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As of today, 28 December 2019, I will no longer be maintaining this report page.

The incidence is sufficiently low that it hardly makes sense, but it has been an interesting experience.

Steve

***************************************************************************************************

There have been a couple of recent threads regarding gross underexposure (essentially black) on some or all photos. While it is not fully clear whether these reports are related or (shudder) whether there is an emerging problem similar to the aperture block failure common to the K-30/K-50 models, it seems reasonable to provide a clearinghouse thread in an attempt to determine who is having problems and the evident point of failure. For the sake of clarity and accountability, it would be good to limit experiences to those of our users and not reference claims from other forums or rumor sites.

NOTICE: This thread is curated and keeping track of pertinent reports and updates will be easier if we abide be a few simple rules. Please use this thread for:

• Reports of problems with underexposed or dark frames from Pentax Forums users. Please include written details and whether you were able to confirm that it is an issue with aperture control (see below for instructions).
• Updates regarding cause, repairs, and repair details (when known)

Do NOT use this thread for:

• Discussion of the aperture control block problem on K-30/K50/K500 models or reports for any model other than the K-70
• Troubleshooting poor exposure. A separate thread in the K-70 subforum or in the troubleshooting section of the site might work better.
• Photos of dark frames. If it is happening, your word is enough. Photo examples, even with full EXIF, are of limited or no value for troubleshooting or confirmation.
• Complaints about Ricoh/Pentax product or service or business practices
• Complaints or comments about the K-70 in general
• Complaints about repairs from authorized facilities, including: timeliness, cost, outcome, or communication

In regards to the last three points, neither Ricoh/Pentax nor the authorized repair shops they contract with monitor activity on the Pentax Forums site.

**********************************

To date, I am aware of the following Pentax Forums users having problems with dark frames:

User @dudesohungry (31 Aug 2018) : K70 ISO problem - PentaxForums.com
Not known if this was an aperture or other problem.

User @drumhead (17 Sept 2018) : Strange behaviour from my K-70...aperture block? - PentaxForums.com
Presumptive aperture control issue. Camera sent for warranty service.

User @CodyH (30 Sept 2018): K-70 aperture motor question - PentaxForums.com
Confirmed aperture control issue with root cause not known. Warranty service may be attempted (camera barely out of warranty). Update -- camera is being sent for service and will probably be covered under warranty.

User @RichFam (5 Oct 2018): K-70 Underexposed Photo Reports - PentaxForums.com
Confirmed aperture control issue with root cause not known at about one year post purchase. Did not seek warranty service.

User @asalwa (11 Nov 2018): K70 aperture block? - PentaxForums.com
Confirmed aperture control issue with root cause not known, August 2018. Out-of-warranty repair was performed, though it is unknown what was replaced/adjusted.

User @Eric_Hall (10 Dec 2018): Dark images - PentaxForums.com
Confirmed aperture control issue with root cause not known with camera to be sent for service under warranty.

User @fernoh123 (6 Jan 2019): K-70 Underexposed Photo Reports - PentaxForums.com. Symptoms similar to aperture control issues with other model cameras. Unknown whether repair was sought.
Confirmed Camera was sent for warranty repair with root cause confirmed as aperture control block failure by statement of work performed.

User @pentax360 (30 Jan 2019): K-70 Underexposed Photo Reports - PentaxForums.com. Dark frames on first few captures of a session. It is unknown whether the cause is due to failed aperture control.

User @SharkyCA (31 Mar 2019): K70 aperture block? - Page 3 - PentaxForums.com.
Confirmed aperture control issue with root cause determined to be diaphragm control block. Dark frames interspersed with properly exposed frames (middle two out of four effected in initial report and many in subsequent discussion). User sent camera to Sun Camera in Canada where they confirmed the diagnosis.

User @disasterfilm (16 Jun 2019) New K-70 - Metering issues between Live View and OVF - PentaxForums.com originally reported as dark frames when using optical viewfinder only. This is apparently a metering issue, but is recorded here just in case.

