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10-14-2016, 04:29 AM - 6 Likes   #31
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One possible fix !

I would like to share my experience, it seems I successfully managed to fix the aperture problem on my K-30. And I discovered later a Russian forum talking about the same electronic part...
Anyway, the aperture controller mechanism is composed of several parts, including some kind of brake. This braking system didn't trigger in my case, causing the aperture blades to close all the way down at the few firsts activations. At first, I had to warm it up with 3 to 4 activations, then 5 to 6 a few months later, then about ten and then... I got bored, and took my screwdrivers !



Next to this double coiled electromagnetic brake trigger, are the aperture gears.
The way it works is not that difficult to understand when you can watch it by activating depth of field preview.

Here are the main steps :

- The gears are by some actuator.

-- So, the aperture lever translates.
-- So, the slotted encoding wheel turns.
-- So, the camera can count the number of slots passing through an optical sensor.

- When the required translation is achieved, those gears need to be stopped.

- The camera sends a current pulse in the brake trigger coils.

- The pulse releases the metal part (drawn in blue) from the attraction of the magnet.

-- So, the brake lever gets down.
-- So, the gears get stopped.
-- So, aperture is controlled !



The problem in my case, was the metal part not willing to leave the magnet's attraction. The gears were still working, the brake lever too. The pulse of current was also sent. So, I came up with the idea to slightly increase the distance between the magnet and the metal part by applying a thin layer of tin with a soldering iron (actually, it was more of a big drop that I thinned to the desired thickness afterwards). Logically, any non-magnetic material should do the trick !



After two times (the first one was two thick), it made my aperture controller working again !
The best part in this fix, is that the coils can be accessed just by removing the plastic covers. No need to recalibrate anything !

I hope this post will help you !

10-14-2016, 06:07 AM   #32
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Nice explanation.
10-15-2016, 10:58 PM - 1 Like   #33
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That same magnetizing problem happens with old phone ringer bells, they get magnetized and then the little striker that hits the bell sticks to the magnetized bell and it's silent.
10-19-2016, 12:56 PM   #34
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QuoteOriginally posted by Shephard Quote
I would like to share my experience, it seems I successfully managed to fix the aperture problem on my K-30. And I discovered later a Russian forum talking about the same electronic part...
Anyway, the aperture controller mechanism is composed of several parts, including some kind of brake. This braking system didn't trigger in my case, causing the aperture blades to close all the way down at the few firsts activations. At first, I had to warm it up with 3 to 4 activations, then 5 to 6 a few months later, then about ten and then... I got bored, and took my screwdrivers !



Next to this double coiled electromagnetic brake trigger, are the aperture gears.
The way it works is not that difficult to understand when you can watch it by activating depth of field preview.

Here are the main steps :

- The gears are by some actuator.

-- So, the aperture lever translates.
-- So, the slotted encoding wheel turns.
-- So, the camera can count the number of slots passing through an optical sensor.

- When the required translation is achieved, those gears need to be stopped.

- The camera sends a current pulse in the brake trigger coils.

- The pulse releases the metal part (drawn in blue) from the attraction of the magnet.

-- So, the brake lever gets down.
-- So, the gears get stopped.
-- So, aperture is controlled !



The problem in my case, was the metal part not willing to leave the magnet's attraction. The gears were still working, the brake lever too. The pulse of current was also sent. So, I came up with the idea to slightly increase the distance between the magnet and the metal part by applying a thin layer of tin with a soldering iron (actually, it was more of a big drop that I thinned to the desired thickness afterwards). Logically, any non-magnetic material should do the trick !



After two times (the first one was two thick), it made my aperture controller working again !
The best part in this fix, is that the coils can be accessed just by removing the plastic covers. No need to recalibrate anything !

I hope this post will help you !
Out of interest, do you have any desire to fix other people's broken K30's? My symptoms sound the same as yours. I bought a K3ii to replace it, but would be nice to rescue the K30 before sale.



