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04-09-2019, 05:09 AM   #31
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As I tried to describe how the solenoid functions within this complex sychronized mechanism of actually three mechanisms but in a different thread:

Dark exposure problems on K-30 or K-50? Discussion Thread - Page 20 - PentaxForums.com

Also there is a link to the original US patent and I added a photo just quickly taken to show how these 2 toothed wheels next to the solenoid act
with this optical sensor. With AF and A lenses they work together with the solenoid, but with manual lenses in M-mode the solenoid is not at all in action!

06-22-2019, 09:58 AM   #32
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Just wanted to say thanks for the detailed instructions, just fixed mine last night, went much easier than i could have imagined having this post to refer to.
06-25-2019, 08:16 AM   #33
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You're welcome.

It is pretty easy, the most difficult part usually is one's own uneasyness and holding back.

Not that everybody could do it. If one has shaky hands the soldering could be impossible to do.
06-25-2019, 02:17 PM - 1 Like   #34
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Another big thanks to @photogem and others that took the time to research and document this fix. I repaired my daughter in laws K-50 last weekend with the white solenoid from ebay. I was very worried about the process of opening the camera but the detailed explanation made it go smoothly.

In particular the images for the screw placement were very helpful. I printed them and then glued them to a piece of corrugated cardboard, then poked a small hole at each location. As I took off each screw it was placed in the assigned hole in the cardboard. This made putting things back together very easy.

The process took about 2 hours start to finish. I suspect I could do it in 30 minutes the next time. Camera is back in working order and all is well.

07-10-2019, 01:50 PM   #35
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Thank you very much Photogem for the detailed explanations.
I just repaired the green solenoid of my K-30 with success. In parallel I ordered a white solenoid on abay. It is quite expensive from Europe, but around 55 USD will be a-just-in-case insurance for me.

Why did I repair my green solenoid? Because I understood, that mainly the magnetic force of this green solenoid is too high compared with the white and better version. May be other parameters like tolerances are also important, but the green original solenoid in my camere did not make a bad impression. Just the high force. So I decided against the soldering solution described on a russian website, where the length and depth of the metall U-Shape has to be modified. I also think, that this is a bad idea. I decide to file the top of the "U" with an angle (see attached photo). Due to this the magnetic force will be lower, because the physical contact area of the metal "U" to the permanent magnet is reduced.

I do not expect any negative impact (compared to the soldering or drastic length modification), because only the physical contact (and magnetic force) between u-shaped metal and permanant magnet is reduced.

An my camera does work again!!!
Attached Images
 
07-11-2019, 12:59 AM - 1 Like   #36
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I have tried the filing method myself several times. There is no question that it works because you do change the holding force.

There is a difference how the solenoid switches. The complete diaphragm control mechanism is by itself a very special and clever mechanism. Normally it has to be aligned. If parts go out of alignement, this is quite complicated.

I have experienced 3 x K-30's with filed green solenoids where the diaphragm-control-unit afterwards went out of alignement.
This is due to the fact, that the plunger moves less accurate, more sloppy.

You can even hear the difference just by listening to the switch-sound of a K-30 with the original white made in Japan solenoid compared to those with either soldered
plunger of those with a filed plunger.

I have explained this many times: The white PTFE or green PET body acts as a bearing for the plunger. Now if you file it there is this little more tilt of the plunger.
It is allowed to tilt due to the oval hole which sits on the lever but the movement becomes more sloppy.
This you also notice with the K-30 in use.
The problem is that most do not have several indentical K-30's at hand so they can directly compare. I do. My wife has 1 x K30 in her car which had a filed green solenoid and misfired every time and then. It first was fine for a while but then started to misfire. So he was fedup and gave it to me, I tried to fix it by changing the solenoid with the white one but it was too late, the gear mechanism is slightly out of alignement. Because it has a damaged battery-lock I chose to keep it as an emergency DSLR with a WR kitlens for my wife in her car. Still better than the camera of a smart-phone and it was cheap.