User @Alex74 (10 Jul 2019) K-70 Exposure issues - Page 3 - PentaxForums.com
Ambiguous Aperture actuation problems of unclear nature (based on repair report); root cause ambiguous...repair report "exchanged aperture mechanism and controller". User initially reported severely underexposed as well as overexposed frames despite no change in camera settings. Initially it was unknown whether this was a problem of lazy aperture or aperture control. Making no assumptions, I trust that the problem has been fixed. Report is retained in the interest of making as complete a count as reasonable.

User @rwhynacht (15 Aug 2019) New K-70 - Metering issues between Live View and OVF - PentaxForums.com
Confirmed aperture control issue based on repair outcome; root cause ambiguous...repair involved replacement of Aperture Control Assy and Resistor Chip. NOTE: This camera had been recently purchased.
Severely underexposed photos in auto exposure modes that, though unclear whether the issue is metering or something else, but included here just in case. The camera was serviced with report noted here.

User @tanz (23 Aug 2019) K-70 Underexposed Photo Reports - Page 7 - PentaxForums.com reports severely underexposed frames when using the optical viewfinder with live mode not having obvious problems. Likely aperture control failure based on description of stop-down behavior.

User @riverrock (9 Sept 2019) https://www.pentaxforums.com/forums/193-pentax-k-70/377096-k-70-underexposed...ml#post4721041
Confirmed Aperture Control Failure/Issue, root cause unknown. Reports severely underexposed frames with visual confirmation of inappropriate aperture stop-down.

User @davedyer (12 Sept 2019) first picture is dark - PentaxForums.com
Confirmed aperture control failure/issue, root cause unknown. Reports underexposed first frame with properly exposed frames thereafter with visual confirmation of inappropriate aperture stop-down.

User @corbinco2 (25 Oct 2019) https://www.pentaxforums.com/forums/53-pentax-dslr-camera-articles/377096-k-...ml#post4778685
Confirmed aperture control failure/issue, root cause unknown. Consistent dark frames after two years ownership confirmed as aperture control problem by visual inspection.

User @Progbusters (19 Nov 2019) https://www.pentaxforums.com/forums/53-pentax-dslr-camera-articles/377096-k-...ml#post4818734
Confirmed aperture control failure/issue, root cause unknown. Consistent dark frames after a few months ownership confirmed as aperture control problem by visual inspection. Grey market purchase with unknown warranty options. User opted to not repair and sold camera "as-is".

User @photogem (23 Dec 2019) https://www.pentaxforums.com/forums/53-pentax-dslr-camera-articles/377096-k-...ml#post4870093
Confirmed aperture control failure/issue corrected by user replacement of solenoid. Failure at after one year ownership, camera still under warranty.


**********************************


Three (initial) similar problems in less that a month's span are a potential cause for concern. Any future reports may be logged here in an effort to determine if these are isolated incidents or evidence of a larger issue. At the very least, this thread may serve to qualify claims of multiple reports from the Web regarding K-70 aperture control problems.

Note: Terminology is important and it is good to be clear on terms. Here are a few starters along with working definitions:

• Exposure problems: images are over or underexposed. Cause may be anything from user inexperience to hardware meltdown
• Metering issues: Bad meter readings leading to inappropriate settings
• Dark Image Syndrome (DIS): Term coined by user @reh321 for unexplained dark frames despite correct settings
• Aperture Control Failure/Issue: Iris opening during exposure does not reflect set value. Example: Camera is set to wide open, but exposure is made with lens stopped down to smallest opening. This sort of behavior may have many different causes as diverse as damage or failure in the lens itself and water incursion causing damage to body electronics.
• Aperture Block Failure: This is the specific failure of the so-called aperture block solenoid used for aperture control on a wide span of Pentax SLR bodies dating back as far as the early 1980s. Failure of this component affected a large number of K-30, K-50, and K-500 bodies and was the cause of aperture control failure on those cameras. A similar unit was fitted to the K-S1 and K-S2. It is possible that the K-70 has a similar part, hence this thread.
• Diaphragm control block : G100 Proper name and part number for the assembly that controls the aperture opening on most Pentax cameras since the early 1980s. "Aperture block" and "Aperture control block" are synonyms in common usage.
• Diaphragm control block : G200 Proper name and part number for the assembly that controls the aperture opening on flagship models since the release of the K-7. As of 11 Oct 2018, it is not clear whether the K-70 uses this part or the G100 part above.

