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.


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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...)

[SharkyCA]

Interesting, because the picture of the control block in a K-70 posted on the German Pentaxians forum has a different configuration. The infamous green solenoid is mounted diagonally. The block you show looks similar if not identical to the earlier assembly. I recall someone saying the K-70 block is not compatible with the K-S1/S2 and K-30/50.

Did Sun list a part number as well on the invoice/work order?

BTW: there appears to be two dates on it - 2017.7.14 and 2017.8.10. Assembly and inspection dates?

The part Sun Camera sent me back looks an awful lot like this one:Pentax 77860-G0100 Diaphragm Control Block | K-S2 | K-30 | K-50 | PartsUSCamera

Attached Images

 

[reh321]

@Not A Number

Do you have a link for the German site??
No part # only description, not sure about date stamps.

I bought the camera in Sept 27 2017!!

If they are using the same way of representing dates that is used by technical users in the US, that would put roughly a month between their assembling the camera {Aug 10} and your purchasing it {Sept 27} - then 1-1/2 years to failure; that fits a K-30 timeline {to go with a K-30 DCB}, but I would expect a lot more noise about the K-70 if that were the case, I wonder if they are using two different 'Diaphram Control Blocks' in the K-70.

[Not a Number]

My bad, translating the German via Google of this page (see picture in 7th post):

Tutorial - Reparatur Pentax K-70 Blendensteuerung Solenoid ? Pentaxians

It says the solenoid is already unscrewed thus the different orientation of the solenoid

But then hasn't a member here claimed to have communicated with the President of Ricoh how said the K-70 uses a new component? Maybe the solenoid is different. Do you have a multi or ohm-meter to measure the resistance across the coil? Measuring the breaking force between a K-70 and K-50 solenoid would be great but how do you calibrate "finely tuned fingers"?

[stevebrot]

Finally got my camera back from SunCamera Service, I have only taken 1 Photo but at least that worked.

Here is the part they replaced Diaphragm Control Block, I bought the camera Sept 2017, I notice the date stamp on the returned part is July 2017 ???

Thanks for closing the loop. I'm glad they were able to do a repair so that you can continue to enjoy your camera.


Steve

[SharkyCA]

My bad, translating the German via Google of this page (see picture in 7th post):

Tutorial - Reparatur Pentax K-70 Blendensteuerung Solenoid ? Pentaxians

It says the solenoid is already unscrewed thus the different orientation of the solenoid

But then hasn't a member here claimed to have communicated with the President of Ricoh how said the K-70 uses a new component? Maybe the solenoid is different. Do you have a multi or ohm-meter to measure the resistance across the coil? Measuring the breaking force between a K-70 and K-50 solenoid would be great but how do you calibrate "finely tuned fingers"?

Looks like a thorough explanation but I too do not read German so the translator had to do and becoming a member of a German Forum to follow the links seemed a little much.
I do have a multi-meter what were you looking to do ?

I am still interested in finding out the manufacture date of my camera because if the part in the picture for the solenoid they sent back to me is before (2017.7.14) then the part they sent is not from my camera.

Found the manufacture date re EXIF data and this Forum Check Camera Shutter Count and Manufacture Date

[stevebrot]

I am still interested in finding out the manufacture date of my camera because if the part in the picture for the solenoid they sent back to me is before (2017.7.14) then the part they sent is not from my camera.

The part in the photo is stamped 14 July 2017 and 10 Aug 2017. On another thread you posted date of manufacture from EXIF as 14 Aug 2017. You purchased the camera 27 Sept 2017.

It all looks good to me. There is no inconsistency in the dates.


Steve

[Not a Number]

I do have a multi-meter what were you looking to do ?

Measure the resistance of the solenoid coil. The green solenoids come in 30 and 15 ohm - used for the aperture control and flash popup, respectively. The white solenoid used in the K series DSLRs measures at 30 ohms also. The white solenoid in AF film cameras (MZ/ZX etc.) measures at 27 23 ohms. You may have to un-solder one of the power leads to the solenoid (pink and grey leads as I recall).

