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02-22-2017, 08:51 AM   #16
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QuoteOriginally posted by ekip Quote
It has that gold/brown coloured ribbon cable that you get in electronics. Flexible flat cable? I don't know how you tap into or solder these things.
Sorry, I now understand that the part shown on the left of the picture is after you removed the ribbon and soldered in the wires. It's not showing the part as directly salvaged from the CD Drive, which I guess would have shown the ribbon instead of two wires we see on the picture. ...

02-22-2017, 09:32 AM - 1 Like   #17
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QuoteOriginally posted by Not a Number Quote
Or the power circuit could to the coil could drop so not enough current is applied to overcome the permanent magnet. Using AA batteries have less voltage than the Li-ion battery but they may have a lower internal resistance and have a higher current. You'd have to measure the voltage and current between say a K100D, a failing K-50/30 and a functioning K-50/30 to draw any conclusions.

Or the coil itself can be failing. If the insulating varnish on the wire is deteriorating the coils could be partially shorting out resulting in a weaker field (less windings). In order for the horseshoe to become more attractive its magnetic properties would have to change. It has been reported that on failing units it does not attract filings.

Or the mechanical mechanism that pulls the horseshoe out could be failing. You'd have to measure the timing and the force on this part of the aperture block to draw any conclusions.
1) Power circuit - doesn't explain anything - with a changed solenoid (from K100D) everything works perfectly. If in the beginning it worked well in tandem with the green coil, then the obviously most likely something has changed in the green solenoid - or at least it is the faulty part.
2) You didn't understand my point with magnetization - I am talking about INDUCED MAGNETIC MOMENT which becomes ZERRO when you remove an external magnetic field. I will give you an example - Let's take a regular bolt (regular steel) and let's take a bolt made out of stainless steel. Now take a permanent magnet - which bolt will stick to the magnet with higher force? Bingo - the regular one. So the cores of transformers are not made out of stainless steel but instead iron - because you can magnetize it to a higher degree. My Idea is that the inner structure (on microscopic scale) of the horse-shoe material (metal) somehow changes with time and in presence of external magnetic field (the permanent magnet which is attached at the top). I don't know - lets call it a magnetic "creep" - I can't think of better comparison. Like with mechanical creep - there are materials which don't creep and there are materials with very strong creep - like all superplastic materials. So back to magnets - the magnetization of the core (horse-shoe) increases with time thus making the attractive force also stronger - does it now makes sense? And when you remove the horseshoe from the field of the permanent magnet then its total magnetic moment again collapses to zero. The horse-shoe part doesn't need to become a weak permanent magnet itself for the attractive force to increase!
3) There is no mechanism that pulls the horse-shoe out - it is a PUSH-type solenoid. Electromagnet part pushes the horse-shoe out and the permanent magnet sucks it back in. I suppose that the current pulse on the solenoid is so short that it cannot manage to overcome extra force - this is why when you do a burst set - it starts to work for a while...you apply subsequent "demagnetization" thus weakening the attractive force and at some point it starts to work properly again.
02-22-2017, 09:52 AM   #18
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QuoteOriginally posted by madphys Quote
3) There is no mechanism that pulls the horse-shoe out - it is a PUSH-type solenoid. Electromagnet part pushes the horse-shoe out and the permanent magnet sucks it back in. I suppose that the current pulse on the solenoid is so short that it cannot manage to overcome extra force - this is why when you do a burst set - it starts to work for a while...you apply subsequent "demagnetization" thus weakening the attractive force and at some point it starts to work properly again.

There is a pin on an arm which connects through the horse shoe. Is this sprung to try and keep the horse shoe closed or open?
02-22-2017, 10:06 AM   #19
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QuoteOriginally posted by ekip Quote
Is this sprung to try and keep the horse shoe closed or open?
When you remove the solenoid the pin stays in place - so it for sure doesn't want to "pull" the horse-shoe out + what would be the point of using PUSH-type solenoid?!
But to be fair - I didn't check how strongly it is sprung the other way - it should be (from logic). I didn't want to f something up so I didn't touch anything else - my operation was IN and Out...that is why I don't have more and better quality pics.