To test for Aperture Control Failure/Issue:

The so-called gold standard for diagnosing an issue with aperture control is to put the camera in M mode (auto ISO off, aperture ring not being used) with aperture set wide open and shutter speed at something slow (e.g. 1-2 seconds). Release the shutter while observing the aperture opening through the front of the lens. Anything other than the aperture remaining wide open is indication of a problem with the controller. If the problem has been intermittent, it may help to do the test after a period of non-use. Even one failure is significant.

Hopefully, there is no cause for alarm.


Steve

(...not a K-70 owner, but was heavily involved in the first wave of K-30 problems several years ago...)

[reh321]

One can do it this way. But much better and easier is to buy the white Japan Solenoid on ebay
which is a final solution or to get it from any DSLR from the *istD up to the K-r.
The K30 was the first Pentax to use the green solenoid in the diaphragm assembly.

If anyone is thinking of purchasing a solenoid, this is good time to do it. Right now they have only 2 left.

[photogem]

Finally it hit my own black Pentax K-70, purchased Dec.2018. It was my backup Pentax, not so much used because my KP is my workhorse, so low shuttercount under 2000 actuations!
I would have had another year warranty on it which of course now I lost but as I had little trouble with Pentax otherwise and trust it to work well and because I know through my own experience that the Japan Solenoid is the best solution, I chose to go this way (If I would have it repaired I would know that the solenoid could fail again and ... worse, all the screws in the plastic housing have less hold because unscrewed and screwed-in one extra time, meaning the inner-threads would be more worn i.e. "screwed"


The usual tests were very clear, the easiest is actually in Live-View-mode:
If the solenoid is stuck the lens isn't preset to f4 anymore but closed!
I did the test with my SMC Pentax F50mm/f1,7: Stuck at f22!

The green China-Solenoid inside had the usual problem, the plunger would not release anymore. It had the same holding-force as those green China-solenoids taken out from K-30's, K-50's etc., i.e. a stronger holding force than the white made in Japan solenoid.


So next step was swapping this green gremlin against the white made in Japan solenoid and voila: The K-70 works fantastic again.



So my recommendation: As soon as warranty is gone, go for DIY and apply my


Tutorial for replacing the solenoid in the Pentax K-70



with the white "made in Japan solenoid":

[stevebrot]

Finally it hit my own black Pentax K-70, purchased Dec.2018. It was my backup Pentax, not so much used because my KP is my workhorse, so low shuttercount under 2000 actuations!
I would have had another year warranty on it which of course now I lost but as I had little trouble with Pentax otherwise and trust it to work well and because I know through my own experience that the Japan Solenoid is the best solution, I chose to go this way (If I would have it repaired I would know that the solenoid could fail again and ... worse, all the screws in the plastic housing have less hold because unscrewed and screwed-in one extra time, meaning the inner-threads would be more worn i.e. [url=https://i.etsystatic.com/16095270/r/il/e01885/1925970317/il_570xN.1925970317_okso.jpg]"screwed"[/url)


The usual tests were very clear, the easiest is actually in Live-View-mode:
If the solenoid is stuck the lens isn't preset to f4 anymore but closed!
I did the test with my SMC Pentax F50mm/f1,7: Stuck at f22!

The green China-Solenoid inside had the usual problem, the plunger would not release anymore. It had the same holding-force as those green China-solenoids taken out from K-30's, K-50's etc., i.e. a stronger holding force than the white made in Japan solenoid.


So next step was swapping this green gremlin against the white made in Japan solenoid and voila: The K-70 works fantastic again.



So my recommendation: As soon as warranty is gone, go for DIY and apply my


Tutorial for replacing the solenoid in the Pentax K-70



with the white "made in Japan solenoid":

OK...adding you to the list. Just for clarity's sake, can you confirm that you were getting dark exposures and that this repair was not done as prevention? FWIW, I have found the live view test to yield false positives (stops down to minimum under normal daylight conditions) and potential for false negatives (may not stop down at all indoors), at least on the K-3 with FA 35/2.0 mounted.


Steve

[photogem]

You should know that when I wrote "it finally hit my K-70" it means I got dark exposures.
When the solenoid is stuck it means "dark exposures" of course!

