[ewhac]

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Well, you'll need to take the camera apart and de-solder the plunger to try demagnetising the plunger [ ... ]

Erm... All the photos I've seen suggest that, once you've unscrewed the solenoid, the plunger can just pull right out. The coils and permanent magnet would remain soldered to the wires.

[photogem]

Your question belongs actually into the K-S2 section.
Here we have the K-70 section!

Erm... All the photos I've seen suggest that, once you've unscrewed the solenoid, the plunger can just pull right out. The coils and permanent magnet would remain soldered to the wires.

Either WRONG or you stopped reading in the middle of the tutorial!

This very thread is ONLY about the correct repair
i.e. exchanging the bad green China Solenoid against the good white Japan-Solenoid!

And this tutorial shows ALL steps which... concering your question... are:
- not to unscrew the solenoid first


but:
- unsolder the wires from the solenoid
- then unscrew the solenoid
- insert the correct DSLR Japan solenoid
- screw the screw in.... and so on

Not a single photo of the solenoid screwed out dangling on the wires!

It looks like my K-S2 has developed this problem after sitting mostly idle during the pandemic.....
Since the root issue appears to be induced magnetism in the plunger, it seems to me it could be addressed by simply running the plunger through a degausser for a few seconds. While it wouldn't be a permanent solution, it seems far less precarious since no soldering is involved, and you wouldn't have to trawl eBay looking for rare solenoids.

Has anyone tried just degaussing? If so, what were the results?

Degaussing does not work at all, it is totally useless but would in a way even hurt* any Pentax!
This is because:
- the magnet itself is too strong (filing the magnet itself to weaken it destroys it, no chance)
- the alloy used for the plunger is not of the same composition as the Japan Solenoid! It seems it changes its structure over the time and is more prone to be stronger magnetized.
- it magnetizes very quickly again (you don't even need to degauss it, it loses it's magnetized charge just when away from the magnet after a few seconds.
- degaussing would not change the molecular structure

This solution is the worst of all because having the Pentax disassembled, 95% of all work is already done
so why "cheat" when one can do it right?

*it actually in a way harms your Pentax because you will for sure have to open it again for a proper repair:
Each time you disassemble and assemble you weaken those many plastic threads.
Some screws do not hold that well anymore right after the 2.nd disassembly. I had that problem several times when I had to repair Pentax bodies repaired under warranty but with the same green China-Solenoid which very often fails again. Then one has to find other ways to tighten the screws. Particular that screw deep inside the battery chamber is vulnerable. If lose, the camera doesn't work correct anymore.


The DSLR Japan-solenoid can be purchased on ebay for around $ 59
That price is very sensible, finding a DSLR Pentax with solenoid inside such as the K100D is getting more difficult.
Those solenoids are tested and save you trouble. These days one finds quite often defunct K-bodies but either with solenoids take out with green Chinasolenoids built in. No return possible if stated "for parts/not working etc"

Taking the solenoid out and wiggling with the plunger with the wires still connected is about as difficult as unsoldering the wires.
IMO it is actually more risky.

I'd say 99% of all who tried the real work with soldering managed to do it.

If you feel you can't try to find somebody here in the forum or send it to California:
Pentax Camera Repair - Aperture Control Repair
They file but give some good warranty. I hesitatingly recommed that repair now because it is at least cheap enough and warranty is given.
With other repairs such as the one in Scotland for @luckylu I'd check very carefully. Although very reasonable it either is the same China solenoid again (often even the cheap Lenovo-Version for DVD-Burnes such as offered on ebay "en masse") or filed. In this Scottish case the repairshop invented a lot of fairy-tales of what would have to be done, well actually a lot of rubbish!

So if you want to discuss this issue further, please open an appropriate thread in the K-S2 section.
Thank you.

[MarkJerling]

Erm... All the photos I've seen suggest that, once you've unscrewed the solenoid, the plunger can just pull right out. The coils and permanent magnet would remain soldered to the wires.

You8 could try. But the rest of my quoted text said:

So, it would appear to make far more sense to replace the solenoid with one of the "Japan made" white solenoids which almost never fail if you're going to go to all the effort to get into the camera in the first place.

