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05-28-2019, 01:00 AM   #16
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Present! I substituted the solenoid on my k-30 with the white one and after some months the black picture problems arised again.
Actually I can only take pictures using the AA battery adapter, with the li-on original battery only in continuous drive mode and only some
pictures are correctly exposed.

05-28-2019, 05:23 AM   #17
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QuoteOriginally posted by pvanni Quote
Present! I substituted the solenoid on my k-30 with the white one and after some months the black picture problems arised again.
Actually I can only take pictures using the AA battery adapter, with the li-on original battery only in continuous drive mode and only some
pictures are correctly exposed.
Wow that's very surprising. I would be very interested to know if replacing the solenoid in this case gets it operating correctly again. This could help to identify the actual cause of the problem...
05-28-2019, 09:24 AM   #18
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now you can try the filing method too.
I've had luck with the filing method on 3 cameras (out of 3).
05-28-2019, 10:11 AM   #19
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QuoteOriginally posted by Ajax156 Quote
Wow that's very surprising. I would be very interested to know if replacing the solenoid in this case gets it operating correctly again. This could help to identify the actual cause of the problem...
In the mean time I bought a KP, I dont want to spend another 50$ to substitute the solenoid another time, the K-30 it's uset by my wife, when it stops to work probabily I buy an used k5 or try the filing system

05-28-2019, 01:08 PM   #20
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QuoteOriginally posted by Ajax156 Quote
I wasn't aware of any reports of people replacing the solenoid and everything working, with a repeat of the failure some time later? Do you have any links?
Once I purchased a KP, my K-30 became a perfectly usable backup camera; it is packed in a bag with FA 28-105 and Sigma APO 70-300 lenses - each has aperture ring so it works fine with "green button metering".
05-31-2019, 10:28 AM   #21
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i have a different quesdtion.

has anyone looked at demagnetizing the parts? common process on old tape machines,
06-14-2019, 06:33 AM   #22
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QuoteOriginally posted by Lowell Goudge Quote
i have a different quesdtion.

has anyone looked at demagnetizing the parts? common process on old tape machines,
What do you want to demagnetize?
Old tape machines would not magnetize necessarily: Only 3-head tape-machines needed demagnetizing.
2-head tape-machines demagnetize everytime one recorded because the bias automatically demagnetized the head!
With a 3-head tape-machine the playback- and recording heads are separate and thus the playback-head does not receive and bias i.e. demagnetizing!
Particular older tape-machines had softer material on their heads which could magnetize easier and needed therefor attention.

A tape-machine head is made out of ferromagnetic material (as opposed to paramagnetic materials such as air, aluminium, platinium etc. and diamagnetic materials such as water, copper and very strongly pyrolytic carbon). There are better materials and not so good ones. Permalloy, Sendust, Ferrite etc. But all are ferromagnetic and thus will strengthen a magnetic field (either a permanent magnet or an electromagnet!). It has an effect when it is in contact with the magnet and can even saturate. When it is away from the magnet it the left over magnetism goes quickly away, but this is of zero interest to us because with this solenoid the ferromagnetic plunger is 99,999% of its live in contact with the magnetic field of the permanent magnet and ... receives another magnetic field from the electromagnetic coils which counteracts that one of the of the permanent magnet.

So it is of zero interest if the plunger would have left-over magnetism, of course it has but only for a short time. The interest is how it behaves because it is in touch with a magnetic field!

But when it is away for the short time the leftover short magnetism is of zero interest either because the solenoid then works.

So you could only demagnetize the permanent magnet and then the solenoid wouldn't work anymore.

The problem of the solenoid is linked with several factors and Ricoh has not yet solved it completly but they made it better.

And yet some K-70 solenoids do fail.

---------- Post added 06-14-19 at 07:22 AM ----------

QuoteOriginally posted by pvanni Quote
Present! I substituted the solenoid on my k-30 with the white one and after some months the black picture problems arised again.
Actually I can only take pictures using the AA battery adapter, with the li-on original battery only in continuous drive mode and only some
pictures are correctly exposed.
Very rare that this happens. There are few white solenoids on the market which actually have a stronger holding force. I have a few here for my records.
They look identical. And if the person who sold them to you got some of those, too bad.

Also some use the white solenoids from analog bodies such as the MZ50 or MZ6. Those solenoids are slightly different and some even have opposite polarisation!
I have explained this in my manual.

