K-S2 Aperture block failure repaired Locked

Hello flectogon

In this link there is a nice description how it work:

https://www.pentaxforums.com/forums/151-pentax-k-30-k-50/321871-k-30-k-50-aperture-block-failue-repair-solution-available-3.html

Go to page 3 and read what IgorZ posted.

My two cents (I hope you say so) to this is:

This H -core what you see in the picture 4 of the OP, get permanent 'attracted' by the permanent magnet , therefor it be subject to a permanent magnetic alignment.

Even when you try a demagnetization, it would get quickly back a magnetisation via being permanent magnetic alignment in it's normal position. Therefore, I'm not sure if this problem has something to do with this.

Now the coils built up also a magnetic field, but it is revers to the magnetic field of the permanent magnet .... so that than both magnetic field sum up to a 'zero magnetic field'. This is the moment where the H-core can get draw out. This is done by the force of a spring.

I really think that in most cases this H-core simple jam and draw out therefore not quickly enough.

Have a look how this h-core get drawn out. It get draw out by the pin. In many pictures you can see that the alignment of the pin/H-core is not in the middle.

Now it's a little bit like you try to draw out a drawer:

no problem when you draw out it at it's centre knob.

but when this drawer has two knobs (one on the right side, one on the left side), your drawer jam quickly when you draw it out only at on knob.

Now because this pin is not aligned in the centre of the H-core, for me it's a little bit the situation above, it can jam.

Therefore some round the edge of this H-core. I personally would also try to spray it with Teflon.

But this is only my personal view and it is pure theoretical, because I have not such a camera and read only about what others described about this problem.

best regards KPM2

KPM2 wrote:

Hello flectogon

In this link there is a nice description how it work:

https://www.pentaxforums.com/forums/151-pentax-k-30-k-50/321871-k-30-k-50-aperture-block-failue-repair-solution-available-3.html

Go to page 3 and read what IgorZ posted.

My two cents (I hope you say so) to this is:

This H -core what you see in the picture 4 of the OP, get permanent 'attracted' by the permanent magnet , therefor it be subject to a permanent magnetic alignment.

Even when you try a demagnetization, it would get quickly back a magnetisation via being permanent magnetic alignment in it's normal position. Therefore, I'm not sure if this problem has something to do with this.

Now the coils built up also a magnetic field, but it is revers to the magnetic field of the permanent magnet .... so that than both magnetic field sum up to a 'zero magnetic field'. This is the moment where the H-core can get draw out. This is done by the force of a spring.

I really think that in most cases this H-core simple jam and draw out therefore not quickly enough.

Have a look how this h-core get drawn out. It get draw out by the pin. In many pictures you can see that the alignment of the pin/H-core is not in the middle.

Now it's a little bit like you try to draw out a drawer:

no problem when you draw out it at it's centre knob.

but when this drawer has two knobs (one on the right side, one on the left side), your drawer jam quickly when you draw it out only at on knob.

Now because this pin is not aligned in the centre of the H-core, for me it's a little bit the situation above, it can jam.

Therefore some round the edge of this H-core. I personally would also try to spray it with Teflon.

But this is only my personal view and it is pure theoretical, because I have not such a camera and read only about what others described about this problem.

best regards KPM2

Hello KMP2,

Yes, I agree that the solenoid "getting stuck" problem is very unlikely caused by some residual magnetism. Yes, the solenoid (H-shaped core) has to be a permanent magnet, which is kept by some spring only partially immersed into the fixed armature/coil. When the coil gets activated (by a short electric pulse). the solenoid moves quickly in (if it doesn't get somehow stuck!). That pin which resides at the hole of the solenoid has to be the other side of the lever, which moves the aperture control lever of the lens. It is possible that this (body, not lens) lever  causes some "side" force, which can have your mentioned "drawer closing" effect. Now it makes sense that filing off the sharp edges of the core could help. I would be then curious, what is the difference between this part and the original (Japanese) part used in the previous cameras. Maybe just better tolerance (smaller gaps between movable parts of the electromagnet).

Hello flektogon

flektogon wrote:

KPM2 wrote:

Hello flectogon

In this link there is a nice description how it work:

https://www.pentaxforums.com/forums/151-pentax-k-30-k-50/321871-k-30-k-50-aperture-block-failue-repair-solution-available-3.html

Go to page 3 and read what IgorZ posted.