The plastic on the solenoid is green correct? Although most plastics can be made just about any color so not too much should be made of the color.

---

Last edited by Not a Number; 06-27-2019 at 08:35 AM.

[stevebrot]

The plastic on the solenoid is green correct? Although most plastics can be made just about any color so not too much should be made of the color.

Yay! So much has been made about the solenoid color based on assumptions about materials. So, what will measuring the coil resistance on the defective unit tell us?


Steve

[Not a Number]

So, what will measuring the coil resistance on the defective unit tell us?

If the resistance is significantly different from 30 ohms it might tell us that this is a different solenoid from the earlier ones used. If you look on the Shinmei website the different models of solenoids have different resistances as well as latching/breaking forces.

[SharkyCA]

The part in the photo is stamped 14 July 2017 and 10 Aug 2017. On another thread you posted date of manufacture from EXIF as 14 Aug 2017. You purchased the camera 27 Sept 2017.

It all looks good to me. There is no inconsistency in the dates.


Steve
The part in the photo is stamped 14 July 2017 and 10 Aug 2017. On another thread you posted date of manufacture from EXIF as 14 Aug 2017. You purchased the camera 27 Sept 2017.

It all looks good to me. There is no inconsistency in the dates.


Steve

The part in the photo is stamped 14 July 2017 and 10 Aug 2017. On another thread you posted date of manufacture from EXIF as 14 Aug 2017. You purchased the camera 27 Sept 2017.

It all looks good to me. There is no inconsistency in the dates.


Steve[/quote]

Yes Steve I updated the message with "My manufactured date" sorry I wasn't clear on that.

[SharkyCA]

Measure the resistance of the solenoid coil. The green solenoids come in 30 and 15 ohm - used for the aperture control and flash popup, respectively. The white solenoid used in the K series DSLRs measures at 30 ohms also. The white solenoid in AF film cameras (MZ/ZX etc.) measures at 27 ohms. You may have to un-solder one of the power leads to the solenoid (pink and grey leads as I recall).

The plastic on the solenoid is green correct? Although most plastics can be made just about any color so not too much should be made of the color.

Checked with multi-meter, solenoid leads are PINK & PURPLE plastic housing for the coil is GREEN the resistance I measured across the leads is 30.1 ohms. I am still unsure as to what this is going to confirm other than the fact the solenoid has continuity or is open.

I have taken a few images since the repair and so far I have not had a dark image, fingers crossed that it does not fail again around 8000 images, the first signs of failure were about the 4500 shutter count!

[photogem]

Finally got my camera back from SunCamera Service, I have only taken 1 Photo but at least that worked.

Here is the part they replaced Diaphragm Control Block, I bought the camera Sept 2017, I notice the date stamp on the returned part is July 2017 ???

This is very interesting!
Here is a photo of the diaphragm control block as I found it in a Pentax K30 which was repaired under warranty:

Front side:


Back side:



Now it would be very interesting if you could make a macro photo of the plunger (horseshoe).

Just unscrew the solenoid without unsoldering it (if that's too difficult). Then you just plug out the plunger.

Particular the bottom side, i.e. this part, which faces upwards towards this tiny magnet.

You can see very clearly:


The screw for the solenoid on your K70 Diaphragm Control Block is on the left side (as it is on the new K30 block!!!)


while the old Diaphragm Control Block has the screw on the right side!


So the unit has some minor changes but actually seems to fail every time and then.


So I am very curious for the macro photos if that's possible!?

[stevebrot]

This is very interesting!
Here is a photo of the diaphragm control block as I found it in a Pentax K30 which was repaired under warranty:

Front side:


Back side:



Now it would be very interesting if you could make a macro photo of the plunger (horseshoe).

Just unscrew the solenoid without unsoldering it (if that's too difficult). Then you just plug out the plunger.

Particular the bottom side, i.e. this part, which faces upwards towards this tiny magnet.

You can see very clearly:


The screw for the solenoid on your K70 Diaphragm Control Block is on the left side (as it is on the new K30 block!!!)


while the old Diaphragm Control Block has the screw on the right side!


