[photogem]

I definitely have the aperture block problem on my K30, and have read many threads. I can dismantle the camera to reach the solenoid block - if I remove and then de-magnetise the horseshoe armature, will that make matters better or worse?

Neither nor, it just will get magnetised again!

If it is soft iron it would not need to be magnetised to be attracted by the coil windings.

It isn't soft iron but an alloy which is pretty hard.

Also, I cannot understand why the block will work after a few actuations, then not work the next day until a few more actuations are made.

Because when the camera does not actuate (or isn't in use) the horseshoe-armature/plunger is constantly pulled by the magnet.
Because the magnet is stronger, it magnetises stronger.
The magnetism goes off pretty quickly but this does not help us because of the constant magnetised state!

Mine is the green solenoid of course, would polishing the armature (rather than fling bits off it improve matters?

It aways is the green solenoid. Polishing never helps. Sanding the corners helps often but only for a certain time, either the problem re-occurs later
or ... due to a sloppier movment of the plunger ... it brings the careful aligned mechanism with many more components linked to it into disorder,
or worst, blocks it and does further damage.

I apologise if these questions have already been answered- the seem numerous posts and my eyesight isn't too good. Thanks!

Go and find a white made in Japan solenoid, this way you don't play around with an inferior part but replace this part with a far superior one!
Not only final peace of mind but also slightly faster actuations of the solenoid.

[OldChE]

If i still have any on my memory card i'd be happy to post them and would most likely do it on the new post made by @Stevebrot about under exposed photos on the K70



I will share any information that the repair shop provides me.



Yes, I apologize for making duplicate posts. I was responding to 2 separate threads and was frustrated shortly after the failure occurred. I have sent the camera off to Precision Camera and contacted Ricoh USA and they have contacted Precision on my behalf. I will provide all further updates and information on the new post about the concern.

CodyH - how did this turn out?

[photogem]

CodyH - how did this turn out?

He already posted results:

*Update* Pentax has agreed to cover my repairs under warranty at no cost to me. I sent the camera in on October 1 and they approved the repairs last week. Now I am waiting on parts is the status I'm getting. I will share any your of a repair story or explanation that I receive. So far they have still only confirmed aperture failure.

[OldChE]

He already posted results:

*Update* Pentax has agreed to cover my repairs under warranty at no cost to me. I sent the camera in on October 1 and they approved the repairs last week. Now I am waiting on parts is the status I'm getting. I will share any your of a repair story or explanation that I receive. So far they have still only confirmed aperture failure.

Thanks. I guess they repaired it satisfactorily?

[AloneInthehills]

Just wanted to update this thread with my aperture block failure last week on my K70. I was traveling with a single 18-55 lens and the pictures were all dark unless I cranked the exposure through the roof. It had done this on a few shots a month or so ago and then began working when I swapped away and back to this lens.

I was able to follow a YouTube video and remove the horseshoe shaped piece from the solenoid coils, file and sand it and it's working again. It was quite tight when I removed it, like it had jammed.

It looked like the same exact solenoid in the K50 video. This is the same K70 that my autofocus failed on back in August. Because it was well out of warranty and my other lens has a built in focus motor I haven't tried to replace that yet and just manually focus with the 18-55 lens. Overall I'm disappointed that they'd use a part with seemingly known issues in this camera body.

[photogem]

2 issues:
1. Failing Autofocus: Not known yet if it is the K-70 or the DA 18-55 WR. Needs the test with another screwdrive AF-lens.
2. Solenoid. Well, we have written/discussed a lot here. The filing/sanding is a pretty bad method which can mess things up further, often has.

The solenoid looks the same but isn't exactly the same. And yet, a few do fail, several factors, all has been described in all detail why.

Also if you read the article about the history of the solenoid you will understand that it isn't that easy.

[sergiogonzalez]

Please read:

Dark frames or dark expositure problems in KS2, K30, K50, etc. - Page 2 - PentaxForums.com. #29


Best Regards!

---

Last edited by sergiogonzalez; 03-26-2020 at 05:50 PM. Reason: Ad information

[photogem]

I definitely have the aperture block problem on my K30, and have read many threads. I can dismantle the camera to reach the solenoid block - if I remove and then de-magnetise the horseshoe armature, will that make matters better or worse? If it is soft iron it would not need to be magnetised to be attracted by the coil windings. Also, I cannot understand why the block will work after a few actuations, then not work the next day until a few more actuations are made. Mine is the green solenoid of course, would polishing the armature (rather than fling bits off it improve matters?) I apologise if these questions have already been answered- the seem numerous posts and my eyesight isn't too good. Thanks!