[reh321]

You should know that when I wrote "it finally hit my K-70" it means I got dark exposures.
When the solenoid is stuck it means "dark exposures" of course!

Steve is just trying to be accurate - as you should understand. He is trying very hard to accurately record K-70 performance. From what I am seeing, he is showing that Pentax's fixes to the K-S2 and K-70 have resulted in a camera which has more reliable aperture control that the K-30/50 did, but still has aperture control as a very weak area. I got a KP to avoid the issue altogether - but as a K-70 owner and fixer, would you agree with that assessment?

[photogem]

To test for Aperture Control Failure/Issue:

The so-called gold standard for diagnosing an issue with aperture control is to put the camera in M mode (auto ISO off, aperture ring not being used) with aperture set wide open and shutter speed at something slow (e.g. 1-2 seconds). Release the shutter while observing the aperture opening through the front of the lens. Anything other than the aperture remaining wide open is indication of a problem with the controller. If the problem has been intermittent, it may help to do the test after a period of non-use. Even one failure is significant.

Hopefully, there is no cause for alarm.


Steve

(...not a K-70 owner, but was heavily involved in the first wave of K-30 problems several years ago...)

This method is misleading because it actually cannot work!

I don't understand why I never became aware of this error because this should have "jumped into my awareness".
Possibly because I always did the test in simple Av-mode or TAV-mode.
Usually I take a F50/1,7 or similar and set it wide open = f1,7 and do a test shot:
Picture very dark = stuck solenoid
Then the (logical) opposite test, in this case f22 + test shot:
Picture fine (because the solenoid doesn't have to open!)

The other easy way of testing is liveview as I have explained:
Right away when set on liveview a Pentax with functioning solenoid will set itself to f4 i.e. relative open
Aperture - Wikipedia

But with stuck solenoid the iris will remain closed = f22 and will
look like this

I had stumbled over this claim but whenever I had a K30 or similar for repair forgot about it, had only done the tests with the green button (which of course had to be similar).


Today I had the chance to repair another K30 and finally did the test. (M-Mode, Auto-ISO off, lens on f1.7)
The iris did nothing but remained wide open!
So I opened the K30 for a precise test, i.e. to see the solenoid in action.
I unsoldered the wires: No change.
I built the white solenoid in: No change (but of course AV, TAV work again as to be expected!)

So to test it again I opened a K100D. The K100D is a bit more difficult to test with seeing the solenoid in action because one has to reassemble it partly for being able to install the batteries.
I intentionally took a working K100D with high shuttercount because I then installed the faulty green solenoid into this K100D!

The result was as expected: Also in the K100D the solenoid does not actuate in M-Mode!

On this photo of the K100D with the faulty solenoid from the K30 you can see one cable of the solenoid unsoldered:


It doesn't matter if the solenoid is faulty, soldered or unsoldered, has a filed plunger or not, you even can take the solenoid out completly, the camera will still work in M-mode because in M-Mode the solenoid is not working.

I had explained it here once:
Dark exposure problems on K-30 or K-50? Discussion Thread - Page 20 - PentaxForums.com

So I invite you to check this yourself on any camera with a faulty solenoid.

It does not matter which Pentax you use as long as it is one with a solenoid for aperture control!

And may I bring your attention to this post which you wrote recently:

.... I have never seen one of the suspect solenoid plungers, modified (filed) or unmodified.... Steve

The plunger of the solenoid is of course part of the solenoid.
You need to see the solenoid in action to be able to know if it works in M-Mode or not!

[SharkyCA]

Three (initial) similar problems in less that a month's span are a potential cause for concern. Any future reports may be logged here in an effort to determine if these are isolated incidents or evidence of a larger issue. At the very least, this thread may serve to qualify claims of multiple reports from the Web regarding K-70 aperture control problems.

