get the solenoid out with wires attached bends them and one has to fiddle around to get it lose

for access to the plunger. Then it has to be placed back on the mechanism and rod which is far more difficult with wires attached.

So just for sake of saving a bit cost by not granting the K-S2 (or K-70 or all those other Pentax bodies) the proper part (white Japan solenoid)
one risks further damage.

One makes all this effort for printing out the photos for the screws, disassembly and then saves costs at the very worst place?

It is o.k. for those who do it but they should not encourage others or just defend their method in public.
There are those who do it because they repair cameras with this method.
So of course they must defend it.

Many official workshops repair it like this because it is cheap. Just work involved.
At least some do it a bit more clever such as an official workshop did.
But the solenoid failed again shortly after the official warranty was over and done with.

**photogem** · 10-25-2019, 05:15 AM

Originally posted by Marktax

Another person has also reported ovf/green button stop down working for a while, then becoming possible in Live View only. It seems like a second stage failure that does not always occur.

I have checked now with a K-S2 and K-50:

The solenoid is not in action with stop-down-metering / green button.

But the test was very useful:

Of course there has to be the according setting to be done in the menu:

C4-28 = "Using Aperture Ring = 2 Enable (only then Stop-Down-Metering is possible)

- I set the lens for example on f1.7
- I press the green button:

= the white toothed wheel moves to the exact position it is aligned to for f1.7 (or any other aperture!). One hardly can see the other wheels which move accordingly but this shows that if this complex mechanism is messed up i.e. out of alignment (due to either forcing the solenoid to work by applying serial shots or when filing the plunger which can lead to disalignment) then stop-down-metering will not work anymore as it should!

If stop-down-metering does not work anymore, of course the first to check is C4/28 in the menu.

But if this is set correctly, then it means the complete diaphragm-control-block needs to be swapped because one has messed up this one as well.

**reduno** · 10-25-2019, 11:16 AM

Originally posted by photogem

The solenoid is not in action with stop-down-metering / green button.

That would make sense, as the mechanism will want to move through the entire range, just in case the aperture ring is set to f 22.

**photogem** · 10-26-2019, 05:22 PM

Originally posted by reduno

That would make sense, as the mechanism will want to move through the entire range, just in case the aperture ring is set to f 22.

Yes! And if the solenoid is in action, it works something like this, which I had tested longer time ago already:

The plunger/horseshoeof the solenoid stops the aperture from closing down when the mirrormotor isactivated.
The "white"plastic toothed wheel" sitting at the right side of the solenoid (plunger downwards) moves/turns according to the aperture...i.e. more or less.
Behind this white toothed wheel sits a metal toothed wheel with holes whichturns within an optical rotation sensor! This metal wheel has tiny openingswithin which give the optical sensor the correct position of the aperture, itdetects how far the aperture has opened. The lever stops then at the choseaperture by actuating the solenoid.

The solenoid releases the plunger according to the length of the chosen shutterspeed.

When the solenoid releases, the aperture closes according to the chosenvalue (with AF and A lenses):

- If you chose Tv = 2", the solenoid will release the plunger for exactlythose chosen 2 seconds.
- If you chose Tv = 20", the solenoid will actually release the plungerfor those 20 seconds.
- But if you chose fast Tv such as 1/1000, the solenoid cannot be that fast.You can still see the difference at 1/15 or 1/30, from 1/60 on it releases withabout the same speed up to whatever max speed is possible for the chosen body.

Last edited by photogem; 10-26-2019 at 10:58 PM.

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10-10-2019, 01:45 PM	#16
photogem Site Supporter Join Date: Apr 2015 Location: Winterthur Posts: 892	I guessed you would do the filing method as a very quick choice on your side to repair it, so no time to get a white solenoid. Anyway: This black wire was soldered to the silver coloured metal connector being part of a metal ring beneath the K-bayonet. The connection is situated above the solenoid and is important because it connects essential parts of the main circuit with minus/negativ/ground (which in this cas is the same) You might not necessarely notice any disadvantage yet but it is like having no earth connection on a mains-plug in your house! It is protective and if some parasitic voltage builts up which shouldn't be there it cannot be dissipated away anymore. This metal ring and the K-bayonet are integral part of the bodies grounding. So make sure you solder this connector back there! The attached photo shows were it is connected on the other side. Last edited by photogem; 04-16-2020 at 12:07 AM.

10-10-2019, 03:23 PM	#17
Marktax Site Supporter Join Date: Jun 2013 Location: Washington DC Photos: Albums Posts: 544 Original Poster	Thanks again for the helpful information. I'll need to get a precision soldering kit, and a clamp system to hold the camera while I do the work. This was an unexpected discovery. But now I know how to open the camera, at least. Thanks again for the earlier pictures.

10-10-2019, 03:37 PM	#18
photogem Site Supporter Join Date: Apr 2015 Location: Winterthur Posts: 892	Then better change the solenoid as well. I saw the pictures of your plunger, it gave me the shivers. Don't take this wrong, I think you are brave and you go and do things, but it is worth to do it the right way. Your K-S2 is a great camera and worth having it done the right way.