02-22-2017, 01:26 PM   #20
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QuoteOriginally posted by madphys Quote
When you remove the solenoid the pin stays in place - so it for sure doesn't want to "pull" the horse-shoe out + what would be the point of using PUSH-type solenoid?!
But to be fair - I didn't check how strongly it is sprung the other way - it should be (from logic). I didn't want to f something up so I didn't touch anything else - my operation was IN and Out...that is why I don't have more and better quality pics.
The design of cd trays is to hold the horse shoe in constant tension pulling it outwards with a spring with just less than the holding force of the permanent magnet and therefore only a small amount of current is needed to separate the magnet and open the cd drawer. Closing the drawer makes you push the magnet close enough to make contact with the horseshoe and overcome the spring once again.

Given that there's no obvious way the camera resets the solenoid it must be that the electromagnet has to overcome the permanent magnet and also the spring action of the aperture brake and when current is stopped the pin (attached to aperture brake) sends back the horseshoe until it clicks against the magnet once again. This method must need a lot more juice.
02-23-2017, 06:45 PM   #21
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QuoteOriginally posted by madphys Quote
My Idea is that the inner structure (on microscopic scale) of the horse-shoe material (metal) somehow changes with time and in presence of external magnetic field (the permanent magnet which is attached at the top). I don't know - lets call it a magnetic "creep" - I can't think of better comparison.
To speak to that a little, here is an experiment I did. Anecdotal and sample size of one, so keep that in mind:
- I had 2 green solenoids. One good, one bad (inside a K-30)
- I took the good fork only and put into the bad solenoid. It did not fix the problem.
- I replaced the entire bad solenoid with a good one and it worked fine. (and has been for months)

This seems to point to the non-fork part of the solenoid as the root cause, so some speculation might be:
- something to do with the permanent magnet.
- insulation breakdown over time of the copper windings causing shorts.
- poor quality impure copper causing some kind of problem over time. Microscopic fracturing ??
- something else.

This stuff is way beyond my expertise level so I hope others can add more insight.
02-23-2017, 08:09 PM   #22
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Too bad madphys didn't install the "bad" green solenoid unmodified into the K100D. That might have told us something if it worked fine without modification. Or if he did I missed it
02-24-2017, 12:36 AM   #23
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QuoteOriginally posted by caliscouser Quote
- something to do with the permanent magnet.
Nice to hear you did some experiments! Everyone should do a bit so we gather more information - I sure will report what happens to my unfortunately MODIFIED Green solenoid inside K100. There have been reports that also modified solenoids go bad again after some time. As I don't use the K100D it just sits on a shelf - it will be a time-dependent process. The only drawback is that I can't stick Li-Ion inside K100D.

And yes - I think the permanent magnet can be also a very likely cause. Often people, myself included, report that the Black frame appears after they haven't used the camera for a while - so I can't imagine what so crucial can happen to the copper coil when it just sits around...Doesn't quite add up. Only one thing is for sure - the green solenoid is the faulty part.

02-24-2017, 09:47 AM   #24
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Permanent magnets don't get stronger with age. If anything they weaken. That's why measuring the separation force needed on a "working" green solenoid vs a "failing" green one vs a white solenoid would be useful. The green ones probably use a stronger magnet to begin with. For all we know green vs white is a coding for the strength of the magnet. Measuring the amount of force that the aperture mechanism that withdraws the plunger would be useful too.

Yes, the green solenoids appear to be failing. But the loss of function could be a combination of failures which is maybe why the entire block gets replaced. If you put an unmodified "failing" green solenoid into a working system (swap out the "good" solenoid with a "bad" one) and the system continuing to function normally would indicate a combination of failures.

On the DIY thread there are links to photos on a German forum that shows a metal plate with the solenoid, gear box (with distinctive cross shaped part) and motor. Given other Pentax parts diagrams which show the so-called shutter block to be a plate with a gear box or so-called gear block - a plate with a gear box on it I believe what the German forum is showing is the infamous aperture block.

Time may tell its tale. We will just have to see what the longevity of the DIY filing/sanding repair turns out to be.

Perhaps somebody who has had their camera repaired by an authorized center would open it up and see if the green solenoid is still being used or if it was replaced with a different make/model. This would void the warranty but if it is out of warranty.....
02-24-2017, 10:30 AM   #25
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QuoteOriginally posted by Not a Number Quote
Permanent magnets don't get stronger with age
I didn't say that the permanent magnet got stronger - I said that the induced magnetic moment of the core (horse-shoe) could change with time (which would also impact the force of attraction). Like in my previous example - going from let's say stainless steel to regular steel (it's a major exaggeration but in principle).