My two cents (I hope you say so) to this is:

This H -core what you see in the picture 4 of the OP, get permanent 'attracted' by the permanent magnet , therefor it be subject to a permanent magnetic alignment.

Even when you try a demagnetization, it would get quickly back a magnetisation via being permanent magnetic alignment in it's normal position. Therefore, I'm not sure if this problem has something to do with this.

Now the coils built up also a magnetic field, but it is revers to the magnetic field of the permanent magnet .... so that than both magnetic field sum up to a 'zero magnetic field'. This is the moment where the H-core can get draw out. This is done by the force of a spring.

I really think that in most cases this H-core simple jam and draw out therefore not quickly enough.

Have a look how this h-core get drawn out. It get draw out by the pin. In many pictures you can see that the alignment of the pin/H-core is not in the middle.

Now it's a little bit like you try to draw out a drawer:

no problem when you draw out it at it's centre knob.

but when this drawer has two knobs (one on the right side, one on the left side), your drawer jam quickly when you draw it out only at on knob.

Now because this pin is not aligned in the centre of the H-core, for me it's a little bit the situation above, it can jam.

Therefore some round the edge of this H-core. I personally would also try to spray it with Teflon.

But this is only my personal view and it is pure theoretical, because I have not such a camera and read only about what others described about this problem.

best regards KPM2

Hello KMP2,

Yes, I agree that the solenoid "getting stuck" problem is very unlikely caused by some residual magnetism. Yes, the solenoid (H-shaped core) has to be a permanent magnet, which is kept by some spring only partially immersed into the fixed armature/coil. When the coil gets activated (by a short electric pulse). the solenoid moves quickly in (if it doesn't get somehow stuck!). That pin which resides at the hole of the solenoid has to be the other side of the lever, which moves the aperture control lever of the lens. It is possible that this (body, not lens) lever causes some "side" force, which can have your mentioned "drawer closing" effect. Now it makes sense that filing off the sharp edges of the core could help. I would be then curious, what is the difference between this part and the original (Japanese) part used in the previous cameras. Maybe just better tolerance (smaller gaps between movable parts of the electromagnet).

I do not know what the difference is, but a better tolerance is a plausible cause to get no problems. I only read about this problem, because I once recommended my father a K500...and will be prepared to fix it when his camera get this problem. I have already Teflon spray and a syringe from a apothecary at home, because I would try also to apply Teflon, with the help of the syringe, on this H-shaped core.

To the problem itself:

I did even read that not every camera has the same part. It looks like Pentax has more than one external suppliers for this part (I mean the H-shaped core). Maybe that's why you can not general say such a camera must get this problem, like the users itself post: some have still no problem, some do.

best regards KPM2

Hello peterpainter

peterpainter wrote:

KPM2 wrote:

Hello flektogon

flektogon wrote:

KPM2 wrote:

Hello flectogon

In this link there is a nice description how it work:

https://www.pentaxforums.com/forums/151-pentax-k-30-k-50/321871-k-30-k-50-aperture-block-failue-repair-solution-available-3.html

Go to page 3 and read what IgorZ posted.

My two cents (I hope you say so) to this is:

This H -core what you see in the picture 4 of the OP, get permanent 'attracted' by the permanent magnet , therefor it be subject to a permanent magnetic alignment.

Even when you try a demagnetization, it would get quickly back a magnetisation via being permanent magnetic alignment in it's normal position. Therefore, I'm not sure if this problem has something to do with this.

Now the coils built up also a magnetic field, but it is revers to the magnetic field of the permanent magnet .... so that than both magnetic field sum up to a 'zero magnetic field'. This is the moment where the H-core can get draw out. This is done by the force of a spring.

I really think that in most cases this H-core simple jam and draw out therefore not quickly enough.

Have a look how this h-core get drawn out. It get draw out by the pin. In many pictures you can see that the alignment of the pin/H-core is not in the middle.

Now it's a little bit like you try to draw out a drawer:

no problem when you draw out it at it's centre knob.

but when this drawer has two knobs (one on the right side, one on the left side), your drawer jam quickly when you draw it out only at on knob.