10-10-2019, 08:06 PM	#19
Marktax Site Supporter Join Date: Jun 2013 Location: Washington DC Photos: Albums Posts: 544 Original Poster	Originally posted by photogem Then better change the solenoid as well. I saw the pictures of your plunger, it gave me the shivers. Don't take this wrong, I think you are brave and you go and do things, but it is worth to do it the right way. Your K-S2 is a great camera and worth having it done the right way. . Yes, I know I did a sloppy job of it. I refined the filing and cleaned the plunger up some after that picture. I was surprised by the loose wire. I can't help saying that it looks like an extremely tenuous and weak connection to start with. And stripping the wire a bit to resolder it looks very difficult also. There is very little slack to work with.

10-11-2019, 01:37 AM	#20
photogem Site Supporter Join Date: Apr 2015 Location: Winterthur Posts: 892	The problem is the filing method, which is not at all less difficult work, it is the opposite: Losening the green solenoid with the wires attached is not what was intented the way those Pentax bodies are built. The K-S2 (and K-70 with the same body!) are small bodies, so everything is even more tight. The wires are and have to be thin! If the wires are unsoldered properly, nothing gets damaged. The pins of the solenoid just hold those wires, nothing else. But trying to get the solenoid out with wires attached bends them and one has to fiddle around to get it lose for access to the plunger. Then it has to be placed back on the mechanism and rod which is far more difficult with wires attached. So just for sake of saving a bit cost by not granting the K-S2 (or K-70 or all those other Pentax bodies) the proper part (white Japan solenoid) one risks further damage. One makes all this effort for printing out the photos for the screws, disassembly and then saves costs at the very worst place? It is o.k. for those who do it but they should not encourage others or just defend their method in public. There are those who do it because they repair cameras with this method. So of course they must defend it. Many official workshops repair it like this because it is cheap. Just work involved. At least some do it a bit more clever such as an official workshop did. But the solenoid failed again shortly after the official warranty was over and done with.

10-25-2019, 05:15 AM	#21
photogem Site Supporter Join Date: Apr 2015 Location: Winterthur Posts: 892	Originally posted by Marktax Another person has also reported ovf/green button stop down working for a while, then becoming possible in Live View only. It seems like a second stage failure that does not always occur. I have checked now with a K-S2 and K-50: The solenoid is not in action with stop-down-metering / green button. But the test was very useful: Of course there has to be the according setting to be done in the menu: C4-28 = "Using Aperture Ring = 2 Enable (only then Stop-Down-Metering is possible) - I set the lens for example on f1.7 - I press the green button: = the white toothed wheel moves to the exact position it is aligned to for f1.7 (or any other aperture!). One hardly can see the other wheels which move accordingly but this shows that if this complex mechanism is messed up i.e. out of alignment (due to either forcing the solenoid to work by applying serial shots or when filing the plunger which can lead to disalignment) then stop-down-metering will not work anymore as it should! If stop-down-metering does not work anymore, of course the first to check is C4/28 in the menu. But if this is set correctly, then it means the complete diaphragm-control-block needs to be swapped because one has messed up this one as well.

10-25-2019, 11:16 AM	#22
reduno Loyal Site Supporter Join Date: Apr 2008 Location: Upstate NY, USA Posts: 573	Originally posted by photogem The solenoid is not in action with stop-down-metering / green button. That would make sense, as the mechanism will want to move through the entire range, just in case the aperture ring is set to f 22.

10-26-2019, 05:22 PM	#23
photogem Site Supporter Join Date: Apr 2015 Location: Winterthur Posts: 892	Originally posted by reduno That would make sense, as the mechanism will want to move through the entire range, just in case the aperture ring is set to f 22. Yes! And if the solenoid is in action, it works something like this, which I had tested longer time ago already: The plunger/horseshoeof the solenoid stops the aperture from closing down when the mirrormotor isactivated. The "white"plastic toothed wheel" sitting at the right side of the solenoid (plunger downwards) moves/turns according to the aperture...i.e. more or less. Behind this white toothed wheel sits a metal toothed wheel with holes whichturns within an optical rotation sensor! This metal wheel has tiny openingswithin which give the optical sensor the correct position of the aperture, itdetects how far the aperture has opened. The lever stops then at the choseaperture by actuating the solenoid. The solenoid releases the plunger according to the length of the chosen shutterspeed. When the solenoid releases, the aperture closes according to the chosenvalue (with AF and A lenses): - If you chose Tv = 2", the solenoid will release the plunger for exactlythose chosen 2 seconds. - If you chose Tv = 20", the solenoid will actually release the plungerfor those 20 seconds. - But if you chose fast Tv such as 1/1000, the solenoid cannot be that fast.You can still see the difference at 1/15 or 1/30, from 1/60 on it releases withabout the same speed up to whatever max speed is possible for the chosen body. Last edited by photogem; 10-26-2019 at 10:58 PM.

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