The problem can also arise, if one tried too long with the defunct green solenoid and particular if one tried "to losen it up" with series shooting!
Or with AA batteries because one runs the complete diaphragm-control-unit, a quite complicated and actually clever and wonderful designed part...
well.... with a faulty unit. What to expect?
06-14-2019, 09:59 AM   #23
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QuoteOriginally posted by photogem Quote
What do you want to demagnetize?
Old tape machines would not magnetize necessarily: Only 3-head tape-machines needed demagnetizing.
2-head tape-machines demagnetize everytime one recorded because the bias automatically demagnetized the head!
With a 3-head tape-machine the playback- and recording heads are separate and thus the playback-head does not receive and bias i.e. demagnetizing!
Particular older tape-machines had softer material on their heads which could magnetize easier and needed therefor attention.

A tape-machine head is made out of ferromagnetic material (as opposed to paramagnetic materials such as air, aluminium, platinium etc. and diamagnetic materials such as water, copper and very strongly pyrolytic carbon). There are better materials and not so good ones. Permalloy, Sendust, Ferrite etc. But all are ferromagnetic and thus will strengthen a magnetic field (either a permanent magnet or an electromagnet!). It has an effect when it is in contact with the magnet and can even saturate. When it is away from the magnet it the left over magnetism goes quickly away, but this is of zero interest to us because with this solenoid the ferromagnetic plunger is 99,999% of its live in contact with the magnetic field of the permanent magnet and ... receives another magnetic field from the electromagnetic coils which counteracts that one of the of the permanent magnet.

So it is of zero interest if the plunger would have left-over magnetism, of course it has but only for a short time. The interest is how it behaves because it is in touch with a magnetic field!

But when it is away for the short time the leftover short magnetism is of zero interest either because the solenoid then works.

So you could only demagnetize the permanent magnet and then the solenoid wouldn't work anymore.

The problem of the solenoid is linked with several factors and Ricoh has not yet solved it completly but they made it better.

And yet some K-70 solenoids do fail.
the reason i asked is because A), i am quite familiar with the magnetization issue on tape decks having owned many since the early 1970's and have a degaussing tool? and b) i have seen many electro mechanical devices become slightly magnetized (especially direct current solenoids and their ferrous parts) and develop pull in problems because the residual magnetism while small comes in contact with other ferrous parts and the residual magnetism is sufficient to prevent the coil from pulling the core away from its rest. since the force is inversely proportional to the air gap in the curcuit, when far away there is very little force and residual magnetism is sometimes enough to cause things to fail.

the solution i have seen which includes sanding down the tips of part of the core, might just be related to hard contact and minor perment residual magnetim, which leads to another question. has any on etried to coat the end of the core with nail polish or enamel, to prevent hard metal to metal magnetic contact

06-14-2019, 11:17 AM   #24
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QuoteOriginally posted by Lowell Goudge Quote
the reason i asked is because A), i am quite familiar with the magnetization issue on tape decks having owned many since the early 1970's and have a degaussing tool? and b) i have seen many electro mechanical devices become slightly magnetized (especially direct current solenoids and their ferrous parts) and develop pull in problems because the residual magnetism while small comes in contact with other ferrous parts and the residual magnetism is sufficient to prevent the coil from pulling the core away from its rest. since the force is inversely proportional to the air gap in the curcuit, when far away there is very little force and residual magnetism is sometimes enough to cause things to fail.

the solution i have seen which includes sanding down the tips of part of the core, might just be related to hard contact and minor perment residual magnetim, which leads to another question. has any on etried to coat the end of the core with nail polish or enamel, to prevent hard metal to metal magnetic contact
Hmmm... yes, there is always the danger of residual magnetism. But demagnetising never helped, until 2 month ago I had a professional demagnetizer here. I have worked professionally with analog recording for decades and I sold high-end analog recording equipment all over the world, partly modified to modern needs, mainly tube/valve electronics. Almost all of them are still in use and some in recording-studios in USA and Australia.


The idea with nail varnish was one I had thought about but I realized that the pull of the solenoid against the metal on the other will destroys the laquer and make it crumble in form of fine dirt and dust inside the camera, something you urgently want to avoid, not a good idea after all.


Also there is this question of speed: with the proper white solenoid the body fires very fast, you can actually here the difference.
Worse with a sanded/filed solenoid. I have once measured it, it was inferior.

Because students often have no money some I know refered to the sanding method. They did it very precise but in most cases failure came back, in some cases

final death of the camera as more got damaged.

It is a very simple question: Why ... as one undertakes this work and opens the camera... not do it the right correct way?
Kind of mean towards oneself to go the cheap (and silly) way. Only if it is urgent and really a question of very little money.

Last edited by photogem; 06-14-2019 at 09:38 PM.
08-21-2019, 06:54 AM   #25
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Hello folks!

Helping my brother-in-law here. Last December he realized that his camera , a K-30, was acting up. He asked me to look into it. It seemed like the aperture block problem, the aperture wouldn't open correctly, it was particularly easy to see using an F1.4 lens and trying to stop it down.