As you wrote in another thread, you purchased a faulty Pentas *istDL.
As you already know how to disassemble your K-30, take the solenoid from the *ist DL's flash compartment and reinstall the green solenoid into your *istDL!

If you read what Sergio Gonzales did in the beginning with the solenoid of his Pentax K-S2, i.e. applying graphite to the inner part of the green PET body and then to the plunger, this should be enough, don't file/sand it nor lube it.
The solenoid isn't used as complex in the flashcompartment than it is used for aperture control.
And as you have your *istDL open, take the back with the LCD off as well, carefully take the LCD and other parts off and clean it well, the assemble it and check, if it works fine now. Otherwise take out the other white solenoid and keep it if ever you buy another solenoid-driven Pentax.

[Cee Cee]

I definitely have the aperture block problem on my K30, and have read many threads. I can dismantle the camera to reach the solenoid block - if I remove and then de-magnetise the horseshoe armature, will that make matters better or worse? If it is soft iron it would not need to be magnetised to be attracted by the coil windings. Also, I cannot understand why the block will work after a few actuations, then not work the next day until a few more actuations are made. Mine is the green solenoid of course, would polishing the armature (rather than fling bits off it improve matters?) I apologise if these questions have already been answered- the seem numerous posts and my eyesight sin't too good. Thanks!

Just my take on what's happening here..

The coil assembly has a fixed magnet which keeps the armature engaged, energizing the coil creates an opposing magnetic force which allows the armature to be withdrawn. Over time the armature retains some residual magnetism, it reaches a tipping point where the magnetic field produced by the coil is no longer strong enough to overcome the the combined force of the fixed magnet and the magnetized armature and allow the armature to be released. The action of activating the coil produces a reverse magnetic field to cancel the fixed field, this also has a demagnetizing effect on the armature, so firing shots in quick succession demagnetizes the armature and puts it the other side of the tipping point and the camera starts working normally again. Left alone, the armature will again be re magnetized and will fail again.
The issue I believe is that the manufacturer of the magnetic solenoid changed the magnetic structure and upset the balance
Filing the armature can work because it reduces the coupling to the fixed magnet and slows the build up of residual magnetism.
I'm not sure that degaussing the armature will work long term, at best it could only return to it's natural state which will make the camera work but the problem will eventually re occur, as the core issue of the magnetic structure of the coil assembly hasn't been addressed. If you wish to experiment then try the other solutions and see, but if you just want to fix the camera then I think changing the coil would be the best solution.

[photogem]

Just my take on what's happening here..
The coil assembly has a fixed magnet which keeps the armature engaged, energizing the coil creates an opposing magnetic force which allows the armature to be withdrawn. Over time the armature retains some residual magnetism, it reaches a tipping point where the magnetic field produced by the coil is no longer strong enough to overcome the the combined force of the fixed magnet and the magnetized armature and allow the armature to be released.

Maybe there is a different use of names for that part which is released when the solenoid actuates:
It is the plunger which is released/withdrawn (the name horseshoe because of its shape was used by myself long time ago)
The plunger sits on the armature which itself does not retain any measurable magnetism, it is to far away from the magnet.
The amarture is held by a spring which acts when the plunger is released.

This is important because we need a precise language here. As soon as I realised that the name plunger is the best I started to use this one.
I thing this is sensible and helpful to everybody.

It is only the plunger which magnetises due to the fact that it sits right next to the permanent magnet when the camera is not in use, i.e. 99% of its live.

The action of activating the coil produces a reverse magnetic field to cancel the fixed field, this also has a demagnetizing effect on the armature, so firing shots in quick succession demagnetizes the armature and puts it the other side of the tipping point and the camera starts working normally again.

At the beginning, yes, but sooner than later the camera does not work anymore, all photos are dark (exept full closed aperture)

Left alone, the armature will again be re magnetized and will fail again.

The plunger, not the armature (depending of course how you intened to use the name/word)

The issue I believe is that the manufacturer of the magnetic solenoid changed the magnetic structure and upset the balance

No, the manufacturer did not change any structure. The manufacturer moved production from Japan to China. The manufacturer was no longer the manufacturer and most important, didn't even tell Ricoh that production had changed.
The solenoid was from now on manufactured in China with complete new materials but same form and supposed same function.
New materials are:
- magnet
- alloys
- PET body instead of PTFE

It is not a "magnetic solenoid" but a solenoid, in this case with two different type of magnets, a permanent magnet and a field-coil electro-magnet.