10-19-2016, 01:00 PM   #35
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Why not just degauss the metal part?
10-19-2016, 01:31 PM   #36
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QuoteOriginally posted by Ian.morgan Quote
Out of interest, do you have any desire to fix other people's broken K30's? My symptoms sound the same as yours. I bought a K3ii to replace it, but would be nice to rescue the K30 before sale.
Please make sure to include you have opened it up and altered the camera to repair an issue when you sell it.
10-19-2016, 01:54 PM   #37
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QuoteOriginally posted by Not a Number Quote
Why not just degauss the metal part?
The same thought occurred to me. Doing it in situ would make the whole process a lot simpler, but I'm not sure (not having a K30) if the keeper is that accessible. You also have to figure out the polarity, to apply a reverse field, but I guess that would be the same on each body, so once one person has determined it, the rest can follow.
10-19-2016, 02:08 PM   #38
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Advance Camera does this on K30's and K50's for about $150. So, there is some thought that it might actually work. I've given up on consumer grade Pentax and now have a K5 iis that I really like along with my m42 only K30.

10-19-2016, 02:30 PM   #39
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QuoteOriginally posted by kernos Quote
Advance Camera does this on K30's and K50's for about $150. So, there is some thought that it might actually work. I've given up on consumer grade Pentax and now have a K5 iis that I really like along with my m42 only K30.
Where is Advance Camera, just in case mine ever gives out? Do they do the repair specified above by Shepard, disassembling? Or do they do the demagnetizing, mentioned by Not a Number?

So far, so good with my K30.
10-20-2016, 12:47 PM - 1 Like   #40
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QuoteOriginally posted by yucatanPentax Quote
Where is Advance Camera, just in case mine ever gives out? Do they do the repair specified above by Shepard, disassembling? Or do they do the demagnetizing, mentioned by Not a Number?

So far, so good with my K30.
My understanding is that they work with the magnets. Advance camera is in Portland Oregon and they have a website. I spent a bit of time talking to a someone who understood repair and got general info on the fix and price. Website is Advance Camera Repair
10-24-2016, 08:46 PM   #41
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QuoteOriginally posted by RobA_Oz Quote
You also have to figure out the polarity, to apply a reverse field, but I guess that would be the same on each body, so once one person has determined it, the rest can follow.
Degaussing is accomplished using an alternating current electromagnet. At least that's how we used to degauss CRTs. I think tape heads are demagnetized the same way. You gradually decrease the current, or move the degaussing coil away from the component you are trying to degauss. People used to magnetize the CRTs in their televisions all the time when they put their speakers beside the TV. Maybe there are other ways to do it...

Anyways, my K-50 is starting to develop the problem. I'm an electronic technician, so you can be damn sure I'll be cracking open the camera soon. Thanks for the heads-up, Shephard!
10-24-2016, 09:05 PM   #42
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QuoteOriginally posted by DougieD Quote
Degaussing is accomplished using an alternating current electromagnet. At least that's how we used to degauss CRTs. I think tape heads are demagnetized the same way. You gradually decrease the current, or move the degaussing coil away from the component you are trying to degauss. People used to magnetize the CRTs in their televisions all the time when they put their speakers beside the TV. Maybe there are other ways to do it...

Anyways, my K-50 is starting to develop the problem. I'm an electronic technician, so you can be damn sure I'll be cracking open the camera soon. Thanks for the heads-up, Shephard!
You're correct, of course - don't know what I was thinking of. Anyway, that makes it simpler, still
06-30-2017, 05:02 PM   #43
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Poor quality aperture motor in K50

After reading about aperture motor issue in K50 and K30, it seems pentax made a deliberate choice to use poor quality component in the camera.
My K50 aperture motor died @ 13000 shots.
I upgraded to K3-ii but i miss the ease of using K50. My camera is out of warranty and i don't want to spend 200$ on repairs.

Any cheap fix OR DIY option you experts can recommend? Or any youtube video showing the repair steps?
07-01-2017, 04:46 AM   #44
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swadhingandhi, take a look at the Pentax K-30 - K-50 section of this forum. There's plenty of info there about the problem and DIY solutions, including videos.
07-09-2017, 09:35 AM   #45
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QuoteOriginally posted by swadhingandhi Quote
After reading about aperture motor issue in K50 and K30, it seems pentax made a deliberate choice to use poor quality component in the camera.
My K50 aperture motor died @ 13000 shots.
A forum moderator edited a derogatory comment I made about what Pentax was doing in AutoFocus twenty-two years ago, but they allow endless bitching here about K-30/50 aperture control.

The simple fact is that there is zero evidence Pentax intentionally used inferior parts.

The K-n0 line is a consumer line. A consumer is more likely to have a usage pattern like mine .... fewer than 1K shots per year .... so 13K would be more than ten years, more than enough life for the average consumer. Those who got less than 2K have a genuine complaint, however.
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