[Not a Number]

Youtu.be

Youtu.be

[Cee Cee]

Read
my post # 653

it is not that easy and many people have done sufficient research.

The sanding method can lead to much worse results, the SANDING METHOD is for sure NOT THE CORRECT SOLUTION.

It is always recommended first to do a prober research (for example here on the forum) to see what was already done before investing a tons of thoughts into something that already has been studied and researched.


Imo all those "new theories" can mislead "newcomers" to this shutter-problem because they then think those last postings are the actual state of affairs when they aren't at all.

really..... I thought this forum was for open debate and exchange of ideas on all things pentax & photographic, I don't think its the job of the forum to provide a technical reference for newcomers. Besides I clearly stated this was " My Theory ... " I can't imagine how wet behind the ears someone would have to be to read this as indisputable fact.

I threw it out there for others to consider and comment based on their experiences, my theory is based on my experiences, In fact I've already changed my mind on certain aspects of the operation of the solenoid. Bench testing the old solenoid today I've realized that the fixed magnet is quite strong and it takes considerable force to break the magnetic bond, such voltages & current required to break the bond and move the armature are just not available in the camera. Instead I would now suggest that the energizing field counters the fixed magnetic field and allows the solenoid to release under spring tension of the connected mechanism. ( BTW it only requires 3.3V which produces a current of appx 110mA to counter the fixed magnet and allows the armature to be released with very little resistance). As time permits I will read up on what others are saying again, I did read some time back, but I didn't have the problem and only mildly interested as I do have a K30.

[reh321]

really..... I thought this forum was for open debate and exchange of ideas on all things pentax & photographic, I don't think its the job of the forum to provide a technical reference for newcomers. Besides I clearly stated this was " My Theory ... " I can't imagine how wet behind the ears someone would have to be to read this as indisputable fact.

I threw it out there for others to consider and comment based on their experiences, my theory is based on my experiences, In fact I've already changed my mind on certain aspects of the operation of the solenoid. Bench testing the old solenoid today I've realized that the fixed magnet is quite strong and it takes considerable force to break the magnetic bond, such voltages & current required to break the bond and move the armature are just not available in the camera. Instead I would now suggest that the energizing field counters the fixed magnetic field and allows the solenoid to release under spring tension of the connected mechanism. ( BTW it only requires 3.3V which produces a current of appx 110mA to counter the fixed magnet and allows the armature to be released with very little resistance). As time permits I will read up on what others are saying again, I did read some time back, but I didn't have the problem and only mildly interested as I do have a K30.

K-30 may be the camera most likely to suffer from this problem. Since I have a K-30, I've been carefully following these threads for at least a year now, and I've been using what seem to be "best practices". Even so, mine finally started developing symptoms in May, when it was about three years old, but because I've been prepared I already had a "battle plan" in place. It is best to do thinking before it becomes a 'crisis'.

[reh321]

Maybe we need a "theory" thread and a "fact" thread. Someone care to start those - and we can close this one?

It might be difficult to decide which classification applies to certain statements

My theory is that there are several different problems being lumped together here.
This thread does have too much free-ranging guesswork for a "sticky" however.
It would be good to come up with a more restricted subset for a "sticky", and then CLOSE it, but the subject is so volatile that moderators may have to be the ones who decide what goes into it.

[Not a Number]

Sanding can work. A few people have reported success. The problem is no one has done any measurements to say exactly how much and where to sand. It's pretty much a one shot deal - you can't restore the removed material. Don't take off enough and you may still experience failure and conclude the sanding didn't work.

[Cee Cee]

K-30 may be the camera most likely to suffer from this problem. Since I have a K-30, I've been carefully following these threads for at least a year now, and I've been using what seem to be "best practices". Even so, mine finally started developing symptoms in May, when it was about three years old, but because I've been prepared I already had a "battle plan" in place. It is best to do thinking before it becomes a 'crisis'.

A wise man to have a plan in place, mine was little more than "I'll deal with it if and when it happens" I must have been having a wise day 5 years ago when I purchased a 5 Year extended warranty which still had a couple of months left when I eventually remembered I had purchased it. How lucky am I, its usually 2 months after the warranty expires that something goes wrong!

