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02-12-2018, 10:28 PM   #1
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Pentax K-50 problematic aperture block repair--shutter speed compromised!

After following the Pentax Forum troubleshooting threads for some time on the K-50 aperture block problem, I went in for the DIY repair. My K-50 has been a real workhorse the last 3 years for me in all weather and I LOVE this camera. It's at 18000+ exposures.

I gently diamond-filed and 600 grit sanded the "horseshoe" from the over-magnetized solenoid and carefully put the body back together, being sure to avoid pinching any wires.

But when I fired it back up, it did shoot beautiful exposures, just with a very slow shutter speed whatever it's been set to. This means that I hear the mechanism for about 1/2 second. I'm unsure what I'm hearing--if it's for example the mirror movement that's delayed?

Any thoughts or questions that could help me clarify this further?

I've made the leap of faith in Pentax and bought the K 3-II which is, I understand, about to phase out.
But as I said--I really loved this K-50 and have taken it on some good adventures and hope to salvage it as a back-up camera now. Thanks in advance!

02-13-2018, 01:04 AM   #2
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First of all I see you are fairly new, so welcome to the Forum. I must say I am impressed that you have the confidence to get into any digital camera and affect repairs. Today I used my k-50 for a few hours and had a lot of fun with it. I only have less than 3,500 clicks and so far no problems. I find it fascinating that you had not noticed the noise until after you had made changes. Is it possible that the filing and sanding may have created a gap which may be causing the sound that you are hearing? At any rate, thanks for posting as I will be living here to see the responses you receive.

TT
02-13-2018, 03:01 AM   #3
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Hi and welcome!.
Are you saying that in good light you have a long exposure time?, if so that sounds like a partial failure where the camera is compensating for the aperture not fully opening.
It would seem then that the fix is unreliable, my advice would be to buy an old non-functioning body for spares (should be dirt cheap) and salvage the solenoid for replacement.
Having done that the problem is gone for good and you have a back-up camera .
The full repair is a small step beyond where you were.

I bought a K-3ii because I wanted one and initially put the K-50 back in its box. After a couple of months I could not bear it lying there unused and put a lens on it and started using it again. It was weird though, it seemed so small and light, but I really like the thing.
Good luck!
02-13-2018, 02:35 PM - 1 Like   #4
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Nothing wrong with having a smaller, lighter body as an alternative in your toolbox. My K-S2 serves me well for when I need such, although I have my K-5 IIs, and KP alternatives. Te K-S2 remains the smallest and lightest.

In your case, your K-50 also has its built-in flash. Great easy-packing for casual get-togethers and events in venues of modest dimensions. It is certainly worth the repair.

02-13-2018, 06:47 PM   #5
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Pentax K-30 K-50 K-S1 K-500 Genuine Aperture Solenoid Plunger Part -Japan - | eBay

or if you can find somewhere cheaper or a donor camera.

I am not sure if the Solenoid that is in the pop-up flash same as the aperture block, may be that can be used in the aperture block?

Don't take my word, get consultation from other gurus here before you attempt this.

Like you after I bought a K3, I took a chance and fixed my K50.

Or you can just buy one of these, basically it's almost new and comes with 1 yr warranty. I have bought lenses from them, pretty good collection and fast shipping.

Pentax K-50 16.3MP Digital SLR Camera Body K50 (Used - Mint- Condition)
02-14-2018, 05:54 AM   #6
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QuoteOriginally posted by suraswami Quote
I am not sure if the Solenoid that is in the pop-up flash same as the aperture block, may be that can be used in the aperture block?
They are identical, IIRC the assembly of the solenoid for the pop up flash has the screw going through the left hole, which may have some locking varnish remaining. The aperture solenoid has the screw going through the right hole, and the left hole is used for alignment.

I used the pop up flash solenoid for my aperture since in usage terms it will be like new, pop up flash actuation is infrequent compared to aperture operation.
02-15-2018, 08:11 AM   #7
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QuoteOriginally posted by Kevin B123 Quote
Hi and welcome!.
Are you saying that in good light you have a long exposure time?, if so that sounds like a partial failure where the camera is compensating for the aperture not fully opening.
It would seem then that the fix is unreliable, my advice would be to buy an old non-functioning body for spares (should be dirt cheap) and salvage the solenoid for replacement.
Having done that the problem is gone for good and you have a back-up camera .
The full repair is a small step beyond where you were.

I bought a K-3ii because I wanted one and initially put the K-50 back in its box. After a couple of months I could not bear it lying there unused and put a lens on it and started using it again. It was weird though, it seemed so small and light, but I really like the thing.
Good luck!
Yes, that's right--in good light there is a longer than "set" exposure time. Or at least that is what is sounds like. Using the Manual setting for aperture and shutter speed (e.g. 1/80 - 1/250) it will sound like a much longer shutter release (e.g. 1/2-1 second).

I read that the repair for the solenoid (rather than replacement) has been about 20% effective for others reporting it to the forum.
It is a pity that the solenoid isn't available directly from Pentax, although I get that. It's a mass market part used in many electronics.

For now I'm of course keeping the K-50 as my lighter backup. And if one day in the future I've learned how to use a soldering iron, perhaps I'll take a crack at replacing the solenoid. That's a repair my father (who's retired) would probably enjoy doing with me and my son.

Thanks again!
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