He decided to pay for repairs, using services provided by PentaxCameraRepairs which had been recommended by several people. As we are in Canada, shipping back and forth was complicated but relatives traveling to the US helped us.

The camera worked fine for a good while, now it started acting up again, but the symptoms are weird. At first it appears to be the same type of problem, but here's what I observe.

1-Generally dark frames
2-Burst mode or repetitive step-down doesn't do anything
3-Using a small aperture (F9, F11, etc) underexposes but does create a usable image, while using fast apertures (F5.6 or wider) yields black images (this is the weird part)
4-Using manual mode, or bulb, lets me take pictures, but images are underexposed vs what they ought to be
5-Once, after using bulb mode, the camera operated fine for a short while
6-In P mode, the exposure meter seems to think things are brighter than they are actually

I've tested several lenses of course. The battery is somewhat old but I have no backup to test for the moment.

Does anyone have an opinion regarding this? It doesn't seem to be exactly the aperture block problem.

Thanks!
08-21-2019, 08:48 AM   #26
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QuoteOriginally posted by bdery Quote
Does anyone have an opinion regarding this? It doesn't seem to be exactly the aperture block problem.
Your description sounds about right for aperture block failure. What happens is the actuator moves in an uncontrolled manner with the error being towards excessive travel (narrower apertures) or travel where none is indicated. As a result, there is less error with narrower intended apertures and gross error at wide apertures. Symptoms are often intermittent and worse after a period of inactivity and may improve with exercise.

A good demonstration of what is happening might be had by mounting a lens where the diaphragm action is clearly visible from the front and doing a series in full stop increments from maximum to minimum apertures while observing the action from the front (M mode, 1s shutter works well).


Steve
08-21-2019, 09:48 AM   #27
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The aperture problem you simply test with

- Live-View: often the camera works
- TAV or AV and aperture f22: thus no need for the solenoid to act: With proper exposure-time you should have a photo which is fine
- TAV or AV and aperture f5.6 towards wide open: Of course complete underexposure: The solenoid should act but is stuck
- but: M-Mode should work fine, the solenoid isn't used at all! If M-Mode worked before and now doesn't, something else is hurt.
08-21-2019, 11:22 AM   #28
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QuoteOriginally posted by photogem Quote
- Live-View: often the camera works
- TAV or AV and aperture f22: thus no need for the solenoid to act: With proper exposure-time you should have a photo which is fine
- TAV or AV and aperture f5.6 towards wide open: Of course complete underexposure: The solenoid should act but is stuck
- but: M-Mode should work fine, the solenoid isn't used at all! If M-Mode worked before and now doesn't, something else is hurt.
You had me scratching my head on the first three points, but without having actually observed the mechanism in operation , one can't say for sure what the solenoid's role is. The last point, however, makes little sense unless there is confusion between M-mode and using the aperture ring. If the body is set to control aperture, it is the aperture control block that controls the action. Leaving the solenoid out of the discussion (sort of a red herring when doing diagnosis), the expected actions run like this:
  • Body set to control to maximum aperture -- coupling on body remains stationary*
  • Body set to control to other than maximum aperture -- coupling on body moves appropriate to the set aperture
  • Lens mounted does not support aperture control by body (no "A" contact detected, F-- displayed on LCD) -- coupling on body moves full range in M, X, and B modes and not at all for automated exposure modes.
With classic K-30/K-50 aperture block failure, the first two points are compromised towards underexposure,** while the third usually (always?) works for M, X, and B modes. This happens in all automated exposure modes as well as M, X, and B and applies to both the optical viewfinder and live view (lens stop-down is required for both).


Steve

* This has to do with how the "A" contact encoding works. Wide open, regardless of f-number, is always no-action.

** Less effect is generally seen at narrower apertures.

Last edited by stevebrot; 08-21-2019 at 11:52 AM. Reason: clarity and completeness
08-21-2019, 01:23 PM   #29
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QuoteOriginally posted by Ajax156 Quote
I wasn't aware of any reports of people replacing the solenoid and everything working, with a repeat of the failure some time later? Do you have any links?
If you replace the solenoid with the white (made in Japan) solenoid, then the camera will be repaired. Replacing the green solenoid with another green solenoid will mean that the replacement green solenoid may fail too.
08-22-2019, 12:07 AM   #30
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QuoteOriginally posted by labidas Quote
for an unknown amount of time
I can ensure you - at lest the swapping out the solenoid is a permanent fix. In my K500, when I changed out the solenoid, I used it a bit afterwards and then when I shortly after that got a k3II, I have neglected it - just gathering dust for ~2 years. Recently I started it up again - works just perfect. I cannot vouch for the filing method, as the filed down green solenoid went back into the K100D flash compartment (where it still works) - but that is not a corect evaluation.

Hope this helps
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