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06-16-2019, 06:52 AM   #1
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Why you shouldn't file/sand the plunger of the green Chinasolenoid but replace it

Often people recommend filing/sanding/grinding the plunger of the green China-solenoid which is supposed to do the trick.

For some this method worked, at least for a while, but for others it didn't and there can be further consequences applying this method which can lead to complete failure of the "diaphragm-control-unit"

The reasons for this isn't just the plunger itself which gets filed/sanded but it is a combination of other facts!

I had done a comparison of

- the latest solenoid of a K-70
- the latest solenoid used for official repair of a K-30 (which failed again due to failure of the solenoid)
- the solenoids of a K-S1 and K-S2
- a green China solenoid with special etched plunger done by an official repairplace in Germany
(this failed as well just shortly after the 1 year warranty)

and
- the well regarded white "made in Japan solenoid"

You find the results HERE

It shows the steps Ricoh implied for solving the solenoid problem and it also shows why still some K-S1's and K-S2's and very few K-70's did fail and what could be done to solve this finally.

But back to the filing method:

Me (and many others) have tried this method several times. There is no question that it works because you do change the holding force.

But there is a difference how the solenoid switches now!
The complete diaphragm control mechanism is by itself a very special and clever mechanism.
Normally it has to be aligned. If parts go out of alignement, new alignement is quite complicated.

I have experienced 3 x K-30's with filed green solenoids where the diaphragm-control-unit afterwards went out of alignement.
This is due to the fact, that the plunger moves less accurate, more sloppy. I have uploades photos to show this in the manual for replacing the solenoid in the K-30 .

You can even hear the difference just by listening to the switch-sound of a K-30 with the original "white made in Japan solenoid" compared to those with either soldered plunger of those with a filed plunger.


The reason for this:

The white PTFE body (teflon!) as well as the green PET body act as a bearing for the plunger!
The green PET material is inferior to the more expensive PTFE.
The plunger has anyway some allowence for a slight tilt/movement due to the oval hole which sits on the lever but filed/sanded this movement becomes more sloppy.
This you also notice with the K-30 in use! With the prober white Japan-Solenoid it fires faster.


But there is another problem when filing the plunger.

The surface now can corrode and rust!
You can see this here as well as here

Now: You sure don't want rust particles in your K30 or K50 at all!

Aligning the diaphragm-control-mechanism is not easy, one has to know quite a bit to do this the correct way. The white solenoid was used with success in so many DSLR bodies and never failed in any repaired K-30 etc.! So if you make the effort and disassemble a K-30 or similar it is just better to play 100% safe and just use the white made in Japan solenoid. I don't think it makes sense to fiddle around and take risks which can lead to total damage.

Here 3 pages from the service-manual of the *istDL which show how to align the diaphragm-control-unit:
page 16
page 17
page 18

Another problem which can result if this diaphragm-control-mechanism is no longer correctly aligned:
Stop-Down-Metering with the green button no longer works correctly!
This also can result if one just tries to force the green solenoid to work by applying serial shots, if the plunger of the solenoid all the sudden "snaps open" the force ... particular during serial shots... can be that strong that those complex interlinked toothed wheels get out of alignement together with this metal toothed wheel sitting in the optical sensor!

But the worst that can happen is that when the mechanism goes out of alignment and the spring which returns the white plastic wheel to its original position 'jumpes out' and not only stops any possibility for manual metering in M-Mode (because here the solenoid is not in use) but also it can block the wheel which then evidently will interfere with the mirror/shutter-release mechanism or even do damage to it!

The result is complete failure, here a photo of such an example:


You want to avoid this by all means because then your Pentax is pretty much beyond repair.


Last edited by photogem; 01-11-2020 at 04:17 AM.
10-25-2019, 05:39 AM   #2
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I have added the latest findings which resulted by doing further tests based on questions in in this thread by member "Marktax" whose Pentax K-S2 had the stuck solenoid and later on didn't work anymore with OFV stop-down-metering/green button. He knows another person having the same problem.

I checked OFV stop-down-metering on a K-50 and K-S2, both with "stuck solenoid".
The solenoid is not in action when using this method in Manual-Mode but:

If the solenoid either by applying serial-photos to let the plunger of the solenoid snap back or if filed brings the complex mechanism of the diaphragm-control-block out of alignement, stop-down-metering is no more possible.

Then the complete diaphragm-control-block either needs to be aligned (very complex work) of the block needs to be replaced!
Replacing the solenoid (with the white Japan-version) is peanuts complared to replacing the complete block!

I have done it once and will not do it ever again! Way way to time consuming and and a feast for your nervous system, particular the sympathetic part (which then is not at all symphathetic to you anymore but quite the opposite)
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