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11-15-2018, 09:27 AM   #16
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I have the same problem, the first few shots are dark, rapid shutter use or four or five releases seems to clear it.
I've looked at a number of comments, and many suggest that the solenode sticks due to residule magetism.
In old relay technology this was delt with by a small pip on the armature that prevented total contact, and assisted quick release by reducing the affect of the residule magnetism.
I've tried to find a diagram / image of the assembly to see if this is a practical solution, not that I think it's my job to do design mods for Pentax but because it's XXX annoying.
Any details would be appreciated as I would like to know what the problems are before risking pulling my camera apart, can anyone offer info.

11-15-2018, 09:37 AM   #17
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QuoteOriginally posted by David Marriott Quote
I have the same problem, the first few shots are dark, rapid shutter use or four or five releases seems to clear it.
I've looked at a number of comments, and many suggest that the solenode sticks due to residule magetism.
In old relay technology this was delt with by a small pip on the armature that prevented total contact, and assisted quick release by reducing the affect of the residule magnetism.
I've tried to find a diagram / image of the assembly to see if this is a practical solution, not that I think it's my job to do design mods for Pentax but because it's XXX annoying.
Any details would be appreciated as I would like to know what the problems are before risking pulling my camera apart, can anyone offer info.
Welcome to Pentax Forums.

There are a whole lot of discussions about this issue in the K30 & K-50 Section.
https://www.pentaxforums.com/forums/151-pentax-k-30-k-50/
I really doubt we want to repeat them here. In summary, the issue is much more complicated than residual magnetism; the current solenoid seems to have both a new plastic {PET instead of teflon} as well as a new metal.
11-15-2018, 09:52 AM   #18
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QuoteOriginally posted by reh321 Quote
Welcome to Pentax Forums.

There are a whole lot of discussions about this issue in the K30 & K-50 Section.
Pentax K-30 & K-50 - PentaxForums.com
I really doubt we want to repeat them here. In summary, the issue is much more complicated than residual magnetism; the current solenoid seems to have both a new plastic {PET instead of teflon} as well as a new metal.
Thanks for that, is there a way of knowing the part number for the new version as there is no point fitting one of the old type?
11-15-2018, 10:32 AM   #19
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QuoteOriginally posted by David Marriott Quote
Thanks for that, is there a way of knowing the part number for the new version as there is no point fitting one of the old type?
Read this page in particular.
K-30 / K-50 Aperture Block Failue - Repair Solution available - Page 51 - PentaxForums.com

The problem is with new solenoids, which seem to have pale green plastic; old solenoids, which seem to have pure white plastic, seem to be the ones you want.
A guy on eBay has made a business taking solenoids out of old cameras and selling them
Pentax K-30 K-50 K-S1/S2 K-500 Genuine Aperture Solenoid Plunger Part - Japan - | eBay

One of the problems here is that all parts have the same number, regardless of construction of the solenoid; the only difference is how they 'age', which normal acceptance inspection would never catch.

03-18-2019, 08:11 AM   #20
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QuoteOriginally posted by reh321 Quote
....... the only difference is how they 'age', which normal acceptance inspection would never catch.
Not the only difference but:

1. Holding force of the early DSLR white made in Japan solenoid is not as strong
2. Material: White solenoid is made out of teflon (PTFE): better bearing abilities
3. unknown: Material composition (alloy) of the plunger
03-18-2019, 12:01 PM   #21
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QuoteOriginally posted by photogem Quote
Not the only difference but:

1. Holding force of the early DSLR white made in Japan solenoid is not as strong
2. Material: White solenoid is made out of teflon (PTFE): better bearing abilities
3. unknown: Material composition (alloy) of the plunger
We don't disagree here.
The solenoids work OK when the camera is new.
When I talk about "aging", I am saying these factors cause the solenoid to change over time so they no longer meet requirements.
For example, the teflon "wears' better than the PET does; the metal's magnetic/mechanical qualities may change over time.
Catching changes that will occur in the future is not what Acceptance Inspection does.
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