Note: Terminology is important and it is good to be clear on terms. Here are a few starters along with working definitions:

• Exposure problems: images are over or underexposed. Cause may be anything from user inexperience to hardware meltdown
• Metering issues: Bad meter readings leading to inappropriate settings
• Dark Image Syndrome (DIS): Term coined by user @reh321 for unexplained dark frames despite correct settings
• Aperture Control Failure/Issue: Iris opening during exposure does not reflect set value. Example: Camera is set to wide open, but exposure is made with lens stopped down to smallest opening. This sort of behavior may have many different causes as diverse as damage or failure in the lens itself and water incursion causing damage to body electronics.
• Aperture Block Failure: This is the specific failure of the so-called aperture block solenoid used for aperture control on a wide span of Pentax SLR bodies dating back as far as the early 1980s. Failure of this component affected a large number of K-30, K-50, and K-500 bodies and was the cause of aperture control failure on those cameras. A similar unit was fitted to the K-S1 and K-S2. It is possible that the K-70 has a similar part, hence this thread.
• Diaphragm control block : G100 Proper name and part number for the assembly that controls the aperture opening on most Pentax cameras since the early 1980s. "Aperture block" and "Aperture control block" are synonyms in common usage.
• Diaphragm control block : G200 Proper name and part number for the assembly that controls the aperture opening on flagship models since the release of the K-7. As of 11 Oct 2018, it is not clear whether the K-70 uses this part or the G100 part above.

To test for Aperture Control Failure/Issue:

The so-called gold standard for diagnosing an issue with aperture control is to put the camera in M mode (auto ISO off, aperture ring not being used) with aperture set wide open and shutter speed at something slow (e.g. 1-2 seconds). Release the shutter while observing the aperture opening through the front of the lens. Anything other than the aperture remaining wide open is indication of a problem with the controller. If the problem has been intermittent, it may help to do the test after a period of non-use. Even one failure is significant.

Hopefully, there is no cause for alarm.


Steve

(...not a K-70 owner, but was heavily involved in the first wave of K-30 problems several years ago...)

Just a quick clarification about the "diaphragm control block" in the K-70, mine was repaired by Sun Camera an authorized service center for Pentax in Canada, they replaced the "control block" and sent me back the "used part" please see image

The control block from my camera appears to be the G100 as available from US Camera Pentax 77860-G0100 Diaphragm Control Block | K-S2 | K-30 | K-50 | PartsUSCamera

Just to enlighten for your previous post (see attached image) which does not make clear which control block they are using in the K-70.

Attached Images

 

[stevebrot]

This method is misleading because it actually cannot work!

Funny that it not only does work, but also does so as part of normal operation with lens on camera. In other words, we are testing aperture actuation on an intact camera in an attempt to catch the failure as it actually happens.

I suspect that you might get different results if you mount a lens with A contacts.

Part of the disconnect here is that the intent of the test is to determine if there is a failure of aperture control on an intact camera during standard operation. It is not intended to test a part that requires disassembly to evaluate.

As for detection using the auto-protect feature of live view, yes this may work, though it will fail to detect under dim conditions (may not stop down) and may provide false positive under bright conditions*. I invite the reader to test both on a healthy camera. I would also caution that the live view auto-protect behavior is not part of a shutter release sequence and may not account for related or alternative causative factors (e.g. mirror timing/positioning problems).** Another option might be to simply attempt optical DOF preview with the body-set aperture at maximum. Again, I don't suggest this because it is not part of the normal shutter cycle.


Steve

* I have observed at least f/16 with the camera pointed at a clear December sky at 45.8° N.

** With both the K-30 and K-50, mirror issues were a common "co-morbidity" and it was not clear what caused which and whether mirror sequence was needed to detect, hence the testing of the full shutter sequence.

[Not a Number]

The control block from my camera appears to be the G100 as available from US Camera Pentax 77860-G0100 Diaphragm Control Block | K-S2 | K-30 | K-50 | PartsUSCamera

Just to enlighten for your previous post (see attached image) which does not make clear which control block they are using in the K-70.

The G100 block uses the solenoid. The G200 assembly uses a motor and worm gear. Since the K-70 has a solenoid it must be a version of the G100.

[stevebrot]

The G100 block uses the solenoid. The G200 assembly uses a motor and worm gear. Since the K-70 has a solenoid it must be a version of the G100.

Yes, this is well-known based on repair records. What is doubtful is whether the G100 used in the K-70 is the same as the G100 used in earlier models.* User photogem reports there are subtle differences between the G100 in the K-70 and those from earlier models and I take their word for it. FWIW, the G100 designation is used for the similar, but different assembly for my Pentax Super Program; apparently the same is true on down the line since the early 1980s.