[ewhac]

Degaussing does not work at all, it is totally useless but would in a way even hurt* any Pentax!
This is because:
- the magnet itself is too strong (filing the magnet itself to weaken it destroys it, no chance)
- the alloy used for the plunger is not of the same composition as the Japan Solenoid! It seems it changes its structure over the time and is more prone to be stronger magnetized. [ emphasis mine ]
- it magnetizes very quickly again (you don't even need to degauss it, it loses it's magnetized charge just when away from the magnet after a few seconds.
- degaussing would not change the molecular structure

Thank you. I've never heard of this effect before. But then I'm not a metallurgist, so I will accept it at face value. I'll go hunting on eBay for a white Japanese solenoid, and practice my soldering skills while I wait for it to arrive.

[17dew]

Thanks to photogem for all the work posting the tutorials.I fixed my K70 with a white solenoid.Works fine now!

[smmoore]

Thanks Photogem, for the tutorial. I was able to repair my K-S1 (with a little disassembly help from Naula's post). I got a white solenoid off ebay and was able to replace it in a little over an hour. I had given up on it and only been taking pictures with a cell phone since 2018, but now I have a real camera again! Woohoo!

[photogem]

Thanks Photogem, for the tutorial. I was able to repair my K-S1 (with a little disassembly help from Naula's post). I got a white solenoid off ebay and was able to replace it in a little over an hour. I had given up on it and only been taking pictures with a cell phone since 2018, but now I have a real camera again! Woohoo!

Thanks and well done.
But you know, we have a tutorial for the K-S1 as well:
Manual: Solenoid replacement: Pentax K-S1 - PentaxForums.com

[DCalciu]

Can I use a solenoid from an *ist DS? Can I use the solenoid from the flash release instead of the one from the aperture block? Thank you in advance for your answers

[photogem]

Can I use a solenoid from an *ist DS? Can I use the solenoid from the flash release instead of the one from the aperture block? Thank you in advance for your answers

Yes, you can, both solenoids are fine.
If you are carefull and don't lose parts you can even use the green China solenoid in your *ist-DS in the flash-circuit.
But not in the aperture-block!

The *ist DS is a historical camera, worth to keep working.
The green solenoid was tested for about 6 years in the flash-circuit of the K100D, K110D, K100D Super, K-m, K-x and K-r. Never failed there.
Just don't sell your DS without the notion that the flash solenoid was replaced!

[DCalciu]

Thank you very much for your answer.
My K-70 is still working, but I noticed a few shots inexplicably heavy underexposed at the beginning of the shot session.
Shutter count is ~ 12800 and manufacturing date 2017/03/28. I suppose that is about aperture block failure.
I intend to repair it with parts from my old DS. Since the green solenoid of the K-70 is still working, I guess it's better to do the repair sooner than later and replace the parts among them.
Please, do you have any advice on how to clean the green solenoid before installing it in the flash circuit of the DS?
I want to clean it with isopropyl alcohol (immerse it for a few minutes) or maybe not? There is some sort of grease on it from the fabrication?
Thank you again and yes, you're right, when selling DS, I must warn about solenoid change. But I'll keep it, it's my first DSLR camera.

[photogem]

Please, do you have any advice on how to clean the green solenoid before installing it in the flash circuit of the DS?
I want to clean it with isopropyl alcohol (immerse it for a few minutes) or maybe not? There is some sort of grease on it from the fabrication?
Thank you again and yes, you're right, when selling DS, I must warn about solenoid change. But I'll keep it, it's my first DSLR camera.

No need to clean it unless obviously dirty. No grease! Just use it as it is
and make sure you don't lose that tiny plastic black rod (right side behind that hook which holds the popup flash down.
This rod is very important! When you unsolder the solenoid, keep the top upside down, otherwise this rod will fall out!

[photogem]

Thank you very much for your answer.
My K-70 is still working, but I noticed a few shots inexplicably heavy underexposed at the beginning of the shot session.

Typical sign, it will soon get worse.
Best idea to do it now and then have peace of mind.

[DCalciu]

Thank you very much!

[DCalciu]

Thank you very much Photogem!
I succeeded to replace the green solenoid in my K-70 with the white one from my DS – flash release mechanism.
I installed the green one in the DS and now both are working very well!
For those who want to open the top plate of the DS I uploaded a few pictures.

[MarkJerling]

Great photos and sketch!