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Forum: Pentax K-30 & K-50
02-21-2019, 01:52 AM
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Navmaxlp, I'd suggest you use an anti-static wrist band and clip the lead to the metalwork as soon as you have removed the bottom cover. Unfortunately my K30 developed the 'random flapping mirror' problem at some stage while operating the camera with the covers off, after replacing the solenoid. I don't know the reason why, but I guess I could have zapped it.
Polarity-wise; just physically compare the old solenoid with the new one and wire the same way. The way this system works is that the bar magnet normally holds the horseshoe in place. When you take a shot, a short pulse is applied across the solenoid creating an electromagnetic force which is opposite to the force from the bar magnet. This is not strong enough to 'eject' the horseshoe, but an additional downward pull is applied by the system mechanism, and the horseshoe is released.
So you can see that the polarity is important, because if connected the wrong way around, the magnetic force created by the pulse on the solenoid coil will just add to the bar magnet force, rather than opposing it.
You can also see from this that there are a few other variables which may result in the same apparent problem including; wear on the solenoid slot and mating pin (this may reduce pre-load, reduce downward force movement range when mechanism operates, and explain why filing the horseshoe sometimes works). The electronics that produces the pulse could be faulty; e.g. pulse width too narrow and/or timing marginal (this may explain why different battery voltages may appear to influence performance, but not offer a real solution.
But you can safely rule out ideas that the horseshoe has become 'partly magnetised' or that any differences in plastic former material are causing the problem.
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Forum: Pentax K-30 & K-50
11-21-2018, 03:06 PM
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I carried out some further investigation on my K-30 today.
Long-story-short, I think any evaluation of solenoid break/release force using a d.c. supply is a waste of time, as that is not the way the solenoid is controlled in the camera. I cannot see a great difference between the green & white solenoids when testing using a d.c. supply, but there is a big difference when operating via a pulse.
As I have a white solenoid to use as a replacement for the apparently faulty green one, I'm going to move on and work on my flapping mirror problem, but my notes from today are here (Captain Bodgit: Fixing my Pentax K-30 exposure problem: #4 more details on solenoid ) for anyone interested.
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Forum: Pentax K-30 & K-50
11-20-2018, 07:56 AM
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Not exactly sure what you are asking, but I would estimate the difference between the white & green solendoids is approx 5%. However please read my notes as the test was very crude: Captain Bodgit: Fixing my Pentax K-30 exposure problem: #3 one problem leads to another!
I'm going to open the camera one more time to investigate the 'flapperty-flap' mirror problem, but If I can't fix that I'll gladly hang both solenoids on a variable d.c. supply and see what it takes to operate each of them.
---------- Post added 11-20-18 at 08:51 AM ----------
More...
I don't know about the white solenoid, but I can put 4.8V d.c. across the green one and it still does not release.
I'll definitely try the white one when I reopen the K-30.
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Forum: Pentax K-30 & K-50
11-20-2018, 06:28 AM
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One thing that I've noticed about the green solenoid is that the coils and former do not appear to be parallel.
However, this may not be significant, as the force needed to pull the solenoid apart is over 600g.
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