Steve

* The part on the U.S. Camera site is offered for the K-30, K-50, and KS-2 models (LINK)

[stevebrot]

This method is misleading because it actually cannot work!

Funny that it not only does work, but also does so as part of normal operation with lens on camera. In other words, we are testing aperture actuation on an intact camera in an attempt to catch the failure as it actually happens.

I suspect that you might get different results if you mount a lens with A contacts.

I reread your account and it dawned on me what you may be trying to explain; that you are not seeing the solenoid energized when the body is set to control the lens to maximum aperture. Never-the-less, hundreds of users on this site have diagnosed aperture control failure using the procedure outlined at the top of this page and it is not unusual to have dark frames reported with the lens set to maximum aperture. It appears there is a crack somewhere.


Steve

[photogem]

Funny that it not only does work, but also does so as part of normal operation with lens on camera. In other words, we are testing aperture actuation on an intact camera in an attempt to catch the failure as it actually happens.

Of course an intact K-70 will work in M-Mode (as a normal operation).

Nobody questioned this!

But no, "we" are not testing aperture actuation on an intact camera in an attempt to catch the failure as it happens.
"We" can only test aperture actuation on a failed camera in an attempt to catch the failure because it already happened.
Of do you think "all of us" will stand for hours/days/month with an intact camera in hope that we might catch the failure to happen?

You suggested test was meant for finding out if the aperture-control does either work or if it fails.

I suspect that you might get different results if you mount a lens with A contacts.

No, the results are the same, because lenses with A contacts allow the solenoid to act, if for example in Av mode.
But again here the solenoid does not act if in M-Mode. Thats the whole point!

Part of the disconnect here is that the intent of the test is to determine if there is a failure of aperture control on an intact camera during standard operation.

Failure of aperture control on an intact camera?

If the aperture control is failing, how can the camera be intact?

It isn't anymore intact, it has failed!

It is not intended to test a part that requires disassembly to evaluate.

No, of course not, but for those who want to understand the test and see if the solenoid does or doesn't fire in M-Mode as suggested by you
the only way is to evaluate with a disassembled body.
And anybody who repairs a Pentax K30 or K50/500 can do so very easy, because as soon as the body is open one can plug a lens onto the k-bajonett, push in the battery, set the camera in M-Mode, lens wide open or f2 or f4 or f5,6 or f22 and then press the release button and then observe if the solenoid does act or not. It will never act in M-Mode! Thats the point. That is why this test is 100% useless to determine any root cause. You cannot do so with a K-S1, K-S2 or K-70 because with those the top- and frontcover are just one piece and thus you'd have to cut an opening/window into the front!

As for detection using the auto-protect feature of live view, yes this may work, though it will fail to detect under dim conditions (may not stop down) and may provide false positive under bright conditions*.

You see, the problem is all those "may or may not"!
This is because as you mentioned it, you are not a K-70 owner, so all those claims are based on guessing which doesn't help at all.

Your idea that it will fail to detect under dim conditions (may not stop down) is based on how the K5, K3, KP and K-1 work! They don't stop down to f4 like the K30, K50, K-S1, K-S2 and K-70!
The K-70 stops down to f4 in live-view and stays there no matter which light conditions.
And if the solenoid is stuck (i.e. does not work anymore= dark/underexposed photos) it will not stop down to f4 but whatever the maximum of the given lens is, for example f22 or f32 and the iris remains just completly closed.

I invite the reader to test both on a healthy camera.

But your test:

To test for Aperture Control Failure/Issue:The so-called gold standard for diagnosing an issue with aperture control is to put the camera in M mode (auto ISO off, aperture ring not being used) with aperture set wide open and shutter speed at something slow (e.g. 1-2 seconds). Release the shutter while observing the aperture opening through the front of the lens. Anything other than the aperture remaining wide open is indication of a problem with the controller. If the problem has been intermittent, it may help to do the test after a period of non-use. Even one failure is significant

was meant for a "failed camera"! To find out if there is Aperture Control Failure. How can the reader test "Failure of Aperture Control" on a healthy camera? It has to have the failure. Of course will the reader applying this test to a healthy functioning body that the aperture stays wide open.
And if he sets the lens on its ring to f22 the aperture closes down to f22 when he releases the shutter. That's how it ought to be. And it will do so with a dead or without a solenoid because in M-Mode the solenoid is not in action!

