[altopiet]

It took me about two hours from removing the first screw to assembling everything back, including about one hour to file the "horse shoe" and test the actuation force again and again.
But I have spent many hours to search solutions, search how to disassemble the body, and decide to do this by myself.
By the way, I printed this as a screw map to keep all screws in their position. Transparent double-sided adhesive is very helpful in case you move the paper by accident.

Very nice, perhaps I'll shelve mine till I retire, and then try the fix.... before going for my original "death by rock" method that I contemplated

[xunwp]

Good to hear more are fixed. I am curious if just pulling the shoe off the magnet would fix it, at least for a while.

I'm afraid not.
The magnet is too powerful. Both solutions, including filing the shoe and enlarging the space, are aimed to weaken the actuation between the shoe and the magnet.

[Imagery By George]

Has Pentax yet to acknowledge that there is a problem with the K-50? It seems that it wasn't on the market very long. I had to return one under warranty because of aperature problems and they replaced it with a new camera; my second one developed aperature problems this past spring. I'm very disappointed and don't know what to do - I understand they charge $200+ just to look at the cameras for repair. This is really disheartening. I loved my K-50 at first, now cannot use the TTL features one owns an SLR for, I can only take photos by using the LCD panel - through the lens is extremely dark no matter what I do.

George

[reh321]

Has Pentax yet to acknowledge that there is a problem with the K-50? It seems that it wasn't on the market very long. I had to return one under warranty because of aperature problems and they replaced it with a new camera; my second one developed aperature problems this past spring. I'm very disappointed and don't know what to do - I understand they charge $200+ just to look at the cameras for repair. This is really disheartening. I loved my K-50 at first, now cannot use the TTL features one owns an SLR for, I can only take photos by using the LCD panel - through the lens is extremely dark no matter what I do.

George

There's a guy who fixes the problem for something like $100.

[patrick9]

There's a guy who fixes the problem for something like $100.

I had him fix mine.

[paolo11]

Has Pentax yet to acknowledge that there is a problem with the K-50? It seems that it wasn't on the market very long. I had to return one under warranty because of aperature problems and they replaced it with a new camera; my second one developed aperature problems this past spring. I'm very disappointed and don't know what to do - I understand they charge $200+ just to look at the cameras for repair. This is really disheartening. I loved my K-50 at first, now cannot use the TTL features one owns an SLR for, I can only take photos by using the LCD panel - through the lens is extremely dark no matter what I do.

George

try pentaxcamerarepair.com

[tsvetan]

Dear All,
I thank to you all for this helpful discussion and your experience! I was very happy to manage to repair my k-30 aperture control after shooting manual for more than a year. It was my second k-30, the first k-30 got dark images after aprox. 10 K shots, I sent it back and after 2 months without any reply received a new body. This second body developed the same problem again around 9 K shots and since then I have been shooting only manually.
I used the russian method, I filed some material off the U part and now it works again! Thank you so much! This is a great community!

Attached Images

   

[paolo11]

Now after seeing the excellent photos, I wish I had tried it. I mailed it out to a guy in CA who does this sort of thing. My K50 failed after about 1 k shots. Getting it back tomorrow. It will be interesting to find it if this is a permanent fix, so keep us all posted.

[xunwp]

Thank you for the detailed disassembly instruction.
I tried to repair my K-30 last night and it looks I did it. The aperture works normally with both AA batteries and Lion battery, at least till this moment. Cheers!
I filed two ends of the "horse shoe", following the advise from our Russian friends. https://www.pentaxforums.com/forums/151-pentax-k-30-k-50/321871-k-30-k-50-ape...ailable-2.html
I prefer the Russian solution because in this way the magnet can still hold the horse shoe reliably while the actuation between them is weaken.