Suppose the good green solenoid has a weaker magnet and a "stronger" coil, while the bad green solenoid has a stronger magnet and a "weaker" coil (all components are subject to distribution) - and the horse-shoe material is the same (from the same batch). Both work at first - but then one starts acting up - what has changed? I can only point fingers to properties of horse-shoe. Those who are lucky with weaker magnet+stronger coil don't experience problems. But when you just swap the horseshoe from green to green - nothing changes - same batch, same material, same properties.

My hypothesis could be quite easily checked (Now I regret that I didn't do it myself) - a core from an old "white" solenoid should be put inside the failing green one.
03-03-2017, 02:39 AM - 2 Likes   #26
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Pentax K-30 // K-50 // K-500 // K-S1 // K-S2 shutter solenoid-problem investigation

Meanwhile I have 6 Japanese made solenoids here (including a faulty K50) on my workbench to make sure I don't come to conclusions just by diagnosing just one single unit.

I took a Pentax K50 apart and, checked it with a lens, it was obvious, the solenoid didn't function.

I then unscrewed the green solenoid and then unsoldered the two wires (which I prefered to unsoldering the wires from the printed circuit board)

Then resoldered those wires to the japanese made (origin Pentax K100D), calm hands and fingers and secure handling of a fine-tip soldering iron required here! I have a dentists magnifying lamp which helps.

I checked the K50 with the same lens: Wonderful, it works perfectly fine. Reassembled the K50... Great, my first DSLR taken apart and repaired.
All works like it should.

Now I investigated the difference of those solenoids:

- Coil resistance identical!
- magnetic force seems to be similar!

Then I moved the "plunger" (horseshoe) of both solenoids. I checked play through tilting them slightly when they were hold in place by the magnet and found out that the plunger (horseshoe) of the green solenoid has some play! Compared to the Japanese solenoid when unlocking the plunger from the magnet via tilting it, it took force to get it out of this hollow body with the coils. I did not find the magnetic force to be different but there was a difference getting the plunger off, which I think is linked with the play. This gave me an idea.

The solenoid moves the lever connected to a spring, you can see how it functions very well on this video:

This lever brings a force from the right side to the plunger (horseshoe)! This force tilts the plunger!
If there is more play, the metal plunger might "scratch" the plastic material it move in and out from and leave traces or changes it structure.

Anyway, I took photos of the two solenoids next to each other.

The first photo shows the two solenoids with the plunger in its place (held by the magnetic force)
The second photo shows the plunger tilted. For this I inserted a tiny piece of wood (from a match) inside the right hollow part.
Here one can see very well how much more play the plunger has, the gap between the sidewalls of the hollow part is much larger.

I am positive that this causes the problem.

Also clearly obvious:

The hole of the chinese plunger is uneven, it looks almost like the surface detoriated

The surface of the Japanese plunger is way smoother!

I believe that sanding off the corners of the plunger does work (at least for a time) but it might have an effect over a longer period on the
lever (force of the spring etc.)
I don't believe soldering solder onto the plunger is a good solution! This might work but the plunger and thus the lever are now in a different position which could cause further problems!
Attached Images
View Picture EXIF
PENTAX K-3  Photo 
View Picture EXIF
PENTAX K-3  Photo 

Last edited by photogem; 03-03-2017 at 02:55 AM.
03-03-2017, 09:18 AM   #27
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Excellent! Thank you for taking the time to look at possible causes. The videos are very helpful to.

QuoteOriginally posted by photogem Quote
Meanwhile I have 6 Japanese made solenoids here (including a faulty K50) on my workbench to make sure I don't come to conclusions just by diagnosing just one single unit.
So you have one with a white solenoid that is malfunctioning? How does that compare to the others?
QuoteOriginally posted by photogem Quote
The first photo shows the two solenoids with the plunger in its place (held by the magnetic force)
The second photo shows the plunger tilted. For this I inserted a tiny piece of wood (from a match) inside the right hollow part.
Here one can see very well how much more play the plunger has, the gap between the sidewalls of the hollow part is much larger.

I am positive that this causes the problem.

