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06-16-2019, 04:49 AM - 9 Likes   #1
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Solenoid in Pentax K-70

Many have wondered if Ricoh have changed something about the solenoid which is the main culprit when the aperture control unit (also called diaphragm control block) fails.

Luckily member SharkyCA had send his failed K-70 in to an official repairshop and got it repaired at an official repairshop + even more lucky to some of us they sent the bad "diaphragm control unit" back to him.

When I read this thread and saw the photos SharkyCA and me myself noticed the similarity to the unit offered by US.Cameras

Just a few weeks ago I received a Pentax K-30 which had been repaired officially under warranty in Europe and which failed again but just after the warranty.
So when I opened it I was very surpised to find this new diaphragm control block inside:


I changed the solenoid against the "made in Japan" white solenoid and it works perfectly since!

But I was curious about the solenoid and inspected it further and SharkyCA send me some photos of his solenoid from the K-70 and allowed me to use them for this thread.


But I start fthis documentation first with a faulty solenoid I recently took from a K-S1, which I had just repaired and used for a repair manual . There was already some modification done to the solenoid, it had been filed by the manucturer of the solenoid!


And it had failed again. Why: Very clear, they just sanded the two bottom plates:



And if you have a close-up look, you will see that this surface started to rust:




Also very clear to be seen, the corners are already slightly round. But the plunger wasn't machined that well at all!:





So here we come to the solenoid from the new diaphragm-controll-block inside the K-30 repaired under warranty:




Sideview, showing it was machined much better and again: Corners are rounded!


Closeup shows already some slight corrosion:




Compared to the plunger of a white "made in Japan" solenoid which I took out of a K10D:
Zero corrosion at all
(it is now 12 years old and I have seen older ones from *istDS bodies plus those from the analog MZ-series, none ever had rust...

but those from the MZ-Series can have opposite polarisation and have a slightly different size and holding force!).
Also look how nicely this plunger was machined:




So here we come to the photos of the first solenoids out of the Pentax K-70, they are quite new and one can see:
100% identical to the solenoid which came out of the repaired Pentax K-30 but: There is no corrosion at all!:




Here the photos of SharkyCA's K70:






To me it is very clear: Ricoh did demand a modification of the plunger. The modification worked because very few K-S1 and K-S2 failed, we don't know yet about the K-70 but I am positive that we will have only very few failures.

And yet, some did fail. So a very precise modification to the plunger similar to very precise sanding and polishing did bring success but not yet 100%.


Studying the photos of the K-70 plunger of the K-70 I think the manufacturer got it and anodized after sanding/polishing as I cannot see no sign of corrosion!
Also it could be a different alloy alltogether. When I have some time I shall invest that further on.

So I think Ricoh did a good job over the time, they learned their lessen....


.... and if I may say, this was also thanks to all of those who applied DIY and tried to solve it by themselves!


It started with the Russians who first added solder and then filed and sanded the plunger, some named it the "LADA*-approach"... in case not everybody knows anymore what a LADA was: A very sturdy rugged reliable car for rough Russian roads

There remains one important problem to be solved:

The late "green made in China" solenoids still have a stronger holding force than the "white made in Japan" versions!



I can feel it by just pulling out the plunger. I have not done any measurements and will not do so because I don't need to! The difference is very obvious to me. So that slightly bit less magnetic force and all should finally be well.


So whoever attempts a DIY repair, this is the best way to go: Find the original white "made in Japan solenoid" which Pentax used in DSLR cameras.

I have described/explained all in detail HERE .



All photos uploaded here show very clearly why sanding/filing/grinding the plunger is not be be recommended as a cheap DIY method at all!

It will work for some time but the surface of the made in China plungers are anodised!
This anodised surface gets damaged and thus corrosion waits for you and your plunger.

