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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:
Another solution was tried by one of the official German repair-shops:
The plunger was sanded as well but in a very different way:
You can see very clearly how they tried to lessen the surface of the plunger by carving/inscribing those notches into the surface, but I came across this K-30 and its modified solenoid because it failed again after the 1 year warranty:
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; 08-15-2019 at 05:32 AM.