But the whole point is to find out if the solenoid is NOT WORKING!

I would also caution that the live view auto-protect behavior is not part of a shutter release sequence and may not account for related or alternative causative factors (e.g. mirror timing/positioning problems).

Can you explain what you mean with "the live-view auto-protect behavior"? Never heard about this.
Anyway, the K-70 with aperture control failure does show in Live-View-Mode very quickly if the solenoid is stuck or it isn't.

** Another option might be to simply attempt optical DOF preview with the body-set aperture at maximum. Again, I don't suggest this because it is not part of the normal shutter cycle.

Optical preview does not work if the solenoid is stuck!

* I have observed at least f/16 with the camera pointed at a clear December sky at 45.8° N.

Yes, but not with a K-70! That's the whole point:

...not a K-70 owner....

** With both the K-30 and K-50, mirror issues were a common "co-morbidity" and it was not clear what caused which and whether mirror sequence was needed to detect, hence the testing of the full shutter sequence.

I had many K30/50/500/K-S1, K-S2 and now 2 x K70 for repair with "aperture control failure" and I have helped many to repair theirs.
I only came across "messed up mirror sequence" when people applied the sanding/filing method because here the complex mechanism can get messed up.
Otherwise, there was never ever any co-morbidity and it was always 100% clear that what caused the problem was the stuck solenoid only!
Every official repair done in Germany and Switzerland was either replacement of the complete "diaphragm control block" (G-100) or when they finally realized that it was only the solenoid and that repair was much more simple, they just replaced the solenoid.
By the way, the "diaphragm control unit" in the K70 differs in 2 ways to the early version:
The plunger of the solenoid is of better quality
The screw fixing the solenoid into the assembly sits left instead of right
I have now found already 2 x this new version in "officially repaired K-30's" and they failed again just after 1 year.
After exchange of the green China-Solenoid against the white Japan-Solenoid all was fine and still is fine!

I reread your account and it dawned on me what you may be trying to explain; that you are not seeing the solenoid energized when the body is set to control the lens to maximum aperture. Never-the-less, hundreds of users on this site have diagnosed aperture control failure using the procedure outlined at the top of this page and it is not unusual to have dark frames reported with the lens set to maximum aperture. It appears there is a crack somewhere.

Can you link posts by those who actually claim having used this method diagnosing the failure using your recommended prodedure?
I have not found any.

Also you will not find any post where somebody has "dark frames" with the lens set to maximum aperture because then the solenoid is not acting!
There is no "other crack". I have verified it many many times.

[stevebrot]

Can you link posts by those who actually claim having used this method diagnosing the failure using your recommended prodedure?
I have not found any.

Also you will not find any post where somebody has "dark frames" with the lens set to maximum aperture because then the solenoid is not acting!
There is no "other crack". I have verified it many many times.

I have reviewed your comments on this site regarding this problem and have been doing some additional research. The reason I said there were "cracks" is because there are puzzles in regard to your description of behavior in cameras you have repaired. I have decided to puzzle this out, but will no longer be interacting with you on the subject.

Given the low level of activity of actual reports of K-70 aperture control issues, I am asking the mods to close comments and mothball this article.


Steve

(...armature...)

[Sandy Hancock]

The one user who has consistently taken issue with the content in this thread will no longer be contributing.
I hope this may encourage the OP to maintain his stewardship.

[SharkyCA]

The G100 block uses the solenoid. The G200 assembly uses a motor and worm gear. Since the K-70 has a solenoid it must be a version of the G100.

Yes, thanks for the feedback! My post was to draw attention to the fact My camera was professionally repaired at a Pentax site and the part they replaced is pictured as they returned the used part to me which is identical to the part sold by USCamera.Pentax 77860-G0100 Diaphragm Control Block | K-S2 | K-30 | K-50 | PartsUSCamera Which appears to fit KS-2,K-30, and K-50.



Without an actual service manual displaying parts and part numbers a lot of information is speculative at this point!
Cheers!