I have so often warned about this method.
But the corrosion of the surface is not the only reason, again, all this is explained in THIS POST


Last edited by photogem; 1 Day Ago at 04:18 AM.
06-16-2019, 05:06 AM   #2
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Very informative post! Thanks for taking the time to document this
06-16-2019, 07:01 AM - 1 Like   #3
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Interesting stuff. You're a braver man than me.
06-16-2019, 07:37 AM - 2 Likes   #4
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Thanks so much for your insight and diligence in pursuing this problem. Hopefully this puts the whole issue to rest regarding the aperture block. It's too bad that Ricoh/Pentax didn't take the time to assure it's user base that steps were taken to rectify this issue. I'm sure that sales suffered as some buyers were reluctant to invest in one of these cameras because of this issue. I know I've been interested in a camera with an articulating rear screen for some time, but unwilling to consider a Pentax because of the issue. Hopefully, Ricoh can find a few more of the K-S2's that were offered for $300 a few days ago. If so, I'll get one.


Last edited by T Evergreen; 06-16-2019 at 07:45 AM.
06-16-2019, 08:55 AM   #5
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QuoteOriginally posted by photogem Quote
And yet, some did fail. So a very precise modification to the plunger similar to very precise sanding and polishing did bring success but not yet 100%. Studying the photos of the K-70 plunger of the K-70 I think the manufacturer got it and anodized after sanding polishing as I cannot see no sign of corrosion!

I can feel it by just pulling out the plunger. I have not done any measurements and will not do so because I don't need to! The difference is very obvious to me. So that slightly bit less magnetic force and all should finally be well.
Couldn't the differences you've detected
* no corrosion
* slightly less magnetic force
also be a result of using a different alloy of steel for the entire plunger?
06-16-2019, 09:06 AM   #6
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QuoteOriginally posted by reh321 Quote
Couldn't the differences you've detected
* no corrosion
* slightly less magnetic force
also be a result of using a different alloy of steel for the entire plunger?
Could very well be the case, I added this to my post and when I have time I will see what I can find out.
06-16-2019, 09:08 AM   #7
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Are you saying that Ricoh has been disassembling, sanding, and refinishing* made-in-China green solenoids for the entire K-70 production run since at least 2017 and perhaps before with the K-S2 and K-S1, though with less effectiveness?

I have a few questions for you, but will ask them in a private message since they would be of interest to me, though off-topic for this thread.


Steve

* Anodizing, powder coat, plated, or whatever
06-16-2019, 09:19 AM   #8
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QuoteOriginally posted by stevebrot Quote
Are you saying that Ricoh has been disassembling, sanding, and refinishing* made-in-China green solenoids for the entire K-70 production run since at least 2017 and perhaps before with the K-S2 and K-S1, though with less effectiveness?
No, I haven't said this!


I'd say they gave orders to the manufacturer of the solenoids!


I guess that as somebody wrote once that Ricoh might pay 35 Cents for a solenoid. Something like this.
So if then damand a better solenoid and tell the manufacturer what was the problem with the old one, the manufacturer had to get bottoms up and do some refinement for avoiding "more bad air"

06-16-2019, 10:19 AM   #9
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QuoteOriginally posted by photogem Quote
No, I haven't said this!


I'd say they gave orders to the manufacturer of the solenoids!
Cool! Sometimes details suffer in the translation. Thanks for doing the edit to clarify. Are we no longer thinking that the green vs. white plastic type causes the problem due to differences in physical resistance?


Steve

(...also wondering why we call the green ones "made in China"...)
06-16-2019, 10:37 AM   #10
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QuoteOriginally posted by stevebrot Quote
Are we no longer thinking that the green vs. white plastic type causes the problem due to differences in physical resistance?
The difference between PET and PTFE still remains and PTFE is the better material and will wear less.

But I believe that if this very last problem of a "too strong holding force" is solved, all shall be perfect. I think now with the K-70 it is near perfect and we have a great body with the K-70. Sadly sanding/grinding the magnet won't do it, I have tried it.

Anyway:

QuoteOriginally posted by Not a Number Quote
Measuring the breaking force between a K-70 and K-50 solenoid would be great but how do you calibrate "finely tuned fingers"?
Well, this is very simple..

You yourself make the effort and find out for you yourself instead of demanding it from others!
*Sarkasm is the lowest form of wit*... can/t you do any better.....