Accurately it is a 'single direction push' "plunger solenoid".

Filing the armature can work because it reduces the coupling to the fixed magnet and slows the build up of residual magnetism.

It can work but it damages the surface of the alloy and thus invites corrosion.
Also filing has led to
- same problem occuring again
- opposite problem: overexposure, the plunger remains open sometimes/often/all the time

I'm not sure that degaussing the armature will work long term, at best it could only return to it's natural state which will make the camera work but the problem will eventually re occur, as the core issue of the magnetic structure of the coil assembly hasn't been addressed.

Degaussing is useless, the plunger demagnetises after a relative short time but magnetises very quickly due to its alloy-mix and due to few other important factors:
- stronger magnet/holding force
- weakening of the PET which acts as a bearing for the plunger which "shoots" out with quite some force and thus due to:
- more tolerance between plunger and PET body..... which allows the plunger to be stuck because it can tilt to left and right

By now I had many green solenoids (new and used, filed and treated with other methods) in my hands, inspected them closely mechanically, electrically and "close up" with my precise old fashioned microscope (which does not allow me to take photos, I regret).
I have worked for decades with something quite similar because I repaired and installed "moving coil phonocartidges" (and to a lesser degree "moving magnet" and "moving iron" cartridges) I had to stop with this work due to "aging" eyesight but know enough about it because the pentax solenoid is kind of a rough diamond compared with those very fragile and super presice devices. Or we could say a Pentax solenoid is a tractor when a v.d.Hul or Benz or EMT cartridge is a sportscar.


I also had the chance to compare many Pentax used early SLR and late white Japan made DSLR solenoids
as well as several "replacement China-Solenoids".

If you wish to experiment then try the other solutions and see, but if you just want to fix the camera then I think changing the coil would be the best solution.

Indeed, and particular on the K-70 I would not take the risk of cobbler-solutions when a nice prober one is obvious and not really expensive.
If I take on this work to disassemble my Pentax (which already is quite some work) then to sand/file/grind or worse, to lube is kind of throwing pearls in front of swine.

Those who do it have often just the shortsighted intention to sell their bodies as "100% working" which is ... after all... cheating the buyer, i.e. similar as selling a car which has a damaged cylinderhead-gasket and just cleaning of the foam and changing motor-oil.

[Cee Cee]

Maybe there is a different use of names for that part which is released when the solenoid actuates:
It is the plunger which is released/withdrawn (the name horseshoe because of its shape was used by myself long time ago)
The plunger sits on the armature which itself does not retain any measurable magnetism, it is to far away from the magnet.
The amarture is held by a spring which acts when the plunger is released.
This is important because we need a precise language here. As soon as I realised that the name plunger is the best I started to use this one.
I thing this is sensible and helpful to everybody.
It is only the plunger which magnetises due to the fact that it sits right next to the permanent magnet when the camera is not in use, i.e. 99% of its live.

I agree "armature" is the wrong term here, although I've generally considered the "armarture to be the moving part of a motor assembly,( as in a simple DC motor ) but this is incorrect. By definition the armature is the part of a electrical machine that carries ac current (the armature windings) (Wikipedia) So in fact there is no "armature" at all in this device. "Plunger" is a good term to describe the removable part of the solenoid, perhaps the other part with the coil & magnet is best referred to as the solenoid "Body".

---------- Post added 04-19-20 at 09:23 AM ----------

At the beginning, yes, but sooner than later the camera does not work anymore, all photos are dark (exept full closed aperture)

once again agreed, but studying or considering what happens in this transitional phase when the camera is sometimes working and sometimes not working gives important clues to understanding the nature of the failure.

---------- Post added 04-19-20 at 09:50 AM ----------

No, the manufacturer did not change any structure. The manufacturer moved production from Japan to China. The manufacturer was no longer the manufacturer and most important, didn't even tell Ricoh that production had changed.
The solenoid was from now on manufactured in China with complete new materials but same form and supposed same function.

I didn't word particularly well and clearly I got this wrong, but regardless my main point here was that the magnetic structure changed or the relationship between the magnetic circuit and the electrical circuit changed.

[Cee Cee]

It is not a "magnetic solenoid" but a solenoid, in this case with two different type of magnets, a permanent magnet and a field-coil electro-magnet.
Accurately it is a 'single direction push' "plunger solenoid".

