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4 Days Ago   #1
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trying to help a friend diagnose his K-50 problem

A friend just handed me his K-50 and showed me it was taking black photos. After a variety of testing, I have determined, using a lens with an aperture ring, that it shoots more or less correct exposures at smallest aperture and then progressive darker shots as the aperture opens up (same EV throughout). So, at f22 it works well enough, but moving down from there to f4 produces darker and darker images even with the shutter speeds adjusting to keep the same EV.

Diagnosis?

4 Days Ago   #2
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Sounds like the dreaded aperture block problem.

Detection of aperture block/diaphragm-block failure/stuck solenoid K-30, K-50, K500 - PentaxForums.com
4 Days Ago   #3
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^ That. I'd say that it's a 99% probability that the green aperture motor has failed.
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Worth fixing? CAN it be fixed? And if so, how much moolah?

4 Days Ago   #5
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Certainly worth fixing. I have fixed a K30 and a KS2. If you don't feel you have the diy skills try and find someone who does. This is the procedure:

Manual solenoid replacement Pentax K30 / Discharge flash-condenser / Solenoid choice - PentaxForums.com

The other part is finding a replacement solenoid.
4 Days Ago   #6
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Will Pentax repair do this? What is it called now: Precision??
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^ Precision can do it, but here's the catch. They're going to replace it with another green solenoid & there is a 50/50 chance that it will eventually fail again.

The only permanent 100% fix is getting a white solenoid to replace the green one. This you have to do on your own 'cause not even Precision will do that. I already did that to both my K50 bodies. Been trouble free for 4 years now.
3 Days Ago   #8
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QuoteOriginally posted by sholtzma Quote
A friend just handed me his K-50 and showed me it was taking black photos. After a variety of testing, I have determined, using a lens with an aperture ring, that it shoots more or less correct exposures at smallest aperture and then progressive darker shots as the aperture opens up (same EV throughout). So, at f22 it works well enough, but moving down from there to f4 produces darker and darker images even with the shutter speeds adjusting to keep the same EV.

Diagnosis?
It is with 99,9% certainty the solenoid whose PET body is green since manufactured in China.

@ suirrel mafia: That's of course not a green aperture-motor in the K50 nor any other similar bodies but I guess you know this and just mixed up the name?! So just for those who don't know it because it is important.
The only bodies using an aperture-motor are K7 (which was the first one!), K5, K3, K1, KP and K-01.
All other bodies use a solenoid. More details about the solenoid you find here:
A LITTLE BIT OF HISTORY: Development of the solenoid in Pentax cameras - PentaxForums.com

The way you tested was exactly how one tests this problem, another possibility is to look into the lens, active live-view:
Aperture should close down to f4.0 but will be fully closed, i.e. f22 or higher depending on the lens.

The link how to repair it was already posted

If you send it to any official repairplace they will exchange it for the same component which in many cases fails again.

If you are up to DIY, you can find the Japan-Solenoid (with a white PTFE body) in all Pentax bodies except those with aperture-motor.
In most cases 2 of them except K10D/20D which have just one. Also in their Samsung equivalents.
A person sells this solenoid on ebay.com as well.

It is sure worth doing it yourself, the K50 will work better afterwards then it ever did before, because the Japan-Solenoid actuates quicker.
With max. of US$ 45 or so (if ebay): Which DSLR could compete for this price. Work is about 1 hour plus/minus


Last edited by photogem; 3 Days Ago at 05:08 AM.
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