---------- Post added 06-16-19 at 10:50 AM ----------

QuoteOriginally posted by T Evergreen Quote
Thanks so much for your insight and diligence in pursuing this problem. Hopefully this puts the whole issue to rest regarding the aperture block. It's too bad that Ricoh/Pentax didn't take the time to assure it's user base that steps were taken to rectify this issue. I'm sure that sales suffered as some buyers were reluctant to invest in one of these cameras because of this issue. I know I've been interested in a camera with an articulating rear screen for some time, but unwilling to consider a Pentax because of the issue. Hopefully, Ricoh can find a few more of the K-S2's that were offered for $300 a few days ago. If so, I'll get one.
I'd get the K-70, it is not that much more expensive and worth the extra money!
06-16-2019, 11:13 AM   #11
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QuoteOriginally posted by photogem Quote
*Sarkasm is the lowest form of wit*... can/t you do any better.....
The full quote (usually attributed to Oscar Wilde) goes like this:
QuoteQuote:
“Sarcasm is the lowest form of wit, but the highest form of intelligence.”
I personally, believe pun to be the lowest form of wit, but quite possibly requiring even more intelligence.

That being said, @Not_a_Number makes a good point. A lot of assumptions have been made in the bread crumb trail of conclusions regarding the diaphragm control block failure. It helps that most of those have been made by persons having actual access to dissected cameras where the failure has occurred. For the reader on this forum, the actual point of failure is taken on the basis of faith and the validity of the repair on the apparent success of the process. In short, you are the obvious person to ask about such things.


Steve

Last edited by stevebrot; 06-16-2019 at 11:14 AM. Reason: completeness
06-17-2019, 12:46 AM - 1 Like   #12
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Dear Photogem,
many thanks for taking the trouble in documenting all this. I really hope that I won't have to use this knowledge on my K-50, but when I have to, it'll be good to know this stuff.
all the best,
Hans
06-23-2019, 04:21 AM   #13
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aperture failure on my K-S2 and I replaced the green solenoid with a white one:fixed!

I also had bad luck with my K-S2 with shuttercount of 31000. I orderedthe white solenoid in the U.S. it was 45 $ . But a friend of mine helped with replacing the green solenoid with the white one and it was fixed.

So indeed , the only solution is in my opinion rder an original white one.
06-23-2019, 08:05 AM   #14
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QuoteOriginally posted by krgroothuis Quote
I also had bad luck with my K-S2 with shuttercount of 31000. I orderedthe white solenoid in the U.S. it was 45 $ . But a friend of mine helped with replacing the green solenoid with the white one and it was fixed.

So indeed , the only solution is in my opinion rder an original white one.
QuoteOriginally posted by photogem Quote
The difference between PET and PTFE still remains and PTFE is the better material and will wear less.

But I believe that if this very last problem of a "too strong holding force" is solved, all shall be perfect. I think now with the K-70 it is near perfect and we have a great body with the K-70. Sadly sanding/grinding the magnet won't do it, I have tried it.

Anyway:


Well, this is very simple..

You yourself make the effort and find out for you yourself instead of demanding it from others!
*Sarkasm is the lowest form of wit*... can/t you do any better.....

---------- Post added 06-16-19 at 10:50 AM ----------


I'd get the K-70, it is not that much more expensive and worth the extra money!
Having seen a lot of posts referencing "the white solenoid" to be purchased but I have not seen any links to where it may be purchased?

If anyone has a link where it can be purchased it would be good!

Cheers!
06-23-2019, 08:46 AM - 1 Like   #15
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QuoteOriginally posted by SharkyCA Quote
Having seen a lot of posts referencing "the white solenoid" to be purchased but I have not seen any links to where it may be purchased?

If anyone has a link where it can be purchased it would be good!

Cheers!
Most people 'harvest' them from old cameras; I hate to see working cameras turned into organ-donors - but I have to admit having no personal interest in a camera that old.

An eBay seller did take apart old cameras has two left at $45
Pentax K-30 K-50 K-S1/S2 K-500 Genuine White Aperture Solenoid Part - Japan - | eBay
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