[reh321]

It certainly looks like Dark Image Syndrome - the entire histogram is squished into the left one-fourth. To see if this is the aperture control issue, you should follow the test described by @stevebrot;

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.

Attached Images

 

[stevebrot]

Hello there.

I have been using K-70 for couple of weeks and I have experienced some issues. In random the photos are over or mostly under exposured.

Two photos with same settings:





Anyone had the same problem?

Thanks

Welcome to the Pentax Forums!

As noted above, there may be a problem with aperture control by the body. Given that you also report overexposure, it might be good to also rule out sticky/lazy iris. This is done by taking the lens off the camera and using a finger to flick the aperture actuator lever while observing through the back of the lens. The action to open and close should be snappy and without hesitation.

As noted above by reh321, one can test aperture control by switching to "M" mode, setting the aperture to its widest setting, setting shutter to 1 second or longer, and observing the iris action through the front of the lens while releasing the shutter. Anything other than staying wide open indicates an error in aperture control. Whether the error is due to failure of the aperture control block requires a visit to a service center or expert amateur tear-down. I have added your report to the list of reported underexposure problems for the K-70 on the list maintained on a dedicated thread:

https://www.pentaxforums.com/forums/193-pentax-k-70/377096-k-70-underexposed-photo-reports.html

On the practical side, if the camera was recently purchased, I suggest contacting the seller for return and refund.


Steve

[alex74]

Just got answer from service...

They have to change aperture mechanism and some electronics.
The cost is around 160 EUR.

Looks like, there are still problems with K70 like with other models...

[stevebrot]

Just got answer from service...

They have to change aperture mechanism and some electronics.
The cost is around 160 EUR.

Looks like, there are still problems with K70 like with other models...

Thanks for circling back. I was wondering what your outcome was since your symptoms were puzzling. The fact that that more than one component is involved in the repair indicates that your camera's problem is similar to, but probably not the same as with the K-30/K-50. One other user had a two-component repair, so perhaps the two are related. At least we can take comfort that the incidence of this sort of problem is quite low, at least on this site.

Do you have the option of warranty repair?


Steve

[alex74]

Do you have the option of warranty repair?

I bought camera in England and I had to send it back to England.
But I give it to service in Slovenia and they don't recognise the warranty.

[photogem]

Just got answer from service...

They have to change aperture mechanism and some electronics.
The cost is around 160 EUR.

Looks like, there are still problems with K70 like with other models...

It is for 99,0% certainty just the solenoid and not at all any other "some electronics".
The costs are typical for this repair, all they have to do is to exchange the solenoid (but sadly they will use the same China-made solenoid again).

In Europe it is usually € 250 for exchange of the complete diaphragm unit.
This would actually be necessary only in 1% of all cases, most unlikely in yours.


The best way would be to DIY!

If you read how it is done with the K-30/50
and use the photos here you can do it by finding the white Japan solenoid, which is the best solution.

Read about the history of the solenoid , sadly it seems that still some K-70's fail, but it is much less since the K50 with any other Pentax.

[reh321]

It is for 99,0% certainty just the solenoid and not at all any other "some electronics".
The costs are typical for this repair, all they have to do is to exchange the solenoid (but sadly they will use the same China-made solenoid again).

I don't have the info right at hand (*), but another member sent a K-70 with similar symptoms to the Pentax repair facility, and they replaced solenoid plus an associated resistor. Back in the days of the K-50, user @RedSky posted in despair because users here kept pointing him to the solenoid, and the solenoid had already been replaced. I am quite willing to believe that "some electronics" besides the solenoid might be involved when LCD and OVF differ in meter reading - the "some electronics" may even eventually drag down a weak solenoid.

edit: it was user @rwhynacht in post #110 of
https://www.pentaxforums.com/forums/53-pentax-dslr-camera-articles/377096-k-...ml#post4714311

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Last edited by reh321; 11-03-2019 at 04:06 PM.

[photogem]

I don't have the info right at hand (*), but another member sent a K-70 with similar symptoms to the Pentax repair facility, and they replaced solenoid plus an associated resistor. Back in the days of the K-50, user @RedSky posted in despair because users here kept pointing him to the solenoid, and the solenoid had already been replaced. I am quite willing to believe that "some electronics" besides the solenoid might be involved when LCD and OVF differ in meter reading - the "some electronics" may even eventually drag down a weak solenoid.

edit: it was user @rwhynacht in post #110 of
K-70 Underexposed Photo Reports - Page 8 - PentaxForums.com

It is very simple:

For a repair the repairshop needs first to take the camera apart.

And all those ancient posts by @RedSky weren't really helpful at all, not a good idea to refer to those!


And if any repairshop wrote that they had to replace a resistor: Paper is very patient!

To make people scared or worried or uneasy is a great way to make money.

[reh321]

It is very simple:

For a repair the repairshop needs first to take the camera apart.

And all those ancient posts by @RedSky weren't really helpful at all, not a good idea to refer to those!

No, neither the Pentax repairmen nor the people here were helpful to @RedSky.
Maybe, just maybe, he needed that extra resistor replaced also.

[photogem]

No, neither the Pentax repairmen nor the people here were helpful to @RedSky.
Maybe, just maybe, he needed that extra resistor replaced also.