Now because this pin is not aligned in the centre of the H-core, for me it's a little bit the situation above, it can jam.

Therefore some round the edge of this H-core. I personally would also try to spray it with Teflon.

But this is only my personal view and it is pure theoretical, because I have not such a camera and read only about what others described about this problem.

best regards KPM2

Hello KMP2,

Yes, I agree that the solenoid "getting stuck" problem is very unlikely caused by some residual magnetism. Yes, the solenoid (H-shaped core) has to be a permanent magnet, which is kept by some spring only partially immersed into the fixed armature/coil. When the coil gets activated (by a short electric pulse). the solenoid moves quickly in (if it doesn't get somehow stuck!). That pin which resides at the hole of the solenoid has to be the other side of the lever, which moves the aperture control lever of the lens. It is possible that this (body, not lens) lever causes some "side" force, which can have your mentioned "drawer closing" effect. Now it makes sense that filing off the sharp edges of the core could help. I would be then curious, what is the difference between this part and the original (Japanese) part used in the previous cameras. Maybe just better tolerance (smaller gaps between movable parts of the electromagnet).

I do not know what the difference is, but a better tolerance is a plausible cause to get no problems. I only read about this problem, because I once recommended my father a K500...and will be prepared to fix it when his camera get this problem. I did even read that not every camera has the same part. It looks like Pentax has more than one external suppliers for this part (I mean the H-shaped core). Maybe that's why you can not general say such a camera must get this problem, like the users itself post: some have still no problem, some do.

best regards KPM2

In the past I've come across posts where it happened after the camera has not been used for a while, and wondered if there was some commonality across failures.

In this post https://www.dpreview.com/forums/post/60341237 the aperture block performance was restored by a cycle of using the DOF preview function (on the RAW/fx button) a number of times plus test firing etc. although when this was posted on pentaxforums Adam said that a number of people had tried the same fix but the problem recurred later. Mmmm. Actually, it seems odd to me that the RAW/fx button should work with an aperture block failed camera, presumably the function operates using some different components etc......

I think this DOF-trick is great. When you use the DOF, this jammed H-shaped core has more time to move...and get eventually back in a un-jammed position. For test firing that would mean (to my mind) a longer shutter speed  is better than a short one....for to let this jammed part time to move.

best regards  KPM2

You know, repeatedly and quickly checking DOF is just one way exercising with the aperture mechanism. It's possible that this aperture driving solenoid has some lubricant inside, which needs to be periodically "stirred out".  The same effect should have taking a burst of pictures, just I am not 100% sure whether during such operation the aperture won't stay in the working position. In the LV mode I am sure that the burst mode would exercise with the lens aperture, as everything is in a move there, including the mirror.

Thanks PIngp0NGMW!

Sunday I can't use my Pentax K-S2. It was verry frustrating. I found your post and I watch the video and I repair my camera. It work again!

Wow! it worked for me too. I have a little plastic O ring that I don't know where it came from and one of the screws by the strap mount doesn't have any thing to bite into. I am not going to take it apart to find out why!!

I filed a bit and then used a nail file?

ceoga

Hi. I have just suffered the same failure on my K-S2.

Your review is really helpful and I am going to try this in the next couple of days.

Can you clarify for me. Is it just the screws on the base of the camera + the screw just under the flash button holding the skin on or is there another screw hidden somewhere that is covered or otherwise hidden.

Thanks for your help with this.

Regards

So I had the same problem. Just did the repair and it seems to be working. Let's see for how long. The sanding part was tricky so i just sanded with 400 paper a bit.

Hard-to-find screws are:

2 on viewfinder

And those under the glued rubber.

Here is badly drawn sketch.

It was a very good idea to plug the screws in the paper because they all are different length. And would be very easy to misplace.

Before attempting the fix i got quoted 180 and 144 by 2 different companies (in uk) + i would have to organise delivery to the service center.

I have seen the whole pare on ebay between 7 and 11 pounds. Not sure if they are better byt i wouldn't fancy soldering job...

Hope it helps!

edit:

have been taking pictures all day and all worked fine untill i switched to manual focus.

it no longer works. have no idea. doen't matter if i switch to auto or manual it always stays in auto focu mode :/