---------- Post added 07-13-18 at 03:12 PM ----------

Sanding can work. A few people have reported success. The problem is no one has done any measurements to say exactly how much and where to sand. It's pretty much a one shot deal - you can't restore the removed material. Don't take off enough and you may still experience failure and conclude the sanding didn't work.

as I understand it, the armature (moving part) is a "U" shape with the upward arms of the U extending into the coil and meets the permanent magnet fingers that extend into the coil from the other end, Filing some material from the top of the arms probably a 45` angle to reduce the surface area will reduce the attraction and make the magnetic bond easier to break, but as you say how much material do you remove. If you attempt the repair yourself I feel a better approach would be to fit a small spacer between the inside bottom of the U and the coil, if you can find the right thickness this will have a similar effect and reduce the magnetic strength, this approach leaves the armature part as original, and you can add or remove packing as needed to.
I think the best approach ( short of sending it off for repair) would be to purchase the correct replacement part and change it over if you can.

[photogem]

Clearly we are having a misunderstanding.

Indeed that is possible. Maybe we should shake hands and move on then?

---

Last edited by Racer X 69; 07-14-2018 at 04:13 PM. Reason: Playing nice can be fun.

[Cee Cee]

Indeed that is possible. Maybe we should shake hands and move on then?

Sure, why not?

[photogem]

Sure, why not?

OK then, friends.

[caliscouser]

Anyone who can bring new facts, data or even theories to this topic is welcome and encouraged, whatever your credentials.


However before posting I think it is incumbent on individuals to thoroughly read up on the knowledge base of info already on this topic.
Information compiled by by many people over many years now. Otherwise we end up regurgitating a lot of the same discussions over and over again and cluttering up the threads causing confusion for casual readers.


I believe the current summary is that the only permanent solution to the problem is to replace the green solenoid with the better quality white solenoid.

These can be got from other donor Pentax cameras, or there are some people on eBay selling them,

Other 'solutions' may work for a while but most likely will fail down the road. (This may be sufficient for some people):
- Shaving the horseshoe
- Building up the horseshoe base with solder
- Replacing the green solenoid with another green solenoid (as Pentax repair does)
- Switching to AA batteries
- Doing a rain-dance around a rare orchid from the Panamanian rainforest at full moon....etc...etc

[Not a Number]

This thread has gone off-topic. It should just be about diagnosing the dark frame problem - not all the speculation on cause and cure.

[Cee Cee]

OK, I'm done with trading bards we could keep at it forever, but it's tiresome, taking up too much time and distracting from the point of the thread. I will not be responding to any post questioning my integrity.

except to say the comment on the TV degaussing wand was a joke, as indicated by placing it inside brackets with a LOL emoji. -which seems to be missing from your re quote.

ask your self how many people on this forum have a degaussing wand in their bottom draw. Ask your self how many people on this forum would know what it was or would even be able to recognize what it was, then ask how many of those people are reading this thread. I think anyone with the knowledge to know about CRT degaussing wands also has the knowledge not to try to degauss their K30. But I do take your point

PLEASE DO NOT ATTEMPT TO DEGAUSS YOUR K30 there is a fair probability of inducing high circulating currents into the circuitry and frying the sensitive electronics
Back to the topic, it seems to me that we know the cure ( replacement solenoid) but I don't know that anyone has come up with a definitive reason for why the problem is occurring. ( correct me if I'm wrong) With only a sample size of 1 ( my K30) I can only speculate but one has to ask....

What has changed so that after 4.5 years of use and many shutter actuations the camera fails -

has the solenoid gone faulty ? my original solenoid ( which really was returned to me) seems in pristine condition, no corrosion no signs of heat stress or mechanical stress, no fouling of the armature, if it wasn't for the soldering on the terminals I think you could easily pass this off a new spare part. It measure 28.5 ohms, if anyone can confirm that's a normal resistance reading for this coil then I would say that the solenoid has't failed at all.

So if the solenoid hasn't changed or failed then why did the camera stop working. I can only see two remaining possibilities ( at this stage )

1. something in the electronics has changed or deteriorated until reaching a tipping point and the camera begins to malfunction. - I find this unlikely as (without getting to technical) the type of problems that could cause this don't fix themselves and it just doesn't make sense that fiiring off a few shutter acuations would restore the electronics to working condition. Although poor solder connections can reconnect if some current is forced through then. The main reason I reject this is that replacement with a lower impedance coil ( correct me if I'm wrong) would mean higher current which would only exacerbate the failing electronics an the camera would soon begin to fail again.


2. something in the mechanics that is connected to solenoid has changed - this presents a range of possibilities.

without knowing the specifics of what the mechanism is or how it works I suppose its only speculation on my part, but mechanical systems start to wear the moment you start using them, its only logical that over time bearing points will wear, spring tensions may change, lubrication may dry out. Its also logical that the parts of the mechanism will have manufacturing tolerances - no mater how small so no two assemblies will be exactly the same, well they could be close enough to be considered the same but some may be less the same than others - see where this is heading ?


