[reh321]

Really, the plm doesn't use the solenoid? I didn't know that. How does that work?

BTW, the plm is the zoom that always works. I found that one of my other zooms failed once or twice today (55-300 wr , not plm)

found the answer here:
Unlike earlier Pentax lenses, the aperture stop-down lever in the camera is not used to control the diaphragm of this lens. A DSLR launched in 2013 or later is needed to operate this new system (the K-500 is not

The issue is not the PLM motor; the issue is that the 55-300mm PLM lens is a "KAF4" lens. This latest variant of the K-mount sends electronic messages to the lens, and electronics / motor within the lens control the aperture; only recent cameras can send the needed commands to the lens. Older K-mount lenses use mechanical linkages to move the aperture; the solenoid in question causes the linkages to move properly. The earliest Pentax lenses - "Takumar", "Pentax", and "Pentax-M" lenses - lack the ability for the body to control the aperture, so the user has to control the aperture via the aperture ring.

A similar process is involved in controlling auto-focus. Older lenses control AF through use of a motor within the camera which drives the "screw-drive" which conveys motion to the lens; in more recent lenses, signals are sent to a motor {such as the "PLM" motor} within the lens.


https://www.pentaxforums.com/articles/photo-articles/evolution-of-pentax-k-mount.html

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Last edited by reh321; 08-30-2020 at 01:16 PM. Reason: added link to article about evolution of K-mount

[Desperado]

i have had aperture block symptoms(one or two underexposed photos when the camera just started) when sigma 17-50 f2.8 mounted.Now i got my kitlens on my ks2 for a few days and no symptoms.is it maybe kitlens aperture needs less torque?
wrong alarm : underexposed pics continue with kitlens too

[photogem]

I had aperture block symptoms (one or two underexposed photos when the camera just started) with the sigma 17-50 f2.8 mounted.
Underexposed pics with the kitlens as well

Thank you very much for the quick response. I have also the K100D. Its solenoid would work properly in K-S2?
And after that repair will I be able to use my K100D with M (manual) lenses?

Did you meanwhile transplant the white Japan-solenoid from the flash-circuit of your K100D into the aperture-control of your K-S2 and the green China-solenoid
into your K100D (flash)?
It should give you 2 working Pentax bodies without any loss because the green China-Solenoid is less "stressed" in this very simply flash circuit of the K100D.
It works similar as in DVD drives, just a push on the flash-release button brings 7.2 Volts to the solenoid via a very simple transistor protected by a diode.

You just have to be careful, there is a tiny plastic rod connected to the mechanism in the K100D which pops out about 1,5cm behind the metal hook which holds the pop-up flash closed. This plastic rod can fall out when one removes the solenoid. If this rod is missing, the flash cannot pop-up anymore. Also a sign to watch out for when "not working" Pentax bodies are on sale such as this one (The Germany text says as well: Ex-repairshop cameras, I cannot tell if parts have been removed or not.... but he sells repaired K30's etc. with white solenoid):