Bad news, the aperture problem comes back when the Lion battery is fully charged, while it does work well when the battery is not fully charged. However, the aperture problem is slightly different from that before I repaired it using the Russian method, the following are the details.
When I switch to LV mode, the aperture shrink to the correct F stop first, then after a very short delay (maybe less than 0.1s), it continues to shrink to the minimum. So it seems that the solenoid fails to hold the aperture in correct position when it should do. This problem occurs at about 20% probability when I switch on/off LV mode. BTW, the aperture always works fine with depth of field preview button.

I think it is a voltage-related problem since it only occurs with a fully charged Lion battery. This agrees with the fact that AA batteries can help solve the aperture problem. AA did work on my K30 for the last year until it got worse.

Perhaps I have to pick up my AA batteries again. I wonder whether it is because I sand the "horse shoe" too much. However, it is very strange that a fully charged battery causes the aperture failure.

Read more at: https://www.pentaxforums.com/forums/151-pentax-k-30-k-50/321871-k-30-k-50-ape...#ixzz4W6Cn6nTa

[kman42]

I tried this repair on my K50 last night. It appears to have worked, as the solenoid was stuck when I opened the camera up and now moves freely. However, while soldering the cluster of wires to reassemble the camera, I shorted the soldering iron on something . There was a loud pop and now the camera doesnt power on at all I double checked all the wiring and the electrical ribbon - it is all correct. Any suggestions on a solution, or do I now have a weatherproof paper weight?

[victormeldrew]

I tried this repair on my K50 last night. It appears to have worked, as the solenoid was stuck when I opened the camera up and now moves freely. However, while soldering the cluster of wires to reassemble the camera, I shorted the soldering iron on something . There was a loud pop and now the camera doesnt power on at all I double checked all the wiring and the electrical ribbon - it is all correct. Any suggestions on a solution, or do I now have a weatherproof paper weight?

Probably, the short answer is yes. Loud pops/cracks from circuits are generally very serious. If you weren't using ESD-safe soldering techniques, the risks are pretty high.

Was the battery connected at the time?

Save

[kman42]

Probably, the short answer is yes. Loud pops/cracks from circuits are generally very serious. If you weren't using ESD-safe soldering techniques, the risks are pretty high.

Was the battery connected at the time?

Save

No, the battery was removed.

[steveo-1]

After sitting idle for a few months, I fired up my K-30 to find it was taking black photos only. After some basic troubleshooting, it was obvious that the aperture was closing down all the way, no matter what the camera said it should be. So some internet searches led me here because it seems the only technical article is from a Russian site. One of the members here was good enough to translate it for us, so at least I had a basic understanding of what to look for.

Since I have a long background in electronics troubleshooting and working on small delicate items, I decided to dig into my K-30. It was useless and not worth anything as it was, so what's to loose? Here I'll explain how I did it, and maybe help others that find themselves in a similar situation.

So let’s get started. For the sake of clarity, the right and left sides of the camera are when viewed from the front. Also, work with a body cap to protect all the innards, and keep small parts from flying in there.

1) Remove the bottom plate: Remove all the screws holding the bottom plate. Make careful note of which screw came from which hole. Some screws are fine thread for metal and some are coarse thread for screwing into plastic. There are 3mm, 4mm, 6mm, 7mm and 10mm screws. While you’re at it don’t forget the silver screw down inside the battery compartment. There is a total of 13 screws.



2) Remove the top cover: WARNING: (I hate stupid warning messages, but this IS important, so DON’T take it lightly. The flash capacitor is directly under the PCB that you will be desoldering wires from on the right side, and areas near the PCB do have some “juice” that can give you a NASTY JOLT – one you won’t forget! Be very careful).

Slide the rubber eyepiece up to remove it. There are 2 screws under it that need to be removed. Remove the 2 screws just inside the loops for the neck strap. There is another screw on the right side just under the button for the pop-up flash. Now pop up the flash and remove the 3 screws inside the front. There is a total of 8 screws. The top cover is not difficult to remove at this point. A thumbnail pressed into the top cover seam is all that is needed to get it started. Be gentle. If you pull too hard and it suddenly pops off, the wires inside will most likely get ripped off their solder pads. There is a total of 6 wired to be unsoldered.