There is nor an extra resistor nor an resistor driving the solenoid!
People claiming that they replaced a resistor either don't know what they are talking about or intentionally spread butter on a bread, which doesn't even exist.


He only needed a good Japan solenoid.

But you know what: I found a very interesting solution:

You Tube

You Tube

This solenoid will never fail.
Allthough.... actually.... I must admit:
I lied: The US-made solenoid on my John Deere failed!
I ordered a socalled replacement solenoid, and guess what:
It was "made in China"!

I tried to find an original, no more available, only China version!
Too bad.

Ah... almost forgot: No resistor either for this John Deere solenoid, nor "other electronics"....

[SharkyCA]

There is nor an extra resistor nor an resistor driving the solenoid!
People claiming that they replaced a resistor either don't know what they are talking about or intentionally spread butter on a bread, which doesn't even exist.


He only needed a good Japan solenoid.

But you know what: I found a very interesting solution:
How to Replace Trombetta Solenoid 12V PN 7641211210 on John Deere LA100 Riding Lawnmower - YouTube

This solenoid will never fail.
Allthough.... actually.... I must admit:
I lied: The US-made solenoid on my John Deere failed!
I ordered a socalled replacement solenoid, and guess what:
It was "made in China"!

I tried to find an original, no more available, only China version!
Too bad.

Ah... almost forgot: No resistor either for this John Deere solenoid, nor "other electronics"....

Lol, as you previously documented and referenced with my photo of the K-70 control block photo, "no resistor" on the full assembly.

The above photo is the "original control block" from my K-70 returned to me after repair at Sun Camera in Toronto, Ontario the authorized repair center in Canada.

Have fun, shoot lots!

[stevebrot]

It is for 99,0% certainty just the solenoid and not at all any other "some electronics".

Out of curiosity, what is your source of information? 99.0% confidence is a pretty amazing claim. Are you suggesting that authorized service facilities on two continents are padding their repair quotes with unneeded replacement parts? Alternative, is it possible that their diagnostic software is capable of detecting root cause failure outside the aperture control block?

Honest question. You may PM me your detailed response if that is more comfortable and appropriate. I don't intend to take part in an extended public discussion.


Steve

[photogem]

There is no reason for anything secret.

One just has to study the circuit, actually there are two circuits, because there is the same solenoid (as in many Pentax bodies) for the flash which received the very same short impuls of 7.2 Volts: No resistor in the circuit.
Why an authorized service once mentioned a resistor one can only guess. Possibly an error of who ever wrote the invoice or to make it sound more special.

Diagnostics work via debug-menu and not anykind of secret connector for somekind of unknown diagnostic software!

Since the introduction of the K30 and first failures we know in every detail what was done by authorized service facilities and it was often enough explained in detail,
but for you one more time:

- None of the authorized service places even knew that it was "just the solenoid"! They always replaced either the complete diaphragm control unit or even the body!

after we here in this forum and others in other forums did extensive research, it was finally brought to the very point:

The only faulty part was the green China-made solenoid!

- from then one some authorized workshops either just replaced the solenoid (with the same China-version though), others even filed/sanded it, others carved the surface of the plunger, while some did not even get it and still replaced the complete diaphragm unit.


None ever replaced the solenoid with the white Japan-version because this one was not available anymore: They cannot use 2.nd hand solenoids but must use new ones. Imagine the fun Pentaxbashers would have if they could prove that used old parts are used for repair! So not an option, which is too bad.

But back to the insistance that once they read that there was a resistor replaced: If you can find one, show it to me!
I would be the first to apologize.

[stevebrot]

But back to the insistance that once they read that there was a resistor replaced: If you can find one, show it to me!

Just the reports of two people who have actually had the repair done by authorized service on two different continents where replacement of a resistor chip (not a single resistor) was listed on the account of work done. Now if authorized service with the full access to model-specific diagnostic harnesses is not to be trusted for diagnosis or repair, what can one say?

It must be the solenoid and always the solenoid! I totally get it.


Steve

(...still trying to figure out why the authorized service on my close friend's K-50 is still working properly five years later despite being presumably done with a green solenoid diaphragm control block assembly...)

[photogem]

It was one report!
The other report was wishy washy and not from an authorised service.

It is very simple:

Once an authorised car garage gave me a very strange diagnosis:
I had my summer-tyres stored there and wanted them to be exchanged again against my winter tyres.
I phoned them for an appointment. They mailed me back and told me that the tyres were down to 3mm, no use anymore.
I knew this was impossible, I had driven them just one summer.

Called them and asked them that I wanted them exchanged anyway.

They told me that this wouldn't be a good idea because one tyre anyway is faulty, it has a nail inside!
Right away I drove there and asked them to hand out my tyres:
5 min later I got them: No nails and 7mm, I drove them for a few more years!

But back to the solenoid, whose faultyness you somehow don't like or try to play down:

How often do I have to repeat this?

If there is no resistor in the circuit.....


..... and thus, no diagnostic tool in this universe can find a faulty resistor!

The solenoid is driven by a so called plunger driver, which is an integrated circuit (IC)

It is similar to THIS ONE
If you google, you can even find the patent, filed by Matsushita.

Of course an IC is driven by "other electronics" as well, but not after the IC.

This IC/plungerdriver (luckily) never ever got damaged.

Repairing this circuit would anyway be way too expensive!