Aligning the diphragm-control-mechanism is not easy, one has to understand it very well. The white solenoid was used with success in so many DSLR bodies and never failed in any repaired K-30 etc.! So when I make the effort and I disassemble a K-30 or similar I play 100% safe and just use the white made in Japan solenoid.
It just doesn't make sense to me to fiddle around and take risks which can lead to total damage.

Here 3 pages from the service-manual of the *istDL, it is similar in other service manuals, for example K10D:
page 16
page 17
page 18
07-27-2019, 04:28 AM   #37
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Bad soldering and wrong attachments of the wires onto the solenoid

Yesterday a member of a nearby photoclub sent me his K30. He had tried to fix it but some mistakes which I brought into my manual.

The wires were soldered very badly (glued instead of soldered) but also soldered in a way which is not at all to be copied:

The solenoid has those 2 pins facing upwards for the wires, there onto the two pins facing sideways the wires of the coppercoils are fixed to.

Now, if one solderes the wire not from the side but "in extension of those top-pins" damage is programmed!

There is hardly and space for the left pink wire and if soldered the wrong way it's going get damaged as soon as the top-part is brought back to its place!


Here you see my corrected work, the pinkwire soldered from the side, you can see the tiny space available:


The lilac wire on the right is very badly soldered, almost no solder to be seen.

It is what I call "glued instead of soldered"

The solder of the pink wire has a shiny surface and one can see the wire wasn't moved during this 1sec. long cooling/harding process.
It is not "THE 100% perfect soldering joint" because the person tried several times.


But it is a good way to show about the minimal space, as it can be seen here as well:
08-14-2019, 12:02 PM   #38
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Hello @photogem,

Disclaimer: I'm new to magnetism and I don't know exactly how the aperture system works. Also, I know that the best option is to change the green solenoid with the white one.

Being said that, I've noticed that the magnet that goes in the opposite part of the horse shoe seems to be free, or at least a bit loose so we can remove it, is that true? Because in that case, although taking into account that the magnetism is not the main problem (or not the only one), maybe is the magnet the part that could be sanded instead the horse, so we can reduce the amount of force that magnet applies to the horse shoe without touching the wearing surfaces of the shoe with the coils. What do you think?

08-15-2019, 04:52 AM   #39
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This is a neodymnium magnet. It is coated with Ni-Cu-Ni (Nickel) or Ni-Cu-Ni-Cr (Chrome).

If this coating is gone, the magnet with oxidise that strongly, that it will disappear within few month.

Also with sanding and even worse grinding or sawing a magnet will lose very quickly magnetic force.
Hammering it will make it non-magnetic.

It was tried even with sealing the sanded side with epoxy: It was a disaster.

Swapping magnets didn't work either nor swapping horseshoes/plungers.
08-15-2019, 09:07 AM   #40
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QuoteOriginally posted by photogem Quote
This is a neodymnium magnet. It is coated with Ni-Cu-Ni (Nickel) or Ni-Cu-Ni-Cr (Chrome).

If this coating is gone, the magnet with oxidise that strongly, that it will disappear within few month.

Also with sanding and even worse grinding or sawing a magnet will lose very quickly magnetic force.
Hammering it will make it non-magnetic.

It was tried even with sealing the sanded side with epoxy: It was a disaster.

Swapping magnets didn't work either nor swapping horseshoes/plungers.
Thank you for your quick answer!

What do you mean by swapping? Swapping magnets between other solenoids or swapping between other magnets (not from solenoids) that could have the desired size and force?
08-15-2019, 09:57 AM   #41
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QuoteOriginally posted by k50er Quote
Thank you for your quick answer!