"Magnetic Solenoid" is not my term. It is the name a manufacturer of these types of solenoid uses. I'm not sure about the word push, nothing is pushed here. The plunger is held in position by the fixed magnet, the electrical coil when activated counteracts the fixed magnetic force and allows the plunger to be removed by some other mechanical force. Activating the coil doesn't eject the plunger.

[photogem]

"Magnetic Solenoid" is not my term. It is the name a manufacturer of these types of solenoid uses.

Some manufacturers from China or India don't quite understand the term solenoid, one can read a lot of nonsense-names given to all sorts of
devices. More a problem of language/translation then correctness. There is not such a thing than a magnetic solenoid, but just different types of solenoids. A solenoid works with a magnet

Magnetic is magnetism and clearly defined

I'm not sure about the word push, nothing is pushed here. The plunger is held in position by the fixed magnet, the electrical coil when activated counteracts the fixed magnetic force and allows the plunger to be removed by some other mechanical force. Activating the coil doesn't eject the plunger.

That's true indeed, so it is after all a

plunger-release-solenoid
or a
release-plunger-solenoid

...once again agreed, but studying or considering what happens in this transitional phase when the camera is sometimes working and sometimes not working gives important clues to understanding the nature of the failure.

Which clues would that be?

[malc77]

Hello again,
Thank you again for your replies. Presumably (although I haven't taken my K30 apart yet) the older 'made in Japan aperture block solenoid' has an armature made from low coercivity material such as low carbon (soft) iron, and does not retain its magnetism once the field is removed. Whereas I am presuming the Chinese version does not use a sufficiently low coercivity material armature?
As a clock and watch maker with a workshop, I wonder if it is reasonably possible to make a replacement armature using soft iron etc (eg from an old solenoid or electric bell etc) to replace the Chinese armature? I guess it would be a simple machining job.
Anyway,
Regards,
Malcolm.

[Cee Cee]

Which clues would that be?

generally when working with electronics fault finding & diagnoses, if you have no schematics or specifications then it can be of some advantage to have a fully functional unit to do comparisons & checks. Comparing voltage, current or resistance readings can help identify differences between working and non working units and steer you in the right direction quicker than would otherwise be the case. In the case of the K30 aperture problem when the camera is in this transitional stage and can be made to work by a burst of aperture activation then we have the chance to observe, test or measure in both working and non working states. For example if the problem is due and only due to residual magnetisation build up of the plunger then we should be able to detect the the change in magnetism for both working and non-working states.

Further to this, leaving aside test & measurement, just some clear thinking about what could possibly be happening when the camera can be made to function again by multiple shutter activation could steer us in the right direction. If it's just a matter of fixing the camera then there no issue, the solenoid is faulty, so replace the solenoid and the jobs done. But what is the reason the original solenoid can be made to work with shutter activations ? does the the electromagnetic field generated when the solenoid is activated have a degaussing effect on the plunger.

But pondering the question of why the solenoid was good for 5 years & thousands of activations and now it's no good raises interesting questions. Indeed if the problem is solely due to a build up of residual magnetism then perhaps fully degaussing the plunger may be an effective method to repair the camera, I know the problem will eventually re occur but if it takes another 5 years and thousands of activations then that may be good enough for some folk.
But there may be a simpler solution, I've done some bench testing of the solenoid using a spring gauge to measure the force required to extract the plunger when the coil is activated by a pulse of current. Then reversing the magnetic polarity of the plunger by flipping it over, figuring that the reverse polarity would counteract any residual magnetism the plunger and I detected a clear difference in the required force of 50gf. vs 20gf.
So as previously stated if the problem is entirely due to residual mag. of the plunger then reversing the mag polarity should fix the issue. If not then there is clearly more to this problem.

---------- Post added 04-23-20 at 12:01 PM ----------

Hello again,
Thank you again for your replies. Presumably (although I haven't taken my K30 apart yet) the older 'made in Japan aperture block solenoid' has an armature made from low coercivity material such as low carbon (soft) iron, and does not retain its magnetism once the field is removed. Whereas I am presuming the Chinese version does not use a sufficiently low coercivity material armature?
As a clock and watch maker with a workshop, I wonder if it is reasonably possible to make a replacement armature using soft iron etc (eg from an old solenoid or electric bell etc) to replace the Chinese armature? I guess it would be a simple machining job.
Anyway,
Regards,
Malcolm.

See my comments above, maybe this could work providing the plunger is the only issue , perhaps try flipping the plunger (180`) before going to the trouble making a replacement.