Now back to the solenoid, In my tinkering with my original solenoid I tried increased current to see if the armature would move with a current pulse and concluded no - it was just negating the magnetic field of the permanent magnet to release the magnetic bond, however on a couple of occasions while holding the solenoid in my hand I felt it "kick" a little when the current was applied. I'm only now realizing the significance of this. While its true the armature retains no residual magnetism, when its in its resting state in contact with the permanent magnet its is magnetized so when the pulse is first applied there will be a force acting on the armature pushing in the direction of separation until it separates then there's no more magnetism in armature and the mechanism continues to draw the armature out.

I think that by changing the solenoid to the lower resistance and hence more current flow and greater magnetic force the strength of this starting "kick" jolts a slightly sluggish mechanism into action.


I would suggest that this lower resistance solenoid is what they should have been using all along, after all it was tried tested in previous models (one again correct me if I'm wrong). So why did they change it ? - once again just my speculation, I would suggest that probably to conserve battery power! a coil of double the resistance value only draws half the current, which is nothing to be sneezed at it trying to reduce battery consumption to a minimum. I don't know that one could reasonably predict this outcome a few years down the track.


once again - this is mostly speculation.

[Cee Cee]

- Doing a rain-dance around a rare orchid from the Panamanian rainforest at full moon....etc...etc

clockwise or anticlockwise

[Cee Cee]

The result was, that precious transformers made out of alnico magnets lost their magnetic field.

sorry this is new to me, transformers usually have an iron core which responds to magnetism, and a signal applied to the primary is induced into the secondary due to magnetic fields expanding & collapsing, I've not come across transformers using a steady state magnet, but never too old to learn, I can only imagine that this would be some magnetic bias to overcome or reduce distortion ?

[photogem]

OK, I'm done with trading bards we could keep at it forever, but it's tiresome, taking up too much time and distracting from the point of the thread. I will not be responding to any post questioning my integrity.

Except to say the comment on the TV degaussing wand was a joke, as indicated by placing it inside brackets with a LOL emoji. -which seems to be missing from your re quote.
- Ask your self how many people on this forum have a degaussing wand in their bottom draw.
- Ask your self how many people on this forum would know what it was or would even be able to recognize what it was
- Then ask how many of those people are reading this thread.
I think anyone with the knowledge to know about CRT degaussing wands also has the knowledge not to try to degauss their K30.

Actually: Degaussing or demagnetising has come up in this forum and in others, such as
for example here
or here:
K-S2 Aperture block failure repaired: Pentax SLR Talk Forum: Digital Photography Review
and:
At least M mode works - PentaxForums.com
Fix for the aperture motor failure? - Page 3 - PentaxForums.com

It was suggested as well here just a few days ago but the TO edited his posting eliminating all what he wrote about demagnetising.... possibly he felt embarrased (just guessing)

None of those were meant that as a joke nor was yours really.... c'mon...

By the way: LOL emoji's are used for many reasons and don't indicate a joke. One use of LOL is to emphasise: What a great idea! Fanastic idea!

Back to the topic, it seems to me that we know the cure ( replacement solenoid) but I don't know that anyone has come up with a definitive reason for why the problem is occurring. ( correct me if I'm wrong) With only a sample size of 1 ( my K30) I can only speculate but one has to ask....

You see, meanwhile you could have followed up this most sensible advice by caliscauser instead of forcing others to do your homework:
Of course we know definite reasons:

- one for sure is the stronger holding force of the green solenoid.
- another: PTFE versus PET, the horseshoe glides inside this body. PTFE (Teflon) is a far superior material.
I have given you the link to those reasons but instead of stying you do the very opposite.


This leads to this silly situation of the baker being asked by the breadroll how to bake bread

But the point I really do agree with yours is:

OK, I'm done with trading bards.....

and fully agree with caliscauser's advice, which brings it better to the point than I was able to write it:

Anyone who can bring new facts, data or even theories to this topic is welcome and encouraged, whatever your credentials.

However before posting I think it is incumbent on individuals to thoroughly read up on the knowledge base of info already on this topic.
Information compiled by by many people over many years now. Otherwise we end up regurgitating a lot of the same discussions over and over again and cluttering up the threads causing confusion for casual readers.

because, as you said:

.... it's tiresome

but tiresome because we constantly have to correct those who did not follow up this advise but think they invented anew the wheel
and thus kind of force us to put things straight by telling them that nor a triangle nor a pentagon is a wheel!

So yes, it is tiresome! It is tiresome to do your homework!