What do you mean by swapping? Swapping magnets between other solenoids or swapping between other magnets (not from solenoids) that could have the desired size and force?
Trying the magnet from another solenoid
08-15-2019, 01:06 PM   #42
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QuoteOriginally posted by photogem Quote
Trying the magnet from another solenoid
Then I agree with you. Unless the magnet is faulty (very rare situation), changing it with another green solenoid's magnet is a waste of time because the problem will continue happening, and changing with white solenoid's one is a non sense because in this case you can change the whole solenoid and benefit from its better quality, construction and performance
08-15-2019, 11:48 PM   #43
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QuoteOriginally posted by k50er Quote
Then I agree with you. Unless the magnet is faulty (very rare situation), changing it with another green solenoid's magnet is a waste of time because the problem will continue happening, and changing with white solenoid's one is a non sense because in this case you can change the whole solenoid and benefit from its better quality, construction and performance
I didn't say "changing it with another green solenoid's magnet": This indeed would be foolish.

You might want to invest a bit more time into the history of what others have already worked out since quite a few years now.
This threat is full of it. Its worth it.

There are solenoids from CD and DVD-ROM Drives and others from SONY Walkmans. Sometimes one comes across such a solenoid, we tried all sorts of things,
even sanding and decreasing size of the magnet. But all this led to the usual problem:

"A stick has two ends!"


The other end of the stick might hit back and produce more problems.

The other end of the white Japan-Solenoid is its price, either a tested one from ebay or one sacrifices an old DSLR which has one or two of them.

If this "end of the stick" is too expensive, yes, then one can either file or sand but with the risk of fully ruining the camera or one works with manual exposure.
An end meaning loss of comfort. And yet, for some this is can be the best experience because learning manual is more than worth it, for some a complete new experience, for others a renewal. Whereever I travel, I have almost always one of my manual lenses with me. I value some of them as much as a great limited prime.
It slows down the process, but it makes you think.

Last edited by photogem; 09-10-2019 at 10:30 AM.
08-16-2019, 08:25 AM   #44
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QuoteOriginally posted by photogem Quote
I didn't say "changing it with another green solenoid's magnet": This indeed would be foolish.
I didn't say that that you have said that, it only was an explanation about why I consider it a waste of time


QuoteOriginally posted by photogem Quote
You might want to invest a bit more time into the history of what others have already worked out since quite a few years now.
This threat is full of it. Its worth it.
I have read almost all the repairing methods that have been written in the forum (by the way, thank you for all the information that you have shared, that's amazing!), and that's why I discarded (for example) few days ago the option of sanding the plunger or changing the solenoids for those ones that are in DVD drives (because this is not a good idea as you said in the message).


QuoteOriginally posted by photogem Quote
There are solenoids from CD and DVD-ROM Drives and others from SONY Walkmans. Sometimes one comes across such a solenoid, we tried all sorts of things,
even sanding and decreasing size of the magnet. But all this led to the usual problem:

"A stick has two ends!"


The other end of the stick might hit back and produce more problems.

The other end of the white Japan-Solenoid is its price, either a tested one from ebay or one slaughers an old DSLR which has one or two of 'em.

If this "end of the stick" is too expensive, yes, then one can either file or sand but with the risk of fully ruining the camera or one works with manual exposure.
An end meaning loss of comfort. And yet, for some this is can be the best experience because learning manual is more than worth it, for some a complete new experience, for others a renewal. Whereever I travel, I have almost always one of my manual lenses with me. I value some of them as much as a great limited prime.
It slows down the process, but it makes you think.
I have also started to check the prices of other cameras that include the white solenoid (I made a screenshot with a list you put in another thread), and if I find one at good price, no doubt that I'll buy it Until then, and as the K30 will be a second body, I'll try to learn all I can by trying to solve this issue (although I know that it will be temporally).
11-06-2019, 03:16 AM   #45
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Thank you very much for the excellent description!
I had to change solenoids on a Pentax K-70. The replacement was a complete success. I encourage anyone who has the technical know-how and installation experience to not be afraid to replace.
Best regards, everyone! Attila
(Translated by Google Translate.)
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