Also clearly obvious:

The hole of the chinese plunger is uneven, it looks almost like the surface detoriated

The surface of the Japanese plunger is way smoother!
As I mentioned before (probably in the other repair solution thread) solenoid malfunction can stem from misalignment of the plunger. This leads to wear on both the plunger and sleeve as well. Sanding the plunger is only temporary solution as this does not address the damage in the sleeve. And adding more play to the plunger will lead to more wear. And the alignment issue may not be addressed at all.

Are the parts marked with the country they were made? I've identified a company in Taiwan that makes the solenoids with white or black plastic.

Edit: What position does the green solenoid fail in? I was under the impression it gets stuck in the neutral (power off) position with the horseshoe retracted touching the top plate (magnet end).

Last edited by Not a Number; 03-03-2017 at 12:08 PM.
03-03-2017, 02:51 PM   #28
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QuoteOriginally posted by Not a Number Quote
So you have one with a white solenoid that is malfunctioning? How does that compare to the others?
Where did I say that I have a white solenoid that is malfunctioning?

All white solenoids I own work well.

QuoteOriginally posted by Not a Number Quote
As I mentioned before (probably in the other repair solution thread) solenoid malfunction can stem from misalignment of the plunger. This leads to wear on both the plunger and sleeve as well. Sanding the plunger is only temporary solution as this does not address the damage in the sleeve. And adding more play to the plunger will lead to more wear. And the alignment issue may not be addressed at all.
QuoteOriginally posted by Not a Number Quote
Are the parts marked with the country they were made? I've identified a company in Taiwan that makes the solenoids with white or black plastic.
Yes, there are two possible marks:

Green for China and white for Japan.....

Of course you are right, the only hint we have was made by "athlonus" writing this and I took this for granted.
We have only the word of somebody who worked in the repair business for a long time and gave us all those clues which I followed up and which to are proven to be true:
QuoteOriginally posted by athlonus Quote
Take my word who is in the repair business for a long time and worked with Japanese teams designing cameras.

The culprit is the new CHINESE MADE plunger solenoid. It is out of voltage specs and it MUST be replaced with a quality Japanese product such as Panasonic, Alps or Mitsumi made
My feeling is that this man knows what he is talking about.

But my research brought me to

Zhuhai Fnt Electronic Co. Ltd
3F, Building B, Huasheng Industrial, Village, Wanzi, Zhuhai, Guangdong, China (519030)

http://www.globalsources.com/si/AS/Zhuhai-Fnt/6008813998286/pdtl/High-speed-...1034599128.htm

So you see, it is Chinese indeed.

This one shown has an impendance of 2 ohms, but of course they manufacture it to your very personal demand.
You just have to order several thousands of 'em!

The Japanese Solenoid uses something similar or PTFE as material and the surface of the metal parts is much smoother.
Less friction for the horseshoe/plunger when sliding in the square hollow part.

Also it can be clearly seen, inside the hole of the plunger itself there is corrosion!
The Japanese made solenoid has about 26.500 actuations use! Zero signs of corrosion.


QuoteOriginally posted by Not a Number Quote
What position does the green solenoid fail in? I was under the impression it gets stuck in the neutral (power off) position with the horseshoe retracted touching the top plate (magnet end).
Yes, this is exactly the position it gets stuck. I cannot remember saying anything else.

Last edited by photogem; 03-04-2017 at 03:30 PM.
03-18-2017, 10:23 AM - 1 Like   #29
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QuoteOriginally posted by photogem Quote

was a difference getting the plunger off, which I think is linked with the play. This gave me an idea.

The solenoid moves the lever connected to a spring, you can see how it functions very well on this video:
Pentax k30 true works I - YouTube
Hi everybody, this is my video.
I was a little deal with the problem Aperture k-30/k-50 since August 2016.
I've corrected some models k-30/k-50.

Now I disassembled Pentax K30 about 1 month and I'm going to buy a new component.
05-27-2017, 11:55 AM   #30
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The *istDS has two solenoids, correct? Am I understanding this correctly, that the flash solenoid in the *istDS could be used as the replacement part for the k-50? If so, that would make me a lot less apprehensive about giving this a go with the camera I have vs. ordering a part or donor camera. Out of 10,000+ clicks, I may have used the pop-up flash ten/fifteen times.
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