So the unit has some minor changes but actually seems to fail every time and then.


So I am very curious for the macro photos if that's possible!?

Perhaps a new thread or PM? The purpose of this thread is to track K-70 aperture control reports for Pentax Forums owners and to document outcomes of those reports. This comment, while interesting, is off-topic (not K-70, not a report, not an outcome). The rat hole of speculation regarding cause and blame is noise in the channel and belongs elsewhere.


Steve (OP)

[photogem]

Perhaps a new thread or PM? The purpose of this thread is to track K-70 aperture control reports for Pentax Forums owners and to document outcomes of those reports.

And that's what SharkyCA did, he uploaded a photo of the damaged Diaphragm Control Unit of his K-70.
He was surprised to find out that the Diaphragm Control Unit offered by uscamera.com looks 100% identical to the one from his K-70!

Because actually it is 100% identical*!

This comment, while interesting, is off-topic (not K-70, not a report, not an outcome).

It is by no means off-topic! SharkyCA's reminded me of the Diaphragm-Control-Unit I found in an official repaired Pentax K30.
That this new "designed" Diaphragm-Control-Unit:
a) uses the very same green made in China solenoid
b) is offered and used as a replacement Diaphragm-Control-Unit for the K30, K50, K500, K-S1, K-S2

c) is used in the K-70 and .... fails occacionally

The rat hole of speculation regarding cause and blame is noise in the channel and belongs elsewhere.

Speculation is one way to find access to solutions.


*One neat example is the fact that actually the new replacement "Diaphragm Control Block" for the K30 and all others afterwards and the one now found to be taken out of SharkyCA'*s K-70 are identical.



Of course stupid and particular "intentional misleading speculation" (for political or business reasons) is very much as you say it more directly than indirectly "the method of rats" .... very much so, I fully agree

But my very interest and very intentions come from my own "deep interest and love for Pentax" and not as it could be understood by your response "for blame".

Not at all!


But your response could very much be interpreted as fear of an outcome you would not like?

"Ignorance is as much a rat hole as are 'wrong intentional misleading speculations' ratholes!"
Ignorance is a very large "rat hole" very neat for hiding (facts in this case!).

[SharkyCA]

Perhaps a new thread or PM? The purpose of this thread is to track K-70 aperture control reports for Pentax Forums owners and to document outcomes of those reports. This comment, while interesting, is off-topic (not K-70, not a report, not an outcome). The rat hole of speculation regarding cause and blame is noise in the channel and belongs elsewhere.


Steve (OP)

And that's what SharkyCA did, he uploaded a photo of the damaged Diaphragm Control Unit of his K-70.
He was surprised to find out that the Diaphragm Control Unit offered by uscamera.com looks 100% identical to the one from his K-70!


It is by no means off-topic! SharkyCA's reminded me of the Diaphragm-Control-Unit I found in an official repaired Pentax K30.
That this new "designed" Diaphragm-Control-Unit:
a) uses the very same green made in China solenoid
b) is offered and used as a replacement Diaphragm-Control-Unit for the K30, K50, K500, K-S1, K-S2

c) is used in the K-70 and .... fails occacionally



Speculation is one way to find access to solutions.


Of course stupid and particular "intentional misleading speculation" (for political or business reasons) is very much as you say it more directly than indirectly "the method of rats" .... very much so, I fully agree

But my very interest and very intentions come from my own "deep interest and love for Pentax" and not as it could be understood by your response "for blame".

Not at all!


But your response could very much be interpreted as fear of an outcome you would not like?

"Ignorance is as much a rat hole as 'wrong intentional misleading speculation'!"
A rat hole very nice for hiding (facts)!

I do not see how these posts are "off topic" as it is documentation of "K-70 Diaphragm Control Failure" and the resolve to that failure, suggesting to open a new thread while this thread is already under "Pentax K-70, K-70 UnderexposedPhoto Reports" seems counter productive if we are looking for solutions.

I have to agree with Photogem.