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04-28-2020, 01:13 PM   #346
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QuoteOriginally posted by photogem Quote

...

To disassemble a K30 is already some work.

To disassemble the solenoid with wires connected is prone to more damage than to unsolder the 2 wires with a fine soldering iron.

But then to swap the direction of the plunger in hope it might work again:

To me a total waste of time.

If you do it, do it once and do it right.
I agree that disassembling the K30 is some work, but not too bad with the guidance you provided, thank you.
I did take the solenoid off very carefully with the wires attached. No, damage, but I was careful.
I pulled the plunger out, inspected it, made sure the two ends were clean, and nothing causing them to bind in the two channels of the coil piece.
I put the plunger back in, not paying attention to whether or not I put it back in exactly the same orientation that it came out as I don't think that makes a difference electrically/magnetically.

I didn't expect that it would work once I put it back together, but I was surprised to find that the K30 is back to operating correctly now.

However, I have no confidence that it will last. But like I said in my previous post #340, I also have a K100D that works, but am willing to sacrifice it to get a good 'white' solenoid out of it.

It remains a mystery to me however, why the K30 worked for 5,300 actuations during the first 1 1/2 years, then failed, and now works again after only taking the plunger out and then placing it back in. In my case, the original failure was noticed after the K30 was not used for several months. I have been using it every day now since 'fixing' it last week and so far, so good.

Will the 'green' solenoid from the K30 work in the pop-up flash of the K100d if I take the 'white' one out to use in the K30?

04-28-2020, 02:18 PM   #347
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Even if you just take out the small magnet without removing the solenoid this will release the plunger for a short time.
The plunger demagnetises quickly but will remagnetise again.

It is known and proven that a very regular use usually helps, in a way you could say leaving a car standing all the time unused is not that good for the pistons.
Mechanical parts designed for movement are better used.


We anyway cannot say that eventually every K-30 fails but it is a lot. Nevertheless we can assume that a high number goes unreported, not everybody is going to start searching in the internet or presents the right questions in a forum.
Most likely most affected will just throw their camera away. I have seen those ebay and similar when sellers didn't have a clue what was wrong.

Yes, the green solenoid works without any problems in the pop-up flash of the K100D.

Much less strain on it. This is why Ricoh finally used it in the aperture control, they had tested it in Europe in most K100D, K110D, K200D, K-m, K-x and K-r right there for the pop-up flash successfully.


Take photos before you take the solenoid out of your K100D just in case.

Disassembly is pretty easy but the front constists of 2 parts, that part covering the aperture control and the other side. This side if you can don't take off, you don't need to.
04-28-2020, 05:45 PM   #348
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QuoteOriginally posted by photogem Quote
Yes, the green solenoid works without any problems in the pop-up flash of the K100D.

Much less strain on it. This is why Ricoh finally used it in the aperture control, they had tested it in Europe in most K100D, K110D, K200D, K-m, K-x and K-r right there for the pop-up flash successfully.


Take photos before you take the solenoid out of your K100D just in case.

Disassembly is pretty easy but the front constists of 2 parts, that part covering the aperture control and the other side. This side if you can don't take off, you don't need to.
Thank you so much for that information. Good to know that I will still have a fully functioning K100D if I do steal the 'white' solenoid from it.

If you don't mind, I have a few questions as to de-soldering / re-soldering.
> Did Ricoh solder or glue the wire leads to their solenoids?

> I have a Weller WES51 soldering station with variable tip temperature 350-850 F. What temp do you recommend for this job?

> I think you recommend in your manual to tin the wire lead ends before re-soldering them to the solenoid. Does that allow you to just partially wrap the tinned end of the wire around the solenoid terminal then touch the hot soldering tip to the terminal to melt the tinned wire end onto the terminal without applying more solder?

I have done some soldering work on my vintage stereo equipment. Some easy jobs like replacing speaker crossover capacitors, the most difficult being some little transistors in a Teac reel-to-reel tape deck. This K30 looks to be more challenging.
04-29-2020, 03:54 AM   #349
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With your Weller you should be perfectly fine, I always use very low temperatures and very low temperatur solder.
I prefer leaded solder, it melts and holds better. Either open window or.. always present, a fume extractor.
Don't use silver-solder, in Audio very good but not here.

I never wrap the partially tinned ends of the wires around the pin but just hold the wire-end to the pin (which has solder as well), touch both with the tip of the soldering iron and I can see how the solder melts. Away with the tip and a short moment, all is hardened.

The best approach is how one of my best engineers did it, he was very old fashioned and used soldering tin without flux!
He put flux onto the two pretinned parts to be connected, held the together, the tin without flux on the soldering tip (it won't smoke/burn but just stays liquid)
and then he touched the two components with the tip/melted tin and off, it bubbles because the flux acts with the tin and thats it.
Old fashioned and works very well.


The workers who assemble the cameras solder the wires!

04-29-2020, 07:55 AM   #350
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QuoteOriginally posted by photogem Quote
With your Weller you should be perfectly fine, I always use very low temperatures and very low temperatur solder.
I prefer leaded solder, it melts and holds better. Either open window or.. always present, a fume extractor.
Don't use silver-solder, in Audio very good but not here.

I never wrap the partially tinned ends of the wires around the pin but just hold the wire-end to the pin (which has solder as well), touch both with the tip of the soldering iron and I can see how the solder melts. Away with the tip and a short moment, all is hardened.

The best approach is how one of my best engineers did it, he was very old fashioned and used soldering tin without flux!
He put flux onto the two pretinned parts to be connected, held the together, the tin without flux on the soldering tip (it won't smoke/burn but just stays liquid)
and then he touched the two components with the tip/melted tin and off, it bubbles because the flux acts with the tin and thats it.
Old fashioned and works very well.