3) Unsolder the wires from the PCB on the right side. Position the camera as shown below to minimize the stress in the wire leads. Make note of their locations and unsolder them. (Remember that warning above????)

4) Remove the ribbon connector on the left side.





5) In case you lose track of where the wires go, this should help.

6) Remove the front cover: Remove the rubber grip on the right side of the camera. There are 2 screws underneath. Peel back the left rubber grip slightly and remove the first screw that appears. Lay the rubber back down – there is no need to remove it. Remove the other screw on the left side near the DC power jack. There is one more screw on the bottom between the projections for the lens and hand grip. There is a total of 5 screws. The front cover should pop off – there are no wires connected to it.



7) With the 3 covers removed, we can get to the solenoid. It’s just to the left of the large silver cross in the center of the photo. Unsolder the 2 wires. You will need a long small jewelers size Phillips screwdriver to remove the screw that holds it in place. Now just pick it out by the steel frame, not by the copper coils!



8) Here’s the culprit. The solenoid is shown in it’s activated position, locked in place, even though there is no power applied. When the solenoid is activated, the horse shoe shaped plunger (the bottom piece of steel) is pulled up into the 2 coils, as shown. This activates the arm that controls the aperture opening. The vertical slit in the top of the frame has a powerful neodymium magnet inserted into it. The problem is that the plunger is pulled in so far that the legs of the horse shoe hit the highly magnetized frame at the top of the solenoid. The magnetic pull is so great that the horse shoe plunger is locked in place very solidly. I didn’t think to measure the amount of force to pull the plunger back out, but it has to be at least a couple of pounds. That magnet is surprisingly powerful.





9) Since I didn’t want to make any permanent changes that couldn’t be reversed, I elected to fill in the gap at the bottom of the horse shoe, and then add another .25mm so it would bump the plastic solenoid coil form before the top end of the legs could get magnetically locked to the upper steel frame. So I filled the bottom of the of the horse shoe with solder and then carved it into shape with an x-acto knife (with a new blade) so the legs are now only 3.37mm long, as opposed to the original 3.87mm long.

10) At this point, I put it all back together by just reversing the whole procedure. The camera is taking fine pictures again, and for 0$$. Total time was about 3.5 hours. If you want to try this yourself, here are a few pointers:
Be patient and think things out.
Be gentle - it's a delicate item with even more delicate parts inside.
Have a large, clean and organized work area.
Spread out a clean bath towel over your work area - small parts do not bounce off of a towel.

Thanks. This makes more sense than anything I've read about the problem so far. And I also agree with some comments suggesting a weakened spring may be part of the problem.

Too bad I didn't find your post two days ago when I took my K-50 apart and did the sanding fix - that freed it up for now. But if aperture sticks again, I'll remember to try this fix next. I documented what I did on a different thread and included a youtube link to a video describing how to take the K-50 apart and get to the aperture block. I also included a few pictures of the aperture block in the camera.

Before I dismounted the magnet assembly I pushed the control arm down with my finger. It took a fair amount of pressure for such a small part to get it unstuck from the top of the magnet. Once unstuck it snapped down with authority.

Nice job Clover-leaf!

[redman-f]

I applied a different modification of the "horseshoe" on by K-50.
As the solder added to shorten the legs of the horseshoe will impact on the plastic base of the coils, I feared that it might take some damage over time. Maybe that concern is complete rubbish, but there you are.
So I took a different approach to reduce the magnetic pull on the slider. I filed off some material from the legs without reducing their length. Works nicely so far.

[Nuno Almeida]

I applied a different modification of the "horseshoe" on by K-50.
As the solder added to shorten the legs of the horseshoe will impact on the plastic base of the coils, I feared that it might take some damage over time. Maybe that concern is complete rubbish, but there you are.
So I took a different approach to reduce the magnetic pull on the slider. I filed off some material from the legs without reducing their length. Works nicely so far.

Did exactly the same, also with good results so far