The workers who assemble the cameras solder the wires!
Thanks for all the guidance. I think I have an old spool of leaded solder that I bought in a yard sale last summer. I will probably wear a mask, I have been wearing one quite a bit lately.
04-30-2020, 11:00 AM   #351
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Important that the diameter is of a thin type, otherwise cut it into small pieces.

The usual corona-protective masks will not protect from lead-fumes!
So open window is saver. Anyway, it is a tiny amount.

Last edited by photogem; 04-30-2020 at 10:07 PM.
05-01-2020, 12:19 PM   #352
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First of all: Thanks @photogem for the awesome repair instructions. It helped me fixing my beloved K30.


Since I had one more spare solenoid (the donator, a Samsung GX1S, equal to the *ist DS2, has two solenoids - one for shutter and one for the flash mechanism), I decided to buy another broken camera.


I found a cheap K50 with known aperture block at a second hand dealer and bought it.
The K50 is in mint condition, no dust, no scratches - and according to EXIF data build in late 2014 and the shutter count is as low as 1600. Looked very promising.

When disassembling it, I checked to see if I could find any traces that might indicate that a repair attempt had been made before. But nothing.

So I put in the good old Japanese solenoid, put the camera back together and gave it a try - everything working fine.

Well, at least it worked this one time. Two weeks later, I wanted to take some photos: Camera fully stops down.


Now I opened up the camera again, checking if maybe my soldering work was lousy. But everything looked OK.
Nevertheless, I decided to once more unsolder remove the solenoid and put it back in. Maybe the screw titled or something like that.
While doing so, I also checked the solenoid: Resistance is 30 Ohm, the plunger set free when applying 5 volts to the solenoid. Seems fine.


Unfortunately, after putting things back together, the camera still will stop down.

If someone has an advice for me on what may have gone wrong and what to check next I'd be grateful.
05-14-2020, 08:20 AM   #353
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Does it start with just a dark frame or two?

I was shooting the USAF Thunderbirds yesterday with K-50, Sigma 170-500. I popped a couple of test shots in my back yard and they were dark. Then messed with some settings and fired off a long burst and the first one or two shots of the burst were dark, then they were normal. This happened during the flyover, too. The first couple of shots of each burst were dark, then they were ok.

Should I just go ahead and order the solenoid now?

05-14-2020, 07:25 PM   #354
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Yes, the only correct solution. Just don't buy the cheap green China-version, it will fail again
05-23-2020, 02:36 PM   #355
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Hello everyone, new to the Pentax world and to the forum, I was naive enough to buy a used K-50 from eBay without even knowing of the pretty ubiquitous aperture issue and of course took very little time once received to realize that even mine was affected and in a pretty bad way also. After some web digging into the issue, decided to negotiate a fair discount with the seller rather than returning the camera and try my luck at sanding the infamous green solenoid. Well, considering that before the "cure" even with the aperture preview trick my camera used to function properly just for a few shots, after the sanding everything seems to work perfectly now, let's see for how long, crossing my fingers..
05-30-2020, 02:45 AM   #356
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You're sure the seller didn't mention that there was an aperture issue?
05-30-2020, 02:32 PM   #357
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Nope, he wrote in the item description that it was a problem of the 50-200 DAL that was coming with the camera, which of course it was not as it presented itself also with the 18-55 DAL, therefore I've asked for a discount (selling all back to Japan would have been too unconvenient at that point, so I decided to try my luck with the sanding).
05-31-2020, 02:14 AM   #358
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This was lucky but shows that usually the Japanese are honest in business (my experience at least).

But a shame... the sanding is not really the solution plus the Japan solenoid acts much faster:

Necessary force to pull the plunger:
100g (0,98N) (the strongest ever 120g) Japan Solenoid
200g (1,96N) (strongest ever 250g) China Solenoid

With a powersupply based on a simple microcontrollerboard one can test how quick the solenoids releases.
Tested with 7.2V from the orig. Pentax Li-Ion battery D-LI109:

Releasetime Japan Solenoid: 10ms (and it still functions with an shorter impuls of 4ms!)
Releasetime China Solenoid: 100ms! It won't function at all with 10ms, forget 4ms.

But if one runs the China-Solenoid several times with 100ms/7,2 Volts and then tries with 10ms it does work 1, sometimes even 2 times
but then collapses back into its previous "stronger position".

But worse: If one uses it many times with 100ms and then just lets it stand for a few hours it won't even once release anymore with 10ms but only 100ms!

Now changing over to AA-Eneloops instead of using the Li-Ion D-LI109 things do change:

The releasetime is now between 50ms for the Chinasolenoid and 8ms for the Japansolenoid, which even can at times be switched within just 2ms!


But that the solenoid is sticking and not releasing is not only due to the fact that the plunger is held with more force!
The plunger "wiggles" more in the body of the green solenoid. The body acts as a bearing. The more precise a bearing is, the more presice the function.
This is partly due to the fact that PET (green solenoid) is a cheaper material (and softer) while the teflonbody of the white Japan solenoid can do this job way better.
Teflon (PTFE) is a great bearing material, for example all "Well Tempered turntables" (some of the worlds best) use teflon bearings since about 1988 and the run and run and run without any failing. If such a bearing would be made out of PET... it wouldn't last 1000 hours and soon the shaft would wiggle in the bearing, the platter wobble, you could see it (worse, hear it!)

Next problem: the plunger is made out of an alloy and has shown several times rust.
All this can be read HERE.

The problem is, post like yours can encourage others to go "the cheap way", the result can be final failure.
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